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Soy Protein

Quick Summary Points

  • Soy protein is isolated from the soybean or soya bean (Glycine max), which is a legume that is native to eastern parts of Asia
  • Soy protein can be found in the concentrate, isolate, or hydrolysed isolate forms (increasing in purity). These are often included in a variety of weight gainers, blended proteins, women’s proteins, & protein bars
  • Benefits of Soy protein include increasing strength, lean muscle gains & reducing post workout fatigue
  • Soy protein can be used as a whey protein substitute and can be stacked with absolutely anything to meet your goals

What is Soy Protein?

Soy (also known as Soya) - In China, the soya bean has been cultivated and used in different ways for thousands of years. In recent times increasing popularity of soy foods is mostly attributed to the large amount of health benefits which are associated with the use of soya beans. The role of soy in the prevention of chronic diseases continues to be a top priority for scientists around the world & the American FDA has confirmed that foods containing soy protein may reduce the risk of coronary heart disease (FDA, 1999). Soy has a high protein content and is rich in fibre, vitamins & minerals (FSANZ, 2010). It is generally very low in or free of fat, cholesterol, and lactose. It is approved for those who are lactose intolerant, and is used as a meat substitute thus soy is very important for vegetarians & vegans. 

So what is the best type of soy protein powder? Well just like whey protein, soy also is available in either a "concentrate" or an "isolate". To cut a long story short soy protein concentrate shall always have at least 65% protein with most of the remaining ingredients being carbohydrates. Soy protein isolate on the other hand is the most pure and refined soy protein available. It is made from defatted Soy beans with almost all other products including fats & carbohydrates removed, leaving only protein. Thus a soy protein isolate powder shall have 80% + protein, and is certainly the way to go when choosing your soy supplement. For the purposes of bodybuilding, muscle toning & fat loss, whilst soy protein has a lower biological value than whey protein, it is in general still regarded as an excellent high quality non-meat or vegetarian alternative (Brown et al, 2004).

Whether you're a vegetarian, or an omnivorous bodybuilder, you probably already know that legumes are a great source of protein. Therefore, it should be no surprise that legumes such as soy can be processed into a high quality protein powder, similar in concept to whey. However, although whey protein is popular, it is not for absolutely everyone. Vegans choose not to use whey, and most forms of whey are unsuitable for those with milk protein allergies. Therefore, soy protein may be a viable alternative and can be of great benefit to bodybuilders and athletes looking to increase lean mass and strength.

Where does Soy Protein Come From?

Soy protein is isolated from the soybean or soya bean (Glycine max), which is a legume that is native to eastern parts of Asia. Soybeans have been cultivated for centuries as an inexpensive protein source, and today, is used extensively in the food industry as an ingredient and good additive. Typically, soybeans are 30% carbohydrate, 20% fat, and 36% protein. To make soy protein, most of the fat, and a significant portion of the carbohydrate component can be removed.

Benefits of Soy Protein

Benefits of Soy Protein for Lean Muscle Gains

Muscle anabolism needs a fuel source, and that fuel source is protein. Soy proteins are what are known as a "complete" protein, meaning that they contain all the essential amino acids that we need. Consequently, this makes soy protein ideal for muscle growth. There is a wealth of studies showing that soy proteins can significantly increase muscle mass compared to a placebo. Brown et al (2004) found that after nine weeks of weight training, trained lifters increased muscle mass after the supplementing with soy proteins, whereas those that did not saw no lean gains. Studies such as this have been supported repeatedly by other researchers looking at average young adults (Candow et al, 2006), and even Olympic athletes (Dragan et al, 1992). The reason why soy protein is a good protein source is because, like whey protein, it is rapidly digested and increases protein synthesis in muscles (Tang et al, 2009).

Benefits of Soy Protein for Strength

Many of the above studies also looked at the effects of soy protein on strength gains. In most instances, there have also been reports of strength increase, accompanying lean gains. Additional to this, it has also been found that strength increases as a result of soy protein supplementation is similar to gains achieved with whey protein (Phillips et al, 2005; Candow et al, 2006)

Benefits of Soy Protein as an Antioxidant

An additional property that soy protein has over some other protein sources is its high content of antioxidants. Isoflavones, saponins, and copper in soy either exhibit antioxidant properties, or are components of antioxidants. Consequently, it has been found that using soy protein supplements may actually reduce post workout oxidative damage (Brown et al, 2004), and hence speed up recovery times.

Benefits of Soy Protein for Heart Health

Isoflavones present in soy protein have received some very positive hype over the recent years for their purported ability to lower bad LDL cholesterol and improve heart health. A review by the American Heart Association has concluded that these effects are actually very mild. However, the other properties of soy protein such as low saturated fats, high unsaturated fats, vitamins, and minerals present do in fact help to improve cardiovascular and overall health (Sacks et al, 2006).

