ORIGINAL

 

Blood pressure of omnivorous and semi-vegetarian postmenopausal women and their relationship with dietary and hair concentrations of essential and toxic metals

Presión arterial en mujeres omnívoras y semivegetarianas postmenopáusicas y su relación con los metales esenciales y tóxicos en la dieta y en el cabello

 

 

S. Rodenas¹, F. J. Sánchez-Muniz², S. Bastida², M. I. Sevillano³, T. Larrea Marín⁴ and M. J. González-Muñoz⁵

¹Sección Departamental de Química Analítica. Facultad de Farmacia. Universidad Complutense. Madrid. Spain.
²Departamento de Nutrición y Bromatologia I (Nutrición). Facultad de Farmacia. Universidad Complutense. Madrid. Spain.
³Centro de Espectrometría Atómica. Universidad Complutense. Madrid. Spain.
⁴Centro Nacional de Investigaciones Metalúrgicas. CSIC. Madrid. Spain.
⁵Departamento de Nutrición, Bromatologia y Toxicología. Facultad de Farmacia. Universidad de Alcalá. Madrid. Spain.

This study was partially supported by a Danone- Universidad Complutense de Madrid grant, Project PR248/01-10161 and by the Consolider-Ingenio 2010 project reference CSD2007-00016.

Correspondence

 

 

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ABSTRACT

Objective: This study aims to ascertain the relationships between mineral consumption, hair mineral content, and blood pressure.
Methods: The study involved 26 postmenopausal women from enclosed religious communities, 14 were semi-vegetarians and 12 were omnivores. Mineral dietary assessment was performed using a 14-d precise weight method and Food tables. Hair mineral levels were measured by means Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-OES). Multivariable stepwise linear regression analyses were performed to find out the variables that affected most blood pressure.
Results: In general terms, the omnivorous diet contained a significantly higher mineral content than the semi-vegetarian one. The mineral intake from both diets implied no health risk to the women studied, as their estimated daily intake (EDI) of toxic elements such as Cd and Pb was lower than their respective provisional tolerable weekly intake (PTWI) of these minerals. Hair of the semi-vegetarians contained higher amounts of Al (p < 0.01), Ba (p < 0.01), K (p < 0.001), Na (p < 0.001), Pb (p < 0.001) and Mn (p < 0.01) but lower levels of Ca (p < 0.05) and Zn (p < 0.05) than that of their omnivorous counterparts. The omnivores presented significantly higher systolic (p < 0.01) and diastolic (p < 0.05) pressures than the semi-vegetarians. Levels of hair Co (R² = 0.328; p = 0.032) and hair K (R² = 0.409; p = 0.014)) were explicative for systolic and diastolic blood pressure, respectively.
Conclusion: Several dietary mineral and hair contents were higher in semi-vegetarian women suggesting that the hair is an important mineral excretion via contributing to maintain blood pressure at low levels.

Key words: Minerals. Hair. Diet. Blood pressure. Postmenopausal.

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RESUMEN

Objetivo: Se pretende establecer una relación entre consumo y niveles de minerales en cabello y tensión sanguínea en mujeres postmenopáusicas.
Métodos: El estudio se ha realizado en 26 mujeres postmenopáusicas pertenecientes a dos comunidades religiosas de clausura, siendo 14 semivegetarianas y 12 omnívoras. La determinación de la ingesta de minerales se realizó mediante pesada precisa durante 14 días y las Tablas de Composición de Alimentos. Los niveles de minerales en cabello fueron determinados mediante Espectrometría de Masas con Fuente de Ionización de Plasma de Acoplamiento Inductivo (ICP-MS) y Espectrometría de Emisión Atómica con Fuente de Excitación de Plasma de Acoplamiento Inductivo (ICP-OES). Se realizó un análisis lineal múltiple por pasos para explicar los variables que más influían en la presión arterial.
Resultados: En términos generales, la dieta omnívora posee un contenido en minerales significativamente superior a la semivegetariana. La ingesta mineral de ambas dietas no implica riesgo para la salud de las mujeres estudiadas ya que la ingesta diaria de elementos tóxicos como Cd y Pb, estimada (IDA) está por debajo de sus respectivas ingestas semanales tolerables provisionales (ISTP). En las semivegetarianas el cabello contienen cantidades mayores de Al (p < 0,01), Ba (p < 0,01), K (p < 0,001), Na (p < 0,001), Pb (p < 0,001) y Mn (p < 0,01) y niveles inferiores de Ca (p < 0,05) y Zn (p < 0,05) que las omnívoras. Éstas últimas, además presentan presiones arteriales superiores, tanto sistólica (p <0,01) como diastólica (p < 0,05). Las concentraciones de Co (R² = 0,328; p = 0,032) y K (R² = 0,409; p = 0,014) en cabello fueron explicativas de los niveles de presión arterial sistólica y diastólica, respectivamente.
Conclusión: Los resultados de varios minerales en la dieta y en el cabello de mujeres semivegetarianas sugieren que el pelo es una importante vía de excreción mineral, contribuyendo al mantenimiento de la presión sanguínea a niveles más adecuados.

