SciELO - Scientific Electronic Library Online

 
vol.36 número6Efecto de la suplementación de L-arginina y L-citrulina sobre el rendimiento físico: una revisión sistemáticaTendencias actuales en la determinación analítica de vitamina D índice de autoresíndice de materiabúsqueda de artículos
Home Pagelista alfabética de revistas  

Servicios Personalizados

Revista

Articulo

Indicadores

Links relacionados

  • En proceso de indezaciónCitado por Google
  • No hay articulos similaresSimilares en SciELO
  • En proceso de indezaciónSimilares en Google

Compartir


Nutrición Hospitalaria

versión On-line ISSN 1699-5198versión impresa ISSN 0212-1611

Nutr. Hosp. vol.36 no.6 Madrid nov./dic. 2019  Epub 24-Feb-2020

http://dx.doi.org/10.20960/nh.02673 

Revisiones

Diet, physical activity and telomere length in adults

Dieta, actividad física y longitud telomérica en adultos

María Jossé Navarro Ibarra1  , Jesús Hernández1  , Graciela Caire Juvera1 

1Department of Nutrition. Centro de Investigación en Alimentación y Desarrollo, A.C. Hermosillo, Sonora, Mexico.

Abstract

Telomere length (TL) is a predictive biomarker of premature aging. Telomere shortening has been linked to age-related diseases and noncommunicable diseases (NCD), and may reflect the effects of behavioral, psychosocial and environmental factors on health status. Telomere attrition can be affected by lifestyle factors such as diet and physical activity. The search of studies included in this review was conducted on PubMed Central database. A majority of studies are cross-sectional, as there is a clear lack of prospective studies to evaluate the individual effect of dietary components, dietary patterns, and physical activity on TL in the long term. The current literature suggests that high adherence to Mediterranean diet (MD), with consumption of antioxidants, fiber and vegetables, as well as seeds and walnuts, is associated with longer TL. The dietary components of a healthy diet, such as carotenoids, vitamins A, C, D, E, polyphenols, fiber, and omega-3 fatty acids could help maintain TL. In contrast, a high consumption of sugary beverages, processed meat, and proinflammatory diets is associated with telomere shortening. In a majority of studies TL is positively associated with moderate physical activity. The predominant mechanisms through which a healthy diet and moderate physical exercise could mitigate telomere attrition include decreasing oxidative stress and inflammation. We shall not discuss the associations of possible risk or protective factors in terms of causality since the majority of studies are cross-sectional and randomized controlled trials are limited; accordingly, some results are inconclusive. For future research, we suggest evaluating the individual effects of dietary components, dietary patterns and physical activity, considering repeated measurements and exercise intensity, on TL. It is also advisable to include biomarkers of oxidative stress and inflammation proteins, and to measure telomerase activity.

Key words: Telomere length; Diet; Physical activity

Resumen

La longitud de los telómeros (TL) es un biomarcador predictivo del envejecimiento prematuro. El acortamiento de los telómeros se ha relacionado con las enfermedades asociadas a la edad y las enfermedades no transmisibles (ENT), y puede reflejar los efectos de los factores conductuales, psicosociales y ambientales en el estado de salud. El desgaste de los telómeros puede verse afectado por factores del estilo de vida, como la dieta y la actividad física. La búsqueda de los estudios incluidos en esta revisión se realizó en la base de datos PubMed Central. La mayoría de los estudios son transversales, por lo que está clara la falta de estudios prospectivos que evalúen el efecto individual de los componentes dietéticos, los patrones dietéticos y la actividad física sobre el TL a largo plazo. La literatura actual sugiere que una alta adherencia a la dieta mediterránea (DM) y el consumo de antioxidantes, fibra y vegetales, así como semillas y nueces, se asocia a una mayor TL. Los componentes dietéticos de una dieta saludable, como los carotenoides, las vitaminas A, C, D, E, los polifenoles, la fibra y los ácidos grasos omega-3, podrían ayudar a mantener la TL. En contraste, el alto consumo de bebidas azucaradas, carne procesada y dietas proinflamatorias se asocia al acortamiento de los telómeros. En la mayoría de los estudios, el TL se asocia positivamente con la actividad física moderada. Los mecanismos predominantes que, a través de una dieta saludable y un ejercicio físico moderado, podrían mitigar el desgaste de los telómeros son la disminución del estrés oxidativo y la inflamación. No se discute la asociación de posibles factores de riesgo o de protección en términos de causalidad, ya que la mayoría de los estudios son transversales y los ensayos controlados aleatorios son limitados; por consiguiente, algunos resultados no son concluyentes. Para investigaciones futuras se sugiere evaluar los efectos individuales de los componentes dietéticos, los patrones de actividad física y dietética, considerando mediciones repetidas y la intensidad del ejercicio, sobre el TL. También es aconsejable incluir biomarcadores de estrés oxidativo y proteínas inflamatorias, y medir la actividad de la telomerasa.

Palabras clave: Longitud de los telómeros; Dieta; Actividad física

INTRODUCTION

Telomeres are cellular structures composed of repetitions of DNA sequences (TTAGGG), located at the end of chromosomes; their function is to protect chromosomes from degradation during each cell cycle (1). Telomerase is the enzyme responsible for the maintenance of TL, and its function is to add TTAGGG repeats to the 3’ end of the sequence by retrotranscription (2). The largest telomerase activity is observed mainly in gametes, stem cells, and tumor cells (3). In somatic cells during cellular replication, TL shortens gradually, and this shortening gives rise to mutagenesis and chromosomal instability; as a consequence, there is tumorigenesis when excessive shortening occurs after reaching a certain threshold (4). TL may reflect the effects of behavioral, psychosocial and environmental factors on health status, and may predict morbidity and mortality (5). Short TL has been linked to age-related diseases and NCDs. In epidemiological studies telomere shortening has been associated with risk for various cancers, such as bladder (6), gastric (7), colorectal (8), and breast cancer (9,10).

Telomere shortening has been related to high levels of inflammation (11), oxidative stress (12-14), and metabolic factors such as abdominal fat, elevated blood glucose levels, and hypertension (15,16). A shorter TL has also been linked to conditions associated with lifestyle that are potentially modifiable factors, such as a decrease in fruit consumption (7) and physical inactivity (17,18). A longer TL has been linked with having a healthy diet, moderate alcohol consumption, maintaining a healthy body weight, abstaining from smoking, and participating in moderate or vigorous physical activity (19). Thus, findings from different studies show that lifestyle changes, including healthy dietary patterns and an increase in physical activity, may decrease telomere shortening. However, some studies have not found such associations, which leads to contradictory results regarding the effect of physical activity or diet on TL. The aim of this review is to examine the results of human studies that evaluated the role of lifestyle factors, such as dietary patterns, nutrients and physical exercise, on the promotion of TL changes. We also discuss the possible mechanisms of action that influence this process, with the perspective that TL could be a novel biomarker, measurable in blood samples, to indicate the risk of suffering age-related diseases or NCDs; it could be useful for promoting healthy lifestyles in the population. TL is highly variable among tissues and blood cell subpopulations due to their different proliferative history (20). Therefore, the studies that were included in this review measured TL from whole blood, buccal cells, and peripheral blood mononuclear cells.

