Dietary intake and bioavailability of trace elements

In order to assess the nutritional importance of trace elements, it is relevant to consider the factors regulating their metabolism. One of the most important factors is the true intake level. Conventional techniques such as diet history and interview studies in conjunction with standard food tables do not provide the true intake levels from prepared meals. Employing the duplicate portion technique, we have investigated the dietary intake of trace elements in prepared meals consumed by children, adults, and elderly in Sweden. The results indicate that the intake of potassium, magnesium, zinc, copper, and selenium is low when compared with the present recommended dietary allowance (RDA) values. It appears that a marginal deficiency of a number of trace elements may exist in the general population of affluent countries. When the dietary intakes are known, it is necessary to consider the bioavailability. This depends on the chemical form as well as the concentration of other dietary constituents such as fiber, phytate, carbohydrates, macrominerals, and vitamins in the diet. Knowledge of these interactions are important to improve the overall nutritional status of the population in general and patients in particuler.     

Dietary phytate,zinc and hidden zinc deficiency

Epidemiological data suggest at least one in five humans are at risk of zinc deficiency. This is in large part because the phytate in cereals and legumes has not been removed during food preparation. Phytate, a potent indigestible ligand for zinc prevents it's absorption. Without knowledge of the frequency of consumption of foods rich in phytate, and foods rich in bioavailable zinc, the recognition of zinc deficiency early in the illness may be difficult. Plasma zinc is insensitive to early zinc deficiency. Serum ferritin concentration ≤ 20 μg/L is a potential indirect biomarker. Early effects of zinc deficiency are chemical, functional and may be “hidden”. The clinical problem is illustrated by 2 studies that involved US Mexican-American children, and US premenopausal women. The children were consuming home diets that included traditional foods high in phytate. The premenopausal women were not eating red meat on a regular basis, and their consumption of phytate was mainly from bran breakfast cereals. In both studies the presence of zinc deficiency was proven by functional responses to controlled zinc treatment. In the children lean-mass, reasoning, and immunity were significantly affected. In the women memory, reasoning, and eye-hand coordination were significantly affected. A screening self-administered food frequency questionnaire for office might help caregiver's identify patients at risk of zinc deficiency.     

Dietary recommendations for the community towards the postponement of coronary heart disease.

The public has recently been confronted with many, often conflicting, recommendations about diet and reducing the risk of coronary heart disease (CHD). Dietary recommendations to the community designed to lower the risk of CHD should be specific, clear, and brief. People should be advised to reduce their intake of foods that are high in saturated fats and replace these partially with foods that are relatively high in polyunsaturated fats. This will lower both total fat and dietary cholesterol intakes and will also change the ratio of polyunsaturated to saturated fats.     

Use of laboratory animals to define physiological functions and bioavailability of zinc

For the past 50 years laboratory animals have been used to ascertain the metabolic bases for signs of zinc deficiency such as sharply reduced food intake, severe dermatitis, slow wound healing, delayed sexual development and function, reduced immunocompetence, severe teratogenic abnormalities, and abnormal metabolism of carbohydrate, lipid, and protein. Current evidence indicates that many of these symptoms may be consequences of inhibition of early steps in nucleic acid metabolism that lead to problems with cellular replication and growth and also that zinc plays an important role in membrane structure and function. Bioavailability of zinc to experimental animals was early shown to be reduced by plant protein diets and to be further reduced by feeding excess calcium. Current evidence indicates phytic acid in plant proteins to be a major inhibitor of zinc absorption, although food-processing methods can either increase or decrease zinc bioavailability. The inhibitory effect of phytic acid is very dependent on dietary calcium in association with phytate and zinc. Usual calcium intakes by humans are much below those demonstrated in animals to cause phytate inhibition of dietary zinc availability.     

