Soy protein B

«Soy protein» — evidence level B. Dosage: 20-40 g per serving; the daily guideline is 1.6-2.2 g/kg. In the meta-analysis the comparison was at the usual servings of 20-25 g. Source: PMID 29722584, permanent link to the source in the list below.

Soy protein isolate is a complete protein with about 8% leucine and high digestibility. In acute experiments it stimulates muscle protein synthesis less than whey, but in long-term training studies no difference in gains of mass and strength is found.

Soy protein isolate (about 90% protein) is preferable to the concentrate in leucine content per gram.

• Meta-analysis of nine studies (266 people): the gain in strength and fat-free mass did not differ from animal proteins
• A complete amino acid profile with a high lysine content
• A cheap protein source, suitable for a plant-based diet

• In acute studies it stimulates muscle protein synthesis less than whey - it makes sense to increase the serving
• Soy is a common allergen; the isolate is tolerated better than the concentrate
• Contains isoflavones; an effect on the hormonal profile in men has not been confirmed in controlled studies, but the topic is debated
• Soy phytates reduce the absorption of iron and zinc from the same serving

• Soy may reduce the absorption of levothyroxine - space the intake by several hours
• Phytates worsen the absorption of iron and zinc from the same serving

• Under 18 years: Soy protein as part of the diet is safe; there are insufficient data on high doses of isoflavones in adolescents.
• Pregnancy and lactation: Moderate consumption of soy as a food is considered safe; concentrated isoflavone supplements have not been studied in pregnancy.
• soy allergy
• hypothyroidism on replacement therapy
• chronic kidney disease with protein restriction

• No Difference Between the Effects of Supplementing With Soy Protein Versus Animal Protein on Gains in Muscle Mass and Strength in Response to Resistance Exercise · Messina M, Lynch H, Dickinson JM · International journal of sport nutrition and exercise metabolism, 2018 · PMID 29722584
• A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults · Morton RW, Murphy KT, McKellar SR · British journal of sports medicine, 2018 · PMID 28698222

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