Dairy products are a staple in diets worldwide, valued for their protein, calcium and vitamin content. Yet growing scientific evidence suggests that certain types of dairy, especially whole milk, may not be as benign as once believed. Recent large-scale research published in Advances in Nutrition has reignited debate over how milk and other dairy foods interact with cancer development and mortality.
Drawing on data from over three million participants across 34 prospective cohort studies, scientists found that high milk consumption, particularly of full-fat varieties, was linked to an increased risk of death from cancers of the liver, ovaries and prostate. Conversely, fermented dairy products such as yoghurt appeared to have protective effects, especially among women.
Video
Why milk’s fat and hormone profile may increase cancer risk
Milk contains a complex mixture of bioactive compounds that can influence human cell growth and metabolism. Among these is insulin-like growth factor 1 (IGF-1), a hormone that promotes cell proliferation and has been associated with higher risks of certain cancers. Researchers in the Advances in Nutrition review found that individuals with high milk consumption tended to have elevated levels of IGF-1 in circulation. Increased concentrations of this hormone have previously been linked with greater risks of breast, prostate and liver cancers.
The study revealed that whole milk, which typically contains more than 3.5 per cent fat, was particularly associated with increased total cancer mortality. Females consuming high-fat milk had a 17 per cent higher risk of dying from cancer compared with those who drank little or none. One possible explanation lies in saturated fats, which may encourage inflammation, insulin resistance and hormonal imbalances that support tumour progression. The link was less evident for low-fat or skimmed milk, suggesting that fat content and related hormonal factors might play central roles in driving these associations.
Interestingly, the effect was more pronounced among women. The authors propose that biological differences in hormone regulation could make female metabolism more sensitive to dairy’s endocrine-active components, which include not only IGF-1 but also natural bovine oestrogens.
How lactose metabolism connects milk to ovarian cancer
One of the most striking findings of the meta-analysis was the association between milk intake and ovarian cancer mortality. Women who drank the most milk had a 32 per cent higher risk of dying from ovarian cancer compared with those consuming the least. This connection is thought to involve lactose, the natural sugar found in milk, and its breakdown product galactose. When consumed in large quantities, galactose and its metabolites, such as galactose-1-phosphate, may interfere with ovarian function by disrupting gonadotropin signalling and accelerating cell death within ovarian tissue.
Previous epidemiological studies, including those cited by the World Cancer Research Fund, have shown similar patterns, indicating that galactose accumulation could contribute to ovarian toxicity over time. This biological mechanism is supported by animal models and metabolic studies, which suggest that chronic exposure to galactose may impair ovarian repair mechanisms. The fact that fermented dairy products, such as yoghurt and kefir, contain lower lactose levels could explain why they are not linked to this increased risk.
Fermented dairy products: The protective side of the story
While plain milk raised concern, fermented milk showed the opposite effect. According to the same analysis, women who consumed high amounts of yoghurt and other fermented dairy foods had a 15 per cent lower risk of dying from cancer compared with those who rarely ate them. The benefit appears to stem from the probiotic bacteria these foods contain. Such bacteria support immune function by enhancing IgA, T cell and macrophage activity, which in turn reduces harmful microbial activity in the gut and limits inflammation.
Research has highlighted that probiotic-rich foods can strengthen gut barrier integrity and modulate microbial composition, producing metabolites that suppress tumour growth. Some evidence also suggests that gut bacteria influence sex hormone regulation, which could partly explain why the protective effects of fermented milk are more prominent in women. These findings suggest that not all dairy products act uniformly in the body; rather, processing methods and microbial content may radically alter their health impact.
Cheese, butter and other dairy fats: Mixed findings on cancer mortality
Cheese and butter, though high in fat, displayed weaker associations with cancer risk. The meta-analysis found no clear relationship between cheese consumption and overall cancer mortality. However, high cheese intake was linked to a 22 per cent higher risk of dying from colorectal cancer. One theory is that the high salt and saturated fat content of cheese may influence gut microbiota composition or promote chronic inflammation in the intestinal lining.
For butter, evidence was inconclusive. Only two studies met the inclusion criteria, involving over 56,000 participants. The pooled data revealed no significant association between butter consumption and cancer mortality, although researchers cautioned that the small sample size limited confidence in these results. Overall, the study emphasised that while total dairy consumption showed no consistent relationship with cancer mortality, individual products differed markedly in their biological effects.
What people can do to minimise risk and make informed choices
Given the mixed findings, experts recommend focusing on moderation and product type rather than complete avoidance. Choosing low-fat or skimmed milk may reduce exposure to saturated fats and hormones linked to elevated IGF-1 levels. Incorporating fermented dairy such as yoghurt, kefir or cultured buttermilk could provide beneficial probiotics that support immune health and gut balance.
Plant-based alternatives like soy, oat or almond milk are also viable options, many of which are fortified with calcium and vitamin D to provide similar nutritional benefits without the same hormonal components. For those with a family history of hormone-related cancers, healthcare professionals suggest monitoring dairy intake and discussing personalised nutrition strategies. Public health agencies continue to emphasise dietary diversity, ensuring that essential nutrients like calcium are obtained from a range of sources, including leafy greens, legumes and nuts.
As scientific understanding evolves, dietary guidance may shift toward recognising the distinct effects of different dairy types rather than viewing them as a single category. The growing body of evidence underscores the importance of evaluating food quality, preparation methods and individual risk profiles when assessing long-term health outcomes related to diet.
