Event Report | Soya’s Health Benefits
Soya and Heart Disease The benefits of soya in heart health have been well documented over the years. As a result of its beneficial action in lowering LDL cholesterol, a number of countries have allowed a cholesterol lowering health claim for soya protein. Recently, however, the degree to which soya protein reduces cholesterol has been questioned. For this reason Dr James Anderson from the University of Kentucky, analysed the results of 42 studies published since 1995 when his first meta-analysis showing the beneficial effect of soya protein on cholesterol levels was published. He also took into account the quality of the study design. When all the results were pooled together he found that soya protein reduced LDL cholesterol by approximately 5% with higher quality studies resulting in even greater reductions. Furthermore, soya protein also increased HDL cholesterol by 3.2% and reduced triglycerides by 9.8%. As a result, Dr Anderson estimated that approximately 15 to 25g of soya protein could reduce the risk of cardiovascular disease by up to 24%. As well as this direct effect of soya protein on
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...triglycerides by 9.8%. As a result, Dr Anderson estimated that approximately 15 to 25g of soya protein could reduce the risk of Cardiovascular Disease by up to 24%.
56 | Complete Nutrition Vol.10 No.6 December/January 2010/11 ’
LDL cholesterol, it’s been suggested that including soya foods into the diet, at the expense of animal proteins, can have an additional benefit on LDL cholesterol. This indirect effect would be due to the reduction of saturated fats in the diet and an increase in polyunsaturated fats. To quantify this, Dr Berryman from Pennsylvania State University presented results from a study where animal protein in a typical American’s diet was substituted for soya protein. Substituting foods containing 13 to 57.8g of soya protein (e.g. from soya milk) for similar foods containing animal protein (e.g. cows’ milk) resulted in a decrease in saturated fat (12.1g), cholesterol (113mg), and monounsaturated fat (3.0g) and an increase in polyunsaturated fat (4.9g). These changes are predicted to further reduce LDL cholesterol by between 3 to 6%.
Dr Jenkins from the University of Toronto
explained that as soya should be considered within the context of a diet, it’s important to consider both the direct and indirect effect of soya protein on cholesterol. In this way Dr Jenkins concluded that soya protein could reduce LDL cholesterol by approximately 10%, a reduction that is clinically significant.
Soya and the Menopause –
Hot Flushes Soya naturally contains compounds called isoflavones which show structural similarities to oestrogen. As such it’s thought they may help to relieve symptoms of the menopause including hot flushes. To date, results from studies examining this have been inconsistent. However Professor Kurzer from the University of Minnesota now has conclusive data to show that soya isoflavones significantly reduce both the number of hot flushes and the severity. She analysed data from 16 trials using between 30 to 100mg of isoflavones a day. Hot flush frequency was reduced by around one fifth and severity was reduced by nearly one third compared to groups who took a placebo. However, when the placebo effect was also taken into account, both the number of hot flushes and the severity was reduced by about a half (50%).
Soya and Breast Cancer There has been some controversy over soya and breast cancer. On the one hand, there is evidence from human studies to suggest that eating soya early in life can protect girls from breast cancer later in life. On the other, it has been questioned whether soya is safe to eat in women at risk of breast cancer and among breast cancer patients. Dr Messina, Associate Professor at Loma Linda University explained that the controversy is largely based on animal studies and that these animals couldn’t be used to determine what ‘might’ happen in humans. This was confirmed by Professor
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