**3. Conclusions and future directions**

administration of PUFA and other nutrients contained in nuts, such as antioxidant vitamins and arginine [179]. Another feeding trial showed that, compared with an isoenergetic Mediterranean diet with similar saturated fatty acid content, a walnut diet attenuated the endothelial dysfunction associated with hypercholesterolemia [199]. Moreover, changes in circulating levels of cellular adhesion molecules critical to leukocyte recruitment on the arterial wall also reflect endothelial dysfunction [201]. Several studies have shown that diets enriched with ALA from walnuts [197, 199, 206] reduce endothelial activation as assessed by decreased plasma cellular adhesion molecules. Walnut feeding also reduced the expression of endothelin-1, a potent endothelial activator in an animal model of accelerat‐

As the interest in incorporating nuts into the diet grows, it is important that consumers understand how to include them in a healthy diet without promoting weight gain. They are high-fat, energy dense foods and are therefore a potential threat for contributing to positive energy balance. Numerous epidemiological and clinical studies have shown that nuts are not associated with higher body weight [208, 209] or weight gain [210-215]. This could be attributed along with other potential mechanisms for the high satiety properties of nuts [216]. The enhanced satiety, which is also achieved via other mechanisms such as the decreased eating rate [217], leads to reduced energy consumption and therefore a

Blomhoff et al. [190] argued that the inverse association between nut intake and cardiovascular and coronary heart diseases in epidemiological studies may, or may not, be associated with antioxidants. According to these authors, epidemiologic studies are not ideally suited for studying the role of specific nuts or biological mechanisms. Nevertheless, they are in agree‐ ment with findings supporting the theory that a complex and rich mix of nut constituents is

Epidemiologic and clinical trial evidence has demonstrated the beneficial effect of nut consumption on coronary heart disease and its associated risk factors. The cardioprotective properties of nuts, due partially to their favourable lipid fatty acid profile (rich in unsaturated fatty acids), exceed the LDL-C lowering. Nuts, especially walnuts, contain (n-3) PUFAs, which have been shown to have a favourable impact on multiple factors related to CVD, such as inflammation, platelet function, arrhythmias, hypertriglyceridemia and nitric oxide-induced endothelial relaxation [218]. Nuts are also excellent sources of other bioactive compounds such as vegetable protein, dietary fibre, potassium, calcium, magnesium, tocopherols, phytosterols, phenolic compounds, resveratrol and arginine [179]. This unique nutrient composition explains the benefits of nut consumption for the prevention of CVD through mechanisms of

able to offer protection against CVD and perhaps other chronic diseases [183].

ed atherosclerosis [207].

*2.2.4. Effects on body weight changes*

220 Antioxidant-Antidiabetic Agents and Human Health

decreased risk of weight gain and obesity.

*2.2.5. Possible mechanism(s) of action*

oxidation, inflammation and vascular reactivity.

Investigation of the mechanisms underlying CVD showed that the disease has a complex cause beyond the accumulation of cholesterol on the arterial wall, with enhanced oxidative stress and a prominent inflammatory response. Diet has been shown to be associated with cardio‐ vascular events. PUFAs are essential in our diet because we cannot synthesize them. They are also essential nutrients for optimal health of the cardiovascular, nervous and undoubtedly other organ systems. Dietary (n-3) PUFAs are incorporated into the cellular membranes of all tissues. The extent of incorporation into tissue membranes is dependent on dietary intake. The enrichment of membranes with (n-3) PUFAs can modulate cellular signalling events, mem‐ brane protein function and gene expression.

Interest in the possible health benefits of flavonoids has increased owing to their potent antioxidant and free-radical scavenging activities observed *in vitro*. There is growing evidence from human feeding studies that the absorption and bioavailability of specific flavonoids is much higher than originally believed. However, epidemiologic studies exploring the role of flavonoids in human health have been inconclusive. Some studies support a protective effect of flavonoid consumption in CVD and cancer; other studies demonstrate no effect and a few studies suggest potential harm. More recently, results from human studies provide evidence that rooibos can offer protection against oxidative stress conditions such as CVD [131,219]. In a study by Pantsi et al., the beneficial effects of dietary rooibos flavonoids were observed *ex vivo* in isolated perfused rat hearts. Epidemiological studies suggest that the beneficial cardiovascular health effects of diets rich in fruit and vegetables are in part mediated by their flavonoid content, with particular benefits provided by one member of this family, the flavonols [49].

Polyphenols are abundant micronutrients in our diet and evidence for their role in the prevention of degenerative diseases is emerging. Bioavailability differs greatly from one polyphenol to another, so the most abundant polyphenols in our diet are not necessarily those leading to the highest concentrations of active metabolites in target tissues. Because there are many biological activities attributed to the flavonoids, some of which could be beneficial or detrimental depending on specific circumstances, further studies in both the laboratory and with populations are warranted.

However, the fatty acid components of nuts may differently influence oxidation processes and this needs to be considered for the synergy or opposition to the effects of constituent antioxi‐ dants. There is growing evidence that dietary polyphenols in nuts, tea and wine may have anti-inflammatory effects, mediated by both their antioxidant action and modulation of signal transduction pathways, such as the nuclear transcription factor kB, with ensuing downregulation of inflammatory genes in endothelial cells and macrophages [220]. The increased diversity and availability of sources of dietary fatty acids will likely allow the continued expansion of food products fortified with these fatty acids, a trend that may result in the attainment of the recommended dietary intake of these nutrients.

Future studies in oils should be carried out in order to elucidate the effects of oils in various models in which effects remain unknown. Little is known about the effects of nuts on a diseased heart. Studies should be performed to test whether nuts may offer protection against the severity or progression of various models of CVD.

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