Soy vs Whey Protein: Which Is Better?

Protein powders are wildly popular nutrition supplements that are used for a variety of reasons. From muscle gain to weight management, protein powder supplementation carries with it a host of health benefits.

While you may be interested in reaping the benefits of protein supplementation, with so many options on the market to choose from, it may be tricky to know where to start.

When comparing soy vs whey protein, which are some of the most popular protein supplements around, how do you decide which is the better choice for you?

We’ll unpack the research and how soy vs whey stack up against each other and how they may help you reach your health and fitness goals.

What Is Whey Protein?

Whey is the liquid portion of milk that separates from the solids when dairy products are being produced. As a supplement, whey protein is typically found in powder form that can be easily mixed with soft foods or liquids. Whey protein is considered a complete protein because it contains all 9 essential amino acids that your body can’t make on its own.

With respect to supporting muscle gain, whey protein is typically considered to be the finest standard. One 2019 review of 28 studies concluded that including whey protein in your diet while engaging in resistance training is an effective way to help increase muscle mass.  Whey protein has also been shown to support weight loss and can help preserve lean muscle for people trying to shed pounds.

Lastly, whey protein provides specific protein fractions specifically designed to support the immune system in mammals. These are Immunoglobulins (the building blocks for white blood cells), Lactoferrin (key in regulating iron within the body) and Serum Albumin (a key component in the production of glutathione and thereby helping the body detoxify itself).

What Is Soy Protein?

Soy protein is plant-based and is the main protein found in soy soybeans and other soy-based products like tofu, soy milk, and tempeh. Like whey protein, soy protein is also considered a complete protein providing all nine essential amino acids.

Unlike whey protein, soy protein contains isoflavones, which may have heart health benefits. One 2015 review examined the effects of soy on cholesterol levels and found that soy intake lowered LDL (bad) cholesterol and helped raise HDL (good) cholesterol.

There is a misconception about soy intake and possible adverse effects for men. However, research has demonstrated that soy supplementation does not affect testosterone levels in men. Furthermore, studies have shown that increasing soy intake may lower your risk of prostate cancer.

Whey vs Soy Protein

One key difference between soy vs whey protein is where they are derived from. Whey is an animal-based protein while soy is plant-based.   

When comparing soy protein vs whey for muscle-building, whey protein may have the upper hand for a variety of reasons. Both soy vs whey proteins are considered “complete” proteins, as they both provide all nine essential amino acids. However, they’re slightly different in their concentrations of certain essential amino acids. For example, whey protein tends to be higher in leucine, isoleucine, methionine, and lysine.  

Lysine is linked with muscle growth and methionine has been associated with accelerated fat loss. Therefore, whey protein may appeal more for people looking to support muscle gain to help them reach their fitness goals.

Evidence suggests that whey protein may be more effective in helping with weight management by reducing body fat and increasing lean muscle mass compared to soy.

If you’re looking for a plant-based alternative to whey protein, soy protein is a solid choice. In fact, soy has more naturally occurring phytonutrients (beneficial plant compounds) than whey protein which may help prevent chronic diseases. One 2017 review found that soy may protect against cardiovascular diseases, obesity-related metabolic syndrome, and cancer, including breast and prostate cancers.

FAQs:

Which is better, soy or whey?

Both soy protein vs whey provide high-quality protein which can help support your fitness goals.

Due to its amino acid profile, whey protein may be more effective in helping you increase muscle gains, thus improving overall fitness.

However, soy protein is a nice plant-based alternative to whey protein for those following a vegan or plant-based diet. Soy protein also has the added benefit of providing phytonutrients which have been linked to lowering your risk of chronic diseases.

There is no one-size-fits-all approach to protein supplementation, so you may have to experiment to find out which protein best supports your fitness goals.

How is soy different from whey?

Soy is a plant-based protein whereas whey protein is animal-based. Both soy vs whey proteins are considered “complete” proteins, but they differ slightly in their concentrations of certain essential amino acids.

For example, whey protein tends to be higher in leucine, isoleucine, methionine, and lysine which may help promote muscle growth and accelerate fat loss.

Is soy or whey better for fat loss?

Both soy and whey can be beneficial for fat loss and weight management as they can keep you feeling fuller for longer and help to reduce cravings.

However, the evidence for taking soy protein for weight loss is not as solid as it is for other proteins like whey.

References

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   https://doi.org/10.2147/NDS.S166195
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3. Tokede, O., Onabanjo, T., Yansane, A., Gaziano, J., & Djoussé, L. (2015). Soya products and serum lipids: A meta-analysis of randomised controlled trials. British Journal of Nutrition, 114(6), 831-843. doi:10.1017/S0007114515002603
4. Reed KE, Camargo J, Hamilton-Reeves J, Kurzer M, Messina M. Neither soy nor isoflavone intake affects male reproductive hormones: An expanded and updated meta-analysis of clinical studies. Reprod Toxicol. 2021 Mar;100:60-67. doi: 10.1016/j.reprotox.2020.12.019. Epub 2020 Dec 28. PMID: 33383165.
5. Applegate CC, Rowles JL, Ranard KM, Jeon S, Erdman JW. Soy Consumption and the Risk of Prostate Cancer: An Updated Systematic Review and Meta-Analysis. Nutrients. 2018 Jan 4;10(1):40. doi: 10.3390/nu10010040. PMID: 29300347; PMCID: PMC5793268.
6. Baer DJ, Stote KS, Paul DR, Harris GK, Rumpler WV, Clevidence BA. Whey protein but not soy protein supplementation alters body weight and composition in free-living overweight and obese adults. J Nutr. 2011 Aug;141(8):1489-94. doi: 10.3945/jn.111.139840. Epub 2011 Jun 15. PMID: 21677076; PMCID: PMC3145217.
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8. Wu, Haoqing & Zhang, Ziang & Huang, Haiqiu & Li, Ziwei. (2017). Health benefits of soy and soy phytochemicals. AME Medical Journal. 2. 162-162. 10.21037/amj.2017.10.04.
9. Baer DJ, Stote KS, Paul DR, Harris GK, Rumpler WV, Clevidence BA. Whey protein but not soy protein supplementation alters body weight and composition in free-living overweight and obese adults. J Nutr. 2011 Aug;141(8):1489-94. doi: 10.3945/jn.111.139840. Epub 2011 Jun 15. PMID: 21677076; PMCID: PMC3145217.