The Value of Soya in Sports Nutrition

Soy protein, extracted from the annual leguminous soybean plant that has been in the food chain for over 5,000 years, is the only plant-based protein considered to be a high-quality protein, containing all of the essential amino acids in the ratios needed to support growth and development.

The soybean was introduced to the US in the 1880s, and before then was, and still is, a staple of the Asian diet.

Soy Beans are the most nutritious plant food available, comprising of 30% carbohydrate (15% of this is fibre), 38% protein, 18% oil (85% of this unsaturated), and 14% moisture. Soy contains all nine essential amino-acids, in the perfect ratio for health and well-being.

Soy also provides a considerable amount of potassium, zinc, iron, vitamin-E, phosphorous as well as the full B-complex.

When soya beans are harvested, they are put through a variety of processes to produce various products:

  • SOY OIL is used in the BAKING Industry;
  • SOY FLOUR is extensively used in BAKING (e.g. breads), SOY MEAT SUBSTITUTES, SOY DAIRY and BEVERAGES;
  • SOY MILK (made from ground soy beans) is used to make SOY DAIRY and BEVERAGES.
  • SOYA PROTEIN CONCENTRATES and ISOLATES are widely used in the Food Industry to make protein – enriched products or High Protein foods / beverages.


Used together in an exercise regimen, soy and whey proteins complement each other well. Whey protein, is high in branched chain amino acids, and used as an important energy source by the body during exercise, while soy protein has high amounts of the amino acids arginine and glutamine.

Arginine is well known as a stimulant of anabolic hormones that stimulate muscle formation, while glutamine is considered essential during metabolic stress.


The latest studies into soy protein suggest it does not decrease testosterone and raise estrogen, as previously thought.

One study found the post-workout consumption of isonitrogenous and isoenergetic soy drink to be statistically significant in increasing muscle mass, fat-bone free mass (FBFM) and increases in strength, when compared to other post-workout formulations (skim milk and maltodextrin beverage), both of which had a similar degree of efficacy.

This study demonstrated that intact proteins from both soy and milk protein are effective in supporting muscle hypertrophy, lending a degree of support to soy as a legitimate post-workout nutritional beverage.

This study’s method involved randomizing 34-subjects to milk (n=12, skim milk), soy beverage (n=11) or maltodextrin beverage (n=11) (note: n= number of subjects per randomized group), using a double-blind allocation process.

Participants trained 5 days-per-week on a whole body split resistance training program and consumed 500ml of their assigned drink immediately and 1h post-exercise following every training bout.

Another study which looked into soy as an effective aid to muscle-building, served to help dispel the notion that testosterone decreases when consuming soy. This study found daily supplementation of soy protein, whey or a soy/whey blend resulted in an increase in lean body mass and did not negatively affect testosterone or estradiol levels in 41 male athletes taking part in a weight-training program.

The study’s purpose was to compare the effect of supplementation of 50 grams / day of four different protein supplements in combination with resistance training on lean body composition and serum sex hormone changes in males.

The method of this study involved, over a 12-week-period, the 41-subjects consuming protein shakes twice daily and participating in three hypertrophy-oriented sessions per-week.

The protein shakes consisted of either soy protein concentrate (SPC), soy protein isolate (SPI), a soy/whey blend composed of a 50/50 mixture of SPI with whey protein concentrate (WPC) and whey protein isolate (WPI), or whey protein composed of a 50/50 mixture of WPC and WPI.

This study found:

  • All of the protein sources resulted in the desired effect of increasing lean body mass. In addition, there was no difference between the supplement sources on changes in testosterone levels.
  • The lean muscle mass gains that were demonstrated in this study are consistent with prior research looking at how soy and whey impact lean muscle mass in conjunction with an exercise regimen.

DISCUSSION based on the research:

  • Athletes who incorporate both soy and whey protein in their nutritional regimens may benefit from their different rates of digestion and amino acid absorption. Whey protein digests more quickly, while soy protein digests more gradually.
  • Together, they may provide a more prolonged, deliberate release of amino acids to key muscle groups.
  • In addition, soy protein consumption may provide additional health benefits including a reduced risk of coronary heart disease when combined with a healthy diet. Recent studies also demonstrate that soy protein consumption may reduce the risk of certain kinds of cancer including prostate cancer.
  • This study is consistent with other studies, which have demonstrated that soy protein has unique benefits for exercising adults in improving antioxidant status. These findings indicate that soy protein can help combat free radical formation during exercise, which may help speed muscle recovery after exercise.


The results of this study show that soy protein is just as effective as whey protein in building lean muscle mass as part of a dedicated exercise and nutrition regimen, while contradicting the myth that soy protein may negatively impact testosterone levels in men.

These results are consistent with prior studies which have compared the effect of whey protein and soy protein on lean muscle mass, and supports the notion that dedicated athletes may benefit from a nutrition regiment that includes both soy and whey proteins.

The researchers say that this study validates that soy protein is safe and just as effective as whey protein in helping exercising males achieve their fitness goals and supports the development of lean muscle mass.


A review of the research into soy consumption for health purposes, identified many benefits:

  1. Soy protein has a 1.0 PDCAAS (Protein Digestibility Corrected Amino Acid score) score – the highest possible. The PDCAAS is the standard measurement of protein quality.
  2. Soy protein increases the nutritional value of other foods due to its complete amino acid profile.
  3. Soy has been shown to reduce the likelihood of heart disease through its ability to lower cholesterol.
  4. Four servings of soy protein/day could reduce LDL cholesterol (the bad type, HDL being the good) by up to 10%.
  5. Although soy helps to lower LDL, it doesn’t affect HDL status, which is also a good thing. The American Heart Association also recommends the consumption of soy protein (with naturally occurring isoflavones) as part of a heart-healthy diet for those with elevated total and LDL cholesterol.
  6. Soy protein has been shown to reduce the risk of other illnesses such as colon, breast and prostate cancer, as well as osteoporosis.
  7. Soy enhances athletic performance. The isoflavones found in soy protein produce antioxidant effects, which speed recovery and reduce muscle soreness and inflammation.
  8. In addition, soy does supply a full complement of amino acids for the exercising muscles – muscles will become larger and stronger with soy protein. In fact, athletes who incorporate both soy and whey protein in their nutritional regimens may benefit from their different rates of digestion and amino acid absorption.
  9. Whey protein digests more quickly, while soy protein digests more gradually. Together, they may provide a more prolonged, deliberate release of amino acids to key muscle groups.
  10. Cost: one of the biggest benefits to the consumer is the considerable reduction in cost of using soy. With whey protein costs soaring, soy might prove to be much less expensive.
  11. Beneficial for women’s health.


Soy protein has been shown to be an excellent anabolic aid in athletes’ diets, used independently, or together with whey protein, to stimulate further gains in muscle.

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