Do Milk and Dairy Products Cause Disease? An Evidence-Based Review of Fractures, Cardiovascular Disease, Cancer, and Lactose Intolerance

The Health Truth About Milk and Dairy Products: Distinguishing Foods, Populations, and Levels of Evidence

The conclusion in one sentence

Milk and dairy products are neither the root of every illness nor essential health products for everyone. The more reliable approach today is to evaluate each question according to the type of dairy product, individual tolerance, life stage, and health outcome—and to reject attempts to present correlation, surrogate endpoints, or cell and animal research as proof of causal efficacy in humans. PMID: 41660415

First, dismantle the blanket claim that “milk inevitably causes disease”

Professor Ching-Shun Lin’s original article consistently rejects the portrayal of dairy products as a common root cause of cancer, cardiovascular disease, diabetes, and other chronic illnesses. It also reminds readers that associations observed in population-based dietary studies cannot by themselves prove that a food causes disease. This methodological position is consistent with the literature: different dairy products, intake patterns, and health outcomes yield heterogeneous results, which do not support an absolute recommendation to eliminate all dairy products. PMID: 41256929、PMID: 41660415、PMID: 41886028

Similarly, the lower incidence of diabetes observed among people with higher dairy-fatty-acid biomarkers is a signal worthy of study, but it cannot be rewritten as “drinking whole milk prevents diabetes,” nor does it prove that whole milk is superior to low-fat or skim milk. Professor Lin’s reading of the original study design and his caution about causal extrapolation are both consistent with the literature. PMID: 27006479、PMID: 31108924、PMID: 34547017

Fractures and bone health: no evidence that milk causes fractures, but no guarantee that it prevents them

Media reports often recast country-level differences or a single observational study as “drinking milk increases fractures.” Professor Lin pointed out that the cited study actually concluded there was no overall association between milk intake and hip fractures. Subsequent evidence syntheses likewise have not shown that higher dairy intake increases the risk of total osteoporotic fractures or hip fractures; some dairy products, including cheese, have even been associated with lower risk. PMID: 20949604、PMID: 31089740、PMID: 40488877、PMID: 41098795

But “not shown to increase risk” does not mean “certain to prevent fractures.” With the literature now updated, the precise formulation is that the overall direction of evidence does not support milk as an inevitable cause of fractures, yet findings are not completely consistent across analyses. Fracture prevention therefore cannot be presented as a definite, universal benefit. This is a calibration of the strength of the language as science evolves; it does not alter Professor Lin’s historical position in rebutting alarmist claims at the time. PMID: 36854093、PMID: 40944114

There is also no established evidence for claiming that naturally occurring dietary phosphorus in cheese or nuts directly causes fractures in the general population. Relevant risk discussions focus mainly on vulnerable groups such as people with chronic kidney disease and on phosphate additives. A dietary management list intended for kidney disease cannot be repurposed as a fracture warning for everyone. PMID: 41654650、PMID: 41774235

Cardiovascular disease, mortality, and cancer: no one-size-fits-all verdict

The literature as a whole does not support the strong claim that drinking milk increases cardiovascular disease or cardiovascular mortality. Associations between dairy products and cardiovascular outcomes are broadly neutral or vary by product, with yogurt showing associations in a protective direction. Because these are largely pooled observational findings, they should not be inverted into a claim that dairy necessarily protects the heart. PMID: 40944114、PMID: 41660415

All-cause mortality illustrates especially clearly why classification matters. Based on the meta-analyses available at the time, Professor Lin described milk and dairy products as unrelated to mortality. The literature has since been updated: newer syntheses suggest differences by product and intake pattern. The findings are not unidirectionally harmful, but neither should they be summarized without qualification as “completely unrelated.” In short-term trials of healthy adults, whole milk did not worsen fasting blood lipids, blood glucose, or insulin, but such trials cannot replace long-term disease and mortality outcomes. Conversely, pooled cohort data have found an association between high-fat milk and higher mortality risk, but that result alone still cannot establish causality. PMID: 29229955、PMID: 33397132、PMID: 41660415

Breast cancer likewise should not be reduced to “dairy is the culprit, so every patient must abstain.” More recent reviews still do not support that simplified causal claim, although findings are mixed and may need to be stratified by fat content and life stage. After allowing for scientific progress, the most defensible conclusion is neither “dairy inevitably causes cancer” nor an unqualified “there is absolutely no association.” PMID: 41886028

For prostate cancer, pooled data show a small positive association, but the signal is weak and may be influenced by screening bias and confounding. Professor Lin’s criticism of portraying this as a severe and certain carcinogenic effect remains evidence-based. If every association were categorically dismissed, however, today’s highest-level evidence would point in a somewhat different direction—while still being insufficient to justify a causal claim. PMID: 35945656

Acne: an association signal exists, but causation is not established

Professor Lin’s original article included the claim that milk increases acne among the exaggerated arguments against dairy. Two later, independent meta-analyses repeatedly found positive associations between milk or dairy products and acne. Reassessed using today’s evidence, saying that no such association exists at all would therefore run counter to the literature. However, these studies rely mainly on observational data, the magnitude of association is limited, and they cannot prove that milk inevitably causes acne. Portraying the correlation as though everyone who drinks milk will develop acne likewise exceeds the evidence. This reflects updated literature and scientific progress; it should not be framed as Professor Lin personally reversing his position. PMID: 30079512、PMID: 29778512

