Does bovine colostrum actually do anything?

Bovine colostrum has become a wellness darling, marketed as a fix for everything from athletic performance to leaky gut to your immune system. The pitch usually leans on the fact that the NCAA bans it, which is supposed to mean it works. The reality is more complicated, and a lot less impressive.

What colostrum actually is, and why the biology is shakier than it sounds

Colostrum is the first milk a mammal produces after giving birth. It's thicker, more yellow, and compositionally different from mature milk. Bovine colostrum, the stuff in the supplements, comes from cows. All mammals produce it, and calves that don't get it from their mothers do worse in measurable ways. So yes, it is biologically important. To a baby cow.

The wellness pitch hinges on a few ingredients. The headliner is IGF-1, insulin-like growth factor 1. Cow colostrum contains anywhere from 50 to 2,000 micrograms per liter of IGF-1, compared to essentially undetectable levels in mature cow milk (per the Bulgarian Journal of Veterinary Science). IGF-1 is a real growth signal. Inject it and your muscles grow. That's why the NCAA and the World Anti-Doping Agency ban it.

Here's the catch. You're not injecting it. You're drinking it. IGF-1 does not get into your blood intact when you swallow it. Some studies that claim it does are actually picking up digested fragments, not the functional molecule. This is the same reason it took years to develop oral GLP-1 drugs. Your stomach is very good at destroying proteins. The NCAA, by the way, doesn't ban colostrum because it makes you stronger. They ban it because it can cause false positives on doping tests, the way poppy seeds can mess up an opioid screen.

The one place the biology has some legs is immunoglobulin A, or IgA. These are antibodies that work in the mucosal surfaces of your nose, mouth, throat, and gut. They don't need to enter your bloodstream to do their job. They can stick to pathogens right there in the GI tract. So there's a plausible mechanism for some local immune effects, even if the IGF-1 story falls apart.

What the trials in athletes actually show

There are a surprising number of studies on colostrum in endurance athletes, mostly highly trained male road cyclists. The British Journal of Sports Medicine ran a 40-kilometer time trial study comparing colostrum to whey protein and found a 2% improvement versus baseline. For a normal person, 2% sounds like nothing. For an elite cyclist losing the Tour de France by four seconds, 2% is everything.

The respiratory infection data is more interesting. A 2003 European Journal of Nutrition study pooled 174 adult men from randomized colostrum-versus-whey trials and tracked upper respiratory symptoms over seven weeks. 32% of the colostrum group reported symptoms versus 48% in the whey group. A separate study in 57 preschool children found a 31% reduction in days with upper respiratory symptoms. Parents would absolutely take that.

I have to be honest about the caveats. These are small studies. When you see a string of small positive trials, you have to worry about publication bias. Negative results in 20-person studies don't get published. Modest positive results do. The preschool study also relied on parental reporting, which is vulnerable to unblinding. The data is medium-quality at best, pointing in a direction.

Why don't we have a definitive large trial? Money. Colostrum is classified as a dietary supplement, which means anyone can sell it. There's no patent, no moat, and no incentive for a pharmaceutical company to spend millions proving it works. This is exactly the kind of question the NIH should be funding, and isn't.

Leaky gut, bacterial translocation, and what colostrum doesn't fix

"Leaky gut" is great marketing. The medical term is intestinal permeability, and your gut is supposed to be permeable. That's how you absorb nutrients. You can measure permeability by giving someone a poorly absorbed sugar like mannitol and checking how much shows up in the blood. Sicker people tend to have more permeable guts. Whether that causes their illness or results from it is unsettled.

The most extreme version of a leaky gut is bacterial translocation, where gut bacteria escape into the bloodstream and cause sepsis. A study of 62 children with newly diagnosed leukemia getting induction chemotherapy randomized them to bovine colostrum or control. Colostrum did not reduce fever or bacterial infection rates. It did improve mucositis, the painful mouth ulcers from chemo, as a secondary outcome. So in the leakiest gut scenario imaginable, colostrum did not prevent the bacteria from getting out.

In athletes, intense exercise does increase gut permeability, and colostrum seems to blunt that rise somewhat. Whether that matters for how you feel or perform is unclear. There are scattered findings elsewhere, including a reduction in diarrhea among HIV patients in Uganda, but a study in children with Shigella infection showed no benefit. The pattern is small studies, modest effects, inconsistent results.

The safety problem nobody talks about

Wellness influencers love raw, unpasteurized colostrum because pasteurization inactivates some of the proteins they're excited about. This is a bad trade. Pasteurization also kills E. coli and other bacteria that will make you genuinely sick.

A 2021 Journal of Dairy Science study tested 1,241 colostrum samples from 39 Czech dairy farms. The average bacterial count was 408,000 colony forming units per milliliter. Only 28.4% met the recommended threshold of under 100,000. A Northern Ireland study found 81% of raw colostrum samples exceeded industry contamination guidelines. If you're taking colostrum to avoid GI problems, raw colostrum is a remarkable way to give yourself GI problems. And the proteins you're trying to preserve still don't make it into your blood intact, even raw.

Bottom line

The biological case for swallowing bovine colostrum is weaker than the marketing suggests. IGF-1 doesn't survive your gut. The IgA story has some plausibility for local immune effects, and there are small trials hinting at fewer upper respiratory infections and modest performance gains in elite cyclists. The leaky gut claims don't hold up where you'd expect them to matter most. The data is suggestive, not convincing, and the stronger findings come from small studies vulnerable to publication bias. If you're an elite endurance athlete or a parent desperate to cut preschool colds, you can make an argument for trying it. For everyone else, save your 50 bucks a month. And whatever you do, skip the raw stuff.

Here's our discussion from the episode:

I covered this in depth on Wellness, Actually. Listen below.

Wellness, Actually Podcast

"What's the deal with colostrum?" — Listen to the full episode, including the week's health news and listener Q&A.