Palabras clave: Minerales. Cabello. Dieta. Presión sanguínea. Post-menopausia.

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Introduction

Elderly persons often alter their nutritional habits, becoming vegetarians for religious, socio-cultural, economic and/or therapeutic motives.¹ However, following vegetarian diets it is not always easy to meet current recommendations for some nutrients, as minerals.² Vegetarian diets differ from one another according to the extent to which they may include animal products. In this regard, the vegan diet is the most restrictive, while the semi-vegetarian diet is the most permissive. Semi-vegetarians, also called partial vegetarians, or moderate vegetarians, consume certain foods of animal origin but usually exclude red meat from their iet.³ Although vegetarian diets, associated with a low incidence of several chronic diseases, and are normally considered healthy, not all of them provide the same health benefits.⁴

The most common deficiencies documented in the elderly have been for zinc,⁵ magnesium and calcium. Ca deficiency is mainly associated with bone resorption,⁶ while magnesium deficiency increases muscle catabolism and cardiovascular risk.⁷ Zn, Cu, Mg and Mn imbalances affect blood pressure values and are thus related to hypertension.⁸ Other metals (e.g. As, Pb, Cd, and Hg) that have no known beneficial biological function may be harmful to health, and may even prove toxic at low doses following long-term exposure.

The mineral status of individuals has conventionally been determined by analysis of biological samples, most commonly blood. In recent years, however, the use of human scalp hair has become increasingly popular as a biomonitor of trace elements to determine nutritional status, as well as for diagnostic purposes.^9,10 The study of this metabolically inactive tissue permits an estimation of environmental exposure levels to minerals and investigation of the status and alterations of trace element concentrations in the body. Nonetheless, the limitations of hair mineral analysis, such as possible contamination by dust and/or sweat, and the effects of age, sex, and place of residence, must be considered together with its potential advantages.¹¹

The aims of the present study were a) to assess the dietary mineral content of semi-vegetarian and omnivorous postmenopausal women; b) to monitor hair mineral content; and c) to study the possible relationships between blood pressure, dietary mineral content, and hair mineral concentrations.

 

Material and methods

Study participants

Volunteers had to fulfill the following eligibility criteria: a) age: women ≥ 45 years, b) postmenopausal, and c) BMI ≥ 18 kg/m². Taking into account the influence of degenerative diseases, sex, age, BMI, drugs, and smoking on blood pressure,¹² exclusion criteria included a) previous cardiovascular, metabolic, or systemic disease, b) treatment with any lipid-lowering, antihypertensive or anti-inflammatory drugs and/or hormone replacement therapy, and c) smoking habit.

Thirty volunteers were selected from among 40 nuns recruited in two enclosed convents from the same town in the centre of Spain and with a regular lifestyle and dietary habits. Two volunteers were excluded due to ongoing use of drug therapy. Three volunteers were 45 years old but were considered premenopausal. Five participants suffered from white coat hypertension. In addition, two volunteers were excluded for habitual use of hair cosmetics, and another two were excluded due to their very short scalp hair, which prevented hair sample collection. Thus, a total of 26 nuns (12 from an omnivorous enclosed community and 14 from another enclosed convent with semi-vegetarian food habits) were studied. Study protocols were approved by an Ethics Committee of the Universidad Complutense de Madrid, Spain, and research activities were performed in accordance with the principles laid down in the Helsinki Declaration.

Dietary assessment

Food intake of each individual was estimated by the precise weighing method during a 14-day period.¹³ Energy and nutrient intakes were calculated using food composition tables for raw weights of foodstuffs and compared with the Recommended Dietary Allowances for the Spanish population.¹⁴ Daily intake of the toxic elements studied was calculated taking into account dietary composition and food consumption according to specialized literature.^15,16

Anthropometric measures

Trained personnel obtained body weight and height using standardized methodology. Body mass index (BMI) [(weight (kg)/height² (m²)] was also calculated. Systolic and diastolic blood pressures were measured using a Hg sphygmomanometer, following WHO recommendations.¹⁷

Mineral concentrations in hair. Sample collection and analysis

Scalp hair samples (1-3 cm) weighing approximately 1.0 g were taken from the occipital region, by cutting hair 2 cm from the hair root using stainless-steel scissors without vanadium and stored in plastic bags. Samples were washed to ensure accurate assessment of endogenous metal content. The washing procedure was carried out according to International Atomic Energy Agency (IAEA) recommendations.¹⁸ Hair samples were first washed with ultrapure water, then washed three times with acetone, and finally washed once again with ultrapure water. The samples were then oven-dried at 100 ^oC.

A 250 ± 0.1 mg portion of each sample was weighed and introduced into a high-pressure, enclosed, Teflon decomposition vessel. Five millilitres of a 2.5:0.25 HNO₃ and H₂O₂ (v/v) mixture were carefully added to each sample and the vessels were gently shaken, sealed and digested in a microwave oven at 330 W for 10 min.

