A single cup of whole milk delivers a surprisingly broad range of nutrients: nearly 8 grams of protein, close to 8 grams of fat, about 11 grams of carbohydrates, and meaningful amounts of more than a dozen vitamins and minerals. Few single foods cover this much nutritional ground in one glass, which is why milk has long been considered a nutritional staple.
Protein in Milk
One cup of whole milk contains about 7.9 grams of protein, roughly the same as one large egg. That protein comes in two forms: casein and whey. Casein makes up the majority (about 80%) and digests slowly, providing a steady release of amino acids. Whey, the remaining 20%, digests quickly and is particularly rich in branched-chain amino acids that support muscle repair. This is the same whey protein sold as a supplement, just in its natural form.
Milk protein is considered “complete,” meaning it contains all nine essential amino acids your body can’t produce on its own. The combination of slow-digesting casein and fast-digesting whey is one reason milk has been studied extensively as a post-exercise recovery drink.
Calcium and Other Key Minerals
Milk is one of the most concentrated food sources of calcium available. A single cup of whole milk provides roughly 276 mg, which covers about 21% to 28% of most adults’ daily needs depending on age and sex. Calcium from milk is also well absorbed compared to calcium from many plant sources, partly because milk’s lactose and protein help the body take it up more efficiently.
Beyond calcium, milk supplies several other minerals that don’t always get attention:
- Phosphorus works alongside calcium to build and maintain bone and tooth structure. A cup of milk provides about 205 mg.
- Potassium helps regulate blood pressure and fluid balance. Milk contributes a meaningful amount per serving, and most people fall short of the daily recommendation for this mineral.
- Iodine is essential for thyroid function, and milk is one of the most reliable dietary sources. An analysis of milk samples found an average of 84 mcg per cup, which is more than half the daily recommended intake for adults (150 mcg).
- Zinc and selenium are present in smaller but still useful amounts, supporting immune function and acting as antioxidants respectively.
Vitamins: What a Glass Delivers
Milk is a standout source of two B vitamins in particular. One cup provides about 1.13 mcg of vitamin B12, which is nearly half the daily recommended amount for adults. B12 is critical for nerve function and red blood cell production, and it’s found almost exclusively in animal-derived foods, making milk an important source for people who eat little meat.
Riboflavin (vitamin B2) shows up in equally impressive amounts: about 0.47 mg per cup, covering roughly 36% of daily needs. Riboflavin helps your body convert food into energy and plays a role in maintaining healthy skin and eyes. Milk is one of the top food sources of this vitamin in the typical Western diet.
Milk also contains smaller amounts of vitamin A (particularly in whole milk, where it’s carried in the fat), niacin, and vitamin B6.
Vitamin D Fortification
Milk doesn’t naturally contain much vitamin D, but in the United States nearly all commercial milk is fortified with it. The FDA allows manufacturers to add up to 84 IU of vitamin D3 per 100 grams of milk. In practice, a standard 8-ounce glass of fortified milk typically provides around 100 to 120 IU, covering roughly 15% to 20% of daily needs. Since vitamin D is essential for calcium absorption, the pairing of these two nutrients in milk is one of the reasons it became a public health tool for preventing rickets and osteoporosis.
Fat and Fatty Acids
A cup of whole milk contains about 7.9 grams of total fat, of which 4.6 grams are saturated. The rest is a mix of monounsaturated and polyunsaturated fats. If saturated fat is a concern, reduced-fat (2%), low-fat (1%), and skim options bring total fat down while preserving most of the vitamin and mineral content. Fat-soluble vitamins like A are reduced in lower-fat versions, though many brands add them back.
The type of fat in milk varies based on what the cows eat. Milk from grass-fed cows contains roughly 2.5 times more omega-3 fatty acids than conventional milk (0.05 g versus 0.02 g per 100 grams). Grass-fed milk also provides more conjugated linoleic acid (CLA), a fat that has been studied for potential benefits related to inflammation and body composition. Three servings of grass-fed milk supply about 300 mg of CLA, while conventional milk provides less than half that amount.
Carbohydrates and Lactose
Almost all of the roughly 11 grams of carbohydrate in a cup of milk comes from lactose, a naturally occurring sugar. Lactose content ranges from about 9 to 14 grams per cup depending on the specific product and fat level. Unlike added sugars, lactose is digested slowly when your body produces enough lactase (the enzyme that breaks it down), and it actually helps with calcium absorption in the gut.
For the roughly 68% of the global population with some degree of lactose malabsorption, this sugar is the main reason milk causes digestive discomfort. Lactose-free milk is treated with lactase enzyme before packaging, which breaks the lactose into simpler sugars. The result tastes slightly sweeter but has the same overall nutritional profile.
How Fat Level Changes the Nutrition
Switching from whole to skim milk cuts calories from about 149 to 83 per cup and drops fat from nearly 8 grams to less than half a gram. Protein stays virtually the same across all fat levels, and calcium, potassium, B12, and riboflavin are largely unaffected. The main tradeoffs are fewer fat-soluble vitamins in unfortified skim milk and a thinner taste that some people find less satisfying. For most nutrients, the fat level you choose matters far less than simply drinking milk in the first place.