Does Dairy Increase IGF-1? What the Science Says

January 7, 2026 •

4 min read

According to numerous studies, consuming milk and dairy products has been consistently associated with higher levels of insulin-like growth factor-1 (IGF-1) in the bloodstream. This article delves into the mechanisms behind this relationship and clarifies what the current scientific consensus suggests about how dairy increases IGF-1.

Quick Summary

Dairy consumption, particularly milk and yogurt, can increase circulating levels of insulin-like growth factor-1 (IGF-1), largely due to its protein content. Research suggests this effect is more pronounced with milk and certain whey proteins than with cheese, though the overall impact depends on individual factors and intake amounts.

Key Points

Dairy increases IGF-1: Scientific studies confirm that consuming milk and other dairy products elevates circulating levels of Insulin-like Growth Factor-1 (IGF-1).
Protein is the primary cause: The increase is mainly driven by dairy protein, specifically the casein component, which stimulates the body's own production of IGF-1, rather than the small amount of IGF-1 naturally present in milk.
Product type matters: The effect on IGF-1 varies by dairy product; milk and yogurt show a stronger positive association, while cheese does not show a consistent link with elevated IGF-1.
Plant-based diets lower IGF-1: Individuals on plant-based diets typically have lower IGF-1 levels compared to those who consume animal protein and dairy.
IGF-1 from milk is not absorbed: Orally ingested IGF-1 from dairy is mostly digested and not absorbed into the bloodstream in biologically significant amounts.
Other factors are important: The overall impact on IGF-1 is also affected by genetics, exercise, total caloric intake, and the balance of protein from different sources.

Understanding IGF-1 and Its Role

Insulin-like growth factor 1, or IGF-1, is a hormone primarily produced in the liver and plays a critical role in cellular growth, metabolism, and proliferation. While essential for growth during childhood, elevated levels of IGF-1 in adulthood have been linked to potential health concerns, including an increased risk for certain cancers, particularly prostate and breast cancer. A balanced IGF-1 level is important for maintaining overall health, with both lifestyle factors and diet playing a significant role in its regulation.

The Connection Between Dairy and IGF-1

Research has provided significant evidence for a link between dairy consumption and increased IGF-1 levels. Studies show that intake of milk and other dairy products is consistently associated with higher circulating IGF-1. The mechanism is complex, involving the nutritional components of dairy, particularly its protein profile. While dairy does contain trace amounts of bovine IGF-1, the human body primarily produces its own IGF-1. The dietary influence comes from the way dairy protein and other components stimulate the body's own production of this hormone.

The Role of Milk Proteins: Casein vs. Whey

The two primary proteins in milk are casein and whey, and research indicates they have different effects on hormone levels. Several studies have focused on isolating these protein fractions to understand their independent impact.

Casein: In intervention studies with children, consumption of a casein-rich diet was found to significantly increase circulating IGF-1 levels. This suggests that casein is a major driver behind the IGF-1 increase observed with dairy consumption.
Whey: Research indicates that whey protein primarily affects insulin levels rather than IGF-1. While highly insulinogenic, whey protein does not appear to raise IGF-1 to the same extent as casein. However, whey is rich in branched-chain amino acids (BCAAs), particularly leucine, which can activate the mTORC1 pathway, a key regulator of cell growth.

Fermented vs. Unfermented Dairy

Different dairy products can also have varying effects on IGF-1 levels. Fermented products like yogurt have shown different associations than milk. A recent study found that kefir consumption, a fermented milk product, resulted in lower IGF-1 levels compared to consuming soy yogurt, suggesting a beneficial effect on IGF-1 modulation. In contrast, research in the UK Biobank found that protein from milk and yogurt, but not cheese, was positively associated with higher circulating IGF-1 concentrations. This difference could be attributed to the way various dairy products are processed, which changes the ratio and structure of their proteins.

Dietary Protein Source: A Key Factor

It is not just the overall amount of protein that influences IGF-1, but also its source. A high intake of animal protein, including dairy, has been consistently linked to higher circulating IGF-1 concentrations. Conversely, individuals following plant-based diets, such as vegans, tend to have significantly lower IGF-1 levels. This indicates that the composition of the protein, specifically the presence of essential amino acids and their ratio, plays a critical role in signaling the body to produce IGF-1.

IGF-1 Levels in Dairy Products Themselves

While dairy stimulates endogenous IGF-1 production, it is important to clarify the IGF-1 content within milk and dairy products. IGF-1 is naturally present in bovine milk, and its concentration can vary depending on factors like the cow's breed and stage of lactation. However, the amount of IGF-1 in milk is thousands of times lower than the amount produced by the human body daily. Furthermore, studies indicate that orally ingested IGF-1 is largely digested and not absorbed intact into the human bloodstream in significant quantities.

