What are the negative effects of dairy milk?

November 25, 2025 •

6 min read

According to a 2017 review, approximately 65–70% of the world's population has some degree of lactose intolerance, an inability to properly digest the sugar in milk. While often celebrated for its calcium content, dairy milk can present several negative health effects, ranging from common digestive upset to more serious concerns like skin issues and certain chronic disease risks.

Quick Summary

This article examines the various health concerns associated with consuming dairy milk, including digestive problems, skin conditions, potential links to specific cancers, hormonal effects, and the impact of saturated fat. It explores common intolerances and allergies, while also providing insight into who might be most affected by these issues.

Key Points

Lactose Intolerance: Many adults cannot properly digest lactose, the sugar in milk, leading to bloating, gas, and digestive discomfort.
Milk Allergies and Sensitivities: Beyond lactose, some people have immune reactions to milk proteins like casein, causing symptoms ranging from digestive issues to severe allergic reactions.
Connection to Acne: Research indicates a link between dairy consumption and increased acne breakouts, potentially due to the hormonal components in milk.
Potential Cancer Risks: Some studies suggest high dairy intake may increase the risk of certain cancers, such as prostate cancer, although research is often conflicting.
Heart Health Concerns: The saturated fat and cholesterol in full-fat dairy products can increase the risk of heart disease for some individuals.
Inflammatory Responses: For those with a sensitivity, milk protein can trigger an inflammatory response, though dairy is not universally inflammatory.
Individualized Health: The effects of dairy are highly individual; a personal dietary approach and potentially a trial elimination period are recommended.
Nutrient Replacement: Vital nutrients from dairy, like calcium, can be replaced by fortified plant-based milks and other whole foods.

Digestive Issues: More Than Just Lactose Intolerance

For many, the most immediate and noticeable negative effect of dairy milk consumption is its impact on the digestive system. While lactose intolerance is the most well-known culprit, other factors contribute to discomfort. Lactose is a sugar found in milk that requires the enzyme lactase to be properly digested. As many people age, their production of lactase decreases, leading to the condition known as lactose intolerance. When undigested lactose reaches the colon, it is fermented by bacteria, causing a range of unpleasant symptoms.

Symptoms of Lactose Intolerance and Other Reactions

Bloating and Gas: The fermentation process in the colon produces gas, which leads to bloating and flatulence.
Abdominal Cramps and Pain: Undigested lactose can draw water into the gut, causing cramps and pain.
Diarrhea: The fluid drawn into the intestine can lead to diarrhea.
Nausea and Vomiting: Some individuals, particularly after consuming large amounts of dairy, may experience nausea and, in severe cases, vomiting.

Beyond lactose intolerance, some individuals experience a casein sensitivity. Casein, the main protein in milk, can trigger inflammation in the digestive system and body, leading to discomfort even for those who are not lactose intolerant. Another, more serious reaction is a cow's milk allergy, which is an immune response to milk proteins and can cause more severe symptoms like hives, wheezing, and even anaphylaxis.

Impact on Skin Health

Research has increasingly linked dairy milk consumption to skin problems, particularly acne. The exact mechanisms are still being studied, but they are believed to be related to milk's influence on hormone levels, including insulin and insulin-like growth factor-1 (IGF-1), which can stimulate oil production and affect follicular growth.

Acne Aggravation: Several studies show a correlation between higher milk intake, especially skim and low-fat milk, and increased acne severity in teenagers and young adults.
Eczema and Psoriasis: Dairy has also been identified as a potential trigger for inflammatory skin conditions like eczema and psoriasis in some individuals.

Chronic Disease Risks and Hormonal Concerns

While dairy products are promoted for their bone-strengthening qualities, some studies have raised questions about their long-term health effects, particularly concerning certain chronic diseases and hormonal imbalances.

Saturated Fat and Heart Disease: Many dairy products, especially full-fat varieties, are high in saturated fat. Excessive intake of saturated fat and cholesterol can increase the risk of heart disease.
Cancer Risks: The link between dairy and cancer is complex and often contradictory in research. Some studies suggest a potential link between high dairy consumption, particularly with regard to IGF-1 levels, and an increased risk of certain cancers like prostate and ovarian cancer. However, other studies indicate a neutral or even protective effect against other cancer types, such as colorectal cancer.
Hormonal Exposure: Milk, even organic milk, naturally contains hormones like estrogen and progesterone. Some research suggests this hormonal exposure could have adverse effects, although more research is needed to determine the impact on human health.
Osteoporosis: Despite the long-standing belief that dairy is essential for strong bones, some studies have found no link or a weak inverse relationship between dairy intake and fracture risk, suggesting it may not offer significant protection against osteoporosis.

Comparison: Standard vs. Plant-Based Milk


Feature	Dairy Milk	Plant-Based Milk Alternatives (e.g., Soy, Almond)
Saturated Fat	Often a major source, especially in full-fat varieties.	Generally lower in saturated fat.
Lactose	Contains lactose, which can cause digestive issues for many.	Naturally lactose-free.
Casein	Contains casein protein, a potential allergen and inflammatory trigger.	Casein-free. Uses plant proteins.
Hormones	Contains naturally occurring hormones, including IGF-1.	Does not contain bovine hormones.
Fortification	Often fortified with Vitamin D.	Often fortified with calcium and vitamins to match dairy milk's nutritional profile.
Acne Risk	Some evidence links consumption to increased acne.	No evidence links these to acne.

