What Bovine Colostrum Actually Is — and What IgG on the Label Means

Bovine colostrum is the first milk a cow produces after calving, and it is compositionally unlike ordinary milk: far higher in protein, much lower in fat and lactose, and rich in immunoglobulins (chiefly IgG), lactoferrin and growth factors. A newborn calf absorbs those antibodies intact for roughly its first 24 hours; an adult human does not have that window.

Colostrum is the milk a mammal produces in the first day or so after giving birth. It is not "very rich milk" — it is a different fluid with a different job, and the composition reflects that.

A newborn calf is born with essentially no circulating antibodies. Unlike humans, cattle do not transfer antibodies across the placenta, so the calf's entire early immune defence has to arrive through the first feed. Colostrum is that delivery.

What is in it

Immunoglobulins, principally IgG. These are antibodies, and they are the headline component — bovine colostrum is roughly 70–80% IgG by protein content in the first milking, dropping sharply over the following days as it transitions to ordinary milk.

Lactoferrin. An iron-binding glycoprotein. It binds free iron, which is relevant because many bacteria require iron to multiply, and it is studied in its own right.

Growth factors — IGF-1, TGF-beta and others, involved in tissue development in the newborn.

Oligosaccharides, which are not digestible by the calf and instead act as substrate for beneficial gut bacteria — a prebiotic function.

Compared to mature milk, colostrum is far higher in protein and much lower in fat and lactose. It is a concentrated delivery of immune and growth factors, not a nutrition source in the ordinary sense.

What the percentage on the label means

Colostrum products are commonly standardised to an IgG percentage — you will see 15%, 20%, 30% and higher.

Two things worth understanding.

Higher is not automatically better. Raising IgG concentration means removing other components, and lactoferrin, growth factors and oligosaccharides are removed along with them. A very high-IgG product is a more processed, more fractionated material. Whether you want the concentrate or the whole colostrum depends on whether you think IgG is the only part that matters.

First-milking matters more than the number. IgG content falls steeply after the first milking. "First milking" or "first collection" on a label is a meaningful sourcing claim, and it is one reason products vary so much.

Also worth checking: whether the calf was fed first. Reputable suppliers collect surplus after the calf has had what it needs. That is an ethics question rather than a potency one, but it is a fair thing to ask.

The honest question: does IgG survive digestion?

This is the obvious objection and it deserves a direct answer rather than being skipped.

Immunoglobulins are proteins. The digestive system exists to break proteins down, and stomach acid and proteases do exactly that to most of what you eat. So the natural question is whether oral IgG is simply digested into amino acids like any other protein.

The honest answer: partly, and the picture is genuinely unresolved.

A newborn calf absorbs intact antibodies into the bloodstream, but only for roughly the first 24 hours of life, through a temporary gut permeability that then closes. An adult human does not have that window. So the idea that oral bovine colostrum delivers antibodies into your bloodstream the way it does for a calf is not supported.

What is more plausible, and where most of the research now sits, is local action in the gut — immunoglobulins and lactoferrin acting within the intestinal lumen before being broken down, rather than being absorbed intact. Some studies find a meaningful fraction of IgG surviving to the small intestine, particularly when acid exposure is limited.

That is a narrower proposition than the marketing usually implies, and it is the accurate one.

What it is not

Colostrum is not a treatment for any infection or illness, and no supplement may be sold as one. It will not substitute for vaccination and it is not a defence against any specific pathogen.

If you are immunocompromised, managing an autoimmune condition, or taking immune-modulating medication, talk to your doctor before adding anything marketed around immune function — that is exactly the situation where an unnecessary supplement is worth avoiding.

Colostrum is dairy. It contains milk protein. Anyone with a milk allergy should avoid it, and while colostrum is much lower in lactose than regular milk, it is not lactose-free.

What we make

Colostrum Immune Factors is 500 mg of bovine colostrum from USA dairies per capsule, and nothing else.

One active, no proprietary blend, no stack of supporting botanicals — the same approach we take on Prostate Health Tabs. It is naturally rich in immunoglobulins, lactoferrin and growth factors, and it is intended to support normal immune function and healthy digestion.

If digestion is the reason you are here, the enzyme side of that is a different mechanism entirely — what digestive enzymes actually do covers it, and enzymes vs. probiotics sorts out which of those two you are actually shopping for.

These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.