Bovine Colostrum

What it is

Bovine colostrum is the first milk a cow produces after giving birth. It is rich in antibodies and other immune-active compounds, and it is sold as a powder or capsule supplement [1]. People mostly use it to support gut health and immunity, especially athletes [2].

How it might work

Researchers propose that the antibodies, antimicrobial proteins and growth factors in colostrum help protect the gut lining and support mucosal immunity [1]. These mechanisms are proposed, and the trials so far have not confirmed them [3].

What the research says

Gut leakiness. The best-supported finding is on intestinal permeability, a measure of how easily substances pass through the gut wall. A meta-analysis (a study that pools many trials) of 10 randomized trials found that colostrum lowered the urinary lactulose/rhamnose ratio by 0.24 and the lactulose/mannitol ratio by 0.01, though trials disagreed widely and blood levels of a gut-damage marker (I-FABP) did not change [4]. In a trial of 16 athletes, 500 mg a day for 20 days brought raised permeability tests back to the normal range, while placebo did not [5]. In 18 men who exercised, 14 days of 20 g a day roughly halved the post-exercise rise in the permeability ratio (148% of baseline versus 273% on placebo) and blunted the rise in I-FABP [6].

Colds and respiratory infections. In a triple-blind trial of university students, 0.5 to 1 g a day for 45 days (plus a one-week booster) cut symptomatic days of upper respiratory infection among medical students, who face more exposure to infections, and improved symptom severity and well-being [7]. A study of 160 children aged 1 to 6 with recurrent infections reported that total infections fell from 8.6 to 5.5 after four weeks of colostrum, but it had no placebo group, so the drop could be partly due to chance or season [8]. A systematic review of studies in athletes and active people found colostrum seemed to help prevent upper respiratory illness [1].

Immune markers. A meta-analysis of 10 trials with 239 athletes and active adults found colostrum had little or no effect on blood immunoglobulins (IgA, IgG), lymphocytes or neutrophils, or on saliva IgA [3]. A 12-week trial of 28 endurance athletes found higher saliva secretory IgA after exercise but no change in blood immunoglobulins [9]. A 24-week trial in young female basketball players found no effect on immune markers [10].

Diarrhea in children. A meta-analysis of five trials in children with infectious diarrhea found colostrum cut stool frequency by 1.42 times a day and lowered the odds of having diarrhea by 71% (odds ratio 0.29) [11]. A double-blind trial of 160 children with acute diarrhea reported less vomiting, diarrhea and lower illness severity scores at 48 hours [12]. A systematic review of 22 trials (1,427 patients) found stool frequency fell in all seven studies that measured it, but most found no change in how long diarrhea lasted [13]. A 2025 review of eight pediatric studies called the evidence inconclusive because the studies differed so much in dose, form and outcomes [14].

Exercise performance. Trials of athletic performance are mixed. Cyclists taking 10 g a day improved a 40 km time trial by about 1.9% after a hard training week [15]. Soccer players taking 3.2 g a day for six weeks recovered jump performance and inflammation markers faster after a shuttle test [16]. But a 12-week trial in swimmers and triathletes [17], a six-month trial in football players [18] and a heat-exercise trial in trained and untrained men [19] found no performance benefit.

Doses used in studies

Doses in trials vary a lot. Immune trials used 0.5 to 1 g a day for 45 days [7] and 500 mg a day for 20 days [5]. Other trials used 3.2 g twice a day for 24 weeks [10], 10 g a day for 10 weeks [15], 20 g a day for 14 days [6] and 25 g a day for 12 weeks [9]. A reviewer of pediatric studies noted that doses and forms differed too much to compare [14].

Safety and interactions

Common side effects: the trial authors described colostrum as safe over 20 days in athletes [5] and as a relatively mild and safe intervention over six months [18]. The abstracts reviewed did not list specific side effects. Upper limits or toxic doses: no maximum safe dose has been established in the studies reviewed here. Medicine interactions: the studies reviewed did not report on interactions with medicines. Pregnancy and breastfeeding: the adult supplement trials reviewed did not include data on pregnancy or breastfeeding. Medical conditions: colostrum comes from cow's milk, and the trials here did not report on people with milk allergy, kidney or liver disease or bleeding disorders, so there are no data to say who should avoid it. Anyone with these conditions or who takes medicines should check with a doctor first.

Caveats and open questions

Most athlete trials are small, with 16 to 28 participants [5][18]. Several were funded or co-written by colostrum makers [7][16][15]. Reviews of colostrum in people aged 35 and over found only one trial, so evidence in older adults is thin [20]. Review authors repeatedly call for larger, well-designed trials with consistent doses [4][13]. A gut-health trial of 140 people has not yet started recruiting (NCT07856979).