The studies included in this review were identified by a literature search conducted in the PubMed Central database. The following keywords were used as search criteria: “telomere length and nutrients” OR “diet” OR “antioxidants” OR “micronutrients” OR “food” OR “vitamins” OR “exercise” OR “physical activity”. We conducted the last search in December 2018. The search included cross-sectional designs, case-control and cohort studies, and clinical trials. We considered studies involving male or female adults, healthy or with any condition such as cancer, diabetes, hypertension, or overweight and obesity. Among the scientific articles dealing with diet or physical activity included in this review, thirty describe the effect of diet on TL (Table I), fifteen evaluate the effect of physical activity (Table II), and five focus on the effects of both diet and physical activity on TL (Table III). The majority of studies are cross-sectional (twenty-nine), eight studies are cohort studies, ten are randomized controlled trials, one is a clinical trial, and two are case-control studies.

Table I. Effect of diet on telomere length 

DII: dietary inflammation index; TL: telomere length; NHS: Nurses’ Health Study; F: Fisher's test; β: regression coefficient; OR: odds ratio; PREDIMED: Prevention with Mediterranean Diet; qPCR: quantitative polymerase chain reaction; TRF: telomere restriction fragment; T/S: the ratio of telomere PCR value to single-copy gene value derived from quantitative PCR; FISH: fluorescence in situ hybridization; PBL: peripheral blood leukocytes; PMBC: peripherial blood mononuclear cells; NHANES: National Health and Nutrition Examination Survey; BMI: body mass index; SFA: saturated fatty acids; PUFA: polyunsaturated fatty acids; EPA: eicosapentaenoic acid; DHA: docosa-hexaenoic acid.

Table II. Effect of physical activity on telomere length 

TL: telomere length; NHS: Nurses' Health Study; β: regression coefficient; OR: odds ratio; CRP: C-reactive protein; qPCR: quantitative polymerase chain reaction; TRF: telomere restriction fragment; T/S: the ratio of telomere PCR value to single-copy gene value derived from quantitative PCR; PBL: peripheral blood leukocytes; PMBC: peripheral blood mononuclear cell; NHANES: National Health and Nutrition Examination Survey; ALPHA: Alberta Physical Activity and Breast Cancer Prevention; BMI: body mass index; MET: metabolic equivalent of task; HDL: high-density lipoprotein; CVD: cardiovascular disease.

Table III. Joint effect of diet and physical activity on telomere length 

PBMC: peripheral blood mononuclear cells; TL: telomere length; PBL: peripheral blood leukocytes; qPCR: quantitative polymerase chain reaction; T/S: the ratio of telomere PCR value to single-copy gene value derived from quantitative PCR; LDL: low-density lipoprotein; HDL: High-density lipoprotein; IQR: interquartile range.

DIET AND DIETARY PATTERNS LINKED TO TELOMERE LENGTH

Several studies reported that adherence to dietary patterns or different dietary components, such as consumption of fiber, antioxidants, fatty acids and vitamins, as well as consumption of food groups such as fruits, vegetables, nuts, seeds, legumes, fish, sweetened beverages, and others, may be related to changes in telomere attrition (Table I). Dietary patterns describe the eating habits of a population; examples include MD, western diet, vegetarian diet, vegan diet, and others. Dietary patterns also reflect adherence to the formal dietary guidelines recommended for disease prevention (21). MD is a healthy diet that has been studied as protective against various chronic diseases (22), and is characterized by consumption of fruits and fresh vegetables, fish, cereals, vegetable fibers, nuts, and low saturated fat. Crous Bou et al. (23) conducted a study involving 4,676 healthy American women, and greater adherence to MD was significantly associated with longer TL. Boccardi et al. (15) reported that older adults without hypertension, myocardial infarction, vascular disease, dementia, stroke or heart failure, and with greater adherence to MD had higher telomerase enzyme activity and consequently longer TL as compared to those with low adherence to MD. In addition, participants also had low levels of some inflammation biomarkers such as C-reactive protein (CRP), interleukin 6 (IL-6) and tumor necrosis factor alpha (TNF-α), as well as low levels of nitrotyrosine.

The pro- or anti-inflammatory potential of diets has been studied in relation to TL using the dietary inflammation index, which is a tool for assessing a diet’s inflammatory capacity; it is thus a population-based index representing a refined scoring algorithm based on an extensive review of the literature. Dietary variables are classified and scored according to their pro-inflammatory effect, anti-inflammatory effect or no effect on inflammatory biomarkers such as, IL-1b, IL-4, IL-6, IL-10, TNF- α, and C-reactive protein (24,25). García Calzon et al. (24) evaluated whether a diet associated with inflammation could modify telomere attrition rate by applying an intervention where MD was used for 5 years in 520 participants at high risk for cardiovascular disease. At baseline, the authors found that participants who had an anti-inflammatory diet had longer telomeres compared to those with pro-inflammatory diets. In addition, after 5 years of follow-up, participants with a pro-inflammatory diet had a 2-fold higher risk of accelerated telomere attrition when compared to participants with an anti-inflammatory diet.

Likewise, a cross-sectional study carried out by Shivappa et al. (25) in American adults evaluated the inflammatory potential of diet from a calculation of the dietary inflammation index obtained by the implementation of 24-hour recalls to participants. This study found that the highest dietary inflammation index scores were associated with telomere shortening. Another study reported no significant associations between TL and dietary inflammatory index or daily energy and fiber intake (26). The findings of these investigations suggested limited results of association studies between dietary patterns and TL. On the other hand, in a cross-sectional study in Chinese adults with diabetes, prediabetes, or normal glucose, Zhou et al. (27) evaluated the influence of diet on leukocyte TL, inflammation markers, and oxidative stress. The authors reported that consumption of legumes, nuts, fish and seaweed are factors associated with reduced telomere shortening, since they found a direct association between consumption of these foods and greater TL.

