Supplement: Runderbiest

What It Is

Colostrum is far denser than mature milk in the compounds a newborn calf needs: immunoglobulins, mainly IgG, the iron-binding antimicrobial lactoferrin, and growth factors including IGF-1. Supplements are made by collecting this early milk, pasteurizing it, and drying it into a powder or capsule. Those same compounds are what makers point to in selling colostrum for immunity and the gut. The compounds are in the powder. Whether they still act once an adult swallows them is the open question: a compound that works inside the gut can, one that must reach the bloodstream cannot.

What the Evidence Shows

The steadiest finding is in people who train hard. A 2016 systematic review pooled five randomized trials, 152 participants in all, of colostrum in regular exercisers. It found about 44% fewer days of upper respiratory infection symptoms (rate ratio 0.56, 95% CI 0.43 to 0.72). Infection episodes fell about 38% (rate ratio 0.62, 95% CI 0.40 to 0.99) over eight to twelve weeks. The trials were small, and reviewers judged four of the five to carry a moderate or high risk of bias from incomplete reporting. An earlier controlled study in adult men pointed the same way: 32% reported upper respiratory symptoms on colostrum against 48% on whey, though symptom duration did not differ.

The second area is the gut. Heavy endurance exercise makes the intestinal barrier temporarily leakier, and two small trials in athletes found colostrum reduced that rise, measured by sugar-absorption tests and stool zonulin. These were surrogate markers of barrier function in samples of 12 and 16 people, not symptoms or disease outcomes. A third strand is mucosal immunity: in 35 distance runners, colostrum raised salivary IgA by 79% over 12 weeks. Salivary IgA is only a marker. The authors called its meaning uncertain at that sample size, so a rise need not mean fewer infections.

The trials stop short where muscle is concerned. One trial gave active men and women 20 g of colostrum or whey a day for eight weeks. Treadmill time to exhaustion, one-repetition-maximum bench press, and repetitions to exhaustion did not differ between the groups. Colostrum did not outperform training plus protein. The anabolic pitch runs through IGF-1, a growth-driving hormone in colostrum: swallow it, IGF-1 rises, muscle grows. A tracer study followed labeled IGF-1 after it was swallowed and recovered about 96% as a broken-down fragment, only about 4% intact. Some training trials recorded a small rise in blood IGF-1 on colostrum, but the rise was modest and came with no gain in muscle or strength.

The Research & Studies

Everything here is based on the research we have collected and checked, sorted into groups and ordered with the strongest evidence first. Click any claim to open the studies behind it.

How it works

Swallowed IGF-1 is broken down in the gut, about 96%, and does not act as an anabolic hormoneModerate · no effect

In plain terms

The growth factor IGF-1 in colostrum is mostly broken down when you swallow it, not absorbed whole, so it does not work as the muscle-building hormone the marketing suggests.

In detail

Mero and colleagues (2002) gave athletes 20 g a day of colostrum and, in a companion tracer experiment, followed labeled recombinant IGF-1 after ingestion: gel electrophoresis of serum 60 minutes later showed about 96% of the radioactivity as a 0.6 kDa fragment and only about 4% at the 40 to 90 kDa range of intact IGF-1, indicating near-complete digestion. Serum IGF-1 rose modestly in the colostrum group in that study and in the same group's 1997 trial in male sprinters, but the rises were small and were not accompanied by measured gains in muscle mass or strength attributable to colostrum.

Who this may not transfer to:The training trials included male and female athletes and the 1997 companion trial was in male sprinters; the digestion of oral IGF-1 is a general physiological finding not expected to differ by sex.

How to use it

Use this to weigh the anabolic marketing: colostrum does contain IGF-1, but it is not delivered intact as a hormone, and any small serum change has not translated into muscle or strength gains in the trials.

The studies · 2

Mero et al., IGF-I, IgA, and IgG responses to bovine colostrum supplementation during training · J Appl Physiol 2002;93(2):732-739

Mero et al., Effects of bovine colostrum supplementation on serum IGF-I, IgG, hormone, and saliva IgA during training · J Appl Physiol 1997;83(4):1144-1151

Colostrum is richer than mature milk in immunoglobulins, lactoferrin, and growth factorsModerate · mixed

In plain terms

Colostrum contains antibodies, lactoferrin, and growth factors at higher levels than ordinary milk, which is why it is studied, but having them in the powder is not the same as them working once swallowed.

In detail

Reviews of bovine colostrum, including Playford and Weiser (2021), document its composition: high concentrations of immunoglobulins (predominantly IgG), lactoferrin, lactoperoxidase, lysozyme, and growth factors such as IGF-1 and transforming growth factors, at levels well above those in mature milk, declining over the first days after calving. These components underlie the immune and gut-barrier hypotheses tested elsewhere on this page; the composition is well characterized, while the clinical effect of ingesting them as an adult is the open question.