Negatives of Soy Protein and Side Effects

What is probably the biggest concern about eating soy protein is the fear that the phytoestrogens present may reduce testosterone levels in men. This topic has been covered in some detail in our "Soy Protein & Estrogen" article. But to summarise, it is generally accepted among experts, that neither soy foods nor their constituents are likely to affect testosterone levels in men (Hamilton-Reeves et al, 2010).

It is worth mentioning that in rare cases, people do suffer from a soy food allergy. In this case, it is recommended that these individuals avoid soy and soy proteins completely.

One other potential negative about soy protein is that, although it is highly beneficial to muscle gain and strength development, it may not improve lean gains to the same extent at whey protein. There has been research that shows dairy (eg whey) proteins are better able to increase muscle protein synthesis (Phillips et al, 2005; Tang et al, 2009). Some studies have shown that after a short duration (up to 12 weeks) of supplementation, there was no significant difference in muscle gain between soy and whey protein (Brown et al, 2004; Phillips et al, 2005). However, a trend was present to suggest that whey supplementation appeared to give greater gains. It is likely that the difference between whey and soy protein supplementation may be more evident in the long term, and that whey may be a better protein source for lean muscle gains. Interestingly, this effect may not actually be related to differences in the amino acid profile, but rather, the way in which the amino acids are delivered to the muscle (Phillips et al, 2005).

It is in this writer's opinion that whey protein may be more beneficial for bodybuilders and strength athletes in the long term. However, soy protein should not be ignored completely as it is still a good alternative to whey protein for those that are unable to use whey protein. Furthermore, soy protein has additional antioxidants and other nutrients that are not found elsewhere.

Soy Protein Recommended Doses and Ingredient Timing

The recommended dosage of soy protein is no different to that of other proteins, which has been covered in detail in our "Recommended Protein Intake" article. Depending on your specific training regimen and goals, your requirements may be anywhere between 1.5 to 2 g/kg/day. Weight training athletes have been found to benefit from the consumption of an additional 33 g soy protein on top of their usual diet (Brown et al, 2004).

The timing for soy intake again is the same for other proteins, and varies according to your requirements and goals. Generally speaking, soy protein should definitely be consumed immediately post training, as this is a vital time for providing fuel for muscle synthesis. Additionally, it may also be consumed in between meals to provide a constant source of protein during the day.

Soy Protein Supplements

Like whey, soy protein can be found in the concentrate, isolate, or hydrolysed isolate forms (increasing in purity). These are often included in a variety of weight gainers, blended proteins, ladies proteins, protein bars, and much much more. However, in these cases, the soy protein is almost always accompanied by other sources of protein such as whey. This is because the soy protein is a good complement to the whey protein, but this makes these products unsuitable for those who wish to avoid animal sourced protein. Pure stand-alone soy protein powders are available. Though, the variety of soy protein products on the market is not as extensive as whey protein. Nevertheless, there is still a good range of tasty soy protein powders that are readily available, effective, and easy to use. The better soy proteins are in the isolate form, which are generally more pure, and lower in carbohydrates and fats compared to soy protein concentrates.

Stacking Soy Protein

Soy protein can be used as a whey protein substitute and thus can be stacked with absolutely anything to meet your goals. Protein should be one of the fundamental supplements that any bodybuilder should always have. If you are a vegan bodybuilder, please read our article on vegan and vegetarian bodybuilding supplements for a more comprehensive guide.

Brown et al (2004), Soy versus whey protein bars: Effects on exercise training impact on lean body mass and antioxidant status. Nutrition Journal, 3 (online)
Candow et al (2006), Effect of whey and soy protein supplementation combined with resistance training in young adults. Int J Sport Nutr Exercise Metab, 16: 233- 244
Dragan et al (1992), Studies regarding the efficiency of Supro isolated soy protein in Olympic athletes. Rev Roum Physiol, 29: 63-70
Hamilton-Reeves et al (2010), Clinical studies show no effects of soy protein or isoflavones on reproductive hormones in men: results of a meta-analysis. Fertility and Sterility, 94: 997-1007
Phillips et al (2005), Dietary Protein to Support Anabolism with Resistance Exercise in Young Men. J Am Coll Nutr, 24: 1345-1395
Sacks et al (2006), Soy Protein, Isoflavones, and Cardiovascular Health. Circulation, 113: 1034-1044
Tang et al (2009), Ingestion of whey hydrolysate, casein, or soy protein isolate: effects on mixed muscle protein synthesis at rest and following resistance exercise in young men. J Appl Physiol, 3: 987-992
FDA (1999), Federal Register 64 FR 57699 October 26, 1999 - Food Labeling: Health Claims; Soy Protein and Coronary Heart Disease; Final Rule. U.S. Department of Health & Human Services
FSANZ (2010), NUTTAB 2010 Online Searchable Database.

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