Contradictory findings have emerged on the consumption of meats and fats, and on their association with TL. In the study by Zhou et al. (27) consumption of meat, fat, and carbohydrates was not associated with telomere shortening but with an increase in inflammation as determined by TNF-α and IL-6 levels. Meanwhile, Fretts et al. (28) found that the consumption of processed meats was associated with a telomere shortening rate of 0.02 units per additional serving consumed per day. This finding is similar to that reported by Nettleton et al. (29), who found that for each additional serving/day of processed meat, the ratio of quantitative polymerase chain reaction telomere to single-copy gene (T/S ratio) was smaller by 0.07. Fretts et al. (28) describe a possible mechanism related to this finding, which is that processed meats have high concentrations of advanced glycation products, which are formed during the processing of meat and have been associated with telomere shortening by its ability to induce high levels of inflammation and oxidative stress. In addition, the authors refer to the importance of paying attention to the portion and frequency of consumption, not only to type of food. In this sense, Kasielski et al. (30) reported that consumption of red meats 1 to 2 times per week is associated with an increase in TL; this finding differs from those published by Fretts et al. (28) and Nettleton et al. (29), who reported that daily intake of meat is associated with telomere attrition.

In an intervention study to promote lifestyle changes in adults, the authors found that healthy changes (diet rich in whole grain foods, vegetables, fruits, and low-fat proteins, and moderate aerobic exercise, stress management, and increased social support) at 5 years of follow-up were associated with an increase in relative TL in the intervention group versus controls (31). Meanwhile, Hovatta et al. (32) obtained different results, since they reported that a lifestyle intervention during a 4.5-year follow-up period of weight loss, increased physical activity, and healthy diet did not have an effect on TL. Similarly, Bethancourt et al. (33) found no associations between blood TL and body mass index or dietary factors such as processed meats, fried/grilled meats and fish, nonfried fish, coconut oil, fruits, vegetables, bread products, and sugar-sweetened beverages. The consumption of the latter was associated with telomere shortening in a cross-sectional study (34). On the other hand, Lee et al. (35) evaluated the association between two dietary patterns and TL in the remote past. The first one was called a prudent dietary pattern, characterized by a high intake of whole grains, seafood, legumes, vegetables and seaweed. The second was the Western dietary pattern, characterized by a high intake of refined grain, red or processed meat and sweetened carbonated beverages. Consistent with previous findings, Lee et al. found that high adherence to a prudent dietary pattern was positively associated with TL. In addition, according to the analysis of particular food items, consumption of products such as legumes, nuts, seaweed, fruits and dairy products, and lower consumption of red meat or processed meat and sweetened carbonated beverages, were associated with longer TL (32,34).

Several studies report that dietary patterns with a high consumption of fruits and vegetables are related to an increase in TL (36-39). However, fruits and vegetables are taken as a whole group, and no particular type of fruit or vegetable is evaluated. Thus, it is difficult to attribute the aforementioned effect to a specific fruit or vegetable. A broader view is observed in the study conducted by Marcon et al. (37), who reported that a higher intake of vegetables was related to a higher mean TL, and the effect was specifically attributed to the intake of root vegetables, peppers and carrots. In an interesting study involving diet, TL and disease, Lian et al. (38) assessed the relationship between consumption of fruits and vegetables with TL in normotensive and hypertensive adults. In normotensive participants, increased intake of vegetables was associated with increased age-adjusted TL. In addition, the authors found that a longer TL was associated with a reduced risk of high blood pressure in participants with a higher consumption of vegetables. These data suggest that a high intake of vegetables in the diet promotes improvement in biomarkers such as TL, which can serve as a prognostic marker for cardiovascular disease.

MICRONUTRIENTS, ESSENTIAL FATTY ACIDS AND TELOMERE LENGTH

Epidemiological studies report a direct association between dietary micronutrients and TL (Table I), including the study by Marcon et al. (37), in which the analysis of the association between micronutrients and mean TL highlighted a significant role of antioxidant intake, especially beta-carotene, on telomere maintenance. Likewise, Yabuta et al. (40) reported that high intake of dietary beta-carotene and alpha-tocopherol protects buccal cells from telomeric shortening. In addition, carotenoids and other micronutrients, such as vitamin C, folate and potassium, have been positively associated with TL in Korean populations according to Lee et al. (41).

In another aspect of dietary information, there are studies that evaluated the relationship between serum or plasma concentrations of carotenoids or vitamins with TL (Table I). A study by Nomura et al. (42) reported that serum carotenoids are positively associated with leukocyte TL. Additionally, Mazidi et al. (43) reported that serum α-carotene, trans-β-carotene, cis-β-carotene, β-cryptoxanthin and combined lutein/zeaxanthin were positively and significantly associated with TL. Min and Min (44) only found a significant association of provitamin A carotenoids, such as alpha-carotene, beta-carotene (trans + cis), and beta-cryptoxanthin with TL; they found no association between nonvitamin A carotenoids (combined lutein/zeaxanthin and trans-lycopene) and TL. Another study provides evidence that higher plasma lutein, zeaxanthin, and vitamin C concentrations are associated with longer TL (45). Furthermore, plasma or serum 25-hydroxyvitamin (vitamin D) levels from diet (46,47) and supplements (48,49) were positively associated with leukocyte TL, while in another study plasma vitamin D concentrations from the diet were not associated with relative leukocyte TL (50).

Studies that consider omega-3 and omega-6 fatty acids cannot be ignored. Thus, in a study performed in adults with coronary heart disease, Farzaneh-Far et al. (51) reported that the consumption of marine omega-3 fatty acids after 5 years of follow-up increased blood omega-3 levels, an increment that was associated with a 32% decrease in the odds of telomere shortening. Indeed, two randomized controlled trials evaluated the impact of omega-3 fatty acid supplementation on telomere shortening. The first trial (52) included 138 participants and demonstrated that supplementation with omega-3 fatty acids has an impact on reducing telomere shortening; the authors suggest the importance of considering the ω-6:ω-3 PUFA ratios for future nutritional interventions. The second trial that evaluated supplementation with omega-3 fatty acids (20) did not show an increase in telomere length, probably due to a smaller sample size (33 participants) as compared to the study by Kiecolt-Glaser et al. (52). In another controlled randomized trial the intake of nuts for two years in older individuals tended to delay telomere attrition compared with individuals with a usual diet without nuts; the authors suggest that nuts are rich in omega-3 fatty acids and other antioxidants that might have an impact on the aging process (53).

