IGF-1 in Colostrum: How Much Is There and Does It Reach Your Blood?
Insulin-like growth factor 1 (IGF-1) is one of the most talked-about components of bovine colostrum, and one of the most misunderstood. Some marketing implies that a scoop of colostrum powder delivers a meaningful "dose" of growth factor to your tissues. Some critics worry about the same thing for the opposite reason. The measured numbers tell a more modest story: colostrum does contain far more IGF-1 than ordinary milk, but the absolute amount in a serving is tiny next to what your body already makes, and the best-controlled human trials have struggled to detect any of it reaching the bloodstream intact.
- First-milking bovine colostrum typically contains roughly 200 to 2,000 ng/mL of IGF-1, versus about 1 to 30 ng/mL in mature cow's milk.
- A 10 g serving of colostrum powder contains on the order of 10 to 50 micrograms of IGF-1, depending on the product and processing.
- An adult's circulating pool of IGF-1 is roughly 500 to 1,500 micrograms, and the liver produces new IGF-1 continuously, so even total absorption of a serving would be a small fraction of daily turnover.
- Bovine and human IGF-1 have identical amino acid sequences, which makes "did the bovine peptide get absorbed?" hard to answer directly with standard blood tests.
- Most controlled trials at 20 to 60 g/day found no rise in blood IGF-1; a small early study reported a modest increase, and interpretation is contested.
What IGF-1 is and why colostrum has so much of it
IGF-1 is a 70-amino-acid peptide hormone with a molecular weight of about 7.6 kDa. In humans it is produced mainly by the liver in response to growth hormone, and it circulates bound to carrier proteins (IGF-binding proteins, or IGFBPs) that extend its half-life and regulate its activity. It plays a role in growth, tissue maintenance, and metabolism throughout life.
Colostrum, the first milk produced after calving, is rich in IGF-1 because the newborn calf's gut is briefly permeable to large molecules and the calf appears to use maternal growth factors to mature its intestinal lining. Concentrations fall sharply within the first day or two as colostrum transitions to milk. If you want the broader picture of how colostrum differs from milk, see what colostrum is. Colostrum also contains IGF-2, often at similar or higher concentrations than IGF-1, along with transforming growth factor beta and epidermal growth factor, but IGF-1 draws the most attention because it is a regulated hormone in sports and a biomarker discussed in aging research.
How much IGF-1 is actually in colostrum?
Published measurements vary widely, which is itself worth knowing. Reported IGF-1 concentrations depend on the assay used, the time since calving, the cow's breed and parity, and how the sample was handled. With that caveat, the typical ranges look like this:
| Source | Typical IGF-1 concentration | Notes |
|---|---|---|
| Bovine colostrum, first milking | ~200 to 2,000 ng/mL | Highest in the first 6 to 12 hours; some samples exceed 2,000 ng/mL |
| Bovine transitional milk (days 2 to 3) | ~50 to 200 ng/mL | Declines rapidly after the first milking |
| Mature cow's milk | ~1 to 30 ng/mL | Pasteurized retail milk usually toward the low end |
| Human colostrum | ~10 to 30 ng/mL | Far lower than bovine; human milk relies more on other growth factors |
| Adult human serum | ~100 to 300 ng/mL | Declines with age; varies with nutrition and body composition |
Translating that to a scoop of powder
Liquid colostrum is roughly 20 to 25 percent solids. Drying a litre containing 500 ng/mL of IGF-1 yields roughly 200 to 250 g of powder holding about 500 micrograms of IGF-1, or about 2 to 2.5 micrograms per gram. Independent analyses of commercial products fall in a broad band, typically from below 1 up to about 5 micrograms per gram, with processing method and the fraction of first-milking colostrum used as the main drivers. Some low-heat, first-milking products may exceed that; some heavily processed or skimmed powders fall below it.
For a standard 10 g daily serving, that works out to roughly 10 to 50 micrograms of IGF-1. For context, the same 10 g typically provides about 35 to 45 kcal, 2 to 4 g of IgG (products are commonly standardized to 20 to 40 percent IgG), and around 6 to 8 g of total protein. IgG content and IGF-1 content are not tightly linked, so a "high IgG" label tells you little about growth factor levels. Our guide to choosing a colostrum supplement explains what specifications are worth reading on a label.
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What happens to IGF-1 in an adult digestive tract
To reach your blood intact, a dietary peptide has to survive stomach acid, pepsin, pancreatic proteases such as trypsin and chymotrypsin, brush-border peptidases, and then cross an intestinal epithelium that in adults is designed to block macromolecules. IGF-1 is a compact, disulfide-linked peptide and is somewhat more resistant to digestion than a loose protein chain, and colostrum contains IGFBPs and casein that may offer partial protection. Even so, studies in adult animals using labeled IGF-1 have generally found that only a very small fraction of an oral dose appears in the circulation, and much of what is detected is fragmented rather than biologically active.
The newborn calf is a different case. For roughly the first 24 hours of life, its intestine can absorb macromolecules by pinocytosis, which is how it acquires maternal antibodies. That window closes quickly. Adult humans do not have it. This is the single most important reason to be skeptical of claims that colostrum "delivers growth factors to your muscles."
