Does milk increase IGF-1? Understanding the Complex Nutritional Link

October 6, 2025 •

5 min read

Multiple studies have indicated that milk consumption can increase circulating levels of insulin-like growth factor-1 (IGF-1) in humans, with some research observing a 9–20% rise in children aged 10–12 and a positive association in adults consuming dairy proteins. While the topic is complex, the evidence suggests that milk's protein content plays a crucial role in this relationship.

Quick Summary

Milk consumption can raise serum insulin-like growth factor-1 (IGF-1) levels, with the effect driven primarily by milk's protein components, particularly casein. The influence varies based on factors like milk type, processing, and individual metabolism, impacting human growth and cell proliferation.

Key Points

Milk proteins, not exogenous IGF-1, are the primary drivers of increased serum IGF-1 levels. The protein content, particularly casein, indirectly stimulates the body's own production of the hormone, rather than significant absorption of IGF-1 from the milk itself.
Casein protein has a stronger IGF-1 stimulating effect than whey protein. While whey causes a rapid insulin spike, casein's slower digestion and amino acid release result in a more potent and sustained increase in circulating IGF-1.
Milk processing affects IGF-1 levels differently. Normal pasteurization does not destroy IGF-1, but high-heat sterilization and fermentation (like in yogurt) can significantly reduce or eliminate its content.
Elevated IGF-1 from milk is a potential risk factor for conditions like acne and certain cancers. The mitogenic effect of IGF-1 on cell proliferation has raised concerns, but the epidemiological evidence remains inconsistent, and further research is needed.
Many other factors besides milk influence IGF-1 levels. These include genetics, age, overall nutritional intake, exercise, and certain diseases, making it important to consider the broader dietary and lifestyle context.
rBGH increases IGF-1 in milk, but processing matters. The hormone used in some dairy farms can increase the IGF-1 in milk, but high-heat processing (sterilization) can destroy it.

What is IGF-1 and its role in the body?

Insulin-like Growth Factor-1, or IGF-1, is a polypeptide hormone that plays a critical role in human growth and metabolism. Produced mainly by the liver in response to growth hormone (GH), IGF-1 is involved in regulating cell proliferation, differentiation, and survival. Its effects are particularly notable during childhood and puberty, where it drives skeletal growth and development. In adults, it continues to influence tissue maintenance and repair.

Unlike growth hormone, which is released in pulses, IGF-1 levels are relatively stable throughout the day, making it a reliable indicator of average GH activity. However, its levels are not static and are influenced by numerous factors, including age, genetics, nutritional status, and various health conditions. The interaction between diet, specifically dairy intake, and IGF-1 levels has been a subject of considerable research and debate.

The Milk-IGF-1 connection: Unpacking the mechanisms

There are two primary ways milk is thought to influence circulating IGF-1 levels. The first is through the presence of exogenous IGF-1 directly in the milk itself, and the second, more significant mechanism is through the indirect stimulation of the body's endogenous IGF-1 production via milk's constituent nutrients.

Direct IGF-1 intake from milk

Cow's milk contains IGF-1 that is structurally identical to human IGF-1, meaning it can bind to human IGF-1 receptors. However, most researchers believe that direct absorption of intact, bioactive IGF-1 from ingested milk is minimal, especially in adults, due to extensive degradation during digestion. Nevertheless, some studies suggest that in suckling infants or under certain conditions, milk-borne IGF-1 can be absorbed and exert biological effects.

Indirect stimulation via nutrients

The more widely accepted mechanism is that milk's nutritional components trigger the body to produce its own IGF-1. This is driven primarily by the high protein content and specific amino acids found in milk.

Amino Acid Signaling: Milk proteins, especially whey, are rich in branched-chain amino acids (BCAAs) like leucine, which stimulate insulin secretion. This, along with other amino acids like tryptophan, up-regulates the signaling pathways involving insulin and growth hormone, which in turn promotes hepatic IGF-1 synthesis.
Hormonal Cascade: The amino acid-induced increase in insulin and growth hormone creates a synergistic effect, providing optimal conditions for enhanced IGF-1 production by the liver and promoting cellular anabolism and growth.

Whey vs. casein: Different effects on IGF-1

Milk proteins are composed of two main fractions: casein (about 80%) and whey (about 20%). Research has demonstrated that these two protein fractions have different and distinct effects on the body's hormonal response.

Casein: Studies have shown that consuming casein leads to a significant increase in circulating IGF-1 levels. Casein is digested more slowly, providing a sustained release of amino acids that can prolong the hormonal signaling for IGF-1 production.
Whey: Whey protein, absorbed more quickly, has a more pronounced effect on insulin secretion than on IGF-1 levels. It is highly insulinotropic, meaning it causes a sharp spike in insulin levels, but its impact on IGF-1 is less potent than casein's.