Associations between copper and zinc intakes from diet and mortality from cardiovascular disease in a large population-based prospective cohort study

Several studies have related cardiovascular disease (CVD) to serum concentrations of copper and zinc but not to their dietary intakes. We thought to examine the association between dietary intakes of copper and zinc with risk of mortality from CVD in a prospective study encompassing 58,646 healthy Japanese men and women aged 40-79 years. The intakes of copper and zinc were determined by a validated self-administered food frequency questionnaire, and their associations with risk of mortality from CVD were evaluated by Cox proportional hazard modelling. During 965, 970 person-years of follow-up between 1989-2009, we documented 3,388 CVD deaths [1,514 from stroke, 702 from coronary heart disease (CHD) and 1,172 from other CVD]. Copper intake was not associated with CHD mortality; however, the multivariable hazard ratios (HRs) with 95% confidence intervals (CIs) for mortality from stroke, other CVD and total CVD in the highest versus the lowest quintiles of copper intake among men were 1.78 (1.16-2.77; P-trend=0.007), 1.61 (1.01-2.81; P-trend =0.03) and 1.63 (1.21-2.33; P-trend=0.001), respectively, and those among women were 1.49 (1.00-2.19; P-trend=0.04), 1.59 (1.09-2.55; P-trend =0.02) and 1.36 (1.06-1.69; P-trend=0.01), respectively. Higher intakes of zinc was inversely associated with mortality from CHD in men; 0.68 (0.58-1.03; P-trend=0.05) but not women; 1.13 (0.71- 1.49; P-trend=0.61). No associations were observed with other mortality endpoints. In conclusion, dietary copper intake was positively associated with mortality from CVD in both genders; whereas, higher dietary zinc intake was inversely associated with mortality from CHD in men but not women.     

Dietary and Non-dietary Factors Associated with Serum Zinc in Indian Women

Women in low-income settings, common in India, are at risk of inadequate zinc intake due to poor diet quality and low consumption of flesh foods rich in zinc. The aims of this study were to assess the prevalence of zinc status of non-pregnant rural and tribal women living in central India and to identify dietary and non-dietary factors associated with the biochemical zinc status of these women. Rural and tribal non-pregnant women 18–30 years of age were selected using proportion to population sampling near Nagpur, Maharashtra, India. Sociodemographic, biochemical (serum zinc), clinical, and dietary data (1-day interactive 24-h recall) were collected. The mean age of women (n?=?109; rural?=?52; tribal?=?56) was 23.2 years and mean BMI was 17.9 kg/m². The majority of the participants identified as being non-vegetarian (72 %). The mean?±?SD serum zinc concentration was 10.8?±?1.6 μmol/L, and 52 % of participants had a low serum zinc concentration according to the International Zinc Nutrition Consultative Group (IZiNCG). The median (first and third quartile) energy, zinc intake, and phytate/zinc molar ratio was 5.4 (4.2, 6.7)?MJ/day, 5.3 (3.8, 7.0)?mg/day, and 26 (22, 28), respectively. Zinc intakes were well below IZiNCG recommendations for dietary zinc of 9 mg/day for non-pregnant women aged 14–18 years and 7 mg/day for non-pregnant women aged ≥19 years. Using linear regression analysis to identify non-dietary and dietary factors associated with serum zinc, a significant association was only found for current lactation (p?=?0.012) and energy intake (p?相似文献   

Zinc supplementation has no effect on lipoprotein metabolism,hemostasis, and putative indices of copper status in healthy men

