Cow’s milk contains a broad range of vitamins, both naturally occurring and added during processing. The two standout natural vitamins are B2 (riboflavin) and B12, while vitamins A and D are typically added through fortification. Beyond those headline nutrients, milk also supplies smaller amounts of B1, B6, E, and folate, making it one of the more vitamin-dense single foods in a typical diet.
Naturally Occurring B Vitamins
Riboflavin (B2) and B12 are the vitamins milk delivers most reliably on its own, without any fortification. A single cup of whole milk provides roughly 25 to 30 percent of the daily value for each. Riboflavin helps your body convert food into energy and supports healthy skin and eyes. B12 is essential for nerve function and the production of red blood cells, and dairy is one of the primary dietary sources for people who eat animal products.
What makes milk a particularly useful source of B12 is how well your body absorbs it. A study at the USDA’s Human Nutrition Research Center gave older adults labeled B12 in water, milk, and fortified bread, then measured absorption with a whole-body gamma-ray counter. Average absorption from milk was 65 percent, compared to 55 percent from water and 55 percent from bread. The difference wasn’t statistically significant, but it confirms that the B12 in milk is at least as bioavailable as supplemental forms, even in older adults who often struggle with B12 absorption.
Fortified Vitamins: A and D
Vitamins A and D don’t occur in milk at high enough levels to meet nutritional goals on their own, so they’re added during processing. This has been standard practice for decades, and the fortification levels are regulated by government agencies.
Vitamin D fortification has increased in recent years. In Canada, for example, a cup of milk now contains 5 micrograms of vitamin D (200 IU), more than double the previous level of 2.3 micrograms. That single cup covers about 25 percent of the current daily value of 20 micrograms (800 IU). In the U.S., fortification levels are similar, typically providing around 100 IU per cup for whole milk and up to 150 IU for reduced-fat varieties.
Vitamin A fortification becomes especially important once you move away from whole milk. When cream is removed to make skim or low-fat milk, the fat-soluble vitamin A goes with it. U.S. federal regulations require that nonfat dry milk be fortified to deliver 2,000 IU of vitamin A per reconstituted quart. This ensures that choosing a lower-fat option doesn’t mean losing a key nutrient.
Fat-Soluble Vitamins and What the Cow Eats
The vitamin content of milk isn’t fixed. It shifts depending on what the cow ate. Milk from cows raised primarily on pasture (grass-fed) contains meaningfully higher levels of several fat-soluble compounds compared to milk from cows fed mixed or total grain-based rations. Beta-carotene, a precursor to vitamin A that also acts as an antioxidant, more than doubles in milk from pasture-fed cows. Levels of retinol (the active form of vitamin A), alpha-tocopherol (vitamin E), and protective plant pigments like lutein and zeaxanthin also rise with higher pasture intake.
These differences are large enough that researchers have proposed using beta-carotene concentration as a biomarker to verify “grass-fed” claims on dairy labels. For you as a consumer, the practical takeaway is straightforward: if you’re buying whole milk partly for its vitamin content, grass-fed or pasture-raised options deliver more fat-soluble vitamins per glass.
How Processing and Storage Affect Vitamins
Pasteurization is necessary for safety, but it does reduce certain vitamins. The good news is that standard high-temperature-short-time (HTST) pasteurization, the method used for most refrigerated milk, causes only limited vitamin losses. Research from Lund University found that more aggressive heat treatments, like high pasteurization, caused the most significant degradation, while HTST and UHT processing preserved vitamins reasonably well.
Storage matters more than most people realize. Vitamin losses during refrigerated storage ranged from 1 to 22 percent across different heat treatments, and the losses were more pronounced with higher initial heat exposure and longer shelf times. B12 was the most vulnerable during storage, declining more over time than B1, B2, or E. Drinking milk closer to its purchase date, rather than letting it sit in the back of the fridge for a week, gives you a slightly better vitamin return.
Whole Milk vs. Skim: What Changes
Switching from whole to skim milk primarily affects fat-soluble vitamins: A, D, E, and beta-carotene. These vitamins dissolve in fat, so when the cream layer is skimmed off, they go with it. Fortification adds A and D back, but vitamin E and beta-carotene are not typically restored. The water-soluble B vitamins, including riboflavin and B12, remain largely unchanged regardless of fat content.
If your main reason for drinking milk is the B vitamin content, skim and low-fat versions deliver essentially the same amount. If you’re looking for the full spectrum of naturally occurring fat-soluble vitamins, whole milk (particularly from pasture-raised cows) is the better choice.
How Plant-Based Milks Compare
Plant-based milks like almond, oat, and soy varieties don’t naturally contain the same vitamins as cow’s milk. Any vitamins they provide come almost entirely from fortification. The FDA notes that fortified soy beverages are the only plant-based alternative with an overall nutrient profile similar enough to dairy milk to be included in the dairy group of the federal Dietary Guidelines. Other plant milks may contain added calcium, vitamin A, vitamin D, and B12, but their total nutritional content varies widely by brand and formulation.
The nutrients in plant-based alternatives depend on the plant source, how it’s processed, and what the manufacturer adds. Some brands match or exceed cow’s milk for individual vitamins like D or B12, while others fall short. Checking the nutrition label is the only reliable way to know what you’re getting, since there are no federal fortification requirements for plant milks the way there are for dairy.
Full Vitamin Lineup in One Cup of Whole Milk
- Vitamin B2 (riboflavin): roughly 25–30% of daily value; supports energy metabolism
- Vitamin B12: roughly 20–25% of daily value; critical for nerve and blood cell health
- Vitamin A: added through fortification in reduced-fat milks, naturally present in whole milk at lower levels
- Vitamin D: added through fortification; one cup provides about 15–25% of daily value depending on the country
- Vitamin B1 (thiamine): small amounts, supporting carbohydrate metabolism
- Vitamin E: present in whole milk, especially from pasture-fed cows; removed with fat in skim versions
- Folate: trace amounts; not a significant dietary source
- Beta-carotene: present in whole milk, concentration varies significantly with the cow’s diet