Milk is high in protein, calcium, potassium, and phosphorus, with meaningful amounts of vitamins A and D, magnesium, and healthy fats. A single 8-ounce cup of whole milk delivers nearly 8 grams of protein, 22% of your daily calcium, and a broad spread of other nutrients that few single foods can match.
Protein
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, which digests slowly and provides a sustained release of amino acids, and whey, which digests quickly and is the same protein isolated for workout shakes. Together they supply all nine essential amino acids your body can’t make on its own, making milk a complete protein source. Low-fat and skim versions contain slightly more protein per cup (around 8 grams) because removing fat concentrates the remaining solids.
Calcium and Other Bone-Building Minerals
Calcium is probably the nutrient most associated with milk, and for good reason. One cup provides about 291 mg, or 22% of the Daily Value. That same cup also delivers 232 mg of phosphorus, which works alongside calcium to build and maintain bone density. Your body needs both minerals in balance; milk happens to supply them in a ratio that’s easy to absorb.
Magnesium rounds out the bone-mineral picture at about 27 mg per cup. It plays a supporting role in converting vitamin D into its active form, which in turn helps your intestines absorb calcium. So these nutrients aren’t just present in milk individually. They function as a system.
Potassium and Electrolytes
A cup of milk contains roughly 366 mg of potassium, putting it on par with a small banana. Potassium helps regulate fluid balance and blood pressure by counteracting the effects of sodium. Most adults fall well short of the recommended 2,600 to 3,400 mg per day, so milk can be a surprisingly effective way to close that gap, especially since people rarely think of it as a potassium source. The sodium content is relatively modest at 107 mg per cup, keeping the potassium-to-sodium ratio favorable.
Vitamins A and D
Whole milk naturally contains vitamin A because it’s a fat-soluble vitamin carried in milkfat. When manufacturers remove fat to make 2% or skim milk, vitamin A goes with it. Federal rules require that reduced-fat and fat-free milk be fortified back to at least 2,000 IU of vitamin A per quart. Whole milk doesn’t have this requirement, though many brands add it voluntarily.
Vitamin D follows a similar pattern. It’s added to most milk at a standard level of 400 IU per quart, which works out to about 13% of the Daily Value per cup. Fortification isn’t mandatory for whole milk but is required for reduced-fat and skim varieties. In practice, nearly all commercially sold milk in the U.S. and Canada is fortified with vitamin D regardless of fat content. Vitamin D is essential for calcium absorption, so the two nutrients in the same glass is more than a coincidence. It’s by design.
Fat and Fatty Acids
Whole milk contains about 7.9 grams of total fat per cup. Around 4.5 grams of that is saturated fat, with the remainder split between monounsaturated and polyunsaturated fats. One fat worth noting is conjugated linoleic acid, or CLA, a naturally occurring fatty acid that has attracted research interest for its potential role in body composition and immune function.
CLA levels vary dramatically depending on what the cow eats. Milk from cows raised on pasture contains roughly twice to four times more CLA than milk from cows fed a standard indoor diet. Research at Penn State found that pasture-raised cows produced milk with 10.9 mg of CLA per gram of fat, compared to 5.4 mg from conventionally fed cows. A Wisconsin study found an even wider gap: 22.7 mg versus 5.6 mg. If you’re choosing whole milk partly for its fat profile, grass-fed or pasture-raised options offer a measurably different product.
Reduced-fat (2%) milk cuts total fat roughly in half, and skim milk removes nearly all of it. The trade-off is that fat-soluble nutrients, including CLA, vitamin A, and vitamin K2, drop proportionally unless they’re added back through fortification.
Carbohydrates
Milk contains about 11 grams of carbohydrates per cup, virtually all of it from lactose, a natural sugar. Lactose is a disaccharide, meaning your body splits it into two simpler sugars (glucose and galactose) during digestion. This process requires the enzyme lactase, which about 68% of the world’s adult population produces in reduced amounts. If you’re lactose intolerant, those 11 grams of sugar reach your large intestine partially undigested, where gut bacteria ferment them and cause gas, bloating, or cramping. Lactose-free milk is treated with added lactase so the sugar is pre-split before you drink it. The nutrient profile stays the same; it just tastes slightly sweeter because free glucose and galactose hit your taste buds more directly than intact lactose.
B Vitamins
Milk is one of the best dietary sources of riboflavin (vitamin B2), providing about 26% of the Daily Value per cup. Riboflavin helps your cells convert food into energy and supports the maintenance of skin and eye health. Milk also supplies meaningful amounts of vitamin B12, which is critical for nerve function and red blood cell production. For people who eat little or no meat, milk can be a practical way to keep B12 levels adequate.
How Much Milk Covers Daily Needs
The 2025-2030 Dietary Guidelines for Americans recommend 3 servings of dairy per day as part of a 2,000-calorie eating pattern. One serving equals one 8-ounce cup of milk, so three cups would deliver roughly 24 grams of protein, 66% of your daily calcium, and 39% of your daily vitamin D. Few people actually drink three glasses of milk a day, but yogurt, cheese, and fortified alternatives count toward the same goal. The key nutrients milk is high in, particularly calcium, potassium, and vitamin D, are consistently flagged as shortfall nutrients in the average American diet, meaning most people don’t get enough of them from food alone.