Pharmacological doses of zinc can adversely affect body copper status. The resulting copper deficiency can impact directly upon cholesterol metabolism and a suboptimal copper status has been observed to influence markers of hemostasis (specifically fibrinogen and the copper-containing coagulation factors V and VIII). The aim of this investigation was to examine the effect of a low level of zinc supplementation, to include dietary intake, at the United States tolerable upper intake level of 40 mg/d upon indicators of lipid metabolism, hemostasis, and copper. Thirty-eight subjects were recruited onto a double-blind placebo-controlled intervention trial and randomly selected to one of two groups. Group 1 took zinc supplements (30 mg/d) for 14 wk followed by copper supplements (3 mg/d) for 8 wk (to counteract adverse effects, if any, of zinc supplementation). A second group took placebo supplements for the full duration of the trial. Estimated dietary zinc intake approximated 10 mg/d. The effect of supplement was analyzed by repeated-measures analysis of variance (anova). Results indicate that no effect of zinc supplementation on putative indices of copper status, lipoprotein metabolism, and markers of hemostasis. These results indicate that short-term low-level zinc supplementation (total intake 40 mg/d) is not detrimental to health.     

Dietary fibre and mineral metabolism

Current dietary recommendations urge, inter alia, an increased consumption of fibre-containing foods. Some experimental studies made on various animals and man indicate that the associated increases in intakes of fibre and phytic acid may prejudice mineral status respecting calcium, magnesium, iron and zinc. An examination has been made of the experimental evidence, also of the epidemiological evidence on numerous types of populations, past and present, developing and developed. It has been concluded that diets high in fibre, characteristically do not have meaningful ill effects on well-being or unequivocally enhance morbidity. In particular populations in certain regions where deleterious effects have been reported it is judged that local factors, not wholly understood, are in operation. In assessing the extent of the benefit to be derived from the dietary changes urged, results must be viewed holistically and not in isolation. It is believed that the beneficial effects respecting reduced pronenesses to various degenerative diseases are likely to far outweigh the possible adverse effects of reduced bioavailability of mineral nutrients.     

Zinc and copper intake and sources in healthy adults living in Bangkok and surrounding districts

The levels of intake and food sources of zinc and copper in 231 20–80 yr old healthy adults living in Bangkok and surrounding districts were determined. Dietary data from 3-d food records collected and validated at Research Center, Ramathibodi Hospital were analyzed. Levels of zinc and copper intake were compared between sexes and age groups (20–39, 40–59, and 60–80 yr). Mean daily zinc and copper intakes (±SEM) in men were 6.3 ±0.2 and 1.9 ±0.1 mg, respectively. Mean daily zinc and copper intakes (±SEM) estimated in women (5.5 ±0.2 and 1.6 +-0.1 mg) were significantly lower. Higher zinc and copper intakes were found in the younger (20-39 yr) age group of both sexes. This could be explained by higher density and percentage from animal source of both nutrients. Consumption of various types of meat, fish, egg, and milk accounted for 42 and 22%, and rice, the staple food of Thai people for 9 and 23% of total dietary zinc and copper, respectively.     

Global diversity of dietary intakes and standards for zinc,iron, and copper

BackgroundThe essentiality of trace elements in human diets is well recognized and adequate levels are a critical component of optimal health. To date, public health efforts have focused primarily on macronutrients or trace minerals that are easily analyzed. The goal of this research is to provide assessment of the dietary standards developed for Zn, Fe, and Cu in 100+ developed, marginal, and developing countries. We summarize the current recommendations and changes from the last decade, categorize and provide scientific basis for values established, factors that affect requirements, and current global challenges.MethodsThe electronic databases of Google Scholar, PubMed, Embase, Web of Science and Cochrane Library were searched using the keywords “trace minerals,” “micronutrients, ““zinc,” “iron,” “copper,” “dietary standards” and “recommendations.” A total of 123 studies published from 1965 to 2019 were included.ResultsThe World Health Organization (WHO) has established dietary standards to address nutrient deficiencies, prevent infections and ensure basic metabolic functions; these are utilized by most developing countries. Developed countries or their alliances have established values similar to or higher than the WHO, primarily for promotion of optimal health and well-being. Transitional countries are more concerned with issues of bioavailability, food security and undernutrition. Globally, Zn and Cu recommendations are lower in women than in men; Fe requirements are higher to compensate for menstrual losses. Important considerations in establishing guidelines for these minerals include bioaccessibility, dietary practices and restrictions, food processing, interactions, and chemical forms. The global challenges of the triple burden of malnutrition, hidden hunger, increased consumption of ultra-processed foods and obesity have been associated with Zn, Fe, and Cu deficiencies.ConclusionThis research provides public policy and health professionals evidenced-based information useful for the establishment of dietary standards world-wide.     