Disclaimer: This article is for informational purposes only and should not be considered medical advice. Please consult a healthcare professional before making any changes to your diet, medication, or lifestyle.
Also Read | Why cutting rice from your diet could be the biggest mistake you are making
Drawing on data from over three million participants across 34 prospective cohort studies, scientists found that high milk consumption, particularly of full-fat varieties, was linked to an increased risk of death from cancers of the liver, ovaries and prostate. Conversely, fermented dairy products such as yoghurt appeared to have protective effects, especially among women.
Video
Why milk’s fat and hormone profile may increase cancer risk
Milk contains a complex mixture of bioactive compounds that can influence human cell growth and metabolism. Among these is insulin-like growth factor 1 (IGF-1), a hormone that promotes cell proliferation and has been associated with higher risks of certain cancers. Researchers in the Advances in Nutrition review found that individuals with high milk consumption tended to have elevated levels of IGF-1 in circulation. Increased concentrations of this hormone have previously been linked with greater risks of breast, prostate and liver cancers.
The study revealed that whole milk, which typically contains more than 3.5 per cent fat, was particularly associated with increased total cancer mortality. Females consuming high-fat milk had a 17 per cent higher risk of dying from cancer compared with those who drank little or none. One possible explanation lies in saturated fats, which may encourage inflammation, insulin resistance and hormonal imbalances that support tumour progression. The link was less evident for low-fat or skimmed milk, suggesting that fat content and related hormonal factors might play central roles in driving these associations.
Interestingly, the effect was more pronounced among women. The authors propose that biological differences in hormone regulation could make female metabolism more sensitive to dairy’s endocrine-active components, which include not only IGF-1 but also natural bovine oestrogens.
How lactose metabolism connects milk to ovarian cancer
One of the most striking findings of the meta-analysis was the association between milk intake and ovarian cancer mortality. Women who drank the most milk had a 32 per cent higher risk of dying from ovarian cancer compared with those consuming the least. This connection is thought to involve lactose, the natural sugar found in milk, and its breakdown product galactose. When consumed in large quantities, galactose and its metabolites, such as galactose-1-phosphate, may interfere with ovarian function by disrupting gonadotropin signalling and accelerating cell death within ovarian tissue.
Previous epidemiological studies, including those cited by the World Cancer Research Fund, have shown similar patterns, indicating that galactose accumulation could contribute to ovarian toxicity over time. This biological mechanism is supported by animal models and metabolic studies, which suggest that chronic exposure to galactose may impair ovarian repair mechanisms. The fact that fermented dairy products, such as yoghurt and kefir, contain lower lactose levels could explain why they are not linked to this increased risk.
Fermented dairy products: The protective side of the story
While plain milk raised concern, fermented milk showed the opposite effect. According to the same analysis, women who consumed high amounts of yoghurt and other fermented dairy foods had a 15 per cent lower risk of dying from cancer compared with those who rarely ate them. The benefit appears to stem from the probiotic bacteria these foods contain. Such bacteria support immune function by enhancing IgA, T cell and macrophage activity, which in turn reduces harmful microbial activity in the gut and limits inflammation.
Research has highlighted that probiotic-rich foods can strengthen gut barrier integrity and modulate microbial composition, producing metabolites that suppress tumour growth. Some evidence also suggests that gut bacteria influence sex hormone regulation, which could partly explain why the protective effects of fermented milk are more prominent in women. These findings suggest that not all dairy products act uniformly in the body; rather, processing methods and microbial content may radically alter their health impact.
Cheese, butter and other dairy fats: Mixed findings on cancer mortality
Cheese and butter, though high in fat, displayed weaker associations with cancer risk. The meta-analysis found no clear relationship between cheese consumption and overall cancer mortality. However, high cheese intake was linked to a 22 per cent higher risk of dying from colorectal cancer. One theory is that the high salt and saturated fat content of cheese may influence gut microbiota composition or promote chronic inflammation in the intestinal lining.
For butter, evidence was inconclusive. Only two studies met the inclusion criteria, involving over 56,000 participants. The pooled data revealed no significant association between butter consumption and cancer mortality, although researchers cautioned that the small sample size limited confidence in these results. Overall, the study emphasised that while total dairy consumption showed no consistent relationship with cancer mortality, individual products differed markedly in their biological effects.
What people can do to minimise risk and make informed choices
Given the mixed findings, experts recommend focusing on moderation and product type rather than complete avoidance. Choosing low-fat or skimmed milk may reduce exposure to saturated fats and hormones linked to elevated IGF-1 levels. Incorporating fermented dairy such as yoghurt, kefir or cultured buttermilk could provide beneficial probiotics that support immune health and gut balance.
Plant-based alternatives like soy, oat or almond milk are also viable options, many of which are fortified with calcium and vitamin D to provide similar nutritional benefits without the same hormonal components. For those with a family history of hormone-related cancers, healthcare professionals suggest monitoring dairy intake and discussing personalised nutrition strategies. Public health agencies continue to emphasise dietary diversity, ensuring that essential nutrients like calcium are obtained from a range of sources, including leafy greens, legumes and nuts.
As scientific understanding evolves, dietary guidance may shift toward recognising the distinct effects of different dairy types rather than viewing them as a single category. The growing body of evidence underscores the importance of evaluating food quality, preparation methods and individual risk profiles when assessing long-term health outcomes related to diet.
Disclaimer: This article is for informational purposes only and should not be considered medical advice. Please consult a healthcare professional before making any changes to your diet, medication, or lifestyle.
Also Read | Why cutting rice from your diet could be the biggest mistake you are making
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