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A Cracker of a Nut
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Walnuts appear protective against heart disease

Professor Geoffrey Savage, Food Group, Lincoln University.

Walnuts are now seen as an important food that has a protective effect against heart disease. The fact that an increased intake of walnuts improves rather than impairs lipid profiles in the blood is now clear from the results of a number of human trials on normal, hyperlipidaemic and diabetic subjects.

A recent study in Australia of 58 adults suffering from Type 2 diabetes showed that the consumption of 30 g of walnut kernels per day (about eight whole walnuts in the shell) resulted in a 10% fall in low density lipoprotein cholesterol in the blood and a significant improvement (an increase of 30%) in the high density lipoprotein cholesterol.

An even more interesting study was carried out recently in Spain on people who had moderately high blood cholesterol levels. A diet supplemented with 10 whole walnuts per day was compared with a control Mediterranean diet which contained olive oil, olives and avocados. The people who ate the walnut containing diets had significantly improved endothelium-dependent vasodilation (this a measure of the artery's ability to keep the blood vessels healthy by maintaining their ability to widen).

Exactly why walnuts have all of these positive effects is still a matter of conjecture. It is quite clear that the mono- and poly-unsaturated fatty acid content of walnut oil are important factors. Walnut oil contains over 60% polyunsaturated fatty acids, higher than any other nut oil, and more modest levels of monounsaturated fatty acids at 18%. As well as containing these lipids, walnut oil is nutrient dense and contains significant amounts of antioxidants such as vitamin E, phytosterols and polyphenols. Whole nuts also contain essential minerals such as magnesium, potassium and copper as well as dietary fibre.

Find out more:

Why you should eat walnuts      Walnuts protect arteries