Soy Isoflavones (Antioxidant Series)

In part 5 of the antioxidants Friday Five series, we are looking at soy isoflavones which can be found in many vegetarian and Eastern meals.  Read on to find out what they are and why they may be good for you.

Antioxidants Venn wheel

1 What are soy isoflavones?

Soy (or soya) is also a popular ingredient in vegetarian and eastern foods.  However, its beneficial properties are probably best associated with post-menopausal women.  Soy isoflavones are a compound within soya made up of four chemical forms.  They are believed to support individuals by having anti-inflammatory properties, reducing the risk of osteoporosis, possible coronary heart disease prevention, and as an antioxidant.

2 How do they work as antioxidants?

Research suggests that isoflavones may help to reduce the activity of free radicals, thus reducing the amount of damage they cause; and they may help reduce the risk of low density (LDL) cholesterol and DNA being affected by oxidative stress.  Furthermore, some studies suggest soy isoflavones may support the activity of antioxidant enzymes.

3 The importance of gut health

When we consume soy isoflavones, the main two chemical forms are in an inactive form.  When they reach the intestines they react with enzymes in the gut wall, which converts them to bioactive forms that we can absorb.  The enzyme, beta-glucosidase, is produced by bacteria in the gut which further emphasises the importance of looking after our guts.

This article by Healthline gives some hints and tips about signs of an unhappy gut, and how to look after it: https://www.healthline.com/health/gut-health#treatment.  Some of the advice refers to health problems, intolerances and supplements – please ensure you consult with an appropriate health practitioner to assess any health concerns and before implementing any significant dietary changes, or taking supplements.

Tofu and soya beans

4 Are soy isoflavones harmful?

There have been several findings shared throughout the media over the years regarding soya’s safety.  As with all areas of science, our understanding of these concerns has been increased through further research.  Some concerns are confirmed, others debunked, and some may be contextualised.  The main concerns for soya are centred around its oestrogen-like properties.  It, and its isoflavones, have been found to be oestrogen antagonists and agonists (they can block or increase the effects of oestrogen).  Soy isoflavones can have a weak oestrogenic or anti-oestrogenic effect on the body.  They are considered to be endocrine disruptors.

One of the problems we have interpreting the science is that isoflavones may behave differently to soya proteins, meaning that the specific compound being studied can make a difference to the outcome.   Many studies focus on supplements and high-dose isoflavones rather than general foods.  Furthermore, animal studies and human studies can produce different results due to the differences in the way our bodies work*.  As I’ve highlighted when discussing personalised nutrition, there are even differences between human bodies meaning that we may each respond to soy isoflavones differently.  Ethnicity and/or pre-existing hormone levels may be factors in this case.

In order to determine if concerns are valid in relation to scientific studies, it is best to review the studies for each particular concern.  Doing this here would make this post extremely long!  However, the paper by Harvard T. H. Chan in the further reading/references section below, provides a fairly good summary of some notable papers related to breast and prostate cancer, the thyroid and heart disease.  As always, if you have concerns regarding any of these conditions (or others mentioned in the papers) please consult your doctor and do not change any medications or treatment you may be already receiving without their input.

Reviewing the science investigating the reproductive hormones of men and boys with regards to soy isoflavones is tricky.  This topic continues to be researched, but there are significant conflicts of interest involving the food industry (directly and indirectly) which may affect the outcome, or interpretation of the findings, making it difficult to be confident of each study’s reliability.  The general guidance is that people should consume soya products in moderation, but soya-based formula is not generally recommended for children under six months of age (consult with your doctor or health visitor before changing your child’s formula!).

*As an aside, have you noticed that the value of an animal study appears to be dependent on whether or not scientists like what the findings tell them?  If the outcome is helpful, the animal study is reliable, if not then we should be cautious that animal and human bodies are different!   I’ll be honest, reading about animal studies is probably the thing I find most uncomfortable about nutritional science.  Unfortunately that is how science has developed and continues to be conducted – acceptance of this fact, is by no means the same as me liking it!

5 Sources

While there are numerous soya products now available in the supermarkets thanks to the vegan movement, the products with the highest isoflavone levels are:

  • tofu
  • tempeh
  • natto
  • miso
  • soyabeans and edamame beans.

Important

If you are considering taking nutritional supplements, please consult with a suitably qualified professional to ensure the supplement is appropriate for you.  This is especially important if you have any health conditions or are taking medications.

Alible Nutrition Nutritional Therapy services consider health conditions and medications prior to providing advice regarding foods or supplements.

Do you need to improve your diet?

While soy isoflavones are something that I cannot specifically measure through the nutritional reviews, I can help you improve your diet.  Take a look at my Nutritional Therapy and Nutritional Review services, to find the right package for you.  Or, request a call.

References/Further Reading