How to use it

Use this as the factual basis for what colostrum is, and keep separate from what it does: the constituents are established, the adult clinical effects are what the graded claims address.

The study · 1

Playford & Weiser, Bovine Colostrum: Its Constituents and Uses · Nutrients 2021;13(1):265

Respiratory Infection

About 44% fewer upper respiratory infection days in people who train, across five small trialsEmerging

In plain terms

In people who train hard, taking colostrum for a couple of months meant fewer days with cold and sore-throat symptoms, roughly 40% fewer, across five small trials. It is the steadiest finding the supplement has.

In detail

The 2016 systematic review and meta-analysis by Jones and colleagues pooled five randomized controlled trials, 152 participants in total, all in adults engaged in regular exercise training, comparing oral bovine colostrum with a concurrent control over eight to twelve weeks. Upper respiratory symptom days fell (rate ratio 0.56, 95% CI 0.43 to 0.72, P < 0.001) and episodes fell (rate ratio 0.62, 95% CI 0.40 to 0.99, P = 0.04). The reviewers judged four of the five included trials to have a moderate or high risk of bias, largely from incomplete reporting, and there were too few data to pool symptom duration.

Who this may not transfer to:The pooled trials included men and women in exercise training; the effect was measured in trained adults and may not transfer to sedentary or general populations.

How to use it

This is the finding with the most support behind it, and it is still built on five small trials. It applies to people in hard training, taken over a defined block, not to the general population seeking everyday immune support.

The study · 1

Jones et al., 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

Fewer adult men reported cold symptoms on colostrum than on whey, 32% versus 48%Preliminary

In plain terms

In one study of adult men, fewer of those on colostrum came down with cold symptoms than those on whey, though when they did get sick the illness lasted about the same time.

In detail

Brinkworth and Buckley (2003) coded logbooks from double-blind placebo-controlled studies in which men had been randomly allocated to 60 g a day of concentrated bovine colostrum protein (n = 93) or whey protein (n = 81) for eight weeks. After excluding the first week to remove pre-existing infections, a lower proportion of the colostrum group reported upper respiratory symptoms during the following seven weeks (32% versus 48%, P = 0.03, 95% CI -30% to -2%), while the duration of symptoms did not differ (6.8 +/- 4.2 versus 6.0 +/- 4.4 days, P = 0.27).

Who this may not transfer to:The analysis was in men only; whether the same reduction in reported infections occurs in women was not tested here.

How to use it

A single-sex study using a high 60 g dose and a retrospective coding of symptom logbooks. It points the same way as the pooled meta-analysis but is best read as supporting, not independent evidence.

The study · 1

Brinkworth & Buckley, Concentrated bovine colostrum protein supplementation reduces the incidence of self-reported symptoms of upper respiratory tract infection in adult males · Eur J Nutr 2003;42(4):228-232

Digestion

Colostrum lowered exercise-induced gut leakiness on lab tests in two small athlete trialsEmerging

In plain terms

Heavy endurance exercise makes the gut lining temporarily leakier, and in two small studies of athletes colostrum reduced that leakiness on lab tests.

In detail

Marchbank and colleagues (2011) ran a double-blind placebo-controlled crossover in 12 volunteers, 14 days of colostrum or placebo before a standardized exercise bout, and found colostrum blunted the exercise-induced rise in the 5-hour urinary lactulose-to-rhamnose ratio, a marker of small-intestinal permeability, with supporting cell-line work on heat-induced epithelial damage. Halasa and colleagues (2017) supplemented 16 athletes during peak training with 500 mg a day of colostrum or placebo (whey) for 20 days; the lactulose-to-mannitol test normalized in the colostrum group and the intervention-related change was significantly lower than placebo, with a smaller but significant effect on stool zonulin.

Who this may not transfer to:Both trials were small and the sex distribution was not clearly reported; results are in trained athletes and may not transfer to non-exercisers.

How to use it

These are surrogate markers of barrier function in very small athlete samples, not symptoms or disease. The finding is specific to exercise-induced permeability and should not be extended to treating a diagnosed gut disorder.

The studies · 2

Marchbank et al., The nutriceutical bovine colostrum truncates the increase in gut permeability caused by heavy exercise in athletes · Am J Physiol Gastrointest Liver Physiol 2011;300(3):G477-G484

Halasa et al., Oral Supplementation with Bovine Colostrum Decreases Intestinal Permeability and Stool Concentrations of Zonulin in Athletes · Nutrients 2017;9(4):370

Across gut diseases the colostrum trials conflict and are too varied to poolPreliminary · mixed

In plain terms

For actual gut diseases, the trials of colostrum point in different directions and cover very different conditions, so there is no clear across-the-board answer.

