The alpha-linolenic acid in walnuts can have a positive effect on reducing LDL cholesterol levels, according to a study from Japan published this week in the July issue of the European Journal of Clinical Nutrition.
Researchers from Kyushu University, led by M Iwamoto, focused on 20 healthy women and 20 healthy men, randomly assigning them to one of two groups. One group was fed a 'normal' healthy diet, while the other was fed a diet rich in walnuts (with 12.5 per cent of the energy derived from 44-58 grams of walnuts per day).
Iwamoto's team discovered that the total cholesterol and serum apolipoprotein B concentrations were significantly lower in men and women when fed the walnut diet, as was the ratio of LDL cholesterol to HDL cholesterol. Women (10.6 per cent) showed a greater reduction in LDL cholesterol levels than men (8.9 per cent) when both followed the walnut diet. Total cholesterol was lowered by 3.8 per cent in men and 4.9 per cent in women
The researchers also found that the most prominent change was in the elevation of alpha-linolenic acid in women (76 per cent) and men (107 per cent), and it was this elevation which was thought to aid the reduction in LDL or 'bad' cholesterol levels. There was no significant change in HDL or 'good' cholesterol levels.
The California Walnut Commission, which sponsored the research, said the findings were the final part of a series of three clinical trials testing the effect of walnuts in cholesterol-lowering Western, Mediterranean and Asian diets. "The results show that walnuts improve the three major diet styles, lowering bad cholesterol significantly in every instance. These studies, in combination with a growing body of other clinical research, show walnuts to be a powerful nutrition package," the Commission said in a statement.