Soy Protein – Soy What?!

soy protein estrogen

Don’t mention the “S” word at your gym.

I’m speaking, of course, about soy protein.

That is, unless you’ve got 20 minutes to kill.

Because you’ll quickly be approached by the resident broscientist, bending your ear with scary stories.

“Don’t use that type of protein, brah. It’s the worst. It won’t build any muscle. It’ll give you bitch tits. In fact, it’s actually bad for you.”

And the worst part?

There’s nothing wrong with it.

But for many years, soy protein has been bastardized in the fitness world.

While whey steals all the headlines – it is awesome – and casein takes plaudits for it’s great supporting role, soy sits in the background, never receiving any praise for the great work it is does.

That’s largely down to the fact that people remain misinformed about myths which have long been debunked in clinical scientific studies.

soy protein

Soy Protein – What Does Science Say?

The main fallacy surrounding the usage of soy protein is that it will lower testosterone.

That statement is enough to scare 99% of men off, right?

Lower testosterone means less muscle building, among other things.

And because soy contains isoflavones, which are similar to estrogen (the female sex hormone), many people make the assumption that taking soy protein will lead to lower testosterone.

And so the soy protein estrogen myth was born.

So it’s no wonder guys are terrified of the stuff.

However, there is ample scientific evidence to show that this is just not true.

In fact, a 2010 study published in Fertility and Sterility reviewed fifteen other studies on soy protein supplementation and concluded that soy does not alter testosterone in men. (1)

So don’t buy into the nonsense.

Quickly on it’s heels comes the myth that soy just doesn’t promote as much muscle growth as whey or casein.

Again, this is linked to the idea that soy reduces testosterone, which we’ve already shown is not true – and again, this theory is also incorrect.

soy protein estrogen

A 2007 study published in the Journal of the International Society of Sports Nutrition confirmed this.

Over the course of 12 weeks, weight trained subjects were given either soy protein, whey protein or a soy/whey blend to test the theory that soy was incapable of promoting as much lean mass as whey protein.

They discovered that all subjects were able to gain a similar amount of muscle mass regardless of what type of whey protein they were using. (2)

A 2009 study then confirmed it again. (3)

soy protein testosterone

Mix Up Your Protein

The wealth of clinical studies has gone a long way to debunk the unnecessary myths surrounding soy protein.

Furthermore, it is far cheaper than whey.

This makes soy ideal for those on a tight budget or – like me – if you always keep a back-up tub of protein in the cupboard just in case you run out of your main product. If that’s the case,  I suggest this one for pure value purposes.

Many of you know I recommend taking a protein supplement which consist of blends, rather than just one form (such as whey isolate).

And if you’ve ready this article you’ll know that the optimal blend includes soy protein.

soy protein side effects

That’s because protein blends have been scientifically proven to be more effective than solo formulas. (4)

Combining a shake which contains a fast-digesting source of protein – like whey – a medium-digesting source – like soy – and a slow-digesting source – like casein – has been shown to elevate amino acid uptake into the muscle versus just whey alone.

It’s also been shown to elevate muscle protein synthesis for a longer period. (5)

So there you have it, get stuck in.

soy protein

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1. Hamilton-Reeves, J.M., et al. “Clinical studies show no effects of soy protein or isoflavones on reproductive hormones in men: results of a meta-analysis.” Fertil Steril. 94 (3):997-1007, 2010.
2. Campbell, B., et al. “International Society of Sports Nutrition position stand: protein and exercise.” J Int Soc Sports Nutr. 2007, 4:8 doi:10.1186/1550-2783-4-8.
3. DeNysschen, C., et al. “Resistance training with soy vs whey protein supplements in hyperlipidemic males.” J Int Soc Sports Nutr. 2009; 6: 8.
4. Reidy, P. T., et al. “Protein Blend Ingestion Following Resistance Exercise Promotes Human Muscle Protein Synthesis.” Journal of Nutrition 143(4):410-416, 2013.
5. Reidy, P. T., et al. “Soy-dairy protein blend and whey protein ingestion after resistance exercise increases amino acid transport and transporter expression in human skeletal muscle.” Journal of Applied Physiology, in press, 2014.

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