In detail

The 2024 systematic review by Hajihashemi and colleagues concluded that evidence on bovine colostrum for gastrointestinal diseases is conflicting, summarising clinical trials across varied conditions without a pooled estimate because the diseases and designs differed too much. The earlier 2014 systematic review by Rathe and colleagues on clinical applications of bovine colostrum therapy similarly found the strongest support in specific settings such as infectious diarrhea and chemotherapy-related mucositis, with the overall picture limited by small and heterogeneous trials.

Who this may not transfer to:The reviews pooled trials in mixed populations across several distinct gastrointestinal conditions, which is itself the main reason no single effect can be stated.

How to use it

Read this as a limitation, not an endorsement: colostrum has been trialed across many gut conditions with inconsistent results, so it is not established as a treatment for any general gut complaint.

The studies · 2

Hajihashemi et al., Therapeutic effects of bovine colostrum applications on gastrointestinal diseases: a systematic review · Syst Rev 2024;13(1):76

Rathe et al., Clinical applications of bovine colostrum therapy: a systematic review · Nutr Rev 2014;72(4):237-254

Immune Function

Colostrum raised salivary IgA by 79% in runners, a marker not tied to fewer infectionsPreliminary

In plain terms

Colostrum raised a mucosal antibody in the saliva of runners in one study, but whether that shift means fewer infections is not established, and other immune markers move inconsistently.

In detail

Crooks and colleagues (2006) supplemented 35 distance runners (20 men, 15 women, aged 35 to 58) with bovine colostrum or placebo for 12 weeks; median salivary IgA rose 79% in the colostrum group and the time-dependent change from baseline was significant (P = 0.0291), holding after adjustment for training volume and reported respiratory symptoms. The authors cautioned that the physiological meaning is uncertain given the small sample. A 2020 systematic review of immunological outcomes of colostrum in trained and physically active people found effects across the various markers measured to be inconsistent.

Who this may not transfer to:The salivary IgA trial included both sexes; the marker was measured in trained runners and its link to fewer infections was not demonstrated.

How to use it

Treat a rise in salivary IgA as a marker change, not a proven reduction in illness; the clinical outcome that matters, fewer infections, is covered by the respiratory claims and rests on separate, limited evidence.

The studies · 2

Crooks et al., The effect of bovine colostrum supplementation on salivary IgA in distance runners · Int J Sport Nutr Exerc Metab 2006;16(1):47-64

Glowka et al., Immunological Outcomes of Bovine Colostrum Supplementation in Trained and Physically Active People: A Systematic Review · Nutrients 2020;12(4):1023

Muscle And Strength

Colostrum did not improve strength or endurance beyond whey plus trainingPreliminary · no effect

In plain terms

In one small trial, colostrum did not improve strength or endurance compared with whey protein, though there was a small difference in how body composition shifted.

In detail

Antonio and colleagues (2001) randomized active men and women to 20 g a day of bovine colostrum powder or whey protein for 8 weeks while training aerobically and with resistance at least three times a week. None of the performance measures, treadmill time to exhaustion, one-repetition-maximum bench press, or submaximal repetitions to exhaustion, differed between groups. The whey group gained body weight (mean +4.7 lb, +2.11 kg) while the colostrum group gained bone-free lean body mass (mean +3.3 lb, +1.49 kg), a difference in composition without a difference in measured performance.

Who this may not transfer to:The trial enrolled both active men and women; it is small and single, so the body-composition signal in particular should not be over-read.

How to use it

A single small trial with an active comparator. The lean-mass difference has not been reliably reproduced, and performance did not improve, so colostrum is not a supported ergogenic or muscle-building aid.

The study · 1

Antonio et al., The effects of bovine colostrum supplementation on body composition and exercise performance in active men and women · Nutrition 2001;17(3):243-247

What the Marketing Overclaims

• The growth-factor story. Colostrum contains IGF-1, and IGF-1 builds tissue, so the pitch is that swallowing it floods the body with anabolic hormone. That flood never happens, and the muscle trials show no edge over plain protein. Colostrum sold as a testosterone-adjacent muscle builder rests on a step the gut never allows.
• The cure-all framing. Colostrum is marketed at once for gut healing, immunity, skin, hair, energy, and anti-aging. The human research reaches only two of those: immunity in hard trainers, and exercise-related gut leakiness on lab tests. Skin, hair, general energy, and anti-aging rest on little direct human data.
• The strength of the base. Several of these trials were run with supplement-industry involvement, and the pooled respiratory result rests on the same small, bias-prone studies. That involvement does not erase the signal. It sets the ceiling on how confidently anyone can claim it.