There are few studies on the association between micronutrients and telomere length, and a majority of such studies have evaluated intakes of vitamin A, C, D, carotenoids, and omega-3 fatty acids. However, other micronutrients may be found in the diet, such as folate, potassium and zinc that could be related to cellular aging. The information compiled in this review highlights the importance of promoting further intervention studies that include supplementation with specific micronutrients and other diet components to determine their causal relationship with changes in TL.

PHYSICAL EXERCISE AND ITS LINKAGE TO TELOMERE LENGTH

As previously described, physical activity has positive effects on TL. In this way, some authors reported that only moderate to vigorous physical activity, which includes walking briskly, jogging, running, bicycling, swimming, tennis, and aerobics, can reduce telomere shortening (54-56). Nevertheless, Ludlow et al. (57) reported that moderate physical activity has a positive relationship on TL, and this effect is lost at higher physical activity levels. Loprinzi and Sng (58), working with data from the National Health and Nutrition Examination Survey (NHANES), reported that running was the only type of physical activity that was positively related to leukocyte TL. A recent study from NHANES performed by Tucker (59) reported that participants with a sedentary lifestyle had 1.95 times the likelihood of having short telomeres compared to those with high physical activity; the results obtained for sedentary patients did not differ for low or moderate levels of activity. Fretts et al. (60), in a cross-sectional study, found that ambulatory physical activity measured by the number of steps taken per day, was related to TL, and therefore, participants who accumulated more steps had longer leukocyte TL than participants who accumulated fewer steps per day. A recent randomized controlled trial (RCT) that evaluated the effect of aerobic exercise (120 min per week) versus usual inactivity reported that exercise induced changes in TL, promoting telomere lengthening (61). A different result was obtained in an intervention study made by Sjögren et al., since no significant associations were found between changes in steps per day and changes in TL (62). Moreover, Friedenreich et al. (63) found no effect of aerobic exercise on telomere attrition.

A study that included 2,401 Caucasian twins, of which 2,152 were women, reported that TL was positively associated with increased physical activity, and the most active subjects had an increase of approximately 200 nucleotides in TL as compared to the least active subjects (14). The above study is similar to a cross-sectional study performed by Dankel et al. (64), in which the participants who had an active life had longer telomeres compared to sedentary individuals. However, this relationship was not found in overweight or obese participants who were active; therefore, the authors suggest that obesity can mitigate the positive effects of physical activity on TL. This is consistent with the study reported by Mason et al. (65) in postmenopausal women, in which the authors did not find changes in TL among women who were overweight or obese, nor did they found significant changes in TL from the effect of dietary weight loss and aerobic exercise for 12 months. Based on these results the authors suggest that exercise intensity or duration may not be enough to change TL. However, moderate physical activity can have a positive impact through a reduction in adiposity, and can also reduce inflammation levels and oxidative stress (66), factors that attenuate telomere attrition. The latter two studies contradict the findings mentioned above and reflect the importance of carrying out more intervention studies to assess the effect of physical activity on TL.

In studies conducted with cancer patients or cancer survivors, the effect of physical activity on TL maintenance seems to be similar. An RCT performed with overweight and obese breast cancer survivors examined the effect of a 6-month diet and exercise-induced weight loss intervention versus usual care on TL. The authors found changes in TL among women with breast cancer in stage 0-I; there was a 7% telomere lengthening in the intervention group compared to an 8% shortening in the usual care group (p = 0.01) (67). Another study conducted by Loprinzi and Loenneke (68) found an inverse association between leukocyte TL and all causes of mortality among men who engage in moderate-intensity exercise, which suggests that moderate exercise prevents telomere shortening and increases survival. Ennour Idrissi et al. (18) found that total and occupational physical activity were positively associated with longer TL in 162 premenopausal and postmenopausal women with breast cancer. Furthermore, in a study performed with breast cancer survivors by Garland et al. (69), participants with moderate to vigorous physical activity had a longer TL compared with sedentary women. Physical activity may protect individuals from aging-related diseases, acting as a regulator of the cellular aging process. In this avenue of research, it makes sense to use TL as a biomarker of breast cancer risk and, at the same time, as an indicator of lifestyle changes.

POSSIBLE MECHANISMS OF ACTION OF OXIDATIVE STRESS AND INFLAMMATION IMPLIED IN THE REDUCTION OF TELOMERE SHORTENING

TL is a major determinant of biological age and represents a measurable outcome of the additive repercussions of both inflammation and oxidative stress (70); however, the mechanisms are not fully understood. Telomeres shorten at a rate of 40-200 bp per division (71). The rate of telomere shortening by cell division is not an innate constant and changes from one cell to another, possibly from one cycle of division to the next, depending on oxidative stress and defensive antioxidants (12). Telomeres are rich in guanines, which are prone to be oxidized to 8-oxo-2′-deoxyguanosine and 2,6-diamino-4-oxo-5-formamidopyrimidine. Reactive oxygen species, especially hydroxyl radicals, produce single-strand breaks, either directly or as an intermediate step in the repair of oxidative base modifications. Therefore, telomeric DNA appears to be deficient in the repair of single-strand breaks, which may increase the sensitivity of telomeres to the accumulation of 8-oxo-2′-deoxyguanosine DNA strand breaks (13,72). In addition, oxidative stress directly triggers the activation of the transcription factor NFκB, which is the key regulator of the inflammatory process that regulates transcription for various molecules such as interleukins and TNF-α, and is involved in the modulation of telomerase activity (73).

A majority of the reviewed studies conclude that the possible effects of diet or physical activity on reduced telomere attrition is due to a decrease in oxidative stress and inflammation. Among the main mechanisms attributable to physical activity and telomeric shortening are improved REDOX balance, favoring an expression response in antioxidant proteins and DNA repairing enzymes, as well as a reduction of reactive oxygen species, and therefore CRP, IL-6 and TNF-α levels (72). Additionally, exercise training potentially facilitates TL maintenance through many molecular mechanisms, since TL is regulated by epigenetic modifications such as histone changes (methylation and acetylation) and DNA methylation (73). Exercise also acts as a stimulus for telomerase transcription or activity. The hypothetical signaling pathways posited by the authors suggest increased TERT gene transcription as a response to exercise (74).

Chilton et al. (75) first reported that acute exercise can lead to the transcriptional regulation of several main telomeric genes in immune cells. Their results show an upregulation of the key telomeric gene TERT mRNA, which plays an important molecular role in telomere maintenance since it is related to telomerase activity, and a downregulation of TERF2IP mRNA. The authors also reported that exercise regulates miRNAs, including miR-186 and miR-96, with the potential to control the downstream expression of genes involved in telomere homeostasis. It is interesting to note that the mechanisms involved may depend on the specific exercise modality (75), such as resistance training adaptability (76) and aerobic fitness levels (77).

