Functional foods are specifically produced to contain certain nutrients that have known and specific beneficial effects. For example, the addition of folic acid to bread produced a functional food designed to reduced the risk of neural tube defects during pregnancy. Other examples include specific cultivars of broccoli selected for their high glucosinolate content in order to reduce cancer risk, and vitamin D fortified milk to prevent vitamin D deficiencies. The addition of certain nuts to create a functional food could be beneficial because nuts have some useful affects on human metabolism that could provide long term health benefits. Of the true tree nuts, walnuts have shown promising effects on blood lipid levels, possibly due to their high α-linolenic acid (ALA, C18:3 (n-3)) content. Evidence suggests that eating as little as 42g of walnuts per day could decrease the risk of cardiovascular disease.
Researchers1 have investigated the effects a functional food containing walnuts on blood lipid levels using a crossover single dose placebo controlled design study. For 5 weeks, 25 subjects were fed a regular meat product, with or without added walnuts, followed by a 1 month washout period. The subjects then crossed over to the alternative treatment. Diet records were used throughout to ensure compliance with the study and also to allow researchers to identify possible confounding variables, should they arise. The results showed that subjects consuming the walnut fortified meat product experienced a 6.8mg/dL decrease in total cholesterol when compared to the unfortified meat product. When compared to a normal mixed diet by using the baseline measurements, fortified walnut meat reduced total cholesterol by 10.7mg/dL, low density lipoprotein (LDL) cholesterol by 7.6mg/dL and decreased body weight by 0.5kg.
These results show that the addition of walnuts to the diet, through the incorporation of a walnut containing functional food, could reduce the risk of cardiovascular disease. This 4.5% reduction in cholesterol compared to the baseline diet, and 3% compared to the meat diet, is substantial considering the small changes necessary to implement the improvement. The researchers could measure the compliance of the subjects by analysing plasma γ-tocopherol levels, walnuts being a good source of this isoform of vitamin E. This is interesting because raised plasma levels of γ-tocopherol may also be protective of cardiovascular disease through the increased antioxidant activity of plasma phospholipids. The loss of weight by the subjects is interesting as no calorie restriction or weight loss plan was incorporated into the study method. This weight loss might be the cause of the decrease in blood lipid levels, as has been shown in previous research.
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