Is dairy bad for you?

The objection

“I grew up on milk, and it’s full of calcium and protein. Every scare story about dairy, from mucus to cancer to acne, seems to come from people who want me off it for other reasons, and the new US dietary guidelines even count full-fat dairy as a healthy fat. If dairy were bad for you, the experts would have said so by now.”

The answer

The experts have said a fair amount about dairy, some of it in its favour and some against. Milk has not been shown to make more mucus in a cold [1], and in pooled cohort studies people who eat more dairy have less bowel cancer and slightly less cardiovascular disease than people who eat little [2][3]. Against that, dairy has been linked to more prostate cancer [4], much of the fat in it is saturated, and too much saturated fat can raise LDL cholesterol [5][6], while about two-thirds of the world’s adults don’t fully absorb the sugar in milk, on a 2017 estimate [7]. The US guidelines for 2025 to 2030 do advise including full-fat dairy and list it among the whole foods that supply healthy fats, but the same guidelines say saturated fat should generally not exceed 10% of daily calories [8][23]. The NHS, Ireland’s Health Service Executive (HSE) and Health Canada all advise choosing lower-fat milk, yoghurt and cheese [5][9][10]. None of this makes dairy necessary in UK advice: the NHS counts unsweetened, calcium-fortified alternatives made from soya, oats or coconut in the same food group, though it says people who go without dairy may be at risk of not getting enough calcium [5]. The World Cancer Research Fund (WCRF), which judges that dairy lowers bowel cancer risk, leaves it out of its cancer prevention recommendations because of the evidence on prostate cancer, and says it has no evidence yet on how plant-based alternatives affect health [11].

Does dairy cause cancer?

Dairy probably lowers the risk of bowel cancer and may raise the risk of prostate cancer, in the judgement of the WCRF, which rates the first as strong evidence and the second as some evidence [11][12]. It also reports some evidence that women who eat dairy have a lower risk of breast cancer [11]. The size of the bowel cancer link comes from a 2017 meta-analysis of cohort studies done for the WCRF (Vieira et al.), which found 13% less bowel cancer for each 400 g of dairy eaten a day, a relative risk of 0.87 (95% CI 0.83 to 0.90) across 10 studies, while cheese on its own showed no link [2]. The WCRF puts the benefit largely down to the calcium in dairy, and it rates the evidence as strong that calcium supplements lower bowel cancer risk too [11].

The prostate figures come from the same programme. A 2015 meta-analysis (Aune et al.) found 7% more prostate cancer for each 400 g of dairy a day (1.07, 1.02 to 1.12, 15 studies) and 9% more for each 50 g of cheese (1.09, 1.02 to 1.18, 11 studies) [4]. Calcium from dairy was linked to prostate cancer but calcium from other foods was not, which led the authors to suggest that something in dairy other than its fat and calcium may raise the risk; calcium supplements were not linked to prostate cancer overall, though they were linked to more fatal cases [4]. The Adventist Health Study-2 (Orlich et al., 2022), which followed 28,737 men in the US and Canada, many of whom ate little or no dairy, found that men at the 90th percentile of dairy intake, 430 g a day, had 27% more prostate cancer than men at the 10th, 20.2 g a day (hazard ratio 1.27, 1.12 to 1.43), with the steepest rise at fairly low intakes, while calcium from other foods showed no clear link (1.16, 0.94 to 1.44) [13].

Dropping dairy without replacing its calcium may give up the bowel benefit. In a 2026 pooled analysis of 1.8 million people in nine cohorts followed for a median of 16 years (Dunneram et al.), vegans had 40% more bowel cancer than meat-eaters (hazard ratio 1.40, 1.12 to 1.75) [12]. That result rests on 93 cases and was no longer statistically significant once the first four years of follow-up were left out, though it held in people who had never smoked [12]. The vegans’ median calcium intake was 590 mg a day, below the UK adult reference of 700 mg, and the authors suggest low calcium might explain the result, citing the WCRF’s conclusion that dairy and calcium supplements probably protect against bowel cancer [12]. The NHS points people who avoid dairy to non-dairy products with added calcium [5], and Do you need dairy for calcium and strong bones? sets out how to reach 700 mg a day.

Is dairy bad for your heart?

Dairy as a whole looks neutral to slightly favourable for the heart in cohort studies, but dairy fat comes out worse than fat from plants. A 2025 umbrella review that updated the meta-analyses (Sharifan et al.) found that people who ate the most dairy had 4% less cardiovascular disease than those who ate the least (relative risk 0.96, 0.93 to 0.99, 30 studies) and 13% fewer strokes (0.87, 0.81 to 0.94, 20 studies), though it rated the evidence weak for cardiovascular disease and only suggestive for stroke, and said more research was needed [3]. For coronary heart disease on its own, the same review found no clear link (0.98, 0.95 to 1.01, 35 studies) [3]. The review was funded by Dairy Farmers of Canada, which the authors say had no part in its design, analysis or writing [3].

