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Research in the nineties indicated that nuts were good for heart health but the reason for that was unknown. Recent studies are shedding light on the matter and finding other benefits of nut consumption?
In the early nineties a large population study made the surprising finding that eating a portion of nuts more than once a week appeared to offer protection against heart attack and stroke - and the more frequently nuts were consumed the greater the protection. Other studies consistently confirmed these early findings and found that nuts had a positive effect on heart health in men, women, the elderly and those with or without high blood pressure.1 As nuts are a high fat food (about 80% of calories in nuts come from fat) this was an intriguing finding and scientists set out to discover what constituents of nuts might be responsible, and how they exert their beneficial effects in the body.

Good fats in a nut

Most of the fats in nuts are high in beneficial monounsaturated and polyunsaturated fats and low in cholesterol-raising saturated fats. Monounsaturated and in particular polyunsaturated fats lower LDL-cholesterol (bad cholesterol) and blood lipid levels. But even after taking the positive fat profile of nuts into account, it has been found they have a greater cholesterol-lowering ability than would be expected. Also because of the apparent benefits of even a modest consumption of nuts, it is likely that nuts exert effects beyond the reduction of cholesterol levels.

Full of nutrients and other beneficial components

Apart from useful fats, proteins and fibre, each type of nut is packed with its own particular mix of vitamins and minerals. Most nuts contain useful amounts of vitamin E, a powerful antioxidant that neutralises free radicals and prevents them from attacking healthy cells; folic acid, which is important for preventing elevated homocysteine (an amino acid in the blood) concentrations (another risk factor for heart disease); and magnesium, involved in the control of blood pressure. Nuts also contain a host of other beneficial compounds such as plant sterols, phytoestrogens, and other phytonutrients, all of which may contribute to heart health.

Anti-inflammatory action

One recent suggestion is that nuts may help to reduce inflammation of the arteries, an early sign of heart disease. Nuts are particularly rich in arginine, an amino acid from protein. Arginine is needed to produce nitric oxide, which in turn helps arteries and other blood vessels to relax, dilate and encourage good blood flow. A recent Spanish study found that a walnut-rich diet helped reduce arterial inflammation and could counteract the effects of a fat-rich meal.2,3 It was not clear whether the polyunsaturated fats (walnuts are rich in omega 3 fatty acids), the arginine, the antioxidants, or a combination of all three were responsible for protecting the blood vessels.

Protection against other diseases

There is evidence that frequent nut consumption is associated with a lower risk of type 2 diabetes mellitus, otherwise known as maturity onset diabetes. Again anti-inflammatory activity is thought to be the reason.4 There is also some speculation that nuts may be protective against certain cancers. For example the European Prospective Investigation into Cancer and Nutrition (EPIC) found that the more nuts and seeds women consumed the lower their risk of colon cancer. There was no association found in men.5

Nut intake

Consuming a handful of mixed nuts a few times a week is good for your health, however there are a few caveats. As nuts are high in calories they should be used to replace something less wholesome, not simply added on top. It is also best to consume nuts in their natural raw state. Roasting or frying may reduce the power of the active ingredients and salted varieties should be eaten in moderation, particularly if you need to watch your salt intake. Finally some people are allergic to tree nuts (Brazil nuts, almonds, hazelnuts etc) or peanuts* (groundnuts) but not usually to both. As nut allergy can result in anaphylactic shock, the offending nuts, and all foods containing any trace of them, must be avoided.

*Peanuts are not true nuts, they are in fact legumes, like a pea or a bean. However they are nutritionally comparable to a nut and seem to be as good for us as tree nuts.

References

1. Sabate J. (1999). Nut consumption, vegetarian diets, ischemic heart disease and all-cause mortality: evidence from
epidemiologic studies. American Journal of Clinical Nutrition 70; 500S-503S
2. Jiang R. et al (2006). Nut and seed consumption and inflammatory markers in the multi-ethnic study of atherosclerosis.
American Journal of Epidemiology 163;222-231
3. Cortes B. et al (2006). Acute effects of high fat meals enriched with walnuts or olive oil on post-prandial endothelial function.
Journal of the American College of Cardiology 48;1666-1671
4. Jiang R. et al (2002). Nut and peanut butter consumption and risk of type 2 diabetes in women. Journal of the American Medical
Association. 288;1544-2560
5. Jenab M. et al (2004). Association of nut and seed intake with colorectal cancer risk in the European Prospective Investigation
into Cancer and Nutrition. Cancer Epidemiology, Biomarkers and Prevention 13;1595-1603