Soya Protein- Should You Or Shouldn't You?

Soya, the favourite cousin of the trusty pea! This plant based source of vitamins, essential fatty acids, sterols, stanols, and amino-acids are also a valid means of delivering protein pre or post training! Soya and Soya protein has been seen to reduce the risk of cancer and heart disease, reduce calcium excretion (supporting bone mineral density), whilst helping to regulate hormonal balance in menopausal women. Soya protein is something of an overall ‘health promoting’ food stuff, yet despite all the positive publicity, soya has faced some scrutiny. The bad press stemmed from reports that it might increase femininity and reduce sperm count in men. This was theoretically attributed to soya proteins high levels of phytoestrogens and its potential to enhance the effectiveness of oestrogen (female sex hormone) in men! This conflicting information has led to a lot of confusion amongst us as what are we supposed to believe!? Well it is far beyond the scope of this article to affirm or refute any of the above accusations, but what we can do is give you some information behind this negative publicity to enable you to make your own judgement on whether it is, or isn’t for you (British Dietetic Association (BDA), 2011).

Positive Effects of Soya

The soya bean provides you with good fats i.e. polyunsaturated fatty acids, in particular the omega-3 and omega-6 varieties. One portion of soya beans (from which soya protein is derived) counts to your 5 a day, and is the only plant based form of protein considered to be ‘complete’, despite lacking methionine i.e. contains all the essential amino-acids. Soya also delivers numerous bio-active isoflavones, a type of phytoestrogen (oestrogen derived from plants) which is thought to have antioxidant effects and help maintain cell health and integrity. In the UK, we consume on average 1-3.5g of soya per day, meaning the average person is unlikely to stray into damaging levels through diet alone. Studies have shown that consuming 25g of soya protein per day can lead to a reduction in cholesterol and thus a 10% reduction of heart disease if you previously had a high risk (Joint Health Claims Committee, 2002). Populations that have consumed approx 25g soya protein per day have also demonstrated higher bone mineral density, but studies are still ongoing to support this. As mentioned above, soya might also support the hormonal regulation of women during their menopause. Finally, soya protein has been seen to elevate thyroid activity which can indirectly increase the rate of fat burning (BDA, 2011).

Reported Negative Effects of Soya

One of the controversial properties of soya (from a male point of view) is its potential enhancement of the hormone oestrogen in men. Phytoestrogens can cause the body to either copy or inhibit the effects of oestrogen in humans, resulting in some invalid scare mongering, yet potentially valid theories that soya might reduce fertility and masculinity (although only if consumed in excess). Soya also contains oxalate and phytate which can inhibit mineral absorption if in excess, although overall calcium absorption is seen to be good. Soya protein has a relatively low biological value due to its lacking in methionine, meaning its absorptive capacity is a bit lower than its competitor whey and casein protein. It is for this reason also that soya protein has been seen as the inferior relation to dairy or egg derived proteins. Soya also has protease inhibitors which can reduce the efficiency of protein breakdown and thus absorption (Potter, 1995; BDA, 2011).

Conclusion: Yay or Nay?

The BDA (2011) states that soya protein has been extensively researched and permitted for use under the Food Safety Act 1999, the UK Committee on Toxicity and the US Food and Drug Administration both state that soya protein is safe for consumption. Therefore any accusations that soya protein might be damaging to masculinity and fertility is just theoretical and not supported by a robust meta-analysis (analysis of many studies on a specific subject) designed to highlight trends or common patterns in research. The overwhelming consensus is that soya per-se should be consumed within the recommended dose (approx 25g per day depending on size) for general health and wellbeing. In relation to exercise, bodybuilding and training....our opinion is the same as many other authorities in the exercise world, that any protein source should be cycled and not taken exclusively e.g. consume whey protein for 1-2 months followed by a week or two’s rest, followed by soya protein for a month, then back onto whey or maybe a whole egg derived protein. Now it would be simplistic and somewhat misleading to assert that soya protein is as useful to training as whey or casein protein....but what can be said is that soya protein seems to offer far more benefits than perhaps we all first thought! It is our opinion that if you don’t exceed the recommended dosage, soya protein would serve as a useful cycle partner of whey protein to deliver health promoting nutrients, as well as delivering a useful source of essential amino acids, protein, and thus muscle (Joint Health Claims Initiative, 2002; BDA, 2011)!


Brink, W, (2003). The Vindication of Soy Protein. Retrieved June 19, from,

British Dietetic Association, (2011). Food Facts. Soya and Health. Retrieved June 19, 2012, from

Haub, M, D., Wells, A,M., & Campbell, W, W, (2005). Beef and soy-based food supplements differentially affect serum lipoprotein-lipid profiles because of changes in carbohydrate intake and novel nutrient intake ratios in older men who resistance-train. Metabolism Clinical and Experimental. 54:769-744.

Joint Health Claims Initiative (2002). Generic health claim for soya protein and blood cholesterol. Retrieved June 18, 2012, from

Potter, M, S, (1995).Overview of Proposed Mechanisms for the Hypocholesterolemic Effect of Soy. Journal of Nutrition. 125: 606-611.

About the Author

Job Role Qualified Dietitian and Sports Nutritionist Qualifications BSc (Hons) Sports Science | BSc (Hons) Dietetics Tom has always participated in sport both recreationally and competitively which led to an unquenchable thirst for information on anything health, nutrition and fitness. After leaving school Tom went on to play for a football academy during which time he studied Sport and Exercise Science. From here he went on to study a BSc (Hons) Sport Science at UEA followed by his second BSc (Hons) degree, this time at the University of Hertfordshire studying Dietetics. Tom has worked in the fitness, educational and clinical nutrition industry starting out at David Lloyd Health and Leisure Clubs. He then went on to work as a Dietitian (RD) in the NHS, during which time he conducted clinics for healthy eating, weight loss and weight gain, as well as specialised consultations on Diabetes, IBS and Coeliac disease to name a few. He has vast amounts of experience at devising diet plans and supplement regimens, as well as working in the community with schools and competitive athletes. As Head Nutritionist and Supplement expert at Discount Supplements Tom is here to provide current and evidence based health and nutrition information to help you reach your health and fitness goals!
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