Milk isn’t universally harmful, but it does carry several well-documented health concerns that affect a large portion of the population. Around 68% of adults worldwide can’t fully digest lactose, the sugar in milk. Beyond digestion, milk has been linked to increased acne, higher hip fracture risk, and elevated hormone levels, particularly in conventionally produced varieties. Whether milk is “bad” for you depends on how much you drink, what type, and your individual biology.
Most Adults Can’t Digest It Properly
The ability to digest milk comfortably is actually the exception, not the rule. A systematic review covering global data estimated that 68% of adults have lactose malabsorption, meaning their bodies produce too little of the enzyme needed to break down milk sugar. When assessed by genetic testing alone, the number rises to 74%.
Regional variation is enormous. In western, southern, and northern Europe, prevalence sits around 28%, which helps explain why dairy-heavy diets became normalized in those cultures. In the Middle East, it’s roughly 70%. In East Asia, rates exceed 90%. If you experience bloating, gas, cramps, or diarrhea after drinking milk, lactose malabsorption is the most likely explanation, and it’s not a disorder so much as the biological default for most humans.
The Bone Health Paradox
The most persistent reason people drink milk is to strengthen their bones, but the evidence on this is surprisingly weak. A large dose-response analysis of nearly 487,000 adults found that milk consumption was associated with incrementally higher risk of hip fractures up to an intake of about 400 grams per day (roughly 1.5 glasses). At that level, hip fracture risk was 15% higher compared to drinking no milk at all. Even above 400 grams per day, milk consumption continued to show elevated fracture risk up to 750 grams daily. At no level of milk intake did the analysis find a significantly lower risk of hip fracture compared to zero intake.
Interestingly, yogurt and cheese told a different story. Yogurt intake was associated with a 15% lower fracture risk per daily serving, and cheese showed a 19% reduction per serving. This suggests that something specific to liquid milk, or the way it’s consumed, may work differently in the body than other dairy products.
Milk and Acne
If you’ve noticed your skin breaks out more when you’re drinking milk regularly, there’s a biological explanation. Milk contains amino acids that trigger your body to produce more insulin and a growth hormone called IGF-1. IGF-1 is considered a primary driver of acne because it stimulates oil production in the skin, promotes the overgrowth of cells lining hair follicles, and ramps up inflammatory responses.
This effect is compounded by sugary or high-glycemic foods, which boost insulin signaling on their own. When combined with milk, the two act together to activate a cellular growth pathway that’s been implicated not just in acne but in a broader spectrum of metabolic conditions including obesity and insulin resistance. A meta-analysis of over 78,000 children, adolescents, and young adults confirmed the association between dairy intake and acne.
Hormones in Conventional Milk
Conventional milk contains measurably higher levels of bovine growth hormone and IGF-1 compared to organic milk. A study testing retail milk samples from nine U.S. regions found that conventional milk had a median bovine growth hormone level of 9.8 ng/ml, twenty times higher than the 0.5 ng/ml found in organic samples. IGF-1 levels were 3.2 times higher in conventional milk (3.5 vs. 1.1 ng/ml).
These differences stem largely from the use of recombinant bovine growth hormone, which is given to cows to increase milk production. While the FDA has not set limits on these hormone levels in milk, the elevated IGF-1 is the same growth factor linked to acne and, in some research, to cancer cell proliferation. If you do drink milk, choosing organic significantly reduces your exposure to these hormones.
The A1 Protein Problem
Most commercial milk comes from cows that produce a protein called A1 beta-casein. When your body digests A1 beta-casein, it releases a fragment that can trigger inflammatory responses in the gut. Animal research has shown that consuming A1 variants significantly increased markers of intestinal inflammation, immune activation, and white blood cell infiltration in the gut lining compared to A2 variants.
This distinction matters because some people who believe they’re lactose intolerant may actually be reacting to A1 protein. A2 milk, which comes from cows that only produce the A2 variant, is now widely available and may be easier to tolerate. It won’t help if you’re truly lactose intolerant, but for people whose symptoms don’t fully resolve with lactose-free milk, the protein type could be the missing piece.
Cancer Risk at High Intake
The link between milk and cancer is not as dramatic as some headlines suggest, but it’s not negligible either. A systematic review of prostate cancer data across 42 countries found a notable correlation (r=0.711) between milk consumption and prostate cancer incidence. Men in the highest category of fermented milk consumption had a 16% higher risk of prostate cancer compared to those in the lowest category.
The mechanism likely involves IGF-1 again. Because milk stimulates IGF-1 production and IGF-1 promotes cell growth, tissues that are already prone to rapid cell division, like the prostate, may be more vulnerable to this effect over decades of regular consumption.
Saturated Fat in Whole Milk
One cup of whole milk contains 4.5 grams of saturated fat, about a quarter of the recommended daily limit for a 2,000-calorie diet. If you drink two or three glasses a day and eat other animal products, you can easily exceed that threshold. That said, the cardiovascular picture is more nuanced than “dairy fat is bad.” A large global analysis published in Nature Communications found that overall dairy consumption was associated with lower risk of stroke and total cardiovascular disease. Cheese consumption showed the strongest protective association, while low-fat dairy was inversely related to cardiovascular and stroke risk.
Whole milk’s association with cardiovascular disease was marginally inverse, meaning it showed a slight trend toward reduced risk rather than increased risk. So the saturated fat in milk doesn’t appear to behave the same way as saturated fat from processed meat. Still, if cardiovascular health is a concern, low-fat dairy or plant-based alternatives are the safer choice.
You Don’t Need Milk for Calcium
Milk provides about 300 mg of calcium per cup with an absorption rate of roughly 26%. That’s decent, but it’s not uniquely efficient. Low-oxalate vegetables like kale and broccoli have fractional calcium absorption rates of 41% to 53%, meaning your body actually absorbs a higher percentage of their calcium than it does from milk. The catch is serving size: you’d need to eat more volume of vegetables to match the total milligrams in a glass of milk.
Calcium-fortified plant milks, tofu made with calcium sulfate, canned sardines, and almonds can all fill the gap. If you’re avoiding dairy entirely, a combination of these foods can meet your calcium needs without supplementation for most people.