Lactose intolerance is not cow’s milk allergy

Lactose intolerance results from insufficient lactase. Undigested lactose enters the colon, where the microbiota ferment it and produce gas, potentially causing bloating, abdominal pain, or diarrhea. This is a problem of digestion and absorption, not an immune reaction to milk proteins. Regular exposure to lactose or dairy products can sometimes produce colonic adaptation and improve symptom tolerance, but that does not mean genetically determined lactase non-persistence has been reversed. PMID: 41843249、PMID: 26287234

Cow’s milk allergy, by contrast, is an immune reaction to milk proteins. It occurs mainly in young children but can also affect adults; severe cases may result in anaphylactic shock or even death. Treating intolerance, allergy, and nonspecific discomfort after drinking milk as the same problem can lead to inappropriate management. Anyone with a history of severe reactions should be assessed by a medical professional. PMID: 41924427、PMID: 41701644、PMID: 41327257

The odor of intestinal gas is mainly associated with volatile sulfur compounds. Lactose intolerance can increase fermentation and gas production, but “frequent foul-smelling flatulence” alone cannot be used to infer colorectal cancer. ECU found no diagnostic research that could directly settle whether foul-smelling flatulence is a sign of colorectal cancer. The correct label is therefore insufficient evidence—not the use of “nothing was found” as proof that the possibility is absolutely excluded. PMID: 9771412、PMID: 19505855、PMID: 41843249

Infant formula and HMO: distinguish safety and substitution from added benefits

When breastfeeding ends early, infant formula is a more appropriate feeding option for infants than directly substituting ordinary cow’s milk. This concerns nutritional design and the life stage for which a product is suitable; it does not mean that every added ingredient provides additional therapeutic benefit. PMID: 41862171、PMID: 40895147

Specific human milk oligosaccharides naturally occur in the milk of most mothers, and formulas containing related ingredients can achieve non-inferior growth outcomes. Yet “similar to the control” does not mean “superior to formula without the added ingredient.” For specific clinical benefits such as enhancing immunity, reducing colic, or preventing colds, systematic reviews currently find inconsistent or underpowered results. Some studies show only that inflammatory biomarkers move closer to those in the breastfed group; a surrogate endpoint cannot be directly described as proof that an infant’s immunity has improved. PMID: 41544710、PMID: 41001441、PMID: 42196590

A multinational survey also found that infant formulas frequently make health claims about the brain and eyes, immunity, and growth, yet many products provide no specific scientific reference. Even when clinical trials are cited, the studies may still carry a high risk of bias. A product’s lawful availability for sale and strong evidentiary support for each added-value claim are two different questions. PMID: 36792145、PMID: 36792116

A1/A2, whey, colostrum, and lattes: do not switch levels of evidence

A1 β-casein has not been shown to cause type I diabetes or multiple chronic diseases, so A2 milk cannot be marketed on that basis as a way to avoid all such risks. Reviews do, however, report a moderate-strength signal for differences in certain digestive symptoms; the two therefore should not be described as completely identical in every respect. Professor Lin’s central position—opposing the extrapolation of weak associations into broad causal claims about disease—is consistent with the literature. PMID: 12601419、PMID: 30722004

If a study of a whey-containing preparation observes changes in regulatory immune cells only in a mouse model of asthma, it cannot claim to have proven efficacy in humans. TGF signaling in the body may participate in asthma or tumor progression, but that likewise cannot be directly extrapolated into a claim that oral whey products worsen human asthma or induce cancer. Professor Lin’s distinction between actual cytokines and marketing terminology, and his reminder that animal studies do not equal human efficacy, are consistent with the literature. PMID: 23068908、PMID: 41774086、PMID: 42043664

Likewise, a cultured mouse macrophage study cannot prove that drinking a latte has a stronger anti-inflammatory effect than drinking an Americano, much less that it prevents dementia. Nor has the combined evidence in athletes or physically active adults shown that bovine colostrum supplementation meaningfully improves commonly used immune markers. A clear boundary must be maintained between the research model and the real-world claim. PMID: 36715127、PMID: 32276466、PMID: 33396972

How to make a personal decision

People who tolerate dairy do not need to eliminate it entirely because of a vague disease-causing slogan. Those who do not consume dairy likewise need not force themselves to do so because of a claim about one nutrient or health benefit. What matters is identifying the type of product, one’s own symptoms, allergy risk, health conditions, and substitute foods—and keeping “an observed association,” “a change in a biomarker,” “non-inferiority,” and “a proven clinical benefit” conceptually separate. Children’s growth also cannot be reduced to the promise that more milk or calcium will necessarily make them taller: calcium supplementation has not been shown to increase height in healthy children, and dairy products still cannot be presented as a guarantee of linear growth. PMID: 17636098、PMID: 31089738