Samples were wet ashed according to the method of González-Muñoz et al.¹⁰ Multi-element analysis of Al, Ba, Cd, Co, Cr, Mn, Mo, Ni, Pb, Sb, Se, Sr, and V was performed with Inductively Coupled Plasma Mass Spectrometry (ICP-MS), 810 Bruker Corporation (Billerica, MA, USA). Other elements were analyzed with Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-OES), Perkin Elmer Model Optima 3300 DV, (Palo Alto, CA, USA) using the multi-element method described by Gonzalez- Muñoz et al.¹⁰ Elements with the highest isotopic abundance, free from isobaric and polyatomic interference, were selected for ICP-MS spectrometry. The validation process of the methods based on ICPOES and ICP-MS techniques was performed according to Eurachem guidelines,¹⁹ with regard to accuracy, precision, sensitivity, and linearity using the experimental setting that provided the optimal conditions. The reagents and methods employed have been described in greater detail by González-Muñoz et al.¹⁰

Statistical analysis

This study was designed to have a power of 80% to detect a 25% relative difference between mineral hair concentrations considering a pooled SD of 25% for most minerals using the Mann-Whitney U test for group comparison [PASS 2008 program, NCSS, (Kaysville, Utah, USA)]. To perform main factor analysis, hair mineral contents, when necessary, were natural logarithmic transformed. For systolic and diastolic blood pressure variables, a stepwise multiple regression procedure was used to identify variables that explained the systolic and diastolic blood pressure variability of the postmenopausal women studied. Explicative variables considered for systolic or diastolic blood pressures were a) and the consumption of cereals, dairy products, eggs, oils, vegetables, pulses, fruits, meat and derivates, fishand derivates, and sugar; b) the intakes of energy, carbohydrates, protein, fat, cholesterol, fibre, and minerals and the energy contribution of carbohydrates, protein, fat, SFA, MUFA and PUFA omega-6 and omega-3; c) the mineral content in hair. The SPSS statistical package (version 15.0, Chicago, IL., USA) was used to analyze the data.

 

Results

Anthropometrical characteristics

Table I summarizes the anthropometrical characteristics and systolic and diastolic blood pressure values of the population studied. No significant differences in anthropometrical parameters were detected between the two groups of women. However, the semi-vegetarians, of whom 25% were overweight, tended to have lower BMI values than their omnivorous counterparts, of whom 50% were overweight (data not shown). Significant differences between the omnivorous and semivegetarian women were observed with regard to blood pressure. The omnivores had significantly higher (p < 0.01) systolic and (p < 0.05) diastolic pressures than the semi-vegetarians.

Dietary intakes

Energy intakes in both communities were not significantly different; However, differed in their protein (p < 0.01), total PUFA (p < 0.01), PUFA omega-6, and PUFA omega-3 energy contributions (all p < 0.01) (table II).

Intake of components of several food groups varied significantly between the two diets (table III). The omnivorous women consumed more cereals (p < 0.001), dairy products (p < 0.01), eggs (p < 0.05), meat (p < 0.001), pulses (p < 0.001), and sugar (p < 0.001), but less fish (p < 0.05) and fewer oils (p < 0.001) and vegetables (p < 0.001) than the semi-vegetarians.

The daily dietary intake of minerals by the postmenopausal women is presented in table IV along with recommended dietary allowances (RDA) and provisional tolerable weekly intake (PTWI) values. Except for I, and K all mineral intakes differ between groups. The omnivores ingested more Ca (p < 0.05), Cd (p < 0.01), Cr (p < 0.001), Fe (p < 0.001), Mg (p < 0.001), Na (p < 0.001), Ni (p < 0.001), and Zn (P < 0.01) and less Mn (p < 0.001) and Pb (p < 0.01) than the semivegetarian women.

Hair mineral levels

The omnivores had higher concentrations of Cd (p < 0.01), Co (p < 0.01), and Zn (p < 0.05), but lower levels of Al (p < 0.01), Ba (p < 0.05), K (p < 0.001), Mn (p < 0.01), Na (p < 0.001), and Pb (p < 0.01) than the semivegetarians (table V).

Multivariant studies

Table VI shows the linear stepwise regression models for systolic and diastolic blood pressures. Three models were assessed: a) food group consumption; b) energy, micronutrients, fibre, alcohol consumption and c) hair mineral concentrations were considered. The food group consumption models explained the 24.5% (p = 0.010) and 28.3% (p = 0.005) of systolic and diastolic blood pressures data variance, respectively. Meat and fat consumption by one hand and meat by the other were positively associated with the systolic and diastolic blood pressures, respectively. The second models explained the 98.2% (p < 0.001) and 88.1% (p < 0.001) of systolic and diastolic blood pressure data variance, respectively. SFA, Cr and I consumptions were positively associated while the energy contribution of PUFA and the cholesterol consumption negatively with systolic blood pressure. Cr and Na consumptions were positively associated but the energy contribution of protein negatively with diastolic blood pressure. The hair mineral content models explained the 32.8% (p = 0.032) and 40.9% (p = 0.014) of systolic and diastolic blood pressure variance data, respectively. Co (as Ln values) in hair was positively associated with systolic blood pressure while K hair negatively with systolic blood pressure.