Dietary Fiber Intake Increases the Risk of Zinc Deficiency in Healthy and Diabetic Women

Phytic acid is a major determinant of zinc bioavailability. Little is known about phytic acid intakes or indices of zinc bioavailability in type 2 diabetes mellitus (DM), a condition that predisposes to zinc deficiency. The aim of this cross-sectional study was to measure and explore the relationships among phytic acid intake, zinc bioavailability, and molecular markers of zinc homeostasis in 20 women with DM compared to 20 healthy women. The phytate/zinc, (calcium)(phytate)/zinc, and (calcium + magnesium)(phytate)/zinc molar ratios were used to indicate zinc bioavailability. Plasma zinc concentrations and zinc transporter (ZnT1, ZnT8, and Zip1) gene expression in mononuclear cells were measured. Participants with DM consumed 1,194?±?824?mg/day (mean?±?SD) phytic acid, an amount similar to the intake of healthy women (1,316?±?708?mg/day). Bread products and breakfast cereals contributed more than 40?% of the phytic acid intake in each group. A positive relationship was observed in all participants between phytic acid and dietary fiber (r?=?0.6, P?<?0.001) and between dietary fiber and the (calcium)(phytate)/zinc ratio (r?=?0.5, P?<?0.001). Compared to the healthy group, the messenger RNA ratio of ZnT1 (zinc export) to Zip1 (zinc import) was lower in participants with DM, which may indicate perturbed zinc homeostasis in the disorder. The plasma zinc concentration was not predicted by age, body mass index, health status, zinc bioavailability, or zinc transporter expression. Healthy and diabetic women consume phytic acid in amounts that are likely to decrease the bioavailability of dietary zinc. Recommendations to consume greater amounts of dietary fiber, much of which is associated with phytate, increase the risk of zinc deficiency.     

Calcium bioavailability and its relation to osteoporosis.

The balance of data suggests that calcium intake has a positive influence on bone mass in premenopausal women and has a preventive effect on the rate of bone loss in postmenopausal women. Even small advantages in bone mass provide great reductions in fracture rates. However, the majority of studies have tested the relationship of calcium intake and bone mass using calcium supplements. Few intervention studies have manipulated calcium intake through foods. Calcium is only useful to the skeleton once it is absorbed. Therefore, the bioavailability of dietary calcium becomes important in the prevention and treatment of osteoporosis. Isotopic tracer techniques have only recently been employed in the labeling of foods with calcium isotopes for evaluation of calcium absorption. Milk calcium is usually the referent food which is typically absorbed at 20-40% depending on the calcium status of the subject. The absorptive efficiency of most vegetable sources is as good or better than for dairy foods, unless they have high concentrations of oxalic acid (spinach, for example) or phytic acid (wheat bran cereal, for example). Few vegetable sources are concentrated sources of calcium. Therefore, it would be difficult to obtain adequate intakes of calcium to protect against osteoporosis without liberal use of dairy products in the diet. Alternately, calcium supplements provide concentrated amounts of absorbable calcium, but they do not provide other nutrients necessary for skeletal growth and maintenance.     

