[Fifth Jesús Culebras Lecture; Tree nuts: effects on health, obesity and metabolic syndrome]

Several epidemiological studies have shown that consumption of tree nuts is associated with lower cardiovascular risk, specific cause of mortality and total mortality. Clinical feeding trials have demonstrated that tree nuts protect from cardiovascular disease risk through different mechanisms: regulating inflammatory processes, oxidative stress and endothelial function, thereby improving various cardiovascular risk factors. In the context of meals high in carbohydrates, tree nuts reduce the postprandial glucose peaks, improving insulin resistance. Frequent consumption of nuts has been associated with a lower risk of diabetes in women, but the effect was not yet elucidated in men. Although tree nuts are energetically dense and they are high in fat, nut consumption does not imply appreciable weight gain nor has been associated with a higher risk of abdominal obesity. Tree nut consumption reduces LDL cholesterol levels, but its effects on atherogenic dyslipidemia associated to metabolic syndrome (MetS) are less clear. The effect of consumption of nuts on LDL cholesterol in subjects with MetS neither has been well established, but it seems that in these patients could lower plasma triglyceride levels. Some studies suggest an inverse association between tree nut consumption and blood pressure or endothelial function, especially in non-diabetic individuals. Nut consumption was inversely related to the prevalence and incidence of MetS. Including tree nuts in the context of a healthy dietary pattern way increase the health benefits. It has been observed a lower prevalence of MetS and a lower incidence of diabetes in people who adhered to a Mediterranean diet supplemented with nuts. Future nutrition intervention studies are needed on large samples of subjects and long follow-up to affirm that tree nut consumption has beneficial effects on the prevention and treatment of MetS.