Are soy products good for me?

Can you tell me if soy products are good for me or not?  I hear that I shouldn't be having soy based products and just wondered why?

There is a very lengthy debate over the use and consumption of soy and soy products, and the short answer is yes they are and no they're not.

The major debate boils down to estradiol (one of the estrogens).  Estradiol has many hormonal functions including: breast development, reproductive organ growth, ovulation, endometrium preparation, pregnancy, fat structure, bone density, mood regulation, liver function, blood flow in certain blood vessels and it also plays a part In male reproduction.

Estradiol excess or deficiency can have a detrimental effect on human health. For example, excess estradiol can be linked to menstrual cramps, and diminished estradiol leads to lower bone density and osteoporosis (as seen in menopause).

Certain cancers (particular reproductive and breast) have a relationship with excess estradiol.

Estradiol works by linking to estrogen receptors in the body.  Once the receptor has received its estradiol, it 'shuts off' temporarily and the estradiol enters the cell. Problems in cellular estradiol occur when the receptors aren't working as they should or when the circulating levels of estradiol in the body are too high or low.

Here's where soy comes in.  Soy contains phytoestrogens (phyto meaning plant) in the form of isoflavones.  Phytoestrogens act in the same way as a human estrogens do in the body, they attach to estrogen receptors and fill the 'gap' that estradiol otherwise would.

This is good, according to research as soy isoflavones exert a less estrogenic effect than estradiol.  This means that if you have excess estradiol circulating, only some will enter the receptors since the soy isoflavones are already taking up some of the spaces.  This helps to lower excess cellular estradiol and therefore all the other problems that go with it - for example reducing the risk of breast cancer. 

The other side of the research coin says that this is bad as soy isoflavones increase total estrogens in the body and therefore lead to ailments of excess estrogen including an increased cancer risk.  But this is also good, if circulating estradiol is already low.  But then this is bad if low-estrogenic isoflavones take up the receptors, thus reducing cellular estradiol even further.

You can see how the pros and cons of soy consumption is such a grey area.

From a personal standpoint, I was told by a top NZ naturopath that if you experience heavy menstrual cramps and other PMS symptoms to avoid soy.  I suffered painfully sore breasts for about 15 years, and decided to cut my daily soy latte and intake of soy derived products and have not had a single problem since.  Needless to say I was pretty well blown away.

It is this effect on the female hormones which has men scratching their heads over soy also.  It is thought that too much soy increases estrogen output in men.

Research attesting to the safety of soy is often funded by the soy and pharmaceutical industries, research against is often funded by those who are affected by soy consumption (eg dairy and meat industries).  The debate continues to rage.

Despite the hormonal argument, soy is however, quite nutritious, it is a complete protein and can be used in place of meat without being deficient in any amino acids, contains omega 3 & 6 fatty acids and helps to lower cholesterol.  The presence of sphingolipids in soy are reported to reduce the risk of colon cancer.

If your family cancer risk is low and you don't suffer from estrogen related problems then there is no reason why you can't include soy as part of a balanced diet.  If you are a high soy consumer and experience problems surrounding the reproductive system (endo, pmt, difficulty with pregnancy etc) you may want to look at cutting soy to see if symptoms improve.

Stacey 2009