On the other hand, a healthy diet that contains antioxidant and anti-inflammatory components, coupled with physical activity, leads to improved inflammation levels and decreased oxidative stress, mechanisms that are involved in telomere shortening. A study reported that a high adherence to MD can stimulate telomerase activity in mononuclear cells, either directly by the effect of some specific nutrients included in the diet or indirectly by the global effect of the diet on the modulation of inflammation and oxidative stress (15,70). Specifically, IL-6 and TNF-α have been associated with telomere shortening due to their promotion of cell renewal, replicative senescence, induction of oxidative stress, and inhibition or promotion of telomerase activity (11). Likewise, the levels of IL-6 and TNF-α have been associated with daily energy intake, diet carbohydrate/fat proportions, cereals, and meat intake (27). The impact of diet on TL can be by dietary components in the food groups, such as isoflavones from legumes and seaweeds, by antioxidants, and by folic acid, all of which play an important role in DNA methylation and integrity. Another example is fish, which contains vitamin D and has anti-inflammatory and antiproliferative properties that limit the turnover of cells, thus potentially reducing their telomere length attrition (27). Figure 1 shows the possible effects of lifestyle factors (diet and physical activity) and their underlying biological mechanisms that may cause changes in telomere length.

Figure 1. Potential influence of healthy diet and physical activity on the maintenance of telomere length. This scheme represents how individually and collectively a healthy diet and the performance of physical activity can modify the mechanisms involved in maintaining telomere length, such as increased antioxidants and DNA repair enzymes, decreases reactive oxygen species, and reduced pro-inflammatory cytokines, as well as in promoting the methylation or acetylation of histones and DNA methylation. 

CONCLUSIONS, LIMITATIONS AND FUTURE RESEARCH

The studies that evaluated the potential association of diet and TL found that adherence to MD and consumption of antioxidants, fiber, vegetables, seeds, and walnuts are associated with greater TL. In contrast, high consumption of sugary beverages, processed meat, and proinflammatory diets was associated with telomere shortening. Therefore, a healthy diet rich in antioxidants, such as carotenoids and vitamins C and E, and in anti-inflammatory components, such as vitamins A and D, polyphenols, fiber, and omega-3 fatty acids, has a greater effect on the decline in the rate of telomere shortening. These dietary components, especially omega-3 fatty acids, influence the potential mechanisms that reduce telomere shortening (51,78,79) due to their anti-inflammatory and antioxidant properties, as suggested by the study by Kiecolt-Glaser et al. (52), in which the intake of omega-3 fatty acids caused a decrease in IL-6, and IL-6 was associated with telomere lengthening.

On the other hand, findings from all studies demonstrated that performing moderate physical activity is associated with a longer TL; only one study reported that obesity attenuates this relationship, which could be related to the inflammation levels usually associated with obesity. Following this hypothesis, it is possible to say that an increase in physical activity together with a healthy diet may reduce inflammation and oxidative stress levels, and consequently telomere shortening rate. By reducing telomere shortening, these potentially modifiable factors can indirectly contribute to lowering the risk of chronic degenerative diseases such as cancer, or to improving the survival rate of people who have had cancer. However, recent papers regarding the relationship between TL and cancer risk revealed a complex scenario with contradictory findings depending on different cancer types (80,81). Likewise, Weischer et al. (82) measured leukocyte TL in a prospective study of 47,102 Danish population who were followed for up to 20 years for cancer diagnosis and death, and the authors found that short telomere length is associated with reduced survival after cancer but not with cancer risk. Therefore, the role of the relationship between TL and cancer risk remains to be demonstrated, and it could be a focus for future research.

It is important to emphasize that most of the studies presented in this review, and that evaluate the effect of diet or physical activity on TL, are cross-sectional in design. Therefore, the associations that were found referred to risk or protective factors and not to causality, since the criterion of temporality is not met. It is suggested that clinical intervention studies should be carried out to evaluate the effect of changes in adherence to a healthy diet and the performance of long-term physical activity on TL, considering the duration and intensity of the exercise ultimately practiced. It is also recommended that repeated measurements of TL over time be included in the design. For future studies food cooking habits of food are worth considering in order to evaluate the relationship between deeply fried or highly roasted foods and telomere shortening or lengthening. It is also recommended that studies be carried out that evaluate the joint effect of diet and physical activity on TL, since there are few studies on the subject – indeed, we only found four studies on this subject (30,31,32,65).

To build a complete picture of the possible mechanisms involved in the impact of these changes on the rate of telomeric shortening, of those that can be modulated with a healthy lifestyle, it is important to include biomarkers of oxidative stress, since telomeres are highly sensitive to the damage produced by this type of stress (14). Likewise, it is important to measure telomerase activity, since lifestyle factors may also affect this enzyme. While considering that diet is important, future research is also needed to provide evidence of the effect of individual dietary components, which in turn are part of the whole diet, on telomere shortening. Based on these findings, dietary guidelines could be created so that the population may acquire a healthier type of diet and, at the same time, reduce the risk of suffering from NCDs related to cellular aging or the shortening of telomeres.

REFERENCES

1. Blackburn, EH. Structure and function of telomeres. Nature 1991;350:569-73. [ Links ]

2. Greider CW, Blackburn EH. Identification of a specific telomere terminal transferase activity in tetrahymena extracts. Cell 1985;43:405-13. [ Links ]

3. Mengual DL, Armando RG, Farina HG, Gómez DE. Telomerasa y telómero: su estructura y dinámica en salud y enfermedad.Medicina2014:74(1):69-76. [ Links ]

4. Wu X, Amos CI, Zhu Y, Zhao H, Grossman BH, Shay JW, et al. Telomere dysfunction: a potential cancer predisposition factor. J Natl Cancer Inst 2003;95(16):1211-8. [ Links ]

5. Lin J, Epel E, Cheon J, Kroenke C, Sinclair E, Bigos M, et al. Analyses and comparisons of telomerase activity and telomere length in human T and B cells: Insights for epidemiology of telomere maintenance. J Immunol Methods 2010;352(1-2):71-80. [ Links ]

6. McGrath M, Wong J, Michaud D, Hunter DJ, De Vivo I. Telomere length, cigarette smoking, and bladder cancer risk in men and women. Cancer Epidemiol Biomarkers Prev 2007;16(4):815-9. [ Links ]

7. Hou L, Savage SA, Blaser MJ, Perez-Perez G, Hoxha M, Dioni L, et al. Telomere length in peripheral leukocyte DNA and gastric cancer risk. Cancer Epidemiol Biomarkers Prev 2009;18(11):3103-9. [ Links ]

