The truth about soy protein

Anthony Barnett (Observer Food Monthly)

After a huge lobbying effort from the soya industry, the US Food and Drug Administration agreed to issue a health claim that eating 25g of soya protein a day can help lower cholesterol and thus reduce the risk of heart disease. This was a view later backed by Britain's Food Standards Agency.

With heart disease one of the biggest killers in the West, this is clearly a major benefit for soya and has allowed many food companies to stamp labels on soya products claiming they help reduce cholesterol.

In such a health and diet-obsessed culture this has been a big boost for the soya industry.

Yet for two senior food scientists who worked within the US Food and Drug Administration, the official backing of the health claim - which ignored the impact of plant-oestrogens in soya - was potentially dangerous.

In a highly unusual move Dr Daniel Sheehan and Dr Daniel Doerge wrote a letter of protest to the department of Health and Human Services at the FDA denouncing the claim, concerned that the problems of soya consumption were being ignored.

An extract from their letter seen by Observer Food Monthly states: 'We oppose this health claim because there is abundant evidence that some of the isoflavones [phytoestrogens] found in soy demonstrate toxicity in oestrogen-sensitive tissues and in the thyroid. This is true for a number of species, including humans. Additionally, the adverse effects in humans occur in several tissues and, apparently, by several distinct mechanisms...Thus, during pregnancy in humans, isoflavones per se could be a risk factor for abnormal brain and reproductive tract development.'

It added: 'There exists a significant body of animal data that demonstrates goitrogenic [effect on the thyroid gland] and even carcinogenic effects of soy products.'

Sheehan was particularly concerned about the increasing number of babies been weaned on soya infant formula. 'We are doing a large uncontrolled and unmonitored experiment on human infants,' he said.

OFM contacted the scientists but was told they are not allowed to comment publicly on the health risks of soya.

Doerge suggested speaking to another expert Dr Bill Helferich, a professor of food at the University of Illinois who has discovered a possible link between the growth of certain breast cancer tumours that require oestrogen and the chemicals found in soya.

Helferich was unwilling to comment on whether a woman at risk of such a cancer should stop eating soya products. But, when asked what the health implications were of increasing amounts of soya in the Western diet, he told OFM : 'It's like roulette. We just don't know.'

It is not just across the Atlantic that the increased consumption of soya has concerned authorities. In Britain, the Food Standards Agency commissioned a report from its Committee on Toxicity of Chemicals in Food to look at the issue. Published in May 2003, and titled Phytoestrogens and Health, the cover of this 400-page tome is illustrated with a soya plant.

In its introduction the report states: 'In 1940 adverse effects on fertility were observed in animals that had been grazing on phytoestrogen-rich plants. In the early 1980s it became clear that phytoestrogens could produce biological effects in humans.'

What follows is a highly complex and comprehensive analysis of every scientific study ever carried out on the subject of plant oestrogens. The scope is immense: interaction with immune systems, central nervous systems, thyroid glands and cardiovascular systems. It analyses evidence for and against the impact of these soya chemicals on breast cancer, prostate cancer, stomach cancer, colorectal cancer and lung cancer.

The findings are inconclusive. Some case studies find soya reduces the risk of one cancer, but possibly increases the risk of another.

Professor Frank Woods was the chair man of the working group that produced this report. He is one of the country's leading toxologists and has been a key government adviser. If anybody can be called an expert on soya, it is him. Yet even he will not be drawn on whether the increase in soya in Western diets is good or bad.

'We still have a lot to learn,' he said. There is, however, one area where his mind is made up. 'If my daughter ever asked me advice on whether she should feed her baby on soya formula, I would say no, unless her doctor had specifically advised her to do so.' Even if the the baby had an allergy to dairy products, he believes that other options, such as hydrolysed cow's milk protein, are safer.

'Soya has been eaten for thousands of years as a mainstay of Asian diets,' said Dominic Dyer of Britain's Soya Protein Association. 'There is no evidence of reduced fertility in these populations or an increased risk in any other of these problems allegedly related to soya. Indeed the opposite is true. They are healthier, live longer and have less chance of dying from diseases like breast cancer.'

This is a powerful argument in soya's favour but scientists such as Professor Woods, who studied this issue as part of the FSA's report, says it is far more complex than just attributing these facts to the intake of soya in their diets.

US nutritionist Kaayla T Daniel who has studied the history of soya consumption dismisses the comparison, arguing that the soya eaten in China and Japan, such as tofu and miso, is very different from the industrially processed variety used in today's Western food. 'Claims that soya beans have been a major part of the Asian diet for more than 3,000 years, or from "time immemorial" are simply not true,' she said.

The soya bean originated in China, and according to Daniel the ancient Chinese called it 'the yellow jewel' but used it as 'green manure' to enrich the soil for growing other crops.

She says soya did not become a staple human food until late in the Chou Dynasty in 1134 BC when the Chinese developed a fermentation process to turn the bean into a paste best know by its Japanese name miso. The liquid poured off during this production of miso is what is known as soya sauce.

She claims that the traditional process of making fermented soya products like tofu or tempeh destroys many of the allegedly dangerous chemicals in soya, unlike modern factory methods used today.