 

Discussion

Blood pressure levels of the semi-vegetarians coincide with those of vegetarians studied by Myers and Champagne.²⁰ Vegetarians have been reported to display lower BMI values and blood pressure levels, and lower incidence rates of type 2 diabetes, colon cancer, and lower energy and macronutrient intakes than non-vegetarians.²

The two diets, rich in fat and relatively poor in carbohydrates, reflected present Spanish eating habits.²¹ Although their fatty acid contributions and profiles differed, the omega-6/omega-3 ratios of the two diets did not vary significantly. This omega-6/omega-3 fatty acids ratio is known to affect blood pressure, while other fatty acids and sources of dietary energy and minerals have little or no influence over blood pressure values²². Vegetarians diets offer a number of nutritional benefits including lower levels of saturated fat, cholesterol, and animal protein as well as higher levels of carbohydrates, fibre, magnesium, potassium, folate, antioxidants such vitamins C and E, and phytochemicals. ² Omnivorous diets tend to have more cholesterol and less fibre than semi-vegetarian ones. The consumption of meat and meat derivates and oil by one hand and that of SFA, Cr, I, and PUFA (%En) and cholesterol by other hand were associated with systolic blood pressure levels. Diastolic pressure appears associated by one hand with meat consumption and by other hand with Cr, Na consumption and energy protein contribution.

These facts clearly explain the differences between the food groups intakes observed in both studied groups. Although both diets were mixed diets rich in fruits, vegetables, eggs, milk and fish but the semi-vegetarians' one was absent of meat-group items.

In some cases, intake of the essential elements was below the levels recommended for adults in Spain.¹⁴ Data from a number of studies performed in Western countries indicate that mean intake of Mg and Zn by the elderly is below recommended levels.^7,23 Results of the present study show that the omnivores and semi-vegetarians consumed only 69% and 57% of the RDA for Mg, respectively, and 56% and 55% of the RDA for Zn, respectively. The semi-vegetarians consumed low but adequate levels of Na, while the omnivores consumed somewhat higher than recommended levels of this mineral.¹⁷ Dietary intake of iron by semi-vegetarian women was lower than RDI¹⁴ and 13% of these individuals did not reach appropriate Fe intakes. Moreover, given the characteristics of their diet, the semivegetarian women would necessarily have less bioavailable dietary Fe than their omnivorous counterparts.²⁴ The omnivores consumed more Ca than the semi-vegetarians, and only 26% had an intake below the RDI, as compared with 33% of the semi-vegetarians. The main sources for Ca in the standards Western diet are milk and other dairy products.²⁵ The fact that the omnivorous women consumed a significantly greater amount of dairy products than the semi-vegetarians would explain their higher Ca levels.

The omnivores in the present study consumed significantly more cereals than the semi-vegetarians, and grains contributed more Cd,¹⁶ Mg²⁵ and Cr²⁶ to the diet than any other food group. According to Anderson and Kozlovsky,²⁷ intake of Cr is highly correlated with intake of K, total fat, saturated fat and Na. The semivegetarians may have consumed less Fe, Na, and Zn than the omnivores as a result of their meatless diet.

In order to assess the health risk associated with the estimated intake levels mentioned above, these consumptions were compared with the current provisional tolerable weekly intake (PTWI) values for these elements.²⁸ The estimated intake of the toxic elements Cd and Pb in both groups was lower than the PTWI values for these minerals and was similar to that reported in other countries. For this reason, these intake levels do not represent a health concern for the women of the present study. Nevertheless, although intake of Ni was 18% below PTWI levels in the semi-vegetarians, it reached PTWI levels in the omnivores. Excess Ni decreases tissue levels of Mg, Mn, and Zn.²⁹ Nonetheless, there is little information available regarding either chronic or acute effects of excess dietary intake of Ni.²⁹

Cd intake is positively correlated with several chronic diseases, particularly hypertension. As previously mentioned, the omnivorous women consumed significantly more of this metal than their semi-vegetarian counterparts.³⁰ The omnivores consumed more Na and less K than the semi-vegetarian women. Several epidemiological studies³¹ have reported the beneficial impact of reducing salt intake on hypertension. A low intake of K has been related to hypertension and cardiovascular diseases.³² The semi-vegetarians had lower blood pressure levels than the omnivores. In this regard, our findings concur with those of Cianciaruso.³³ Elliot et al.³⁴ found that dietary Ca and Mg values are inversely correlated with blood pressure. The omnivorous women although consumed more Mg and Ca than the semi-vegetarians, displayed higher blood pressure levels. Not clear explanation can be drawn but Ca may mitigate some of the toxicity ascribed to Cd³⁵ in omnivore women.