International variability in diet and requirements of manganese: Causes and consequences

Manganese (Mn) is an essential trace element that is critical for human health and development. At the turn of the century when diets were based on whole grains, cereals and other traditional foods, Mn intakes (8–9 mg/d) were much greater than that prevalent today (2 mg/d). As societies have developed, diets have shifted as part of a nutrition transition, to those that are high in processed foods, fat, and sugar. These foods are virtually devoid of Mn. Thus, dietary Mn has declined substantially throughout the world, as confirmed by several wide-scale, total diet studies.International variability in dietary Mn is considerable, due to tremendous diversity in food and culture. In countries where fruit and vegetable intake may be limited, i.e. the United Kingdom, populations may ingest much lower levels of Mn (1.4 mg/d) as compared to Asian cultures (4 mg/d) which have an abundance of plant foods in their food supply and cuisine. The bioavailability of Mn must be considered, including chemical form, oxidation state, mineral-mineral interactions, presence of dietary components and traditional food processing techniques (milling, germination, malting, fermentation). Manganese toxicity is a public health problem that results from exposure to a naturally high water source or contaminated environment of the soil and/or drinking water. In contrast, inadequate intake is associated with adverse health effects such as diabetes, metabolic syndrome, poor birth outcomes and possibly, cancer. Future studies are recommended to set dietary standards for this mineral in countries that lack recommendations to help achieve optimal health.     

Aspects of trace element interactions during development

The origins of nutritional trace element deficiencies are summarized. Inadequate intake results in primary deficiency, whereas secondary or conditioned deficiencies can arise in several ways including trace element interactions. Evidence is presented and discussed for interactions of essential trace elements during prenatal and early postnatal development. Diets of widely different zinc and copper concentrations and ratios were fed to pregnant rats. Analysis of fetal outcome and copper and zinc concentrations of maternal and fetal livers showed that although there is an interaction between these metals it occurs only at levels of dietary copper deficiency. Iron and manganese interact so that high levels of one depress absorption of the other. Mice fed iron-supplemented diets had liver manganese concentrations lower than those of unsupplemented mice. Iron supplements at high but not low levels also depressed absorption of zinc. Conversely, zinc deficiency in pregnant rats caused higher than normal concentrations of iron in maternal and fetal liver. Trace element analyses of proprietary infant formulas indicate that in some, concentrations and ratios of these trace elements may be incorrect. The effects of essential trace element interactions during development should be further investigated. Caution is urged in considering levels of trace element supplements during pregnancy, lactation, or early childhood.     

Comparative Bioavailability of Mineral-enriched Gluconates and Yeast in Rat Liver After Depletion–Repletion Feeding

There are many forms of mineral supplements currently available. Among these mineral-enriched gluconates and yeast are considered two of the more biologically available supplements. The purpose of this study was to use zinc (Zn)- or copper (Cu)-deficient rats to determine whether the organically bound mineral in yeast or the salt gluconate form was more bioavailable, i.e., is absorbed and found in a greater concentration in liver. It was demonstrated that Zn-enriched yeast was 3.7 times more bioavailable than the Zn gluconate and that Cu-enriched yeast was 1.4 times more bioavailable than the Cu gluconate.     

Association Between Zinc, Copper, and Iron Concentrations in Breast Milk and Growth of Healthy Infants in Tabriz, Iran

The aims of this study were to determine the effect of breast milk zinc, copper, and iron concentrations on infants’ growth and their possible correlations with maternal dietary intake. Milk samples and information on food intake were collected from 182 lactating women. Concentrations of zinc, copper, and iron in milk were analyzed using atomic absorption spectrophotometry. The infant’s weight for age Z-score (WAZ) and height for age Z-score (HAZ) were calculated. The mean milk zinc, copper, and iron concentrations were 1.85?±?0.5, 0.53?±?0.3, and 0.85?±?0.2 mg/l, respectively. Only zinc mean level was lower than the recommended range. Association between zinc, copper, and iron concentrations of milk and WAZ or HAZ of infants were not significant. However, the WAZ of infants whose mothers' milk zinc was more than 2 mg/l was significantly (P?<?0.039) higher than for others. The mean dietary zinc (5.31?±?2.3 mg/day) and copper (1.16?±?0.7 mg/day) intake of mothers was significantly less than the required daily intake (RDA) recommendations (P?<?0.05). The mean dietary iron intake (11.8?±?8.2 mg/day) was significantly higher than RDA recommendation (P?<?0.001). No significant association was found between maternal mean dietary zinc, copper, and iron intakes with their concentrations in milk. Dietary consultation or/and zinc supplementation is suggested for lactating women and infants.     

