What is IgG in colostrum? IgG, short for immunoglobulin G, is a type of antibody, and it is the main immunoglobulin in cow's colostrum, the first milk produced after calving. When a colostrum supplement such as Colostrum+™ lists "IgG" on its label, it is telling you how much of these antibody proteins the powder carries. Below is what IgG is, why there is so much of it in colostrum, how to read an IgG figure on a label, and what research does and does not say.
Key takeaways
- IgG, or immunoglobulin G, is a type of antibody: a protein the immune system uses to recognize specific invaders.
- IgG is the main immunoglobulin in cow's colostrum.
- Colostrum labels show IgG either as a percentage of the powder or as milligrams per serving.
- Colostrum+ gives 400 mg of IgG from the 2,000 mg of colostrum powder in each 2.55 g scoop, or 20% of the colostrum by weight.
What are immunoglobulins?
Immunoglobulins are antibodies. IgG, or immunoglobulin G, is a type of antibody: a protein the immune system uses to recognize specific invaders. Each antibody is shaped to fit one particular target, a little like a key cut for one lock. When it finds that target, it tags it so other parts of the immune system can respond.
There are five main classes, each with its own job:
- IgG is the most common antibody in human blood and the main one in cow's colostrum.
- IgA is concentrated in mucous membranes and secretions such as saliva, tears and human breast milk.
- IgM is usually the first antibody made when the body meets something new.
- IgE is involved in allergic responses.
- IgD plays a role in activating immune cells.
Why is there so much IgG in colostrum?
A newborn calf is born with almost no antibodies of its own, because antibodies do not cross a cow's placenta. Instead, the calf receives them by drinking colostrum in its first hours of life. That is why the first milking is so concentrated: it carries the mother's antibodies to the calf.
In cow's colostrum, IgG makes up most of the immunoglobulins. Review papers on bovine colostrum describe it as a rich source of immunoglobulins, alongside lactoferrin, growth factors and other proteins. The concentration falls quickly over the days after calving, so colostrum for supplements is collected early and then dried into a powder.
Human colostrum is different. In people, IgA is the dominant antibody in breast milk, because human babies also receive IgG before birth through the placenta.
How to read IgG on a colostrum label
Colostrum labels show IgG either as a percentage of the powder or as milligrams per serving. Both are useful, and you can convert one into the other:
| How it is shown | What it means |
|---|---|
| Percentage (for example, "20% IgG") | The share of the powder, by weight, that is IgG |
| Milligrams per serving | The actual amount of IgG in each scoop or capsule |
| Neither | You cannot tell how much IgG you are getting |
Milligrams per serving is the easiest to compare, because it already accounts for the serving size. A high percentage in a tiny serving can deliver less IgG than a modest percentage in a larger one.
Here is a worked example. Each scoop of Colostrum+ delivers 2,000 mg of colostrum powder with 400 mg of IgG. Divide 400 by 2,000 and you get 20% IgG by weight of the colostrum powder. Colostrum+ also adds marshmallow root and bovine lactoferrin, and every amount is printed on the label.
What does research say about IgG from colostrum?
Bovine colostrum and its immunoglobulins have been studied for decades, mostly for gut and immune health, and in athletes. Reviews in the scientific literature describe how bovine immunoglobulins taken by mouth largely act within the digestive tract, where they can interact with the gut lining and the microbes that live there. Research findings are mixed and many studies are small, so it is fair to describe colostrum as promising and studied, rather than proven for any one outcome.
What you can say plainly is what the product supports. Colostrum+ supports healthy immune function, supports gut and digestive health, and supports cognitive wellness and focus.* Our article What Is Colostrum? covers the wider research picture.
IgG, lactoferrin and the other proteins in colostrum
IgG is the headline, but it is not the only protein in colostrum:
- Lactoferrin is an iron-binding protein found in milk, and especially in colostrum.
- Growth factors are signaling proteins that help newborn tissues develop.
- Other immunoglobulins, such as IgA and IgM, are present in smaller amounts.
This mix is one reason colostrum is often discussed alongside the gut-immune connection. If you are building a broader gut routine, a probiotic such as Probiotic 40+ is a different kind of support: live bacteria rather than milk proteins. Our explainer on the gut-immune connection shows how the two ideas fit.
Who should be careful with colostrum
Colostrum is a dairy product. Anyone with a milk allergy should avoid it, and anyone sensitive to dairy should ask a healthcare provider first. The Colostrum+ label also advises anyone who is pregnant, nursing, allergic, has a medical condition or takes medication to consult a doctor before use.
Quality matters with any protein-rich powder. Every batch of Colostrum+ is third-party tested for purity and potency by an outside lab, and it is manufactured in USA with globally sourced materials in an NSF-certified, GMP-certified, FDA-registered facility. See Our Standards.
Frequently asked questions about IgG in colostrum
Is IgG in colostrum the same as the IgG in my blood?
It is the same class of antibody, but it comes from a cow and was made in response to what the cow encountered. Taken by mouth, it is a dietary protein that mostly stays in the digestive tract rather than becoming part of your own circulating antibodies.
Is a higher IgG percentage always better?
Not on its own. Look at milligrams of IgG per serving, because that accounts for how much powder you actually take. Also check that the product is third-party tested, so the number on the label is the number in the scoop.
Does cooking or hot liquid affect colostrum?
Very high heat can change proteins in general. Follow your product's label. The Colostrum+ label allows water or your favorite hot or cold recipe, so a warm drink is fine.
Is colostrum the same as regular milk?
No. Colostrum is the first milk produced after birth and is far richer in immunoglobulins and lactoferrin than ordinary milk, which is produced later.
Can people with a dairy allergy take colostrum?
No. Colostrum is milk, so anyone with a milk allergy should avoid it. If you are sensitive to dairy but not allergic, ask your healthcare provider before trying it.
Related reading from our Wellness Hub
- What Is Colostrum? Gut and Immune Support, Explained
- Colostrum for Gut & Immune Health: Meet Colostrum+
- Vitamin C and Zinc Together: What Each Nutrient Does
Sources
- Effects of Bovine Immunoglobulins on Immune Function, Allergy, and Infection (PubMed)
- Bovine colostrums: a review of clinical uses (PubMed)
- Cleveland Clinic: Antibodies
Individual results vary.
*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.