Bibliographic data regarding the ranges of toxic and essential metal concentrations are influenced by numerous parameters, including gender, age, income, dietary habits, and environmental status (food, air, water, soil), which are not always taken into account by investigator.³⁶

The values recorded in the hair samples from the groups studied were within the normal Spanish range. This is an important finding, since according to Durnicz- Sokolowska et al.,⁹ hair concentrations of bioelements that are outside the reference range may be indicative of various pathological conditions. Deficiencies in essential trace elements and/or high levels of toxic metals may, thus, be involved in the development of heart disease. In addition, toxic metals may also reduce absorption of essential elements.³⁷

Hair concentrations of Ca, Fe, Mg, Mn, and Na were lower in the women of the present study than in another group of 60 non-smoking Spanish women aged 52-78 who consumed a Mediterranean diet.³⁸ Touyz and Schiffrin³⁹ found that Mg concentrations in erythrocytes and hair decrease with age. Arnaud et al.⁴⁰ concluded that that Se concentrations decrease in the elderly. The present data regarding Se values in hair coincide with the range previously cited (0.002-6.6 mg/g. Se levels in hair decrease with age as is the case in nails.⁴¹ Hair Cd levels in the women of the present study were lower than those reported for developing countries, but Pb levels were similar to those of individuals in developed countries.⁴²

The fact that the omnivores in the present study had significantly higher blood pressure levels than the semi-vegetarians may be related to their hair levels of certain minerals.

Al is naturally present in many foods. A certain amount of Al in many plant foods due to inappropriate harvesting techniques or soil contamination. In general, vegetables are better sources of Al than animal foods.²³ The high Al values in the hair of the semi-vegetarians may be due to the fact that these women consumed more of most vegetables than their omnivorous counterparts. The amount of Al in tap water, which varies between municipalities depending on the quantity of aluminium salt used by the local water-purification treatment plant, did not affect our results, as study participants lived in the same town and drank the same water.⁴³

Hair concentrations of Ba, an element mainly present in plant foods, were 70% higher in the hair of the semi-vegetarians than in that of the omnivores, although the amount consumed by the former women did not appear to be harmful. In cases of intoxication, Ba ions competitively block the passive efflux of K ions and cause the Na-K ion pump to act continuously, producing an intracellular accumulation of K and extracellular hypokalaemia.⁴⁴ As discussed earlier, present data suggest that hair works as a secretory system, helping the body to eliminate both Ba and K.

The higher hair levels of Ca and Na in the omnivores may indicate that the diet of these women contained a greater quantity of these elements than that of the semivegetarians.⁴⁵ K intake and hair levels in the semi-vegetarians were both significantly higher than the corresponding values for the omnivores. These results are complex and somewhere paradoxical. As previously noted, elimination of K via the hair in the semi-vegetarians was probably caused by excretion of Ba. In a previous paper¹⁰ we found that hair concentrations of Na were significantly higher in hypertensive individuals than in normotensive subjects. Results of the present study contrast with those expected, as aldosterone is known to promote retention of K, lowering levels of that element in hair. Hair follicle cells express aldosterone and Na excretion is aldosterone-dependent,⁴⁶ which contributes to the excretion of Na and the accumulation of K in the hair. These facts help to explain why the semi-vegetarians of the present study displayed lower blood pressure levels than the omnivores. Complete vegetarians present lower blood pressure levels than omnivores, possibly because K-rich vegetarian diets contain low levels of Na.³³

Cd is harmful to human health, and previous publications have reported that high levels of Cd cause hypertension.⁴⁷ Cd increases blood pressure by raising plasma renin activity and modifying catecholamine metabolism or by inducing sodium retention by directly influencing the proximal renal tubules.⁴⁶ Hair Cd values were lower (p < 0.01) in the semi-vegetarians, at least partially explaining, the lower blood pressure levels of this group. The semi-vegetarians presented higher hair Pb levels (p < 0.01) and had a higher estimated intake of this metal than the omnivores. It may be relevant that the semi-vegetarian women lived in the countryside, near a main road. Tetraethyl lead was once routinely added to gasoline as an antiknock agent and certain vehicles may still use leaded gasoline (e.g. tractors). As Pb may share and compete for some of the same cellular transport and absorption receptors as Fe, diets with reduced Fe bioavalilability could potentially enhance retention of this element,⁴⁹ at least partially explaining the similar hair levels of Fe in both groups of women.

As the omnivores presented higher hair levels of Co than their semi-vegetarian counterparts, hair may represent a route of Co excretion, effectively reducing the bioavailability of this mineral. Co enhances the activity of hypoxia-inducible factor (HIF),⁵⁰ and histological examination reveals that Co reduces proteinuria as well as kidney damage. Co increases the expression of HIF-regulated genes such as erythropoietin, vascular endothelial growth factor and heme oxygenase-1.