Comparison Table: Dairy Products and IGF-1


Dairy Product	Primary Protein Type	Effect on Circulating IGF-1	Notable Considerations
Milk (unprocessed)	Casein & Whey	Confirmed to increase circulating IGF-1	Higher protein content drives endogenous production.
Casein Powder	Casein	Increases IGF-1 more than whey in studies	Slow-digesting protein, strong IGF-1 stimulator.
Whey Powder	Whey	Increases insulin more significantly than IGF-1	Fast-digesting, potent insulin secretagogue.
Yogurt	Casein & Whey	Shown to increase IGF-1 in some studies	Fermentation may influence protein and hormone profile.
Cheese	Casein	Not consistently associated with increased IGF-1 in studies	Processing removes whey, altering protein composition.
Kefir (fermented milk)	Casein & Whey	May modulate or even lower IGF-1 compared to other dairy	Fermentation processes and probiotics may affect hormonal response.

The Takeaway: How to Interpret the Data

Yes, studies consistently show that dairy, especially fluid milk and yogurt, can increase your body's levels of IGF-1. This is not primarily due to absorbing the small amounts of IGF-1 from milk, but rather the stimulatory effect of milk proteins, particularly casein, on your body's own hormone production. The level of increase can vary depending on the type of dairy product, with cheese showing a less consistent association. A predominantly plant-based diet, by contrast, has been linked to lower IGF-1 levels.

The health implications of elevated IGF-1 are a subject of ongoing research, with some studies suggesting potential links to chronic diseases while others find no conclusive causal relationship. It is important to consider your entire dietary pattern and lifestyle, not just single foods, when assessing your health risks. Factors such as genetics, exercise, and overall caloric intake also significantly influence IGF-1 levels.

For those concerned about high IGF-1, choosing non-dairy protein sources, including a variety of plant-based options, may be a consideration. However, the decision should be made in consultation with a healthcare provider, taking into account individual health goals and nutritional needs.

Conclusion

The scientific evidence strongly indicates that dairy products, particularly fluid milk and yogurt, can increase circulating IGF-1 levels in humans. The mechanism is largely attributed to the protein content, especially casein, which triggers endogenous IGF-1 production. While the IGF-1 found naturally in milk is not a major factor, the protein acts as a signal for the body to increase its own synthesis. Other factors, such as overall diet, exercise, and genetics, also play a crucial role in determining individual IGF-1 levels. More research is needed to fully understand the long-term health consequences of dietary IGF-1 manipulation.

Authoritative Link - This article discusses the associations of circulating insulin-like growth factor-I with dairy protein source.

Frequently Asked Questions

IGF-1, or insulin-like growth factor-1, is a hormone that regulates cell growth, metabolism, and proliferation throughout the body. While crucial for development, elevated levels in adulthood have been associated with increased risks for certain chronic diseases.

Fluid milk and yogurt are most consistently associated with higher IGF-1 levels. Studies suggest that the protein in milk, especially casein, is a major factor driving this effect. Cheese, however, shows less consistent association with IGF-1 increases.

Yes, individuals consuming plant-based diets, which exclude dairy, typically exhibit lower IGF-1 levels compared to those on a standard diet. Some plant-based options may have their own effects, but generally, plant protein is less potent at raising IGF-1 than animal protein.

The amount of IGF-1 naturally found in cow's milk is very low compared to the amount our bodies produce. Furthermore, the protein hormone is largely digested in the human gastrointestinal tract and not absorbed intact, so its direct effect on human hormone levels is considered negligible.

Research points to the protein content of dairy as the primary driver of the IGF-1 increase. Specifically, the casein and whey proteins signal the body to produce its own IGF-1. Some studies have found a positive association between IGF-1 concentration and milk fat content, but protein is a more significant factor.

Regular physical activity, particularly resistance training, is known to influence IGF-1 levels. Some studies have investigated the interplay between protein intake and exercise on IGF-1, but the relationship is complex. Exercise may modulate the response, but it may not completely negate the effects of high protein consumption.

Making dietary choices, such as reducing dairy, to influence IGF-1 is a personal decision that should be considered with a healthcare professional. While dairy consumption is linked to higher IGF-1, other lifestyle factors like exercise and overall diet also play a role. A balanced approach is often recommended, tailored to individual health goals.