8. Cui Y, Cai Q, Qu S, Chow WH, Wen W, Xiang YB, et al. Association of leukocyte telomere length with colorectal cancer risk: nested case-control findings from the Shanghai Women's Health Study. Cancer Epidemiol Biomarkers Prev 2012;(10):1807-13. [ Links ]

9. Zheng Y-L, Ambrosone C, Byrne C, Davis W, Nesline M, McCann SE. Telomere length from blood cells and breast cancer risk: investigations in two case-control studies. Breast Cancer Res Treat 2010;120(3):769–75. [ Links ]

10. Qu S, Wen W, Shu X-C, Chow WH, Xiang YB, Wu J, et al. Association of leukocyte telomere length with breast cancer risk: nested case-control findings from the Shanghai women's health study. Am J Epidemiol 2013;177(7):617–24. [ Links ]

11. O'Donovan A, Pantell MS, Puterman E, Dhabhar FS, Blackburn EH, Yaffe K, et al. Cumulative inflammatory load is associated with short leukocyte telomere length in the Health, Aging and Body Composition Study. PLoS One 2011;6(5):e19687. [ Links ]

12. Von Zglinicki T. Oxidative stress shortens telomeres. Trends in Biochemical Sciences 2002;27(7):339-44. [ Links ]

13. Houben JM, Moonen HJ, van Schooten FJ, Hageman GJ. Telomere length assessment: Biomarker of chronic oxidative stress?. Free Radic Biol Med 2008;44:235–46. [ Links ]

14. Cherkas LF, Hunkin JL, Kato BS, Richards JB, Gardner JP, Surdulescu GL, et al. The association between physical activity in leisure time and leukocyte telomere length. Arch Intern Med 2008;168(2):154–8. [ Links ]

15. Boccardi V, Esposito A, Rizzo MR, Marfella R, Barbieri M, Paolisso G. Mediterranean diet, telomere maintenance and health status among elderly. PLoS ONE 2013;8(4):e62781. [ Links ]

16. Zgheib NK, Sleiman F, Nasreddine L, Nasrallah M, Nakhoul N, Isma6apos;eel H, et al. Short Telomere Length is Associated with Aging, Central Obesity, Poor Sleep and Hypertension in Lebanese Individuals. A&D 2018;9(1):77-89. [ Links ]

17. Puterman E, Lin J, Blackburn E, O'Donovan A, Adler N, Epel E. The power of exercise: buffering the effect of chronic stress on telomere length. PLoS One 2010;5(5):e10837. [ Links ]

18. Ennour-Idrissi K, Têtu B, Maunsell E, Poirier B, Montoni A, Rochette PJ, et al. Association of telomere length with breast cancer prognostic factors. PLoS ONE 2016;11(8):e0161903. [ Links ]

19. Sun Q, Shi L, Prescott J, Chiuve SE, Hu FB, De Vivo I, et al. Healthy lifestyle and leukocyte telomere length in U.S. women. PLoSONE 2012;7(5):e38374. [ Links ]

20. O'Callaghan N, Parletta N, Milte CM, Benassi-Evans B, Fenech M, Howe P. Telomere shortening in elderly individuals with mild cognitive impairment may be attenuated with ω-3 fatty acid supplementation: a randomized controlled pilot study. Nutrition 2014;30:489-91. [ Links ]

21. Bamia C. Dietary patterns in association to cancer incidence and survival: concept, current evidence, and suggestions for future research. Eur J Clin Nutr 2018. [ Links ]

22. Sofi F, Macchi C, Abbate R, Gensini GF, Casini A. Mediterranean diet and health status: an updated meta-analysis and a proposal for a literature-based adherence score. Public Health Nutr 2014;17(12):2769–82. [ Links ]

23. Crous-Bou M, Fung TT, Prescott J, Julin B, Du M, Sun Q, et al. Mediterranean diet and telomere length in Nurses' Health Study:population based cohort study. BMJ 2014;2(349):g6674. [ Links ]

24. García-Calzón S, Zalba G, Ruiz-Canela M, Shivappa N, Hébert JR, Martínez A, et al. Dietary inflammatory index and telomere length in subjects with a high cardiovascular disease risk from the PREDIMED-NAVARRA study: cross-sectional and longitudinal analyses over 5 y. Am J Clin Nutr 2015;102:897-904. [ Links ]

25. Shivappa N, Wirth MD, Hurley TG, Hébert JR. Association between the Dietary Inflammatory Index (DII) and telomere length and c-reactive protein from the National Health and Nutrition Examination Survey-1999-2002. Mol Nutr Food Res 2016;1600630-6. [ Links ]

26. De Meyer T, Bekaert S, De Buyzere mL, De Bacquer DD, Langlois MR, Shivappa N, et al. Leukocyte telomere length and diet in the apparently healthy, middle-aged Asklepios population. Sci Rep 2018 Apr 25;8(1):6540. [ Links ]

27. Zhou M, Zhu L, Cui X, Feng L, Zhao X, He S, et al. Influence of diet on leukocyte telomere length, markers of inflammation and oxidative stress in individuals with varied glucose tolerance: a Chinese population study. Nutrition Journal 2016;15:39-48. [ Links ]

28. Fretts AM, Howard BV, Siscovick DS, Best LG, Beresford SA, Mete M, et al. Processed meat, but not unprocessed red meat, is inversely associated with leukocyte telomere length in the Strong Heart Family Study. J Nutr 2016;146(10):2013-8. [ Links ]

29. Nettleton J, Diez-Rouz A, Jenny NS, Firtzpatrick AL, Jacobs DR. Dietary patterns, food groups, and telomere length in the Multi-Ethnic Study of Atherosclerosis (MESA). Am J Clin Nutr 2008;88(5):1405–12. [ Links ]

30. Kasielski M, Makandjou-Ola E, Pietruczuk M, Nowak D. The relationship between peripheral blood mononuclear cells telomere length and diet - unexpected effect of red meat. Nutr J 2016;15:68-74. [ Links ]

31. Ornish D, Chan JM, Epel E, Kemp C, Weidner G, Marlin R, et al. Effect of comprehensive lifestyle changes on telomerase activity and telomere length in men with biopsy-proven low-risk prostate cancer: 5-year follow-up of a descriptive pilot study. Lancet Oncol 2013;14:1112-20. [ Links ]

32. Hovatta I, de Mello VD, Kananen L, Lindström J, Eriksson JG, Ilanne-Parikka P, et al. Leukocyte telomere length in the Finnish diabetes prevention study. PLoS One 2012;7(4):e34948. [ Links ]