EPA and DHA--protein, not fat is "where it's at"?

Guidelines and recommendations for the dietary intake of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are topics of debate. Recently, EPA and DHA intakes have been demonstrated to be associated with dietary protein intakes and not dietary fat intakes that are distinct from α-linolenic acid. We presently confirm these observations in a secondary analysis of baseline dietary intake data for the validation of a food frequency questionnaire (n=99). DHA intakes measured by both 3 d dietary record and food frequency questionnaire and EPA intakes measured by food frequency questionnaire were positively correlated with protein intakes. EPA and DHA were not associated with fat intakes in either assessment, while ?-linolenic acid was positively correlated with fat intakes. Future recommendations regarding the intake of omega-3 polyunsaturated fatty acids, and EPA and DHA specifically, should consider these associations that provide insight on dietary sources of EPA and DHA in the food supply.     

Dietary Exposure Estimates of 14 Trace Elements in Xuanwei and Fuyuan,Two High Lung Cancer Incidence Areas in China

Xuanwei and Fuyuan, located in the Yunnan province in southwest of China, are known to have a strikingly high incidence of lung cancer. Among the many factors that have been explored, the association between lung cancer and trace elements has not received enough attention. In this study, dietary samples were collected from 60 families of the lung cancer and control groups and abundances of 14 trace elements were determined using inductively coupled–plasma mass spectroscopy. Accuracy and sensitivity of the method were demonstrated by analyzing national standard reference materials. The results showed that the dietary intake of the trace elements contributed 96.6% of total intake. Among the 14 elements tested, cadmium and titanium were found to be present at a significantly higher level in the food consumed by the cancer group than by the control group. The intake of selenium by the population living in the areas is much lower than what it should be, with the people in the cancer group experiencing even more severe selenium deficiency. In addition, in both groups, the intakes of several essential elements (iron, copper, and zinc) from food and the drinking water were found to be significantly lower than required according to the Chinese Dietary Reference Intakes. The present study of the relationship between trace element intakes of lung cancer cases and controls provides important information urgently needed for the assessment of lung cancer risk of healthy subjects. The study also gives rational dietary suggestions to local residents which is important to the early diagnosis and pretreatment of lung cancer.     

Seasonal hyperphagia does not reduce digestive efficiency in an Arctic grazer

Muskoxen (Ovibos moschatus) consume fibrous plants that grow rapidly over the short Arctic summer. We studied responses of eight castrated male muskoxen to a diet of grass hay and mineral supplements during spring, autumn, and winter. Animals gained body mass in spring (239+/-39 kg) as body fat content increased from 26% to 38% of ingesta-free mass in winter without changes in lean mass and protein. Intakes of dry matter (DM) increased by 74% between spring and autumn as digestible energy increased from 554 to 923 kJ kg(-0.75) d(-1) during mass gain. Digestibility of cellulose (72%-76%) was not affected by increasing food intake between spring and autumn but was reduced to 65% in winter. Digestibility of nitrogen compounds was 61%-66%, even though intake increased by 134% between spring and autumn. Excess dietary nitrogen from hay and supplements increased urea concentrations in plasma and urine. High loads of solutes such as potassium did not affect plasma or urinary osmolality but were associated with increased rates of glomerular filtration and urinary excretion. Low intakes of sodium from grasses may limit intake and digestion during summer, but high food intakes can support deposition of nitrogen, calcium, magnesium, copper, and zinc in body tissue even when dietary concentrations are low. Seasonal increases in digestive and metabolic functions allow muskoxen to rapidly accumulate energy and nutrients in body tissue during the short season of plant growth.