Can you really lower SHBG to free up testosterone naturally?

What did @marekhealth actually say?

The video opens with a striking stat: "up to 44% of all testosterone in the male body is inactive and bound to" SHBG. From there, the creator pitches two interventions, a high-protein diet and four specific minerals (zinc, magnesium, boron, and selenium), as ways to lower SHBG and effectively free up more testosterone. The framing is clean and confident, which is exactly why it deserves a closer look.

The core argument is that SHBG acts as a kind of testosterone trap, and that dietary tweaks can loosen that trap. That is not a fringe idea. It is actually grounded in real physiology and a reasonable body of observational and clinical data. But the confidence of the delivery glosses over some real nuance that viewers should understand before adjusting their diet or supplement routine.

Does the science back this up?

Partially, yes. The protein claim has legitimate support, but it is more complicated than the video suggests. The mineral claims are a mixed bag, with boron having decent evidence, zinc and magnesium being more conditional, and selenium being the weakest link of the four.

A frequently cited cross-sectional analysis by Longcope et al. (2000, Journal of Clinical Endocrinology and Metabolism) found that higher protein intake was associated with lower SHBG levels in older men. That association has been replicated in other observational studies. But observational data does not tell you how much protein, for how long, or whether the effect is clinically meaningful for a healthy young man already eating adequate protein.

On minerals, boron is arguably the most promising. A small but well-designed study by Naghii et al. (2011, Journal of Trace Elements in Medicine and Biology) found that one week of boron supplementation (10 mg/day) significantly reduced SHBG and increased free testosterone in healthy men. Magnesium has some data too, notably from Maggio et al. (2011, Clinical Endocrinology), linking higher magnesium intake to higher free testosterone, likely through SHBG reduction. Zinc's effect on SHBG specifically is weaker, though deficiency is clearly associated with low testosterone overall. Selenium's connection to SHBG is, frankly, thin.

What did they get wrong (or right)?

The 44% bound-to-SHBG figure is in the right ballpark. Most literature suggests roughly 40-50% of testosterone in adult men is SHBG-bound, with another 50-55% loosely bound to albumin and only 1-3% truly free. So that claim is accurate enough.

The protein claim is mostly accurate but oversimplified. The evidence skews toward older men, men with lower baseline protein intake, and observational cohorts. Telling a viewer who already eats 150 grams of protein daily that eating more will meaningfully shift their SHBG is speculative at best.

The mineral claim is where things get sloppy. Packaging zinc, magnesium, boron, and selenium together as if they share equivalent evidence is misleading. Boron has real short-term human trial data. Selenium does not, at least not for SHBG specifically. The phrase "hitting your daily recommended allowance" also conflates RDAs, which are designed to prevent deficiency, with therapeutic doses used in studies. That is a meaningful distinction the video skips entirely.

What should you actually know?

If your SHBG is genuinely elevated and your free testosterone is low despite normal total testosterone, that is a real clinical issue worth addressing with a provider. Lifestyle changes like adequate protein and correcting mineral deficiencies are reasonable first steps, not magic levers.

The honest version of this advice is: if you are protein-deficient, eating more protein may lower SHBG somewhat. If you are boron-deficient (most Western diets are low in boron), supplementing may help. If your zinc or magnesium is low, fixing that benefits testosterone metabolism broadly, though the SHBG-specific effect is less direct.

What this video does not mention: insulin, body weight, thyroid function, and alcohol intake all have well-documented and often larger effects on SHBG than dietary protein or minerals. A person trying to optimize free testosterone who ignores those factors while chasing boron supplements is working around the edges. If you suspect your SHBG is a problem, get a full hormone panel with free testosterone measured, not just estimated.