Effect of dietary phytic acid on zinc absorption in the healthy elderly, as assessed by serum concentration curve tests

Zn absorption was investigated in healthy elderly subjects aged 71-78 years and in young subjects aged 23-43 years using serum concentration curve (SCC) tests. Both groups had similar Zn and protein status. The increase in serum Zn was monitored for 180 min after ingestion of 200 ml of soya milk enriched with 50 mg of Zn. Three levels of phytic acid were used: 0 g/200 ml (totally dephytinized soya milk), 0.13 g/200 ml (half dephytinized), and 0.26 g/200 ml (natural phytic acid content). In a first study the effect of 0 v. 0.26 g/200 ml phytic acid was compared in 10 elderly and 10 young subjects, each subject receiving both treatments. In a second study soya milks with 0 and 0.13 g/200 ml were tested in nine elderly and ten young subjects, again receiving both treatments. Mean areas under the curve of the SCC tests conducted with the 0 g/200 ml soya milk were found to be the same in both studies. Phytic acid strongly depressed Zn absorption in both studies (P < or = 0.05), but to a greater extent at the 0.26 g/200 ml level. No difference was found between the groups of young and elderly subjects. Therefore, no significant effect of aging on Zn absorption, as evaluated by the SCC test, or on the inhibitory effect of phytic acid was detected.

The sizes of the exchangeable pools of selenium in elderly women and their relation to institutionalization

Exchangeable pools of Se after an intravenous injection of 74Se-enriched isotope as sodium selenite were measured in two groups (n 9) of elderly women (free-living aged 64-82 years and institutionalized aged 68-82 years), and a comparison group (n 9) of young women aged 31-40 years to evaluate the effect of age and institutionalization on Se reserves. Dietary Se intake was not different among the three groups. Plasma Se and glutathione peroxidase (EC 1.11.1.9) levels were significantly lower in the institutionalized elderly women (P < 0.05). In each of the three groups, two pools were determined from our model. The size of the first pool and the sum of the two pools were lower in the group of institutionalized elderly women than in the other two groups. The significant correlation between plasma Se level and total Se pool size (r 0.66, P < 0.01) indicated that this last variable could serve as a new marker of Se status. Finally, these data suggest that the Se status of elderly women is more related to lifestyle, in terms of institutionalization or not, than to age per se.

Calcium bioavailability from a calcium- and sulfate-rich mineral water, compared with milk, in young adult women

Some mineral waters have a high calcium content and may contribute a significant part of the human daily requirements. Calcium bioavailability from a calcium- and sulfate-rich mineral water (CS-W) containing 11.2 mmol Ca/L (467 mg/L) was compared with that from milk in nine healthy young women. Calcium absorption was measured in the fasting state with a dual-label stable-isotope technique. Fractional absorption rates from milk and CS-W were 25.0 +/- 6.7% and 23.8 +/- 4.8% (means +/- SD), respectively, and did not differ significantly (P = 0.05). Urine was collected for 36 h after the administration of the oral stable isotope while the subjects consumed a controlled diet and a quantity of milk or CS-W providing 25 mmol (1000 mg) Ca. No significant difference was found in the excretion of calcium, nor in the excretion of the two stable isotopes. Mean urinary sulfate excretion was significantly increased by 35% when the CS-W was consumed. No significant correlation was found between 36-h urinary excretion of the intravenous calcium tracer and sulfate, sodium, or urine volume. Therefore, calcium from the CS-W was as well absorbed and retained as that from milk, and no calciuric effect of sulfate was found, showing that such mineral waters can be valuable dietary sources of calcium.

Zinc absorption in healthy elderly humans and the effect of diet

Absorption of a zinc stable isotope was measured on two consecutive occasions in nine young and eight elderly healthy men aged 24-40 and 70-83 y, respectively. A zinc stable-isotope label (0.8 mg 70Zn) was added to a test meal of either high or low zinc bioavailability, depending mainly on phytic acid content. Zinc absorption from the high-bioavailability test meal was not significantly different (P > 0.05) in the young (38.9 +/- 9.8%, mean +/- SD) and elderly (35.0 +/- 10.9%) subjects. Zinc absorption from the low-bioavailability test meal was 40% and 43% lower, at 23.4 +/- 10.2% and 19.8 +/- 6.1% in these young and elderly men, respectively. Again, no significant effect of age was found. These results show that aging does not lead to nutritionally relevant changes in zinc absorption and in the effect of dietary inhibitors on zinc absorption. Thus, zinc absorption ability seems to be preserved in healthy elderly people, at least until the age of 80 y.

