Wednesday, July 28, 2010

Substance review: Soy isoflavones

Isoflavones are a group of plant derivatives, usually from the soy bean. They are traditionally purported to have a role in reducing heart disease, reducing cancer, assisting in bone health and easing the symptoms of menopause. Soy beans are a native of eastern Asian where they are used extensively in the diet of both humans and livestock and also as a tool for regulating soil in farming. Many popular Asian cooking sauces such as miso are derived from soy-bean, though not all of them contain flavanoids - for example the obvious candidate soy sauce is not usually a source of flavanoids.

Soy beans are considered to be a complete proteins, that is a protein that when consumed also contains the necessary amino acids to maximise the absorption (or bioavailability) of the protein. For this reason it is favoured amongst vegetarians as a good alternative to meat products over other less complete beans.

The mechanism of soy isoflavones come from their chemical structure. The structure of an isoflavone is very similar to the naturally occurring hormone oestrogen and so they are known as a phytoestrogen, in other words an organic substances that can regulate oestrogen in the human body. Soy isoflavones can either compete for oestrogen recptors or increase the amount of oestrogen in the body, depending on the type of phyoestrogen. The two phytoestrogens that are considered to be most beneficial are genistein and daidzen.

Physical effects:
Isoflavones have been seen to cause the feminizing of male animals in a number of trials, due to the effects of there interaction with oestrogen receptors. As a result there is some concern over there effects on male fertility and testosterone levels. Most of these worries however appear to be unfounded, a meta-analysis showed no feminizing effect on healthy men and similarly a clinical trial from the UK found no decrease in virility. Unfortunately that meta-analysis could also be bias as it is paid for in part by the soy industry and conflicts in a minor way with a different trial from one of the same researchers.

Cognitive Effects:
A trial from Australia recorded a significant increase spatial working memory in healthy men. This corresponds with the female ability to out perform in this area, while males generally out perform in visual spatial processing. It should be noted that there appears there is no obvious cognitive improvement in woman, including post-menopausal women for whom soy is purported to be of benefit. Soy has also at times been attributed to memory loss by mainstream media, however this appears to have been taken out of context for the purposes of marketability. The study focus on a number of Indonesian soy consumers, whose tofu is prepared using formaldehyde, compare that to research from the same group which showed tempe (a fermented soy product) improved memory and its not hard to see there was some data clustering.

Soy Isoflavones should be used at low dosages for men in sports where spatial memory (as opposed to spatial processing) is used. Its not hard to see how increased spatial working memory can help in situations where establishing the form of patterns is useful - a quarterback reading a defensive pattern or a martial artist noticing a pattern in a flaw of their opponent's fighting style. Although it has yet to be properly established, it is probably best to avoid higher dosages of soy, for example as an alternative to whey protein. For women this could cause an imbalance in their oestrogen levels and for men this could significantly reduce the positive effects of testosterone.

Further reading:

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