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Colostrum side effects: what the trials report

Written by the Full Measure editorial team, which sells supplements. Approved for publication by the Full Measure owners. Updated .

Drafted with AI assistance from the sources listed below. How we write these

Quick answer

Colostrum is a milk product, so anyone with a milk allergy should avoid it. In trials, side effects were few and mostly mild stomach upset, though many trials did not track them closely. In a 107-day trial at 0.5 to 1 g a day, gut complaints were no more common than with placebo.1,2,3

Key facts

  • Reviewers call colostrum generally well tolerated but note that many trials reported side effects poorly.2
  • Fresh colostrum is about 2 to 3% lactose, less than the roughly 5% in mature milk.1
  • In the first low-dose trial, no one on colostrum reported important digestive side effects over 20 days.4
  • Most studies found no rise in blood IGF-1 with colostrum, the growth factor behind WADA's caution.5

What trials report

Mild stomach problems were reported in one trial, in women only, and generally faded with time. The other trials in the same review reported no side effects or did not say.2

In a 107-day trial at 0.5 to 1 g a day, digestive symptoms were no more common than with placebo, and no serious adverse events were reported.3

Nausea, diarrhea, bloating and abdominal pain are the side effects described for colostrum taken by mouth, usually early in use and fading after a few days.3

In the first low-dose trial, no one taking colostrum for 20 days reported important digestive side effects, while four of the eight on the whey placebo reported loose stools, bloating, nausea or poor appetite.4

That last result is a reminder that the comparison matters. Whey protein, the usual placebo, is itself a milk product, and half of that placebo group reported gut complaints.4

Milk allergy and lactose

Colostrum keeps the proteins of cow's milk, including beta-lactoglobulin, a major trigger of cow's milk allergy that is not found in human milk.1

A milk allergy is a reason not to take colostrum at all. In one trial, 9 of the 271 students recruited withdrew because they suspected a milk allergy.3

Colostrum contains lactose, about 2 to 3% of fresh colostrum against about 5% in mature milk.1

If you are lactose intolerant, ask your doctor before taking it. Our label does not state the lactose content of the powder.

Growth factors and drug testing

WADA does not prohibit colostrum, but since 2013 it has advised athletes against it because its growth factors could affect a doping test.5

Most studies found that colostrum does not raise blood levels of the growth factor IGF-1, either in the hours after a dose or over 4 to 12 weeks, because it is broken down during digestion.5

By one laboratory's measurements, a 10 g serving of colostrum carries about 3.2 times the IGF-1 of a 200 mL glass of milk, about as much as 40 g of whey protein.5

If you are tested, check with your sport's governing body before using any colostrum product.

Very large amounts

At about 120 g a day, the amount one heat study used, a reviewer estimated an extra 70 g of protein and 35 g of lactose a day and warned that this could upset the gut.5

No upper limit has been set for colostrum. Most trials used 10 to 20 g a day for up to 12 weeks, and a few used 60 g a day for 8 to 9 weeks. Reviewers describe it as generally well tolerated while noting that side effects were poorly reported.2,5,6,7

Who should avoid it or ask first

  • Avoid it if you have a milk allergy.
  • Ask first if you are lactose intolerant.
  • Ask first if you are pregnant or nursing. We found no trials of colostrum supplements in pregnancy.
  • Ask first if you are under 18.
  • Ask first if you take prescription medicines. No interactions are documented, but trials did not look for them.

Questions people ask

Is colostrum safe to take every day?

Trials have given it daily for up to 12 weeks, and at low doses over 107 days with breaks, without serious adverse events. Most trials in adults lasted 12 weeks or less, so longer daily use is not well studied.2,3,8

Are colostrum side effects different for women?

One trial in a 2016 review reported mild stomach problems in women only, which generally faded with time. The other trials in that review reported no side effects or did not say.2

Can colostrum cause bloating?

Bloating, nausea, loose stools and stomach pain are the side effects described for colostrum, mostly in the first days. In a placebo-controlled trial at 0.5 to 1 g a day, they were no more common than with placebo.3

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Sources

  1. Playford RJ, Weiser MJ. Bovine Colostrum: Its Constituents and Uses. Nutrients. 2021;13(1):265. Opened 2026-10-01.
  2. Jones AW, March DS, Curtis F, Bridle C. Bovine colostrum supplementation and upper respiratory symptoms during exercise training: a systematic review and meta-analysis of randomised controlled trials. BMC Sports Sci Med Rehabil. 2016;8:21. Opened 2026-10-01.
  3. Baśkiewicz-Hałasa M, Stachowska E, Grochans E, et al. Moderate Dose Bovine Colostrum Supplementation in Prevention of Upper Respiratory Tract Infections in Medical University Students: A Randomized, Triple Blind, Placebo-Controlled Trial. Nutrients. 2023;15(8):1925. Opened 2026-10-01.
  4. Hałasa M, Maciejewska D, Baśkiewicz-Hałasa M, et al. Oral Supplementation with Bovine Colostrum Decreases Intestinal Permeability and Stool Concentrations of Zonulin in Athletes. Nutrients. 2017;9(4):370. Opened 2026-10-01.
  5. Davison G. The Use of Bovine Colostrum in Sport and Exercise. Nutrients. 2021;13(6):1789. Opened 2026-10-01.
  6. Duff WR, Chilibeck PD, Rooke JJ, Kaviani M, Krentz JR, Haines DM. The effect of bovine colostrum supplementation in older adults during resistance training. Int J Sport Nutr Exerc Metab. 2014;24(3):276-285. Opened 2026-10-07.
  7. Brinkworth GD, Buckley JD, Bourdon PC, Gulbin JP, David A. Oral bovine colostrum supplementation enhances buffer capacity but not rowing performance in elite female rowers. Int J Sport Nutr Exerc Metab. 2002;12(3):349-365. Opened 2026-10-07.
  8. Durkalec-Michalski K, Główka N, Podgórski T, Woźniewicz M, Nowaczyk PM. The effect of 12-week high-dose Colostrum Bovinum supplementation on immunological, hematological and biochemical markers in endurance athletes: a randomized crossover placebo-controlled study. Front Immunol. 2024;15:1425785. Opened 2026-10-07.

This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.