Colostrum is the one supplement named after an immune system's first line of defense. But swallowing antibodies is not the same as being vaccinated, and the honest story of how IgG works in your gut is more interesting, and more limited, than most labels suggest.
Bovine colostrum is rich in immunoglobulin G (IgG), the antibody class that dominates it. Taken by mouth, much of that IgG survives digestion well enough to act inside the gut, where it can bind microbes and toxins. It does not enter your bloodstream and boost your own antibody levels. The best human evidence supports fewer upper-respiratory sick days in people under heavy training load, and a small amount points the same way in children. It is support for the immune system, not a cure or a shield.
What IgG actually is
Antibodies are Y-shaped proteins that attach to one specific target, a viral protein or a bacterial toxin, and flag it for destruction. Your body makes several classes. In human blood, IgG is the most abundant. In colostrum, the first milk a mother produces, IgG is also the headline act: in bovine colostrum, IgG1 alone accounts for more than 75% of the immunoglobulins in the whey fraction, ahead of IgM, IgA and IgG2.
For a newborn calf, this is not a nice-to-have. Calves are born without circulating antibodies and absorb them directly from colostrum in the first hours of life. That is called passive immunity: borrowed protection while the calf's own system matures. Human infants are different, since much of our antibody transfer happens before birth, which is the first reason to be cautious about assuming a cow's biology maps neatly onto an adult human's.
Where the antibodies actually work
When you take colostrum by mouth, the IgG does not travel to your blood to join your own antibodies. Its job, if it has one, happens in the digestive tract. That only makes sense if the protein survives the trip, and a 2015 review in Nutrition Journal (Jasion and Burnett) examined exactly that question across human studies. Twelve of the 15 human studies in infants, children and adults found that orally administered IgG, including bovine colostrum-derived IgG, survived gastric exposure and resisted proteolytic digestion. The intact IgG recovered in stool ranged from trace amounts up to roughly 25% of what was swallowed.
So some of it arrives intact in the intestine, and some does not. That matters because IgG can only bind a target if its binding region has not been broken down. What it can do in the gut is physical: attach to bacteria, viruses and toxins and interfere with their ability to stick to the intestinal lining. This is a local, in-the-gut effect, which is why colostrum's immune story and its gut barrier story are really one story.
Three findings, read honestly
| Evidence | Who was studied | What it found |
|---|---|---|
| Jones et al., 2016 meta-analysis, BMC Sports Science, Medicine and Rehabilitation | 5 randomized trials, 152 people in regular exercise training, 8 to 12 weeks | About 44% fewer days with upper-respiratory symptoms and about 38% fewer episodes versus placebo. Authors flagged small samples and called for larger trials. |
| 2020 systematic review and meta-analysis, Nutrients | Trained and physically active people | Little or no effect on circulating IgG or IgA, and inconsistent results for other immune markers such as leukocyte counts. |
| 2023 randomized trial in pre-school children | 57 children, 500 mg twice daily for 15 days, then 500 mg daily for 30 days | Median 31% reduction in days with upper-respiratory symptoms and 37% on severity, with the effect measurable out to week 20. |
Read the first two rows together and they stop contradicting each other. Colostrum does not raise your blood antibody levels, which is what the second row shows. What the first row measures is something else: how often people got sick. That is consistent with the in-the-gut, mucosal mechanism above: an effect on contact with pathogens at the lining, not a boost to circulating IgG.
It is also worth being clear about the limits. The meta-analysis pooled only 152 people, all training hard, so it does not tell you what happens to a sedentary adult. The children's trial is a single study. And none of these trials show colostrum prevents or treats any infection; they measure symptom days, a softer outcome. That is meaningful evidence for support, and it is not proof of protection.
What colostrum doesn't do
A few claims circulate that the evidence does not back. Colostrum is not a vaccine, and the bovine antibodies in it are not tuned to the specific viruses circulating this winter. It does not raise your own serum IgG in healthy adults, as covered above. And it is not a substitute for the basics that move immunity far more than any supplement: sleep, protein intake, vaccination where recommended, and managing training load and stress.
One more point on honesty about dose: most trials used daily intake over several weeks, and effects were seen with consistency rather than after a single dose. That fits what we cover on timelines, and it is why colostrum belongs in a daily routine rather than a sick-day rescue.
How to use it for immune support
AURÔ's colostrum is standardized to 25% IgG, and the label states the dose rather than just the percentage: 575 mg of IgG per 2.3 g scoop of the powder and 125 mg per 500 mg capsule, based on the manufacturer's 25% IgG specification. If you are not sure how to read that, our guide on what 25% IgG means walks through it. Mix the powder into cold or room-temperature liquid, since heat above 140°F denatures IgG. Starting small and building up helps with the mild digestive adjustment some people notice early on, which we cover in colostrum side effects.
Colostrum is a milk product and is not suitable for anyone with a milk allergy. If you are pregnant, nursing, under 18, or managing a medical condition, speak to your doctor first. What our own batch documents do and do not show is laid out on our science page.
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Everything you want to know
Does colostrum boost your immune system?
It may support it, mainly through antibodies acting inside the gut. In a meta-analysis of five trials in people doing regular exercise training, colostrum was associated with fewer days of upper-respiratory symptoms. It does not raise your own circulating antibody levels, and the evidence outside trained adults and children is limited.
Do the antibodies in colostrum survive digestion?
Partly. A 2015 review found that in 12 of 15 human studies, orally administered IgG survived stomach exposure and resisted digestion, with up to roughly 25% recovered intact in stool. Some is broken down, some reaches the intestine intact.
Is colostrum the same as a vaccine?
No. A vaccine trains your own immune system to make antibodies against a specific pathogen. Colostrum delivers bovine antibodies that act locally in the digestive tract and are not matched to the viruses circulating this season.
When is the best time to take colostrum for immunity?
There is no trial showing one time of day is better. Consistency matters more, since the studies used daily intake over weeks. See our guide to when to take colostrum for the practical details, including keeping it away from hot drinks.
Is colostrum safe for children?
A 2023 trial studied pre-school children, but this is not a recommendation. Colostrum is a milk product, and anyone under 18 should only take a supplement after speaking with a pediatrician.
This article is for educational purposes only and is not intended to diagnose, treat, cure, or prevent any disease. These statements have not been evaluated by the Food and Drug Administration. Dietary supplements are not a substitute for a varied diet or medical advice. Consult a healthcare professional before starting any new supplement, especially if you are pregnant, nursing, or managing a health condition.
