Cow’s milk provides a surprisingly wide range of vitamins, but the two it’s best known for are vitamin D and vitamin A. One cup of fortified milk delivers about 12% of your daily vitamin D needs, and milk is also a meaningful source of B vitamins, particularly B12 and riboflavin (B2). Some of these vitamins occur naturally in milk, while others are added during processing.
Vitamins Naturally Found in Milk
Milk straight from the cow contains several vitamins on its own, without any fortification. The B vitamins are the standouts here. Riboflavin (vitamin B2) gives milk a faintly yellowish tint and plays a role in converting food into energy. Vitamin B12, which is essential for nerve function and red blood cell production, is also naturally present. These B vitamins are one reason milk has long been considered a nutritionally complete food, especially for growing children.
Whole milk also contains fat-soluble vitamins A, E, and K in small amounts. Because these vitamins dissolve in fat, their levels drop when the fat is removed to make reduced-fat or skim milk. That’s where fortification comes in.
Why Vitamin A and D Are Added Back
Vitamin D is not naturally present in milk in significant amounts. In the U.S., manufacturers voluntarily add vitamin D3 to milk at levels up to 84 IU per 100 grams. This practice started in the 1930s to combat widespread rickets in children and has continued ever since. One cup of fortified milk provides roughly 12% of the daily value for vitamin D.
Vitamin A fortification follows a different logic. Whole milk is naturally a good source of vitamin A, but when fat is skimmed off, most of the vitamin A goes with it. Federal guidelines require that reduced-fat and skim milks be fortified with at least 2,000 IU of vitamin A per quart so they remain nutritionally equivalent to whole milk. If you’re drinking whole milk, it typically isn’t fortified with extra vitamin A because the natural levels are already adequate. Public health limits cap vitamin A at 6,000 IU per quart and vitamin D at 800 IU per quart, above which levels could pose health risks.
Other Nutrients That Round Out the Picture
Vitamins get the most attention, but milk’s nutritional value extends well beyond them. The FDA lists dairy’s key nutrients as protein, calcium, vitamin A, vitamin D, magnesium, phosphorus, potassium, riboflavin, vitamin B12, zinc, choline, and selenium. Choline, which supports brain health and liver function, is present at about 43 mg per cup of whole chocolate milk and similar levels in regular milk. That’s roughly 8% of the daily adequate intake for adults. It’s not a headline nutrient, but it adds up if you drink milk regularly.
Calcium and potassium are required to appear on the Nutrition Facts label alongside vitamin D, reflecting their importance in the milk nutrition profile. A single cup of milk typically covers about 25 to 30% of your daily calcium needs.
How Plant-Based Milks Compare
If you drink almond, oat, or another plant-based milk, the vitamin content depends almost entirely on what the manufacturer adds. These products don’t naturally contain the same vitamins as dairy milk. Fortified soy milk comes closest: when calcium, vitamin A, and vitamin D are added, it’s the only plant-based alternative the federal Dietary Guidelines consider nutritionally similar enough to include in the dairy group.
Other plant milks may list calcium or vitamin D on the label, but their overall nutrient profile still falls short of dairy or fortified soy. They typically lack the naturally occurring B12, riboflavin, potassium, and protein that cow’s milk provides without any processing. If you rely on plant-based alternatives, checking the Nutrition Facts panel for fortification levels is worth the few seconds it takes. The difference between brands can be significant.
Getting the Most From Your Glass
Your choice of milk fat level affects which vitamins you get naturally versus through fortification. Whole milk delivers more natural vitamin A and slightly more of the other fat-soluble vitamins. Skim and 1% milk compensate through mandatory vitamin A fortification, so the final nutrient numbers end up similar on the label, though the source differs.
Vitamin D absorption improves when consumed with fat, which gives whole and 2% milk a slight edge for that particular nutrient. If you drink skim milk, pairing it with a meal that contains some fat can help your body absorb the added vitamin D more effectively. Storage matters too: riboflavin breaks down when exposed to light, which is one reason milk is sold in opaque containers rather than clear glass bottles.