How It Works

The usual account is that colostrum gives an adult what a calf gets. That means antibodies against infection, lactoferrin to bind iron away from bacteria, and growth factors like IGF-1 to build tissue. But the adult gut digests proteins, and most of these compounds are proteins, so most never act inside the body. The effects that hold up are the ones that happen in the gut itself, before digestion finishes.

Claims that need these compounds to reach the bloodstream intact are the ones the trials do not support.

Anatomy of the Practice

1In the gut, first pass

Colostrum reaches the stomach and small intestine, where its proteins meet digestive enzymes. Immunoglobulins and growth factors are proteins, so most break into fragments and amino acids. Some immunoglobulin and lactoferrin activity survives locally. That surviving activity is the most plausible route for any effect.

2At the gut lining

Lactoferrin and growth factors act on the gut wall itself. That local action is the proposed mechanism behind the permeability findings. The effect stays at the gut wall colostrum touches first.

3Beyond the gut

The trials do not support the pitch that colostrum raises circulating growth factors or delivers antibodies into the blood. Both claims need whole proteins to cross the gut wall intact, and they do not. The reach of colostrum stays in the gut and its immune tissue.

Go Deeper

• Protein and muscle: what actually builds muscle, and why total protein plus training outrank any colostrum-specific growth claim.
• Whey versus whole food protein: the comparator used in most colostrum trials, and the better frame for the muscle question.
• Whole foods: the cheaper foundation for most of what people hope colostrum does for immunity and the gut.
• Probiotics: the other heavily marketed gut supplement, and a useful check on how much of a gut claim the trials support.
• IBS: where gut-barrier ideas meet a defined condition, and what the evidence says about treating it.

Cautions For This Practice

Extra restraint

Everything to be aware of is here, in one place. This practice suits most healthy people; a few situations call for real care.

Dairy allergy

Bovine colostrum is a milk product and carries milk proteins, including casein and whey proteins. If you have a cow milk allergy it is not safe to take, and a severe milk allergy can produce a serious reaction. This is the clearest reason to avoid it.

Lactose intolerance

Colostrum contains some lactose, less than mature milk but enough to cause bloating, gas, or loose stools in people who do not tolerate lactose well. If you are lactose intolerant, start low and stop if it causes gut symptoms.

Sourcing and quality vary

Colostrum is a collected animal product, so quality depends on the herd, the collection, and the processing. Products vary in how much active immunoglobulin they contain and in whether they are tested for contaminants. Favor a supplier that pasteurizes, discloses IgG content, and provides third-party testing.

It is an animal product

Colostrum is an animal product taken from dairy cows, so it does not suit a vegan diet. Some readers also have concerns about collecting the early milk a calf would otherwise receive.

Not a substitute for vaccination or medical care

Colostrum is a supplement, not a treatment. It does not replace vaccines, and it is not a therapy for a diagnosed infection or gut disease. The trials were in healthy, mostly athletic adults, so if you are pregnant, immunocompromised, or unwell, raise it with your clinician before starting.

Athletes should check anti-doping status

Colostrum contains growth factors, including IGF-1. Some anti-doping authorities advise against it for that reason, and because banned substances are hard to rule out in a natural product. If you compete under an anti-doping code, check the current guidance for your sport before using it.

Start slow, be smart, read the research, and consult a professional if you have any concerns. This is here to inform your choice, not make it for you.

Common Questions

Does bovine colostrum actually boost your immune system?

In the average person who is not training to exhaustion, no controlled trial shows colostrum prevents everyday colds. Its makeup cuts against a broad claim too: colostrum's antibodies, mainly IgG, were raised against cattle pathogens, so they are not matched to the viruses that infect people.

Will colostrum build muscle or raise my IGF-1?

No. For muscle, the evidence points to total protein and resistance training. A growth factor in a capsule adds nothing once you hit your protein target and train hard enough to recover from.

Is colostrum good for gut health or leaky gut?

For "leaky gut" as an everyday complaint, or for a diagnosed gut disorder such as IBS, the evidence is different. Across gastrointestinal conditions the trials conflict and are too varied to pool, so colostrum is not established as a treatment for any of them. The one supportive gut finding was in athletes on lab markers, not in people with gut symptoms.

How much do you take, and is it safe?

The upper respiratory trials mostly used about 10 to 20 g a day of colostrum powder through a hard training block. The gut-permeability work used far less, from around 500 mg. In healthy adults it is generally well tolerated, with mild digestive upset the most common complaint. The real limit is that it is a dairy product.

What actually moves the needle for immunity and recovery?

For general wellness, the proven levers cost nothing: sleep, enough total protein, and training you recover from. Colostrum's one supported use is narrower, for fewer sick days through a heavy training block. If that training-block goal is yours, it is a reasonable thing to try.