Comparisons like these don’t show what the people eating little dairy ate instead. In three US cohorts of 222,234 health professionals and nurses (Chen et al., 2016), the result depended on the swap: dairy fat showed no link with cardiovascular disease when compared with the same calories from carbohydrates other than fruit and vegetables (relative risk 1.02, 0.98 to 1.05, for each 5% of calories), but replacing 5% of calories from dairy fat with vegetable fat went with 10% less cardiovascular disease (0.90, 0.87 to 0.93), and replacing it with polyunsaturated fat went with 24% less (0.76, 0.71 to 0.81) [14]. Fat from other animal foods in place of dairy fat went with 6% more (1.06, 1.02 to 1.09), so in these cohorts dairy fat did better than other animal fat and worse than fat from plants [14].

The NHS says much of the fat in dairy is saturated, lists butter, ghee, cheese (especially hard cheese such as cheddar), cream and ice cream among foods high in it, and says too much saturated fat can raise LDL, the “bad” cholesterol, while replacing it with some unsaturated fats can help lower cholesterol [5][6]. Its fats page, last reviewed in 2023, advises men to eat no more than 30 g of saturated fat a day and women no more than 20 g [6]. Cheese seems to behave better than its fat would suggest. In a 2015 meta-analysis of five randomised trials (de Goede et al.), hard cheese lowered LDL cholesterol by 0.22 mmol/L (0.14 to 0.29), or 6.5%, compared with butter that had a similar ratio of polyunsaturated to saturated fat, but cheese raised total or LDL cholesterol when it was compared with tofu or with a cheese whose fat had been modified [15]. If you take a statin or any other heart medicine, speak to your GP before making big changes to how you eat, and don’t stop or change a medicine without their advice.

Can most adults digest milk?

Most adults in the world make too little lactase, the enzyme that digests lactose, the sugar in milk, to absorb all of it, though most of them can manage a modest amount without symptoms [16]. A 2017 meta-analysis of 450 study populations in 89 countries (Storhaug et al.) put the global prevalence of lactose malabsorption in adults at 68% (95% CI 64 to 72), ranging from 28% in western, southern and northern Europe to 70% in the Middle East [7]. A 2010 systematic review of randomised trials (Shaukat et al.) found that most adults with lactose intolerance or malabsorption tolerate 12 to 15 g of lactose, about a cup of milk [17], and in 2013 three of its authors concluded that the public and doctors alike have overestimated how much malabsorption matters, since that much lactose taken with a meal usually causes no noticeable symptoms; symptoms come with larger doses, or when lactose is taken without other food [16].

When lactose intolerance does cause symptoms, the NHS lists tummy pain, bloating, wind, diarrhoea or constipation and feeling sick among them, starting a few minutes to a few hours after eating lactose, and distinguishes it from a food allergy, which can be life-threatening [18]. It advises against cutting foods out without advice from a GP or dietitian, and to see a GP if symptoms keep coming back, if changes to your bowel habits or blood in your poo last three weeks, or if you lose weight without trying [18]. Plant drinks contain no lactose, and Which plant milk is healthiest? compares them.

Does dairy cause acne?

Dairy has been linked to acne in children and young adults, though only in observational studies with known weaknesses, and a large Danish study found no link in adults. A 2018 meta-analysis of 14 observational studies covering 78,529 people aged 7 to 30 (Juhl et al.) found 25% higher odds of acne with any dairy compared with none (odds ratio 1.25, 1.15 to 1.36) and 28% higher odds with any milk (1.28, 1.13 to 1.44), with skimmed or low-fat milk at 1.32 (1.16 to 1.52), above whole milk at 1.22 (1.06 to 1.41) [19]. The authors found publication bias, reported that adjusting for other factors weakened the links, and asked for the results to be read with caution [19]. The same team found no link between milk and acne in 20,416 Danish adults aged 20 to 96, either in what people said they drank or in a gene variant tied to lactase persistence, and so to drinking more milk (Juhl et al., 2018) [20].

Does milk make more mucus when you have a cold?

Milk doesn’t appear to increase mucus during a cold. In a 1990 study (Pinnock et al.), 60 adult volunteers were deliberately exposed to a cold virus, rhinovirus-2, and kept daily records for 10 days [1]. Among the 51 who provided data, how much milk and dairy they had, from none to 11 glasses a day, was not linked to congestion or to the weight of their nasal secretions, which the researchers measured by weighing used tissues sealed straight after use, and the authors applied that finding to infected adults whether or not they had symptoms [1]. Those who believed milk makes mucus reported more cough and congestion, but produced no more secretions [1]. In a later double-blind trial (Pinnock and Arney, 1993), people given 300 ml of either a flavoured cow’s milk drink or a soya drink that testers couldn’t tell apart from it reported more coating in the mouth and throat, more need to swallow and thicker saliva afterwards, but those sensations rose after both drinks, so the researchers concluded they were not specific to cow’s milk [21].

People troubled by persistent mucus, rather than a cold, may be a different case. In a 2019 randomised double-blind trial (Frosh et al.), 108 patients over the age of 15 at an NHS ear, nose and throat department who reported excess mucus went on a dairy-free diet and, for its last four days, were given either a dairy or a dairy-free supplement without knowing which [24]. The mucus they reported fell in both groups at first, then rose again in the group given dairy, while it kept falling, though not significantly, in the other [24]. The authors linked a dairy-free diet with less mucus in people with this complaint, though the measure was the patients’ own rating of their symptoms [24].