Soya Isoflavones

Soya has long been a popular foodstuff in Asia, and there is growing evidence that the consumption of soya may offer a range of health benefits. In this article we’ll look at the science behind the claims, and try to assess the potential benefits of regularly consuming either soya or soya-derived supplements.

What is the Excitement around Soya?

A group of well-known chemicals called “phytoestrogens” are found in some plants, and seem to mimic the action of oestrogen in the body. These phytoestrogens may therefore have particular impacts on health issues that are affected by oestrogen.

A particular focus has been on the potential of phytoestrogens for menopausal women, who may suffer from a range of health issues linked to declining oestrogen production in the body. There is some evidence to suggest that phytoestrogens may make a suitable alternative to Hormone Replacement Therapy (HRT) in controlling the negative impacts of the female menopause.

Soya is possibly the best-known source of phytoestrogens, and is known for having some of the highest concentrations in any commonly-consumed plant source. One particular class of these phytoestrogens are known as “isoflavones” and it is these that have received the most attention for their potentially health-giving benefits.

One interesting observation made by nutritionists is that extensive consumption of soya isoflavones in many Asian diets has continued for years with no obvious side effects. As a result, it has been suggested that we can feel confident about the long-term safety aspects of consuming soya isoflavones.

But what does the science tell us about the potential benefits of consuming a soya-based diet or isoflavone supplements?

Bone Density

Hormonal changes experienced during the menopause can result in reduced bone density with age. It has been suggested that in severe cases women may lose up to 20% of their bone density within seven years of the menopause. This, in turn, can lead to increased risk of skeletal problems such as fractures. Since it is well-known that oestrogen can help to reverse this decline, it follows that soya isoflavones may also offer similar benefits.

At present, the science to back up this claim seems far from clear. While some studies have shown that soya isoflavone supplementation can lead to improved bone density, others have found quite the opposite.

On the positive side, one experiment provided participants with two years of supplementation with genistein (a soya isoflavone) and found positive impacts on bone mineral density. Another year-long trial found that providing 54mg of isoflavones per day showed positive results, and concluded that isoflavones “may be as effective as hormone replacement therapy in attenuating menopause-related bone loss”.

Sadly, just as many studies have found quite the opposite result, and inconsistencies in the findings are a concern. At present, there is enough evidence for scientists to continue studying the potential benefits of isoflavones for improving bone mineral density, but the community is far from agreed on the impacts of such supplementation.

Cholesterol Levels

One health benefit of soya isoflavones that seems to offer more consistently good news comes in its potential ability to lower harmful cholesterol levels. In one recent study, women provided with 100 mg of isoflavones per day showed significant decreases in total cholesterol and low-density lipids in the bloodstream.

A different study included both men and women in their participant group, providing soya supplementation for a period of twelve weeks. Not only did they note significant decreases in LDL (“bad”) cholesterol but also an increase in HDL (“good”) cholesterol. Interestingly, the impacts were found to be greatest in men, with daily doses above 80mg showing the most beneficial impacts.

The evidence suggests that soya isoflavones may well have considerable positive impacts on cholesterol balance while showing very few potential side effects.

Hot Flushes

Hot flushes are a common experience for women undergoing the menopause, but there is evidence to suggest that soya isoflavones may help.

In one study, 90 menopausal women between the ages of 47 and 57 were provided either with an isoflavone supplement or a placebo for a period of twelve months. The occurrence of hot flushes was self-recorded, and the results collated at the end of the study.

The experts found that hot flushes reduced by 22% within just three months of taking isoflavones, and that by the end of the year this had risen to 24%. Furthermore, no common side effects were experienced. In summary, the scientists concluded that isoflavones may “have positive effects on hot flushes”.

Whilst the earlier study provided 54mg of isoflavones per day, another study providing participants with lower doses also found positive impacts on hot flushes. It was found that daily doses of just 30mg were enough to reduce the frequency and duration of hot flushes in menopausal women.

Cognitive Ability

Changes in hormonal balance with the menopause have been linked to reduced mental cognition in some women, with a particular emphasis on verbal memory. Studies have assessed the oestrogen-mimicking properties of isoflavones and found that they may help to improve cognitive ability after the menopause.

In one study, 56 women were provided with 110mg of soya isoflavones per day, for a six month period. At the end, their cognitive abilities were assessed through a range of tests such as asking participants to read and then recall text from a page.

The evidence suggests that women receiving isoflavone supplementation experienced significant improvements in cognitive function, with the most noticeable improvements being in verbal memory.

Mental Wellbeing

The menopause is a difficult experience for many women, which repeated studies have shown may reduce overall quality of life. Side effects of hormonal changes may include changes in personality or feelings of depression. It is interesting, therefore, to consider the impact that soya isoflavones may have on overall mental well-being.

Historically, hormone replacement therapy has been used as a proven way to fight these psychological changes, but HRT is also known to have a range of deleterious side effects in some patients.

In one study 262 women were provided with isoflavones for a period of twelve months before undergoing psychological testing. The results suggest that isoflavones have a part to play in improving the quality of life experienced by menopausal women, including life satisfaction and feelings of depression.


Soya isoflavones seem to offer a host of positive benefits, particularly for women suffering from the effects of menopause. There is evidence to suggest that in some cases isoflavones may benefit cholesterol levels, frequency of hot flushes, cognitive ability and overall feelings of wellbeing. The impact of soya isoflavones on bone density remains a contentious issue, with more study being required.

As few side effects have been experienced despite the multitude of medical studies, soya isoflavones – whether in the diet or in supplement form – may offer a safe and beneficial solution too many issues associated with the menopause.

Thanks to the nutritionists at Simply Supplements for the provision of this article.