Vegetables may be rich in Mo if they are grown in neutral or alkaline soils high in available Mo. The semi-vegetarians tended to present higher levels of Mo in hair than the omnivores, probably as a result of their high vegetable intake.⁵¹

Almost certainly as a result of their higher Mn intake, the semi-vegetarians displayed, through their elevated hair manganese levels, a higher Mn status than the omnivores.⁵² On the other hand, iron deficiency may increase Mn absorption and further increase the body-burden of Mn, especially in vegetarians.⁵³ Mn activates nitric oxide synthase (NOS I), which converts L-arginine into L-citrulline and NO*, and produces O₂ •- in the absence of L arginine. Nitric oxide has been implicated in many physiopathological conditions, including hypertension.⁵⁴

Vegetarian diets usually provide a lower amount of bioavailable Zn than omnivorous diets. Plant foods rich in Zn, such as legumes, whole grains, nuts, and seeds are also high in phytic acid, an inhibitor of Zn bioavailability.⁴⁹ Low dietary intake of Zn by vegans was attributed to heavy reliance on fruits and vegetables that are poor sources of Zn.³ Zn intake is especially correlated with that of protein and largely depends on the protein source. As a consequence of their diet, the semi-vegetarians had lower hair Zn concentrations than the omnivores. Zn levels in the hair of vegetarians are low, compared with those of omnivores.⁴⁹ However, Ball and Ackland⁵⁵ conclude than ovolactovegetarians did not have a significantly greater risk of low Zn status than omnivores. Excessive Zn intake may contribute to elevating systemic BP levels in normotensive individuals, presumably as a result of the oxidative stress produced by superoxide substrates.⁵⁶ The mechanism involved is due likely to a decrease in the action of the vasodilator NO through the formation of peroxynitrite.

Among mineral in hair, Co for systolic blood pressure and K for diastolic blood pressure appear as good explicative models.

 

Conclusions

Although limitations of hair mineral analysis could be influenced by dust and/or sweat, age, sex, and place of residence,¹¹ the strict population selection, the hair sampling and the methodological criteria followed in the present paper permit us to conclude that semi-vegetarian women presented higher Al, Ba, K, Na, Pb and Mn but lower levels of Ca and Zn hair levels than their omnivorous counterparts suggesting the influence of their diet. Differences in hair mineral values between the semi-vegetarians and omnivores of the present study explain, at least partially, the higher systolic and diastolic pressures found in the semi-vegetarians. Meat, SFA, Cr and I consumptions and Co in hair were positively associated, while K in hair negatively with the systolic and diastolic blood pressures. Further studies are needed to better comprehend the relationship between hair mineral content and blood pressure and the mechanisms involved in their regulation.

 

References

1. Suzana S, Earland J, Suriah AR, Warnes AM. Social and health factors influencing poor nutritional status among rural elderly Malays. J Nutr Health Aging 2002; 6: 363-369.         [ Links ]

2. American Dietetic Association. Dieticians of Canada. Position of the American Dietetic Association and Dieticians of Canada. Vegetarian diets. Can J Diet Pract Res 2003; 64: 62-81.         [ Links ]

3. Rauma AL, Mykkänen H. Antioxidant status in vegetarians versus omnivores. Nutrition 2000; 16: 111-119.         [ Links ]

4. Fraser GE. Vegetarian diet: what do we know of their effects on common chronic diseases? Am J Clin Nutr 2009; 8: 1607S-1612S.         [ Links ]

5. Briefel RR, Bialostosky K, Kennedy-Stephenson J, McDowell MA, Ervin RB, Wright JD. Zinc intake of the U.S. population: findings from the third National Health and Nutrition Examination Survey, 1988-1994. J Nutr 2000; 130 Suppl.: 1367S-1373S.         [ Links ]

6. Vaquero MP. Nutrición y enfermedad metabólica del hueso. In: La Nutrición y la Alimentación en el Siglo XIX, Charro A, Varela G, Cabrerizo L, Pousa L, ed. Fundación de Estudios y Formación Sanitaria, pp. 211-225, Madrid, 2001.         [ Links ]

7. Durlach J, Bac P, Durlach V, Rayssiguier Y, Bara M, Guiet-Bara A. Magnesium status and ageing: An uptake. Magnes Res 1997; 11: 25-42.         [ Links ]

8. Taneja SK, Mandal R. Mineral factors controlling essential hypertension-a study in the Chandigarh, India population. Biol Trace Elem Res 2007; 120: 61-73.         [ Links ]

9. Dunicz-Sokolowska A, Graczyk A, Radomska K, Dlugaszek M, Wlazlak E, Surkont G. Contents of bioelements and toxic metals in a Polish population determined by hair analysis. Part 2. Young persons aged 10-20 years. Magnes Res 2006; 167-179.         [ Links ]

10. González-Muñoz MJ, Sánchez-Muniz FJ, Ródenas S, Sevillano MI, Larrea Marín MT, Bastida S. Differences in metal and metalloid content in the hair of normo- and hypertensive post-menopausal women. Hypertens Res 2010; 33: 219-224.         [ Links ]

11. Benes B, Sladka J, Spevackova V, Smid J. Determination of normal concentration levels of Cd, Cr, Cu, Hg, Pb, Se and Zn in hair of the child population in the Czech Republic. Cent Eur J Publ Health 2003; 4: 184-186.         [ Links ]

