Colostrum Side Effects: What's Normal, What Isn't, and Who Should Skip It

By Heather Young, co-founder of magic milk

The short version

Most people who try bovine colostrum have no side effects, or mild ones: nausea, gas, or bloating in the first week or two, per the Cleveland Clinic and Cedars-Sinai. The clearest reason to skip it entirely is a cow's milk allergy, since colostrum is a dairy product. The Cleveland Clinic also flags a real, unresolved question: colostrum's growth factor IGF-1 has a theoretical link to certain cancers that research hasn't settled either way, so cancer history, hormone sensitivity, pregnancy, breastfeeding, and immune conditions or medications all belong in a conversation with your doctor, not a guess. Supplements, colostrum included, are not FDA-approved like drugs, so who you buy from matters more than usual. None of this is a reason to panic, but it's a reason to know your own health history before you decide.

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What colostrum side effects actually look like

Bovine colostrum side effects tend to be unremarkable. The most commonly reported issues are gastrointestinal: nausea, gas, and bloating, per the Cleveland Clinic and Cedars-Sinai. Plenty of people take colostrum powder daily and notice nothing at all. For the fuller picture of what colostrum actually is, this explainer is a good starting point.

Can colostrum cause constipation, diarrhea, or bloating? Bloating and gas are the specific symptoms named in the clinical sources above. Constipation and diarrhea aren't established side effects in the reputable literature, but any new addition to your diet can cause a few days of adjustment. If symptoms are severe or don't ease up after a week or two, call your doctor instead of pushing through.

Does colostrum make you poop? Not reliably, and not by design. It isn't a laxative and isn't marketed as one, and there's no established mechanism showing a consistent effect on bowel movements either way.

Can colostrum cause acne? Acne isn't listed among documented side effects for bovine colostrum. Dairy affects some people's skin individually, so if yours is dairy-reactive, watch for that pattern here too, since colostrum carries trace lactose. Know your own body on this one.

Does bovine colostrum cause weight gain? No good evidence that it does. A typical serving is a small amount of powder, not a calorie-dense meal replacement, and it isn't flagged in the clinical safety literature as a side effect to watch for.

Who should not take colostrum

This is the section to actually slow down and read.

• Severe dairy allergy. Colostrum comes from cows. It is not vegan and not fully dairy-free, and it carries trace lactose. The Cleveland Clinic and Cedars-Sinai both name a cow's milk allergy as a reason to avoid it, and Memorial Sloan Kettering documents a case of anaphylaxis in a 16-year-old with a cow's milk allergy after a colostrum-based cream was applied to a surgical wound. If your allergy is real and diagnosed, this isn't for you.
• Pregnancy and breastfeeding. Cedars-Sinai flags these as situations where effects aren't well studied. Talk to your OB first.
• Immunocompromised individuals, autoimmune conditions, or immunosuppressive medication. Colostrum affects immune-related pathways that haven't been well studied in these populations. This is a conversation for your doctor, not a guess.
• Hormone-sensitive cancers. Memorial Sloan Kettering notes bovine colostrum contains trace estrogen and recommends these patients discuss it with their doctor first.
• Anyone on prescription medication. Mention any new supplement to your doctor or pharmacist so they can flag interactions specific to you.

If you're wondering whether any of this applies differently to kids, we've covered that separately.

Can you take too much bovine colostrum, and is it FDA approved

There's no firmly established upper limit, largely because dosing hasn't been standardized across studies or products, a gap the Cleveland Clinic points out directly. Follow the serving size on your product rather than assuming more is better, and scale back if you notice discomfort.

As for approval: no dietary supplement, colostrum included, is FDA-approved the way a drug is. Drugs get premarket approval. Supplements are regulated more like a category of food: the FDA sets manufacturing standards and can act after a product reaches the market, but doesn't review it beforehand. Cedars-Sinai puts it plainly: without that pre-approval, some products can contain something other than what's on the label, or contaminants that shouldn't be there.