33. Bethancourt HJ, Kratz M, Beresford SAA, Hayes MG, Kuzawa CW, Duazo PL, et al. No association between blood telomere length and longitudinally assessed diet or adiposity in a young adult Filipino population. Eur J Nutr 2017;56(1):295-308. [ Links ]

34. Leung CW, Laraia BA, Needham BL, Rehkopf DH, Adler NE, Lin J, et al. Soda and cell aging: associations between sugar-sweetened beverage consumption and leukocyte telomere length in Healthy Adults from the National Health and Nutrition Examination Surveys. Am J Public Health 2014;104(12):2425-31. [ Links ]

35. Lee JY, Jun NR, Yoo D, Shin C, Baik I. Association between dietary patterns in the remote past and telomere length. Eur J Clin Nutr 2015;69:1048-52. [ Links ]

36. Tiainen AM, MännistöS, Blomstedt PA, Moltchanova E, PeräläMM, Kaartinen NE, et al. Leukocyte telomere length and its relation to food and nutrient intake in an elderly population. Eur J Clin Nutr 2012;66(12):1290-4. [ Links ]

37. Marcon F, Siniscalchi E, Crebelli R, Saieva C, Sera F, Fortini P, et al. Diet-related telomere shortening and chromosome stability. Mutagenesis 2012;27(1):49-57. [ Links ]

38. Lian F, Wang J, Huang X, Wu Y, Cao Y, Tan X, et al. Effect of vegetable consumption on the association between peripheral leucocyte telomere length and hypertension: a case-control study. BMJ 2015;5:e009305. [ Links ]

39. Gong Y, Tian G, Xue H, Zhang X, Zhao Y, Cheng G. Higher adherence to the 'vegetable-rich' dietary pattern is related to longer telomere length in women. Clin Nutr 2018;37(4):1232-7. [ Links ]

40. Yabuta S, Masaki M, Shidoji Y. Associations of buccal cell telomere length with daily intake of β-carotene or α-tocopherol are dependent on carotenoid metabolism-related gene polymorphisms in healthy Japanese adults. J Nutr Health Aging 2016;20(3):267-74. [ Links ]

41. Lee JY, Shin C, Baik I. Longitudinal associations between micronutrient consumption and leukocyte telomere length. J Hum Nutr Diet 2017;30(2):236-43. [ Links ]

42. Nomura S, Robien K, Zota AR. Serum folate, vitamin B-12, vitamin A, γ-tocopherol, α-tocopherol, and carotenoids do not modify associations between cadmium exposure and leukocyte telomere length in the general US adult population. J Nutr 2017;147:538-48. [ Links ]

43. Mazidi M, Kengne AP, Cheskin LJ, Banach M. Serum lipophilic antioxidants levels are associated with leucocyte telomere length among US adults. Lipids Health Dis 2018;17(1):164. [ Links ]

44. Min KB, Min JY. Association between leukocyte telomere length and serum carotenoid in US adults. Eur J Nutr 2017;56:1045-52. [ Links ]

45. Sen A, Marsche G, Freudenberger P, Schallert M, Toeglhofer AM, Nagl C, et al. Association between higher plasma lutein, zeaxanthin, and vitamin C concentrations and longer telomere length: results of the Austrian Stroke Prevention Study. J Am Geriatr Soc 2014;62:222-9. [ Links ]

46. Beilfuss J, Camargo CA, Kamychevas E. Serum 25-hydroxyvitamin D has a modest positive association with leukocyte telomere length in middle-aged US adults. J Nutr 2017;147:514-20. [ Links ]

47. Liu J, Prescott J, Giovannucci E, Hankinson SE, Rosner B, Han J, et al. Plasma vitamin D biomarkers and leukocyte telomere length. Am J Epidemiol 2013;177(12):1411-7. [ Links ]

48. Borras M, Panizo S, SarróF, Valdivielso JM, Fernandez E. Assessment of the potential role of active vitamin D treatment in telomere length: a case-control study in hemodialysis patients. Clin Ther 2012;34(4):849-56. [ Links ]

49. Richards JB, Valdes AM, Gardner JP, Paximadas D, Kimura M, Nessa A, et al. Higher serum vitamin D concentrations are associated with longer leukocyte telomere length in women. Am J Clin Nutr 2007;86(5):1420-5. [ Links ]

50. Julin B, Shui IM, Prescott J, Giovannucci EL, De Vivo I. Plasma vitamin D biomarkers and leukocyte telomere length in men. Eur J Nutr 2017;56:501-8. [ Links ]

51. Farzaneh-Far R, Lin J, Epel ES, Harris WS, Blackburn EH, Whooley MA. Association of marine omega-3 fatty acid levels with telomeric aging in patients with coronary heart disease. JAMA 2010;Jan 20;303(3):250-66. [ Links ]

52. Kiecolt-Glaser JK, Epel ES, Belury MA, Andridge R, Lin J, Glaser R, et al. Omega-3 fatty acids, oxidative stress, and leukocyte telomere length: a randomized controlled trial. Brain Behav Immun 2013;28:16-24. [ Links ]

53. Freitas-Simoes TM, Cofán M, Blasco MA, Soberón N, Foronda M, Serra-Mir M, et al. Walnut consumption for two years and leukocyte telomere attrition in Mediterranean elders: results of a randomized controlled trial. Nutrients 2018;4:(10):E1907. [ Links ]

54. Du M, Prescott J, Kraft P, Han J, Giovannucci E, Hankinson SE, et al. Physical activity, sedentary behavior, and leukocyte telomere length in women. Am J Epidemiol 2012;175(5):414-22. [ Links ]

55. Edwards MK, Loprinzi PD. Sedentary behavior, physical activity and cardiorespiratory fitness on leukocyte telomere length. Health Promot Perspect 2017;7(1):22-7. [ Links ]

56. Latifovic L, Peacock SD, Massey TE, King WD. The influence of alcohol consumption, cigarette smoking, and physical activity on leukocyte telomere length. Cancer Epidemiol Biomarkers Prev 2016;25(2):374-80. [ Links ]

57. Ludlow AT, Zimmerman JB, Witkowski S, Hearn JW, Hatfield BD, Roth SM. Relationship between physical activity level, telomere length, and telomerase activity. Med Sci Sports Exerc 2008;40(10):1764-71. [ Links ]

58. Loprinzi PD, Sng E. Mode-specific physical activity and leukocyte telomere length among U.S. adults: Implications of running on cellular aging. Prev Med 2016;85:17-9. [ Links ]