Comparison of casein and whey protein effects


Feature	Casein Protein	Whey Protein
Digestion Speed	Slow, sustained release	Fast, rapid absorption
Primary Hormonal Effect	Strong IGF-1 stimulation	Strong insulin stimulation
Amino Acid Release	Gradual	Quick pulse
Typical Use	Sustained protein release (e.g., bedtime)	Rapid protein uptake (e.g., post-workout)

The impact of milk type and processing

Beyond the protein fractions, the type of milk and how it is processed can also influence IGF-1 levels.

Fat Content: Research indicates a positive correlation between milk fat content and IGF-1 levels in the milk itself. This suggests that whole milk may contain higher IGF-1 concentrations than low-fat varieties.
Pasteurization and Fermentation: Normal pasteurization does not destroy IGF-1 in milk, and it is still present in commercially sold products. However, fermentation, such as that used to make yogurt, significantly reduces IGF-1 content due to the activity of lactic acid bacteria. This may explain why some studies find no association between yogurt consumption and IGF-1 levels, unlike milk. Extreme heat treatments, like sterilization, can destroy IGF-1.
rBGH: In some countries (but not the EU, Canada, or others), cows are treated with recombinant bovine growth hormone (rBGH) to increase milk production. The use of rBGH stimulates IGF-1 production in the cows, leading to higher levels of IGF-1 in their milk.

Potential health implications

Elevated IGF-1 levels, particularly those sustained over long periods, have been linked to potential health implications, including certain types of cancer and conditions like acne.

Cancer: Several studies have explored the link between milk consumption, increased IGF-1, and the risk of prostate, breast, and colorectal cancers. IGF-1 is a mitogen, meaning it promotes cell growth and proliferation. While the association is a subject of ongoing research and findings are sometimes inconsistent, the hypothesis is that chronically elevated IGF-1 could potentially promote tumor development.
Acne: Increased IGF-1 and insulin signaling, both promoted by milk protein, are thought to contribute to the development and aggravation of acne by stimulating sebocyte proliferation and androgen synthesis.
Infant Growth: In infants, the growth-promoting effects of IGF-1 from milk are considered beneficial and essential for development. However, the continued high IGF-1 signaling from cow's milk in older children and adults is a topic of concern for some researchers regarding long-term health outcomes.

Conclusion: A complex nutritional landscape

In conclusion, the answer to the question "Does milk increase IGF-1?" is nuanced and generally considered to be yes, though the mechanisms are complex. The increase is not simply from absorbing IGF-1 from milk, but primarily due to milk's protein content stimulating the body's own production of the hormone. The effect is influenced by the type of milk (casein vs. whey, whole vs. skim), processing methods, and individual health status. While elevated IGF-1 has been linked to potential risks, particularly with certain cancers and acne, the evidence is not conclusive, and ongoing research is necessary to fully understand the long-term health implications. For most individuals, the effects of a single food like milk are part of a much larger dietary and lifestyle picture. The best approach is to consider overall nutritional habits and consult with a healthcare professional regarding specific health concerns.

For more in-depth scientific research on the functional aspects of milk proteins, see this comprehensive review on ScienceDirect: Functional analysis of the IGF-system in milk.

Frequently Asked Questions

The amino acids in milk proteins, particularly leucine in whey and other amino acids from casein, signal the body to release growth hormone and insulin. This cascade stimulates the liver to produce more of its own IGF-1, leading to an overall increase in serum levels.

No, normal pasteurization does not destroy the IGF-1 found in milk. However, very high-heat sterilization or autoclaving, used in some processing, can eliminate it.

No, the effect varies by product. For instance, studies suggest milk has a stronger association with increased IGF-1 than yogurt, possibly because the fermentation process used to make yogurt reduces IGF-1 content. Cheese may also have a lesser effect compared to fluid milk.

Cow's milk naturally contains some IGF-1. However, milk from cows treated with rBGH contains higher levels of IGF-1. The impact of consuming this milk on human IGF-1 levels is still debated, as digestion may degrade some of the hormone.

The health implications of milk-induced IGF-1 increases are debated and not fully understood. Some concerns have been raised regarding potential links to certain cancers and acne due to IGF-1's role in cell proliferation, but research is inconsistent, and many factors influence individual health.

The IGF-1 content in milk itself has been found to correlate positively with fat content. However, the primary mechanism of action is the protein content, and since skim milk has a higher protein concentration per volume than whole milk, it could potentially have a stronger IGF-1 stimulating effect via that mechanism.

While consuming other animal proteins like meat can also influence IGF-1, studies suggest that dairy products raise IGF-1 levels more significantly than meat and other non-dairy protein sources, possibly due to milk's unique protein profile and hormonal signaling properties.