Nutritional implications of the interactions between minerals

It is well recognized that the absorption, retention and metabolism of most essential minerals can be markedly influenced by the presence of antinutrient factors in the diet (i.e. fiber and phytate). However, in addition, interactions can also occur between essential minerals. Indeed, under some circumstances, these interactions can be profound and have significant implications for human health. Interactions between essential minerals can be broadly classified as direct or indirect. Direct interactions are generally competitive phenomena that occur during the intestinal absorption and/or during the tissue utilization of a mineral. Indirect interactions occur when one of the minerals is involved in the metabolism of the other mineral, or when a deficiency or toxicity of one of the minerals results in hormonal changes or tissue damage which affects the metabolism of the other mineral. In this review we have focused our comments on direct interactions between essential minerals, and we present suggested levels at which an excess of a mineral (coined "X") can significantly alter the metabolism of another mineral (coined "Y") for several of the known competitive interactions. This level is characterized as the lowest X/Y ratio of the dietary intakes which has been shown to produce negative consequences on the metabolism of the element Y (assuming the intake of Y is physiological). Moreover, the importance of the physiological status of the animal with regard to the determination of these ratios is discussed. The calculated X/Y ratio at which interactions may be predicted to occur is generally higher than the ratio calculated for most minerals using typical dietary intakes of X and Y in Western-type diets. However, ratios which might be predicted to result in negative interactions do occur in select food products, and can be reached as a consequence of supplementation (either through food enrichment or therapeutic use of supplements). In fact, considering the ready availability of dietary supplements, such interactions may become commonplace. Finally, the interactions between essential and non-essential minerals (heavy metals) are briefly discussed, as are indirect mineral interactions.

Zinc metabolism in the athlete: influence of training, nutrition and other factors

Serum zinc was measured four times (October, January, March and May) in six young male athletes during a nine-month sporting season in relation to eleven other parameters. A significant decrease in serum zinc was observed after five months of intensive training (all values remaining in the normal range). This cannot be explained by changes in dietary habits, plasma protein concentrations, hormonal changes nor by the existence of minor infectious or inflammatory pathologies. The dietary intakes seemed adequate. These results support the hypothesis that zinc status may be slightly altered in the high-level athlete.

Average mineral and trace element content in daily adjusted menus (DAM) of French adults

This article is based on data on food consumption gathered from 10,000 households. The daily energetic intake of 2,000 to 2,500 kcal (8,360 to 10,450 kJ) (beverages excluded) provides adults with less than 80% of the recommended amount of several essential minerals and trace elements. For women, beverages contribute only slightly to the total amount of mineral and trace element intake, because the major beverage sources of minerals and trace elements are alcoholic drinks (wine, beer). For men, alcoholic drinks could provide an additional amount of these elements. Consequently, it seems the risk of deficiency appears in adults, with women particularly concerned by this problem. The present study demonstrates that the intake of the following elements might be insufficient in women: fluorine, manganese, iron, copper, zinc and magnesium.

Estimation of the share of each water source for adults in France. Water intake provided to the French adults

We have calculated that the approximate amount of the different water intakes for an average adult population consuming 11.8 MJ/day (2,837 kcal/day), where 1.4 MJ (337 kcal) are provided by beverages, is 2.7 liter/day. These intakes include: 'invisible intakes' supplied by endogenous water (348 ml/12.9%) and water contained in food, fruit or dairy products (1,008 ml/37.6%), and 'visible intakes' provided by water contained in commercialized beverages such as bottled water, fruit juices, sodas, fruit drinks, alcoholic drinks (678 ml/25.3%) and tap water (estimate/650 ml/24.2%). We advise to carry out consumption studies according to the various age brackets.

Estimation of minerals and trace elements provided by beverages for the adult in France

The total average amount of beverages absorbed daily (1,378 ml) is split up as follows: tap water (650 ml where from 170 ml are used for the preparation of coffee and tea); bottled water (190 ml); alcoholic drinks (481 ml) and soft drinks (57 ml). Under these conditions, the intake is estimated at (mg/day): Na: 50, K: 450, P: 83, Ca: 141, Mg: 54, Fe: 2.9, Zn: 0.64, Cu: 0.46, Mn: 0.40, F: 0.64, I: 0.09, Cr: 0.013, Se: 0.031. The most significant supplies for both quantity and quality are those of calcium (18% of the needs), iron (29%), copper (19%), fluorine (24%) and magnesium (16%) for the adult. Alcoholic drinks represent 35% of the daily intake of beverages; they are likewise the main source of minerals such as: iodine and iron (wine), selenium (beer), fluorine, calcium and copper (in all alcoholic drinks). Calcium and fluorine are the main minerals provided by the different types of water. We have shown the influence of the geographical origin of the tap water on the Ca and F intake, as well as the influence of individual behaviour with respect to the selection of his main drink.