59. Tucker LA, Physical activity and telomere length in U.S. men and women: An NHANES investigation. Prev Med 2017;100:145-51. [ Links ]

60. Fretts AM, Mete M, Howard BV, Best LG, Siscovick DS, Eilat-Adar S, et al. Physical activity and telomere length in American indians: the Strong Heart Study. Eur J Epidemiol 2018. [ Links ]

61. Puterman E, Weiss J, Lin J, Schilf S, Slusher A, Johansen KL, et al. Aerobic exercise lengthens telomeres and reduces stress in family caregivers: A randomized controlled trial - Curt Richter Award Paper 2018. Psychoneuroendocrinology 2018. [ Links ]

62. Sjögren P, Fisher R, Kallings L, Svenson U, Roos G, Hellénius mL. Stand up for health—avoiding sedentary behaviour might lengthen your telomeres: secondary outcomes from a physical activity RCT in older people. Br J Sports Med 2014;0:1-3. [ Links ]

63. Friedenreich CM, Wang Q, Ting NS, Brenner DR, Conroy SM, McIntyre JB, et al. Effect of a 12-month exercise intervention on leukocyte telomere length: results from the ALPHA Trial. Cancer Epidemiol 2018;56:67-74. [ Links ]

64. Dankel SJ, Loenneke JP, Loprinzi PD. The impact of overweight/obesity duration and physical activity on telomere length: an application of the WATCH paradigm. Obes Res Clin Pract 2016;16:30417-3. [ Links ]

65. Mason C, Risques RA, Xiao L, Duggan CR, Imayama I, Campbell KL, et al. Independent and combined effects of dietary weight loss and exercise on leukocyte telomere length in postmenopausal women. See comment in PubMed Commons below Obesity2013;21(12):E549–E554. [ Links ]

66. Neilson HK, Friedenreich CM, Brockton NT, Millikan RC. Physical activity and postmenopausal breast cancer: proposed biologic mechanisms and areas for future research. Cancer Epidemiol Biomarkers Prev 2009;18(1):11-27. [ Links ]

67. Sanft T, Usiskin I, Harrigan M, Cartmel B, Lu L, Li FY, et al. Randomized controlled trial of weight loss versus usual care on telomere length in women with breast cancer: the lifestyle, exercise and nutrition (LEAN) study. Breast Cancer Res Treat 2018;172(1):105-12. [ Links ]

68. Loprinzi PD, Loenneke JP. Leukocyte telomere length and mortality among U.S. adults: Effect modification by physical activity behaviour. J Sports Sci 2017;36(2):213-9. [ Links ]

69. Garland SN, Johson B, Palmer C, Speck RM, Donelson M, Xie SX, et al. Physical activity and telomere length in early stage breast cancer survivors. Breast Cancer Res 2014;16:413-21. [ Links ]

70. Zhang J, Rane G, Dai X, Shanmugam MK, Arfuso F, Samy RP, et al. Ageing and the telomere connection: An intimate relationship with inflammation. Ageing Res Rev 2016;25:55-69. [ Links ]

71. Notaro R, Cimmino A, Tabarini D, Rotoli B, Luzzatto L. In vivo telomere dynamics of human hematopoietic stem cells. Proceedings of the National Academy of Sciences of the United States of America 1997;94:13782-5. [ Links ]

72. Mundstock E, Zatti H, Mattos F, Goecks S, Guma F, Migliorini M, et al. Effects of physical activity in telomere length: systematic review and meta-analysis. Ageing Res Rev 2015;22:72-80. [ Links ]

73. Denham J, O'Brien BJ, Charchar FJ. Telomere length maintenance and cardio-metabolic disease prevention through exercise training. Sports Med 2016;46(9):1213-37. [ Links ]

74. Lang PF, Fröhlich KU. The influence of physical exercise and sports on telomere length - A model for telomere length and telomerase activity regulation based on a comparative assessment of literature. Peer J Preprints 2016;4:e1965v1. [ Links ]

75. Chilton WL, Marques FZ, West J, Kannourakis G, Berzins SP, O'Brien BJ, et al. Acute Exercise Leads to Regulation of Telomere-Associated Genes and MicroRNA Expression in Immune Cells. PLoS ONE 2014;9(4):e92088. [ Links ]

76. Davidsen PK, Gallagher IJ, Hartman JW, Tarnopolsky MA, Dela F, Timmons JA, et al. High responders to resistance exercise training demonstrate differential regulation of skeletal muscle microRNA expression. J Appl Physiol 2011;110:309–17. [ Links ]

77. Bye A, RøsjøH, Aspenes ST, Condorelli G, Omland T, Wisløff U. Circulating MicroRNAs and aerobic Fitness–The HUNT-study. PLoS One 2013;8:e57496. [ Links ]

78. Paul L. Diet, nutrition and telomere length. J Nutr Biochem 2011;22:895-901. [ Links ]

79. Ornish D, Lin J, Daubenmier J, Weidner G, Epel E, Kemp C, et al. Increased telomerase activity and comprehensive lifestyle changes: a pilot study. Lancet Oncol 2008;9(11):1048-57. [ Links ]

80. Zhang X, Zhao Q, Zhu W, Liu T, Xie SH, Zhong LX, et al. The association of telomere length in peripheral blood cells with cancer risk: a systematic review and meta-analysis of prospective studies. Cancer Epidemiol Biomarkers Prev 2017;26(9):1381-90. [ Links ]

81. The Telomeres Mendelian Randomization Collaboration. Association between telomere length and risk of cancer and non-neoplastic diseases: a Mendelian randomization study. JAMA Oncol 2017;3(5):636-51. [ Links ]

82. Weischer M, Nordestgaard BG, Cawthon RM, Freiberg JJ, Tybjarg-Hansen A, Bojesen SE. Short telomere length, cancer survival, and cancer risk in 47102 individuals. J Natl Cancer Inst 2013;105(7):459-68. [ Links ]

Navarro Ibarra MJ, Hernández J, Caire Juvera G. Diet, physical activity and telomere length in adults. Nutr Hosp 2019;36(6):1403-1417.

ACKNOWLEDGMENTS:This study was supported by the Sectorial Fund for Research on Health and Social Security SS/IMSS/ISSSTE-CONACyT/S0008/2115/1/262211 in Mexico.

Received: May 16, 2019; Accepted: May 20, 2019

Correspondence: Graciela Caire Juvera. Carretera Gustavo Enrique Astiazarán Rosas, 46. Colonia La Victoria. 83304 Hermosillo, Sonora. Mexico e-mail: gcaire@ciad.mx

Creative Commons License This is an open-access article distributed under the terms of the Creative Commons Attribution License