Nut have been extensively investigated for their health effects in both humans and animals. Evidence suggest that consumption of nuts has a number of protective effects against disease. In particular nuts appear to have protective effects against cardiovascular disease. However, despite strong evidence that nuts are protective of cardiovascular disease from clinical trials, no single mechanism exists to explain the reason for this benefit. Of course, this may be due to the fact that nuts are protective of cardiovascular disease through multiple mechanisms. While Animal studies have limitations in terms of their applicability to human physiology, they can be useful at understanding the mechanisms of action with relation to previously observed phenomena. In this respect a more detailed understanding of the mechanisms by which nuts are protective of cardiovascular disease has been provided through feeding studies involving rats. Rats like nuts and so getting them to eat large amounts does not take much persuasion.
For example, in one study1, researchers investigated the effects of supplementary almonds in rats that were fed diets designed to induce dyslipidemia. In particular, the rats were administered tyloxapol, a chemical used to induce elevated levels of plasma lipids in experimental animals through activation of the β-hydroxy-β-methylglutaryl coenzyme A enzyme, or a high fat diet that was used to alter hepatic fat metabolism. Almond supplements inhibited the synthesis of cholesterol (by 65 %) following elevation by administration of tyloxapol. In addition, the almonds were effective at reducing the serum concentrations of aminotransferase (by 56 %), that had been caused by consumption of the high fat diet. The high fat diet also induced high levels of uric acid, phosphorus, alkaline phosphatase and γ-glutamyltransferase, and the almonds significantly lowered these elevated levels to pre-treatment levels. These data suggest that almonds may be protective of the dyslipidaemia
Nuts may be protective of the metabolic syndrome because they have insulin sensitising effects, but these results suggest that they may also be useful at treating the dyslipidaemia that exists once the metabolic syndrome had developed. The researchers also observed that almonds were effective at preventing the inhibition of nitric oxide synthase in isolated aortas, and were also effective at preventing endothelial dysfunction. Nuts have been previously been shown to prevent endothelial dysfunction, most likely because of the antioxidants they contain. These antioxidants inhibits the oxidative stress that inhibits the nitric oxide synthase enzyme, and this allows the production of nitric oxide to proceed. As nitric oxide is essential to the flow mediated dilation of arteries, nut antioxidants may allow the correct function of the endothelium of arteries. In rats at least, nuts therefore appear to display multiple mechanisms by which they may protect from cardiovascular disease.
Dr Robert Barrington’s Comments: Nuts are a healthy food and contain a wide range of nutrients that are beneficial to the health. Nuts are likely protective of cardiovascular disease because they contain essential fats, vitamins and minerals as well as phytonutrient antioxidants. The antioxidants in nuts may protect the endothelium of the arteries from nitric oxide deficient dysfunction. In addition, various components of nuts may also inhibit cholesterol synthesis and modulate fatty acid synthesis rates in hepatic tissue. Nuts may also provide a protective effect against liver damaged caused by fatty acid accumulation in hepatic tissues. In fact in this study the consumption of almonds by the rats decreased liver enzymes associated with hepatic tissue damage. Nuts therefore appear to have multiple mechanisms by which they are protective of some of the metabolic changes associated with metabolic syndrome and this may explain their protective effects against cardiovascular disease.