12. Kivimäki M, Batty GD, Singh-Manoux A, Ferrie JE, Tabak AG, Jokela M, Marmot MG, Smith GD, Shipley MJ. Validating the Framingham Hypertension Risk Score: results from the Whitehall II study. Hypertension 2009; 54: 496-501.         [ Links ]

13. Marr JW. Individual dietary surveys: Purposes and methods. World Rev Nutr Diet 1971; 13: 105-164.         [ Links ]

14. Departamento de Nutrición UCM. Ingestas recomendadas para la población española (revisadas en 2008). In: Tablas de Composición de Alimentos. Moreiras O, Carbajal, A, Cabrera L, Cuadrado C, eds. Pirámide, pp. 127-131, Madrid, 2008.         [ Links ]

15. Moreiras O, Cuadrado C. Theoretical study of the intake of trace elements (nutrients and contaminants) via total diet in some geographical areas of Spain. Biol Trace Elem Res 1992; 32: 93-103.         [ Links ]

16. Llobet JM, Falcó G, Casas C, Teixidó A, Domingo JL. Concentrations of arsenic, cadmium, mercury and lead in common foods and estimated daily intake by children, adolescents, adults and seniors of Catalonia, Spain. J Agric Food Chem 2003; 51: 838-842.         [ Links ]

17. World Health Organization-International Society of Hypertension. Guidelines for the Management of Hypertension. Guidelines Subcommittee. 2003.         [ Links ]

18. International Atomic Energy Agency. Report on the Second Research Co-ordination Meeting of IAEA. Neuherberg, 1985.         [ Links ]

19. Eurachem Working Group. Eurachem Guide. The Fitness for Purpose of Analytical Methods. A Laboratory Guide to Method Validation and Related Topics. http://www.eurachem.org/n, 1998.         [ Links ]

20. Myers VH, Champagne CM. Nutritional effects on blood pressure. Curr Opin Lipidol 2007; 18: 20-24.         [ Links ]

21. Moreiras O, Cuadrado C. Mediterranean diet and lifestyle: special aspects of Spain. Int J Vitam Nutr Res 2001; 71: 154-158.         [ Links ]

22. Anderson SG, Snaders TAB, Cruickshank JK. Plasma fatty acid composition as a predictor of arterial stiffness and mortality. Hypertension 2009; 53: 839-845.         [ Links ]

23. Vaquero MP. Magnesium and trace elements in the elderly: intake, status and recommendations. J Nutr Health Aging 2002; 6: 146-152.         [ Links ]

24. Hallberg I, Hulthen J. Prediction of dietary iron absorption: an algorithm for calculating absorption and bioavailability of dietary iron. Am J Nutr 2000; 71: 1147-1160.         [ Links ]

25. Raghunath R, Tripathi RM, Suseela B, Bahalke S, Shukla VK, Puranik VD. Dietary intake of metals by Mumbai adult population. Sci Total Environ 2006; 356: 62-68.         [ Links ]

26. Campbell JD. Lifestyle, minerals and health. Medical Hypotheses 2001; 57: 521-531.         [ Links ]

27. Anderson RA, Kozlovsky AS. Chromium intake, absorption and excretion of subjects consuming self-selected diets. Am J Clin Nutr 1985; 4: 1177-1183.         [ Links ]

28. FAO/WHO. Evaluation of certain food additives and contaminants; Technical Report Series 837. World Health Organization, Geneva, 1993.         [ Links ]

29. Antico A, Soana R. Chronic allergic-like dermatopathies in nickel-sensitive patients. Results of dietary restrictions and challenge with nickel salts. Allergy Asthma Proc 1999; 20: 235-242.         [ Links ]

30. Hayter J. Trace elements. Tijdschr Ziekenverpl 1981; 34: 896-900.         [ Links ]

31. O'Donnel CJ, Elosua R. Factores de riesgo cardiovascular. Perspectivas derivadas del Framingham Heart Study. Rev Esp Cardiol 2008; 61: 299-310.         [ Links ]

32. Tobian L. Dietary sodium chloride and potassium have effects on the pathophysiology of hypertension in humans and animals. Am J Clin Nutr 1997; 65 (Suppl.): 606S-611S.         [ Links ]

33. Cianciaruso B. Relationship between low-protein diet and hypertension control. G Ital Nefrol 2008; 42: S29-S34.         [ Links ]

34. Elliott P, Kesteloot H, Appel LJ, Dyer AR, Ueshima H, Chan Q, Brown IJ, Zhao L, Stamler J, INTERMAP Cooperative Research Group. Dietary phosphorus and blood pressure: international study of macro- and micro-nutrients and blood pressure. Hypertension 2008; 51: 669-675.         [ Links ]

35. Tubeck S. Role of trace elements in primary arterial hypertension: is mineral water style or prophylaxis? Biol Trace Elem Res 2006; 114: 1-5.         [ Links ]

