Neltner 2024: shilajit and collagen trial

Earlier studies found that shilajit switched on collagen-related genes in muscle and skin. This trial from the University of Nebraska-Lincoln asked the next question: does that show up as more collagen actually being made? The researchers measured pro-c1α1, a fragment released into the blood when the body builds type 1 collagen, the main structural protein in skin, bone, tendons and ligaments.

The marker rose sharply in both shilajit groups and not at all on placebo. It is a clean result on a lab measure, but it says nothing yet about how skin looks or joints feel.

What did the Neltner 2024 study do?

Thirty-five recreationally trained men, average age 21, were randomised to take 500 mg of shilajit a day, 1,000 mg a day, or a placebo for 8 weeks. Blood pro-c1α1 was measured before and after. The researchers also checked how many men in each group had a rise bigger than the “minimal clinically important difference”, a threshold for a change large enough to be meaningful (Neltner et al., 2024).

What did it find?

Average pro-c1α1 nearly doubled in the 500 mg group, from 42.5 to 82.3 ng/mL, and more than doubled in the 1,000 mg group, from 42.7 to 113.1 ng/mL. Both rises were statistically significant and large by conventional standards (effect sizes of 1.2 and 1.3). The placebo group showed no significant change.

The spread was wide, though. The standard deviation after supplementation was 46.5 ng/mL at 500 mg and 78.7 ng/mL at 1,000 mg, meaning some men responded a lot and others little. When the researchers counted individual responders, 75% of the 1,000 mg group passed the meaningful-change threshold, compared with 30% on placebo. At 500 mg the figure was 69%, which was not significantly different from placebo (p = 0.06).

What does this mean?

It is the first evidence that shilajit’s effect on collagen genes, seen in muscle (see Das 2016) and skin (see Das 2019), may translate into more collagen being made in the body. It also fits with the earlier Nebraska trial in which 500 mg a day lowered a marker of collagen breakdown in some men (see Keller 2019).

Put together, these studies tell a consistent story at the level of biology. What they don’t yet do is show a benefit anyone would notice.

What doesn’t it show?

• Better skin, hair or nails. None were measured. More collagen production in the blood doesn’t tell us where in the body it ends up.
• Healthier joints or tendons. No injury, pain or function outcomes were measured.
• Effects in women or older adults. Everyone was a trained man of about 21, so results could differ in older people.
• That 500 mg is enough. Only the 1,000 mg dose clearly beat placebo on the responder analysis.
• Long-term effects. The study lasted 8 weeks.

How much should we trust it?

The design is reasonable, but the evidence is limited. With 35 men split three ways, each group had roughly a dozen people. The abstract doesn’t say whether the trial was blinded, how big each group was, whether anyone dropped out, or which product was used. Natreon, which makes a branded shilajit extract, is listed as funder, and the research team overlaps with the Keller 2019 trial, so this is not independent replication.

That is why we grade shilajit for skin and collagen as weak.

Where does this study fit?

This trial is one of two studies on our shilajit for skin and collagen page, alongside the Das 2019 skin study. It is also the only trial to test 1,000 mg a day for 8 weeks; see dosage for how that compares with other studies, and the research library for the full list.