The short version

Colostrum’s signature component is immunoglobulin G (IgG) — but in an adult gut, oral IgG is largely digested, not absorbed into your bloodstream. So “boosts your antibodies” claims are misleading; any benefit acts locally in the digestive tract. The most promising (still mixed) evidence is a modest reduction in upper-respiratory infections.

The label test: a disclosed IgG percentage or milligram figure, first-milking and low-heat processing, and an honest gram dose — because studies used 10–25 g/day and a single capsule rarely holds even 1 g. A product that won’t state its IgG is asking you to trust it, not verify it.

What it actually is

Bovine colostrum is the first milk a cow produces in the days right after calving. It evolved to hand a newborn calf passive immunity, so it’s dense in immunoglobulins (antibodies), growth factors, lactoferrin and oligosaccharides. Its headline component is immunoglobulin G — IgG makes up roughly 85–95% of the total immunoglobulin content — and IgG concentration is highest at the very first milking, dropping sharply within hours.

Supplements are made by collecting surplus early-milking colostrum, then defatting, pasteurizing and drying it into powder or capsules. Processing matters: too much heat degrades the immunoglobulins, so how a product is handled affects how much intact IgG actually survives to the tub.

Here is the caveat marketing skips: the IgG in bovine colostrum is a bovine antibody, and unlike a newborn calf, adult humans digest most oral immunoglobulins rather than absorbing them intact. So proposed benefits are thought to act locally in the gut — not by raising the antibody level in your blood.

What the research actually shows

We label each use by how strong the evidence is — well-established, mixed, or weak/preliminary — and say plainly where marketing outruns the science.

Weak / preliminary Immune biomarkers in adults. A meta-analysis of ten trials in trained, active people found colostrum had little to no impact on blood IgG/IgA, salivary secretory IgA or white blood cells. If you were hoping to “measure” an immune boost, the data don’t support it.

Mixed Upper-respiratory infections. This is the most promising area: several trials and reviews report fewer or shorter upper-respiratory infections with colostrum. But the studies vary widely in dose and quality, so it’s a plausible, not settled, benefit.

Weak / preliminary Gut permeability (“leaky gut”). Small studies suggest colostrum may reduce exercise- or NSAID-induced intestinal permeability, but human clinical outcomes are limited and preliminary.

Weak / preliminary Systemic “immune boosting,” anti-aging, muscle-building. Not established. The gap between unchanged immune biomarkers and any infection benefit means the mechanism isn’t even well understood — broad disease and anti-aging claims outrun the evidence entirely.

The doses studies actually used

Trials in adults have most often used 10–25 g/day of colostrum powder, run anywhere from about eight days to twelve weeks; a few respiratory-prevention studies used lower “moderate” doses around 3 g/day. There is no established optimal dose.

Crucially, studies rarely standardize by IgG content — which is the whole problem. Two products both labeled “20 g” can deliver very different amounts of actual immunoglobulin depending on sourcing and processing. Grams of powder tell you volume; only a disclosed IgG figure tells you potency.

What to look for on a label

✓A disclosed IgG percentage or mg per serving — e.g. “25% IgG” or a stated milligram amount ✓First-milking and gentle, low-temperature processing (more intact immunoglobulins) ✓An honest gram dose, and the capsule math to reach studied amounts (10–25 g can mean 15–30 capsules) ✓Third-party testing for heavy metals and antibiotics (it’s a bulk dairy product)
✕“Colostrum” weight only, with no IgG figure — you can’t compare potency ✕“Boosts your antibodies” / systemic immune claims — the IgG isn’t absorbed intact ✕Colostrum buried in a proprietary “immunity” blend with no individual amount ✕“Clinically proven” with no citation, or grass-fed marketing used in place of an IgG spec

Dairy note: colostrum is a milk product — people with milk allergy should avoid it, and the lactose-intolerant may react.

Where you’ll find it in what we’ve reviewed

Colostrum is the whole category behind several of our reviews. Earth Energy Pure Bovine Colostrum is the only one in our set that states both its dose (2 g) and its IgG (25%, ≈500 mg/serving) — read the scored Earth Energy Colostrum review (70/100), and note the common-ownership disclosure on it.

For contrast, ARMRA doesn’t state its serving weight or IgG, Cowboy discloses a 3 g dose but not IgG, and WonderCow claims 40% IgG. See them side by side in our best colostrum roundup and the ARMRA vs Earth Energy matchup.

Frequently asked questions

Does colostrum boost my immune system?

Evidence that it raises measurable immune markers in healthy adults is weak. The better-supported (though still mixed) benefit is a possible reduction in upper-respiratory infection frequency, likely acting in the gut rather than by increasing blood antibodies.

Is the IgG actually absorbed into my body?

Largely no. Unlike a newborn calf, adults digest most oral immunoglobulins, so any effect is thought to be local in the digestive tract. That’s why “antibody-boosting” claims are misleading.

How much IgG should a good product have?

There’s no official supplement standard, but reputable products disclose an IgG percentage or milligram amount — be skeptical of any that won’t. In dairy science, high-quality source colostrum is ≥50 g/L IgG, but finished-supplement content varies with processing.

Is it safe?

It’s generally well tolerated, but it’s a dairy product — avoid it with a milk allergy, and the lactose-intolerant may react. Long-term high-dose safety data in adults is limited. This isn’t medical advice; check with your clinician.

Sources

  1. NIH / MDPI Animals review — “Determining Immunoglobulin Content of Bovine Colostrum” (IgG = 85–95% of total Ig; ≥50 g/L quality threshold). mdpi.com/2076-2615/11/12/3587
  2. Immunological outcomes of bovine colostrum supplementation — meta-analysis (no significant effect on immune biomarkers; 10–25 g/day). pmc.ncbi.nlm.nih.gov/articles/PMC7231218/
  3. Bovine colostrum for prevention of URTIs — systematic review & meta-analysis (mixed evidence for fewer respiratory infections). sciencedirect.com/science/article/pii/S1756464622003863
  4. Drugs.com professional monograph — Bovine Colostrum (uses, dosing ranges, safety). drugs.com/npp/bovine-colostrum.html

This explainer describes what research has examined — it is not medical advice and does not prescribe. Talk to your clinician before starting any supplement, especially alongside medication. Medical disclaimer.