Dutch dietary guidelines: impact on blood lipids, blood pressure, body composition and urinary mineral excretion of Dutch middle-aged men.

In this study the impact of the Dutch dietary guidelines diet on various health status parameters was examined. Twelve apparently healthy men aged 35-52 years were given both the guidelines diet (G) and the 'average' Dutch diet (D) in a controlled eight-week study period with a cross-over design. Compared with the D diet, the G diet contained less fat (accounting for 35 per cent vs 44 per cent of total energy intake), about half the amounts of saturated and monounsaturated fatty acids and twice the amount of polyunsaturated fatty acids. The G diet was given either as a high-sugar or as a low-sugar variant (25 per cent and 15 per cent of total daily energy intake, respectively). Serum total, LDL- and HDL-cholesterol decreased during the four-week G diet from 5.76 to 4.99, from 3.95 to 3.35 and from 1.13 to 1.03 mmol/l respectively. Also the apo-lipoprotein A-I, A-II and B concentrations decreased in subjects on the G diet. Blood pressure and body composition did not change significantly. Urinary pH and the excretion of sodium and potassium were significantly lower for the G diet. It is concluded that the combined factors in the Dutch guidelines diet, irrespective of amount of sugar, has favourable effects on total and LDL-cholesterol levels, whereas the decrease of the concentrations of HDL-cholesterol and of apo-A-I and A-II is less desirable. The changes in urinary mineral excretion, in particular of sodium, during the G-diet is considered as a positive effect.

Controlled vitamin C restriction and physical performance in volunteers.

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.

Thiamin, riboflavin, and vitamins B-6 and C: impact of combined restricted intake on functional performance in man.

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.

The effects of a high-animal- and a high-vegetable-protein diet on mineral balance and bowel function of young men.

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 mumol/d). 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 significant influence on mineral retention.

Physiological effects of fibre-rich types of bread. 1. The effect of dietary fibre from bread on the mineral balance of young men.

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 ad 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 less than 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) 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 less than 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/l, 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.