What IGF-1 in colostrum plausibly can do is act locally on the gut lining before it is degraded. Cell and animal studies suggest that growth factors in colostrum may support the integrity of the intestinal epithelium, and this local action, rather than systemic absorption, is the mechanism most researchers now consider credible. Evidence in humans remains limited and mostly comes from small trials.
What human trials show about blood IGF-1
Several controlled studies, mostly in athletes, have directly measured circulating IGF-1 during colostrum supplementation. Their findings are more consistent than the marketing suggests.
| Study | Dose and duration | Change in blood IGF-1 |
|---|---|---|
| Mero et al., 1997 | 125 mL/day liquid colostrum, 8 days, sprinters and jumpers | Small increase reported; short study, small sample |
| Kuipers et al., 2002 | 60 g/day powder, 4 weeks, athletes | No significant change |
| Buckley et al., 2003 | 60 g/day powder, 8 weeks, active men | No significant change |
| Mero et al., 2002 | 20 g/day powder, 2 weeks, athletes | Modest increase; authors did not attribute it to absorption of bovine IGF-1 |
Two points deserve emphasis. First, the larger and longer trials at 60 g/day, roughly six times a typical consumer dose, saw nothing. Second, even where an increase was reported, it cannot be assumed to reflect absorbed bovine peptide. Because bovine and human IGF-1 are identical in sequence, an immunoassay cannot tell them apart. A rise in blood IGF-1 could just as easily reflect the effect of extra high-quality protein on the liver's own IGF-1 production. Systematic reviews of ordinary dairy intake have found that regular milk drinkers have modestly higher circulating IGF-1, and the leading explanation is stimulated endogenous synthesis, not absorption of milk IGF-1.
A back-of-envelope calculation
Suppose a 10 g serving carries 30 micrograms of IGF-1 and, implausibly, all of it were absorbed intact and instantly distributed through about 5 litres of blood. The concentration would rise by roughly 6 ng/mL, on a baseline of 100 to 300 ng/mL, and it would be cleared within hours. That is smaller than normal day-to-day variation and would be hard to detect even in a well-designed trial. Realistic absorption is a small fraction of that.
Practical implications
- For general users: IGF-1 content is not a strong reason to choose or avoid colostrum. Any benefit is more likely to involve local effects in the gut or the immunoglobulin and oligosaccharide fractions than systemic growth factor delivery.
- For tested athletes: Colostrum is not on the World Anti-Doping Agency prohibited list, but WADA has advised caution because of the theoretical possibility of raising IGF-1. The trial evidence suggests this risk is low at ordinary doses, but athletes should make their own risk assessment and check current guidance.
- For people concerned about IGF-1 and long-term health: Observational research linking higher circulating IGF-1 to certain outcomes concerns lifelong endogenous levels, not micrograms from a supplement. There is no evidence that colostrum meaningfully shifts long-term IGF-1 status, but there is also no long-term safety data specific to this question, so anyone with a relevant medical history should discuss it with a clinician.
- Processing matters somewhat: IGF-1 appears reasonably stable under standard pasteurization, but ultra-high-temperature treatment and harsh drying reduce it. If growth factor content matters to you, look for low-heat processing and first-milking sourcing. Dose guidance is covered in dosage and safety.
FAQ
Does colostrum powder raise IGF-1 like injecting it would?
No. Injected IGF-1 bypasses digestion entirely and delivers milligram quantities directly to the circulation. A colostrum serving contains tens of micrograms, most of which is broken down in the gut. The best-controlled trials at doses up to 60 g/day found no measurable rise in blood IGF-1, so the comparison does not hold.
Is bovine IGF-1 the same as human IGF-1?
Yes, the two peptides have identical amino acid sequences. That is why bovine IGF-1 would be biologically active in humans if it were absorbed, and also why blood tests cannot distinguish absorbed bovine IGF-1 from your own. Any change measured in trials could reflect altered endogenous production rather than absorption.
Do "high IGF-1" colostrum products make a difference?
Probably not in terms of blood levels. Doubling the IGF-1 content of a serving still leaves the dose in the tens of micrograms, against a circulating pool hundreds of times larger. If growth factors matter to you for local gut effects, low-heat processing and first-milking sourcing are more meaningful than a headline number.
Should athletes subject to drug testing avoid colostrum?
Colostrum is not prohibited, but WADA has advised against its use because of the theoretical potential to raise IGF-1. The published trials suggest that risk is small at typical doses. Athletes should weigh that evidence against their own governing body's guidance and may prefer to avoid it during competition periods.
Sources
- Mero A, Miikkulainen H, Riski J, et al. Effects of bovine colostrum supplementation on serum IGF-I, IgA, IgG, hormones and saliva IgA during training. Journal of Applied Physiology, 1997.
- Kuipers H, van Breda E, Verlaan G, Smeets R. Effects of oral bovine colostrum supplementation on serum insulin-like growth factor-I levels. International Journal of Sports Medicine, 2002.
- Buckley JD, Brinkworth GD, Abbott MJ. Effect of bovine colostrum on anaerobic exercise performance and plasma insulin-like growth factor I. Journal of Sports Sciences, 2003.
- Elfstrand L, Lindmark-Månsson H, Paulsson M, Nyberg L, Åkesson B. Immunoglobulins, growth factors and growth hormone in bovine colostrum and the effects of processing. International Dairy Journal, 2002.
- Playford RJ, Weiser MJ. Bovine colostrum: its constituents and uses. Nutrients, 2021.
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