Does Whey Protein Cause Your Testosterone Levels to Plummet?

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For two of the most discussed topics in sports nutrition (protein and testosterone), it’s amazing how little is known about the effects on the latter of consuming the former. Here’s what the latest research says about how your protein supplement may impact your levels of testosterone from Chris Lockwood, PhD, CSCS.

Protein decreasing your testosterone levels is an old fear that is grounded in good science. Newer research offers a different picture, and points to a fascinating possibility. Let’s break down both viewpoints.

Circulating levels of testosterone temporarily increase whenever you train with high intensity and volume. It doesn’t matter if you’re male or female, just that you push yourself. And yes, that increase in testosterone from weight training alone has sometimes been shown to be reduced or blunted if you consume protein prior to or immediately after your workout.

whey protein-chris lockwood

Further muddying the waters, other studies have also reported that high-protein diets lower resting levels of circulating testosterone, while others have shown that increasing protein can increase testosterone availability. Does protein increase or decrease your testosterone? A hypothesis raised within a 2008 paper raises the idea that it’s not an either/or proposition.

What if protein–or specific types of protein–cause both an increase in total testosterone, and a lowering of circulating levels of testosterone? Not because the protein is reducing your production of testosterone, but because more circulating testosterone is being removed from the bloodstream and entering cells where it can affect cell function?

whey protein shakeIn other words, what if certain proteins–or something in those proteins–can amplify the training-induced rise in the sensitivity of androgen receptors, those cellular ports that shuttle testosterone into cells and allow it to do its crucial work?

For one thing, it would mean that blood samples that only assess a snapshot of the amount of testosterone circulating outside of tissues (extracellular) would only be telling us a piece of the whole story. It would also mean that protein is seriously powerful stuff.

Pass the Test with Excellence

Unpublished research out of the Molecular and Applied Sciences Laboratory at Auburn University could turn everything we thought we knew about testosterone, as well as how testosterone itself is measured, on its head. Immediately after this “training”, the rats received either 500 milligrams of whey protein, which provided approximately 50 milligrams of leucine, or the rats were given just an additional 54 milligrams of leucine, or water only (the control group). When extrapolated to humans, that’s about 19 grams of whey protein and 2.8 grams of leucine– both pretty standard doses.

Here’s what the researchers found: Supplementing with whey resulted in a 90.5% increase in the intracellular concentration of testosterone present within the exercised muscle, over the non-exercised muscle. Leucine alone, on the other hand, caused an average, but non-significant reduction in intracellular testosterone. Whey raised intracellular levels of testosterone by 150 percent more than leucine alone within exercised muscle.

testosterone test tube blood sample

Such findings seem to support the trends observed by researchers in the 2008 paper, when they reported an increase in the production of androgen receptors within exercised muscles in response to whey, at one and 48 hours post-exercise. If whey increases the uptake of testosterone from the blood and into exercised muscles, then the increased concentrations of testosterone present intracellularly could stimulate the production of more androgen receptors. It could make the muscle more sensitive to the presence of androgens and probably require less protein and allow you to make more of every bit of free testosterone you have.

If this is true, then the question of whether whey is truly anabolic or pro-testosterone would be an unequivocal yes!
The fact that whey produced this response, but leucine alone did not, is also significant. While free amino acids like leucine have their benefits, this study points to the potential to produce new discoveries about the specific value of whey protein. Specifically, there may be bioactive peptides present within whey protein that make whey a superior choice for post-workout nutrition and muscle-building.

More research needs to be done, but for now, don’t skip that shake out of fear that your test levels will take a hit. The opposite may be happening!

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