36. Nowak B, Chmielnicka J. Relationship of lead and cadmium to essential elements in hair, teeth, and nails of environmentally exposed people. Ecotoxicol Environ Saf 2000; 46: 265-274.         [ Links ]

37. Afridi HI, Kazi TG, Kazi GH, Jamali MK, Shar GQ. Essential trace and toxic element distribution in the scalp hair of Pakistani myocardial patients and controls. Biol Trace Elem Res 2006; 113: 19-34.         [ Links ]

38. Sevillano Navarro I. Determinación de Elementos Traza en Cabello Mediante Espectrometría de Emisión en Plasma de Acoplamiento Inductivo.. Facultad de Farmacia, Universidad Complutense de Madrid, Madrid. 2001.         [ Links ]

39. Touyz RM, Schiffrin EL. The effect of angiotensin II on platelet intracellular free magnesium and calcium ionic concentrations in essential hypertension. J Hypertens 1993; 11: 551-558.         [ Links ]

40. Arnaud J, Arnault N, Roussel AM, Bertrais S, Ruffieux D, Galan P, Favier A, Hercberg S. Relationships between selenium, lipids, iron status and hormonal therapy in women of the SU.VI.M.AX cohort. J Trace Elem Med Biol 2007; 21 (Suppl.):66-69.         [ Links ]

41. Hong SR, Lee SM, Lim NR, Chung HW, Ahn HS. Association between hair mineral and age, BMI and nutrient intakes among Korean female adults. Nutr Res Pract 2009; 3: 212-219.         [ Links ]

42. Anwar M. Arsenic, cadmium and lead levels in hair and toenail simples in Pakistan. Environ Sci 2005; 12: 71-86.         [ Links ]

43. Flaten TP. Aluminium as a risk factor in Alzheimer's disease, with emphasis on drinking water. Brain Res Bull 2001; 55: 187-196.         [ Links ]

44. Purdey M. Chronic barium intoxication disrupts sulphated proteoglycan synthesis: a hypothesis for the origins of multiple sclerosis. Med Hypotheses 2004; 62: 746-754.         [ Links ]

45. Liu L, Li P, Li Y, Sun L. Determination of calcium and magnesium in human hair by non-complete digestion-flame atomic absorption spectrometry. Guang Pu Xue Yu Guang Pu Fen Xi 2001; 21: 560-562.         [ Links ]

46. Kenouch S, Lombes M, Delahaye F, Eugene E, Bonvalet JP, Farman N. Human skin as target for aldosterone, coexpression of mineralocorticoid receptors and 11-beta-hydroxysteroid dehydrogenase. J Clin Endocrinol Metab 1994; 79:1334-1341.         [ Links ]

47. CiY-Ch. Microelements and disease. J China-Japan Friendship Hosp 1997; 11: 360-363.         [ Links ]

48. Thevenod F, Friedman JM. Cadmium-mediated oxidative stress in kidney proximal tubule cells induces degradation of Na+/K+-ATPase though proteasomal and endo-lysosomal proteolytic pathways. Faseb J 1999; 13: 1751-1761.         [ Links ]

49. Hunt JR. Bioavailability of iron, zinc, and other trace minerals from vegetarian diets. Am. J Clin Nutr 2003; 78: 633S-639S.         [ Links ]

50. Ohtomo S, Nangaku M, Izuhara Y, Takizawa S, van Ypersele de Strihou C, Miyata T. Cobalt ameliorates renal injury in an obese, hypertensive type 2 diabetes rat models. Nephrol Dial Transplan 2008; 23: 1166-1172.         [ Links ]

51. Holzinger S, Anke M, Röhrig B, Gonzalez D. Molybdenum intake of adults in Germany and Mexico. Analyst 1998; 123: 447-50.         [ Links ]

52. Gibson RS, Anderson BM, Sabry JH. The trace metal status of a group of post-menopausal vegetarians. J Am Diet Assoc 1983; 82: 246-250.         [ Links ]

53. Finley JW, Davis CD. Manganese deficiency and toxicity: are high or low dietary amounts of manganese cause for concern? Biofactors 1999; 10: 15-24.         [ Links ]

54. Weaver J, Porasuphatana S, Tsai P, Cao GL. The effect of divalent cations on neuronal nitric oxide synthase activity. Toxicol Sci 2004; 81: 325-331.         [ Links ]

55. Ball MJ, Ackland ML. Zinc intake and status in Australian vegetarians. Br J Nutr 2000; 83: 27-33.         [ Links ]

56. Yanagisawa H, Wada O. Zinc. Nippon Rinsho 2004; 62 (Suppl.): 295-300.         [ Links ]

 

 

Correspondence:
Francisco José Sánchez-Muniz.
Departamento de Nutrición y Bromatología I (Nutrición).
Facultad de Farmacia.
Universidad Complutense. Madrid. Spain.
E-mail: frasan@farm.ucm.es

Recibido: 7-IX-2010.
1^a Revisión: 8-XI-2010.
2^a Revisión: 28-I-2011.
Aceptado: 1-II-2011.