SOY BEANS
Soybeans and soy products (tofu, tempeh, soy
drink and other soy foods) are the nutritional powerhouse of the legume
family. A staple of Asian diets for thousands of years, they have long
been a mainstay of vegetarian and vegan diets. They are an excellent
source of protein, and rich in fibre, iron, zinc and B vitamins. They
are lower in carbohydrate and higher in fat than other legumes, the
majority of the fat is polyunsaturated.
On the whole, soy foods have not played a major role in the
typical Western diet. In contrast, soy is regularly consumed by many
Asians at all stages of life from weaning to old age. It’s this
difference in levels of soy consumption that got the ball rolling in soy
research says Dr Joanna McMillan. “Scientists found that levels of
heart disease and many cancers, including breast cancer, were far lower
in these soy-eating Asian countries, compared to levels in the West.
Numerous studies followed to try to identify what it was about soy that
might be protective,” she says.
“Research has centred
on two aspects of soy – soy protein and compounds found in soy called
isoflavones. Isoflavones are phytoestrogens (meaning ‘plant oestrogen’)
and are similar in structure to the hormone oestrogen. These
phytoestrogens can act in two ways:
- They can act like oestrogen. This may be beneficial during menopause for example, when natural oestrogen levels are dropping. Theoretically consuming sufficient phytoestrogens-rich soy at this time can reduce menopausal symptoms.
- They can block the action of oestrogen. This is potentially beneficial in for example breast tissue where oestrogen stimulates growth of both normal and cancerous cells. At least one of the isoflavones in soy, called genistein, has been shown in animal studies to inhibit the development of breast cancer.
Read more:
- Soybeans (Better Health Victoria)
- Soy: healthy or toxic? (Dr Joanna)