Navigating Dietary Changes

If you suspect that dairy milk is having negative effects on your health, consulting a healthcare professional or a registered dietitian is the best course of action. They can help you determine if an elimination diet is appropriate and guide you on finding suitable alternatives to ensure you still get necessary nutrients like calcium and Vitamin D. Alternatives like fortified plant-based milks, leafy green vegetables, and legumes can provide these nutrients without the associated risks of dairy.

Conclusion: Making Informed Choices

While dairy milk offers several nutritional benefits, it is not a perfect food for everyone. The potential negative effects of dairy milk, from digestive troubles and skin issues to more complex links with chronic diseases, highlight the importance of individual dietary awareness. By understanding the risks associated with lactose, milk proteins, saturated fats, and hormones, consumers can make informed choices based on their personal health needs. The availability of fortified plant-based alternatives provides a viable option for those who choose to limit or avoid dairy for health or ethical reasons. Ultimately, the decision to consume dairy should be a personal one, made with a full understanding of both its benefits and potential drawbacks.

What are the negative effects of dairy milk? The takeaway

Digestive Discomfort: A significant portion of the population is lactose intolerant, experiencing bloating, gas, and cramps from the milk sugar lactose.
Skin Problems: Dairy consumption has been linked to increased acne, particularly in adolescents and young adults, due to its hormonal effects.
Chronic Disease Risk: High saturated fat and cholesterol in full-fat dairy can increase the risk of heart disease.
Cancer Concerns: Some studies indicate a correlation between high dairy intake and an increased risk of certain cancers, such as prostate cancer.
Alternative Options: Fortified plant-based milks offer nutrient-dense alternatives for those needing to reduce or eliminate dairy from their diet.
Hormonal Impact: The natural hormones present in milk, including IGF-1, may contribute to some of the observed negative health effects.
Individualized Response: The effects of dairy vary significantly from person to person, and a personalized approach is key to dietary choices.

FAQs

Question: Can you develop lactose intolerance later in life? Answer: Yes, it is very common to develop lactose intolerance in adulthood. The production of the enzyme lactase, which is needed to digest milk sugar, naturally declines with age for many people.

Question: Is there a difference between milk allergy and lactose intolerance? Answer: Yes, a milk allergy is an immune system response to milk proteins (casein and whey), which can be severe. Lactose intolerance is a digestive issue caused by the inability to digest milk sugar (lactose) and is not an allergy.

Question: Does switching to low-fat or skim milk help with acne? Answer: No, some studies surprisingly show that low-fat and skim milk intake is associated with an even higher odds ratio for acne compared to whole milk. The hormonal components, rather than the fat content, may be the contributing factor.

Question: Do dairy hormones affect human health? Answer: Milk contains natural hormones, and some studies raise concerns about the potential effects on human hormone balance. While the hormone levels in milk are low compared to what the human body produces, further research is needed to fully understand their impact.

Question: Is dairy consumption linked to inflammation? Answer: The research is mixed, and dairy is not a direct inflammatory food for most people. However, individuals with a milk protein sensitivity may experience an inflammatory response. For many, fermented dairy products may even have anti-inflammatory effects.

Question: Are there any cancers linked to high dairy intake? Answer: Some studies suggest a link between high dairy consumption and an increased risk of prostate cancer, potentially due to hormonal factors like IGF-1. However, the evidence is inconsistent across different cancer types and more high-quality research is needed.

Question: How can I replace the calcium from dairy if I stop drinking milk? Answer: You can get plenty of calcium from various non-dairy sources. Good options include fortified plant-based milks, leafy green vegetables like kale and broccoli, and legumes. Many plant-based alternatives are fortified with comparable levels of calcium and Vitamin D.

Frequently Asked Questions

Many people have lactose intolerance, a condition where the body produces insufficient lactase, the enzyme needed to digest lactose (milk sugar). This leads to digestive symptoms like bloating and gas when lactose-containing products are consumed.

Yes, several studies have linked dairy consumption, particularly skim milk, to an increased risk of acne. This may be due to the influence of milk on hormones like IGF-1, which can affect sebum production and skin cell growth.

For those with heart disease or high cholesterol, low-fat or reduced-fat dairy is generally recommended by health experts to minimize saturated fat intake. However, for the general population, the effects of full-fat vs. reduced-fat dairy on heart health are still debated.

Research on dairy and cancer is complex and inconclusive. Some studies suggest an association between high dairy intake and increased prostate cancer risk, possibly due to IGF-1 levels. Conversely, other research indicates dairy may be protective against certain cancers like colorectal cancer.

Lactose intolerance is a digestive problem resulting from an inability to break down lactose, causing gas and bloating. A milk allergy is an immune system reaction to milk proteins (casein and whey), which can cause more severe symptoms like hives, wheezing, and even anaphylaxis.

Yes, many plant-based milks (soy, almond, oat) are fortified with calcium, vitamin D, and other nutrients to match or even exceed the nutritional content of dairy milk. It is important to choose fortified options to ensure adequate intake.

While dairy is not universally inflammatory, those with a specific milk protein sensitivity may benefit from its removal from their diet. For most people, consuming fermented dairy like yogurt might even have an anti-inflammatory effect. Personal dietary adjustments are best determined with professional guidance.