Effect of a diet high in vegetables, fruit, and nuts on serum lipids.

We assessed the effect of a diet high in leafy and green vegetables, fruit, and nuts on serum lipid risk factors for cardiovascular disease. Ten healthy volunteers (seven men and three women aged 33 +/- 4 years [mean +/- SEM]; body mass index, 23 +/- 1 kg/m2) consumed their habitual diet (control diet, 29% +/- 2% fat calories) and a diet consisting largely of leafy and other low-calorie vegetables, fruit, and nuts (vegetable diet, 25% +/- 3% fat calories) for two 2-week periods in a randomized crossover design. After 2 weeks on the vegetable diet, lipid risk factors for cardiovascular disease were significantly reduced by comparison with the control diet (low-density lipoprotein [LDL] cholesterol, 33% +/- 4%, P < .001; ratio of total to high-density lipoprotein [HDL] cholesterol, 21% +/- 4%, P < .001; apolipoprotein [apo] B:A-I, 23% +/- 2%, P < .001; and lipoprotein (a) [Lp(a)], 24% +/- 9%, P = .031). The reduction in apo B was related to increased intakes of soluble fiber (r = .84, P = .003) and vegetable protein (r = -.65, P = .041). On the vegetable compared with the control diet, the reduction in total serum cholesterol was 34% to 49% greater than would be predicted by differences in dietary fat and cholesterol. A diet consisting largely of low-calorie vegetables and fruit and nuts markedly reduced lipid risk factors for cardiovascular disease. Several aspects of such diets, which may have been consumed early in human evolution, have implications for cardiovascular disease prevention.

Method of administration influences the serum cholesterol-lowering effect of psyllium.

To determine whether psyllium must be mixed with food to lower serum cholesterol, 18 modestly hypercholesterolemic subjects were studied for three 2-wk periods, in random order, separated by a 2-wk return to a National Cholesterol Education Program Step 2 diet. Compared with values for subjects consuming control wheat-bran cereal (63 g/d), after 2 wk of 54 g psyllium-enriched cereal/d containing 7.3 g psyllium, serum total, LDL, and HDL cholesterol, respectively, were reduced by 8% (6.15 +/- 0.15 vs 6.71 +/- 0.19 mmol/L, P < 0.01), 11% (4.24 +/- 0.15 vs 4.78 +/- 0.19 mmol/L, P < 0.02), and 7% (0.99 +/- 0.05 vs 1.07 +/- 0.05 mmol/L, P < 0.01). When 7.6 g of the same type of psyllium as in the test cereal was taken between meals, serum total (6.50 +/- 0.19 mmol/L), LDL (4.50 +/- 0.21 mmol/L), and HDL (1.06 +/- 0.06 mmol/L) cholesterol were no different from control values, and total cholesterol was greater than after psyllium cereal (P < 0.05). We conclude that psyllium must be mixed with foods to have the maximum effect on serum cholesterol.

Effect on blood lipids of very high intakes of fiber in diets low in saturated fat and cholesterol.

BACKGROUND: It is known that soluble fiber in the diet can lower blood lipid levels. It is less certain, however, that eating foods with soluble fiber will further lower blood lipids when the intake of saturated fat and cholesterol has already been reduced to very low levels. Furthermore, the mechanism of the lipid-lowering effect of fiber has not been elucidated. METHODS: To address these questions, we studied 43 volunteers with hyperlipidemia in a crossover study involving two four-month dietary periods. The two metabolic diets contained foods high in either soluble or insoluble fiber and were separated by a two-month National Cholesterol Education Program Step 2 diet. The metabolic diets were low in saturated fat (< 4 percent of total calories) and cholesterol (< 25 mg per 1000 kcal), high in carbohydrate (> or = 60 percent of total calories), and very high in fiber (> 24 g per 1000 kcal). RESULTS: Blood lipids fell to their lowest levels by week 4 of both study diets. When the soluble-fiber period was compared with the insoluble-fiber period, the subjects' total, low-density lipoprotein (LDL), and high-density lipoprotein (HDL) cholesterol levels were found to be lower by a mean (+/- SE) of 4.9 +/- 0.9 percent (P < 0.001), 4.8 +/- 1.3 percent (P < 0.001), and 3.4 +/- 1.3 percent (P = 0.014), respectively. In contrast, the ratio of total to HDL cholesterol was not significantly different during the two dietary periods. The loss of fecal bile acids was 83 +/- 14 percent greater during the soluble-fiber period than during the insoluble-fiber period (P < 0.001) and was related to the differences in total and LDL cholesterol and apolipoprotein B levels (r = 0.42, P = 0.005; r = 0.49, P < 0.001; and r = 0.33, P = 0.035, respectively). The difference in serum cholesterol levels between the two dietary periods was greater among the men (7.5 +/- 1.2 percent, P < 0.001) than among the women (3.4 +/- 1.2 percent, P = 0.008). CONCLUSIONS: Very high intakes of foods rich in soluble fiber lower blood cholesterol levels even when the main dietary modifiers of blood lipids--namely, saturated fat and cholesterol--are greatly reduced.