The humble soybean provides an extremely high quality protein and while anybody can pick up tofu or tempeh from the supermarket, many find it cheaper and more convenient to seek out soy protein powder. But with so many different versions on the market, it can be hard to decide on the best one for your needs. That’s why we’ve put together the best soy concentrate, isolate, the best soy for the money, and more.
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Doesn’t Soy Make It Harder to Gain Muscle?
Soy is a really high quality protein, but there’s a persistent belief that it negatively affects our sex hormones, namely estrogen and testosterone. The idea is that because soy contains phytoestrogen — plant estrogen — that it will cause human estrogen levels to rise and testosterone to fall.
It’s true that soy contains phytoestrogen, but there are a few things important things to note:
- Lots of foods contain phytoestrogen, including apples, oats, rice, and coffee. Those who refuse to tough anything containing soy because of the estrogen should be avoiding a lot of other foods as well.(1)
- Phytoestrogens have been linked to a wide variety of health benefits, possessing antioxidant, anti-viral, and possibly even anti-cancer properties.(2)(3)(4)(5)
- Most pertinently, there’s a lot of high quality research showing that soy doesn’t affect testosterone or estrogen in humans. A meta-analysis of 47 studies concluded as such, even when people were eating up to 70 grams of soy protein a day.(6) Other research saw men taking 50 grams of soy protein powder over a 12-week strength training program, and their testosterone levels were no different to men taking whey.(7)It’s not that there are no studies at all showing negative effects on people, but it’s typically on outliers, like the one about a 60-year-old man growing breasts after drinking three liters of soy milk per day for decades.(8) Most data (again, there are almost 50 studies cited above) show it’s fine to have 70 grams of soy protein a day.
With all that said, people with concerns about their hormonal health should see their physician.
- Soy is a high quality protein, meaning it contains all essential amino acids in roughly equal amounts. So do animal proteins, but this isn’t the case for rice, pea, and some other vegan proteins.
- Although the vast majority of evidence suggests that soy isn’t deleterious to one’s health, it doesn’t mean that it’s a good idea for it to be one’s primary source of protein. Humans are meant to have diverse diets; avoid eating the same thing at every meal.
- The difference between soy concentrate and soy isolate is similar to whey concentrate and isolate, in that concentrate is a bit less processed and contains more fat and carbohydrates, whereas soy isolate has much of the carbohydrates removed. Because of this, soy isolate may produce less flatulence and it’s far more common on the market.
Soy remains a phenomenally inexpensive, high quality protein that can help anybody to meat their desired protein intake, whether they’re vegan or omnivore. Whatever your budget and whatever your preference, the right soy protein is on this list. Enjoy the results!
- Kuhnle GG, et al. Phytoestrogen content of beverages, nuts, seeds, and oils. J Agric Food Chem. 2008 Aug 27;56(16):7311-5.
- Yan L, et al. Soy consumption and prostate cancer risk in men: a revisit of a meta-analysis. Am J Clin Nutr. 2009 Apr;89(4):1155-63.
- Andres S, et al. Risks and benefits of dietary isoflavones for cancer. Crit Rev Toxicol. 2011 Jul;41(6):463-506.
- Bouker KB, et al. Genistein: does it prevent or promote breast cancer? Environ Health Perspect. 2000 Aug;108(8):701-8.
- Pavese JM, et al. Genistein inhibits human prostate cancer cell detachment, invasion, and metastasis. Am J Clin Nutr. 2014 Jul;100 Suppl 1:431S-6S.
- Hamilton-Reeves JM, et al. Clinical studies show no effects of soy protein or isoflavones on reproductive hormones in men: results of a meta-analysis. Fertil Steril. 2010 Aug;94(3):997-1007.
- Kalman D, et al. Effect of protein source and resistance training on body composition and sex hormones. J Int Soc Sports Nutr. 2007 Jul 23;4:4.
- Martinez J, et al. An unusual case of gynecomastia associated with soy product consumption. Endocr Pract. 2008 May-Jun;14(4):415-8.