That gap is exactly why third-party testing matters for any colostrum product, not just ours. We test every batch of magic milk through EuroFins, an independent lab, and publish the actual results rather than a badge, and we're GMP certified with no proprietary blends.

Does bovine colostrum contain estrogen, and does it have IGF-1

Yes to both, and both deserve a straight answer rather than a comforting one.

Colostrum contains trace, naturally occurring estrogen, the same way regular cow's milk does. Memorial Sloan Kettering documents this and recommends anyone with a hormone-sensitive cancer discuss colostrum with their doctor first. Trace hormones aren't a therapeutic dose, but "trace" isn't "zero."

Colostrum also naturally contains IGF-1 (insulin-like growth factor 1), the source of most of the internet's anxiety about it. A controlled study in the European Journal of Nutrition, available on PubMed Central, tested standard colostrum doses over a single sitting and up to twelve weeks daily, and found no meaningful rise in circulating IGF-1 in healthy adults, likely because digestion breaks most of it down before it reaches the bloodstream. That's real, but it only answers whether oral colostrum measurably raises blood IGF-1. It doesn't close the broader question of IGF-1 and cancer risk, which the next section addresses directly.

Does bovine colostrum cause cancer

There is no research showing colostrum causes cancer. There is also no research showing it prevents or treats cancer, and we're not making either claim. What exists is an open, unresolved concern, not a settled myth and not a proven risk, and we'd rather say that plainly than round it toward whatever's convenient for us.

The Cleveland Clinic's own overview raises this directly: a theoretical link between colostrum's IGF-1 and certain cancers, including breast and prostate cancer, presented as a live open question, not something research has ruled out. It also notes researchers don't yet fully understand how bovine colostrum affects the human body, that rigorous research is limited, and that potency can vary batch to batch since it isn't FDA-regulated. Worth saying plainly: the dietitian quoted there says she doesn't personally recommend it. We're citing that source anyway, and quoting it straight, because we'd rather you hear the skeptical case from a major medical center than a filtered version of it from us.

If cancer history, active treatment, or a hormone-sensitive condition applies to you, bring this page to your oncologist and let them weigh in, not us.

Is colostrum banned by the NCAA

The honest answer: colostrum itself isn't named on the NCAA's published banned substances list, which groups banned drugs into classes like stimulants, anabolic agents, and peptide hormones and analogues (the class covering hGH and hCG). IGF-1 sits conceptually in that growth-factor territory, which is why some anti-doping bodies, WADA included, have issued cautionary language about colostrum without formally banning it. Read the NCAA document closely and it says so itself: the list is "neither a complete nor exhaustive list," and any substance chemically or pharmacologically related to a banned class is also banned, with the athlete held accountable either way. So "not on the list" is not the same as "cleared." If you're in any drug-tested program, don't rely on a supplement blog, including this one, to make that call. Check directly with your compliance officer first.

Are colostrum supplements safe in general

For most healthy adults, reported side effects are mild. But "mild in most people" isn't "settled science": the research base is genuinely thin, which is part of why the Cleveland Clinic's own dietitian doesn't personally recommend it, and why "generally safe for most people" isn't "safe for you specifically" if you fall into any group above. Sourcing is part of how we'd judge any supplement's safety, and our buyer's guide covers what to look for.

When to stop and call your doctor

Stop and check in with your doctor if you notice hives, swelling, or trouble breathing (an allergic reaction needing urgent care), digestive symptoms that are severe or don't ease after a week or two, or any new symptom alongside a condition you're already managing. None of these are common, but all are worth taking seriously if they happen.

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If you've read all of this and colostrum still sounds right for you, magic milk is our take on it: 1 gram of grass-fed colostrum and 4 grams of collagen peptides per serving, in a chocolate milk you'd actually want to drink, with every batch tested and the results public. If it's not right for you, that's a genuinely fine outcome too. Our FAQ has more on ingredients and sourcing either way.