A double-blind study of combined restriction of thiamin, riboflavin, and vitamins B-6 and C was carried out with 23 healthy males. During 8 wk of low vitamin intake, 12 deficient subjects consumed daily a diet of normal food products, providing maximally 32.5% of the Dutch Recommended Dietary Allowances (RDA) for thiamin, riboflavin, vitamins B-6 and C. Other vitamins were supplemented at twice the RDA. Eleven control subjects consumed the same diet but with a supplementation of twice the RDA of all vitamins. In deficient subjects blood vitamin levels, urinary vitamin excretion, and erythrocytic enzyme activities decreased; in vitro enzyme stimulation increased. Vitamin depletion had no ill effects on health, physical activity, and mental performance. A significant decrease was observed in aerobic power (VO2max) and onset of blood lactate accumulation (p less than 0.001) of 9.8 and 19.6%, respectively. A combined restricted intake of thiamin, riboflavin, and vitamins B-6 and C causes a decrease in physical performance within a few weeks.

1. Twelve young adult male volunteers were given a low-fibre white bread diet (9 g neutral-detergent fibre (NDF)/d) and a medium-fibre coarse-bran bread diet (22 g NDF/d), each lasting 20 d. In a third period of 20 d the volunteers were subdivided in groups of four, consuming a high-fibre coarse-bran bread diet (35 g NDF/d). a medium-fibre fine-bran bread diet (22 g NDF/d, bran particle size < 0.35 mm) or a wholemeal bread diet (22 g NDF/d), Retention of calcium, magnesium, iron, zinc and copper were determined during each 20 d period.2. An increase of the amount of dietary fibre (through bran in bread) from 9 g to 22 g NDF/d resulted in a significantly increased mineral intake, but also faecal excretion increased significantly; mineral retention remained almost constant.3. Both intake and faecal excretion of all minerals studied, except faecal Ca. increased further (P < 0.05) on the diet providing 35 g NDF/d: only Fe balance decreased significantly. No significant differences with respect to intake, excretion (except urinary Ca) and balance of the minerals could be detected between the coarse-bran bread and fine-bran bread diets providing 22 g NDF/d. Faecal Fe, Cu balance and Mg balance increased significantly during the wholemeal bread period compared to the coarse-bran bread diet providing 22 g NDF.4. Serum cholesterol increased significantly, i.e. by 0.3 mmol/1, during the coarse-bran bread diet providing 22 g NDF, compared to the white-bread diet.5. It is concluded that increasing the amount of bran in bread does not appear to affect mineral balance considerably but there seems to be an influence on mineral availability. The increased intake was accompanied by increased faecal excretion.

1. Twelve young men were given for periods of 20 d, each of three mixed diets, namely a low-protein (LP) diet (9% total energy as protein, 67% of animal origin), a high-animal-protein (HA) diet (16% total energy as protein, 67% of animal origin) and a high-vegetable-protein (HV) diet (16% total energy as protein, 67% of vegetable origin). Retention of calcium, magnesium, iron, zinc and copper as well as various bowel function indices were investigated during each dietary period.2. Neither the HA diet nor the HV diet changed the retention of the minerals considerably. Only Fe balance decreased significantly on the HV diet.3. Substituting the HV diet for the HA diet resulted in significant increases in faecal wet weight (17 g/d), defaecation frequency (0.12 stools/d), faecal volatile fatty acids (2.6 mmol/d) and a decrease in faecal bile acids (128 pmolld).4. It is concluded that a HV diet, rather than a HA diet IS to be recommended with respect to bowel function, whereas the HV diet does not necessarily have a significani influence on mineral retention.For a number of minerals and trace elements recommended daily allowances (RDA) have been formulated. Various dietary factors are known to influence mineral or trace element availability (Rosenberg & Solomons, 1982). These influences are of importance in the evaluation of the RDA of trace elements and minerals. It is known that an increased protein intake may result in enhanced urinary calcium excretion and a negative Ca balance (Wachman & Bernstein, 1968;Hegsted et al. 1981 ;Linkswiler et al. 1981). Little information is available on the influence of protein intake on mineral balance other than Ca. The RDA for protein is slightly different in various countries. For The Netherlands the protein RDA for male adults is 65-70 g (9-10% energy total), UK recommendations amount to 63-72 g (10% total energy), and US recommendations are 56 g protein (8 total energy) (International Union of Nutrition Sciences, 1983). The actual intake mostty exceeds the RDA. In The Netherlands, protein intake often reaches values of 14-147; total energy (Van Dokkum, 1984). The effect of increasing protein intake from an RDA level to the actual intake level on mineral balance is not known. Because of the beneficial influence dietary fibre may have on bowel function, it is generally recommended to increase the dietary fibre intake in Western food patterns (Heaton, 1983). One of the ways to achieve this is to increase vegetable (protein) products and to decrease animal protein intake. This change in dietary pattern is one of the recommendations in The Netherlands (Van Dokkum, 1984). The effect of this proposed change on mineral balance has not yet been studied.In the present paper the results are presented of experiments regarding the influence on mineral utilization and bowel function when both dietary changes are brought about. M E T H O D SDetails of the experimental design are shown in Table 1. Twelve healthy male volunteers (mean age 23 (SE 2) years, weight 72 (SE 7) kg, height I .82 (SE 0...

A double-blind study on the effects of vitamin C restriction on physical performance was executed with 12 healthy men. During seven weeks of low vitamin C intake six subjects were on a daily diet of regular food products, providing 20% of the Dutch Recommended Dietary Allowances (RDA) for vitamin C (Dutch RDA is 50 mg/day). Other vitamins were supplemented at twice the RDA level. After three weeks of low vitamin intake an additional vitamin C dose of 15 mg/day was provided, resulting in a total intake of 25 mg/day (50% of the Dutch RDA). Six control subjects consumed the same diet supplemented with twice the RDA for all vitamins. In the restriction group blood vitamin C levels decreased significantly (p less than 0.01). Vitamin C restriction had no harmful effects on health, aerobic power (VO2-max), and onset of blood lactate accumulation (OBLA). However, an increased heart rate at OBLA level was observed during the period of low vitamin C intake (p less than 0.05), possibly by interference with either catecholamine or carnitine metabolism. These results suggest that short-term marginal vitamin C deficiency does not affect physical performance in single bouts of intensive exercise.