Scientists have emphasized what most vegetarians have known for ages soy products will give you lower cholesterol levels than will animal protein.
Researchers from the University of Kentucky in the US have analyzed 38 scientific studies to confirm that a diet of vegetable or soy protein will dramatically reduce levels of cholesterol in the blood, as opposed to a diet rich in animal protein.
The object of the exercise seems to be to redress a statement made by the the American Heart Association. Two years ago the Association announced that soy protein decreases cholesterol levels in rabbits, but not in humans. This was a surprising pronouncement, as only one of the 38 studies had drawn this conclusion; 34 studies came out with definitive evidence suggesting the benefits of a soy protein diet among humans. The other four that did not agree were studying people who had low cholesterol levels to begin with.
Overall, a daily intake of between 31 and 47 g of soy protein will significantly reduce serum cholesterol; 25 to 50 g of soy protein a
day would decrease serum cholesterol concentrations by 8.9 or 17.4 mg per deciliter, respectively.
These amounts are easily found. For instance, 8 oz of soy milk contains 4 to 10 g of soy protein; 4 oz of tofu has 8 to 13 g of protein. So, by substituting two cups (473 ml) of soy milk for regular milk, and by eating one serving of soy meat substitute, you would be getting the requisite 30 g of soy protein a day (NEJM, August 3, 1995).
But even if this is done, are the benefits worth it? The jury is still out, according to one study. Scientists from the Royal Free Hospital in London reckon that, overall, lower cholesterol is a good thing. But the US National Institute on Aging in Bethesda, in Maryland, feels that there are few benefits for men, although lower levels may help women.
There is evidence to indicate that lower cholesterol levels may be linked to cancer and other diseases, but the Royal Free researchers believe any dangers are outweighed by positive benefits.
They tracked the health of 7,735 men for nearly 15 years, regularly checking their cholesterol levels. Low cholesterol levels, present in about 5 per cent of the men, were linked with the highest death rate from all causes, most significantly cancer. But once adjustments were made for lifestyle habits, such as heavy drinking and smoking, the risks were not significant. However, low cholesterol levels helped to reduce the threat of heart conditions, even after 10 years of follow-up (BMJ, August 12, 1995).
The American study, which tracked 2,527 women and 1,377 men, was not so sure. They found little evidence to link high cholesterol levels with heart problems, and they doubted the wisdom of trying to lower levels, which tend to rise anyway among older people (JAMA, August 16, 1995).