Soya & health: the ultimate guide for health professionals

With over 2,000 publications per year over the last couple of decades, it seems like an impossible task to bring together all the evidence and provide the overarching summary of how soya food impact on various health outcomes. Dr Messina and his team, have done just that, by focusing on the higher quality publications, in the main, systematic reviews and meta-analysis, as well as large cohort studies and opinions of independent health organisations.

This 20-page publication with over 550 references reviews all aspects of soya and its health implications, tackling misguided controversies on the way.

For any health professional wishing to have a concise reference guide to soya, this is a must have.

An introduction to the basics

The guide starts with an overview of the different types of soya foods and their production processes, including fermented and unfermented variants, before discussing soya protein and how it compares to animal protein for quantity, amino acid quality, muscle building and satiating properties.

The guide then provides an excellent overview of isoflavones, the main area of scientific research and one that has produced the most controversies. Dr Messina explains these complex and often misunderstood naturally occurring phytochemicals and how the concerns around negative impact on health are misplaced.

Soya & health outcomes provided in a concise and easy to digest format

The guide then critiques the evidence for each health outcome associated with soya food, soya protein and/or isoflavones consumption. Each section provides a clear overview of the scientific evidence and what this means in practice when advising patients.

Any misconceptions are tackled within each section and there is a reoccurring theme, with most misconception stemming from finding of rat studies or anecdotal evidence which have not been replicated in human studies.

Isoflavone related health outcomes

Breast cancer: a summary of how the negative associations transpired, and how higher quality evidence has put these misconception to bed. The American Institute of Cancer Research and the World Cancer Research Fund as well as the European Food Safety Authority clearly supporting the safety of soya consumption for those at high risk of cancer and for cancer survivors.

Prostate cancer: a clear summary of the evidence concluding that more research is needed to make any claims for improved outcomes.

Osteoporosis: although some evidence exists to show benefit, bone health is determined by multiple dietary and lifestyle factors, all of which play a critical role. Thus, soya foods providing protein and calcium have a role to play alongside other factors.

Cognitive function: small clinical studies are showing some promising outcomes on improved cognition; however, more research is needed.

Hot flushes: based on meta-analysis of clinical trials, there is strong evidence to suggest that consumption of around 20mg of genistein (one of the three main soya isoflavones) and 50-60mg of total isoflavone intakes can provide some relief in the frequency and severity of hot flushes in menopausal women. This equates to approximately 500ml of soya drink or 120g tofu daily.

Thyroid function: the overwhelming clinical evidence supports that soya foods do not interfere with thyroid function.

Male hormones and fertility: once again, despite misconceptions being rife, the overwhelming clinical evidence indicates no effect.

Other isoflavone related health outcomes discussed includes female hormones and menstrual cycle length as well as impact of isoflavone consumption during pregnancy.

Soya protein & health

The guide then discusses the impact of soya protein on health with specific attention to the cholesterol-lowering effect which carries a Canadian and US authorised claim. Additionally it investigates the role of soya protein in gout and allergies.

The guide then assesses the fat profile of soya which is a source of the essential n-3 and n-6 fatty acids.

In summary

This is an exception reference guide for anyone wishing to delve into the detailed science or simply to find, at a glance, the overarching summary of the evidence and what this means in practice when advising consumers and patients on the consumption of soya foods for specific health outcomes.