Fish is one of the most vitamin-rich protein sources available, packed with vitamin D, vitamin B12, and several other B vitamins. The exact vitamin profile varies by species, with fatty fish like salmon and tuna delivering more fat-soluble vitamins and lean white fish offering strong B-vitamin content.
Vitamin D: The Standout Nutrient
Vitamin D is the vitamin most strongly associated with fish, and for good reason. A 3.5-ounce serving of wild-caught salmon contains roughly 988 IU of vitamin D3, nearly five times the FDA’s daily value of 20 mcg (800 IU). That makes a single dinner portion more than enough to cover your daily needs. Farmed trout provides about 388 IU per serving, and fresh tuna around 404 IU. Even cod, a leaner fish, delivers about 104 IU.
Vitamin D helps your body absorb calcium, supports bone health, and plays a role in immune function. Because few foods naturally contain significant amounts, fish is one of the most reliable dietary sources. Fatty fish in particular concentrate vitamin D in their flesh because the vitamin is fat-soluble, meaning it accumulates in fatty tissue.
Vitamin B12: Abundant Across Species
Nearly all fish are rich in vitamin B12, which your body needs to form healthy red blood cells, synthesize DNA, and maintain your nervous system. A single cooked serving of bluefin tuna provides 10.9 mcg per 100 grams, well above the daily value of 2.4 mcg. Canned pink salmon delivers about 4.96 mcg, Alaska pollock around 3.66 mcg, and cooked Pacific cod roughly 2.31 mcg. Even tilapia, one of the milder white fish, contains 1.83 mcg per fillet.
For context, shellfish are even more concentrated. Cooked clams contain a remarkable 98.9 mcg per 100 grams, and king crab provides 11.5 mcg. But finfish alone can easily meet your daily B12 requirement in a single serving, making fish a practical choice for people who don’t eat red meat.
B12 also helps convert a compound called homocysteine into methionine, an essential amino acid. When B12 is low, homocysteine levels rise, which has been linked to cardiovascular problems.
Other B Vitamins in Fish
Beyond B12, fish supplies several other B vitamins. Niacin (B3) is found in meaningful amounts in tuna, salmon, and swordfish, and it supports energy metabolism and skin health. Vitamin B6, important for brain development and keeping your immune system functioning properly, is present in salmon, tuna, and halibut. Riboflavin (B2) and pantothenic acid (B5) round out the B-vitamin profile in most fish, though in smaller quantities.
White fish like cod and tilapia are leaner but still deliver a solid B-vitamin package. If you’re eating fish primarily for B vitamins rather than fat-soluble nutrients, the species matters less. Most finfish will contribute meaningfully to your daily intake.
Fat-Soluble Vitamins: A, E, and K
Fish contains smaller but notable amounts of vitamins A, E, and K. Vitamin A, in its active retinol form, is concentrated primarily in fish liver and fish liver oils rather than the fillet itself. Cod liver oil has historically been used as a vitamin A supplement for this reason. The flesh of most fish provides modest amounts of retinol compared to organ meats.
Vitamin E acts as an antioxidant, protecting cells from damage. Fish roe (fish eggs) is a decent source, with about 1 mg of vitamin E per tablespoon of raw roe. Fatty fish fillets contain some vitamin E as well, though they aren’t a primary dietary source. Vitamin K appears in trace amounts in fish and roe but not enough to make fish a meaningful source of this nutrient.
Wild-Caught vs. Farmed Fish
Where your fish comes from significantly affects its vitamin content, especially for vitamin D. Wild-caught Atlantic salmon averages between 9.4 and 18.5 mcg of vitamin D3 per 100 grams of fillet, depending on where it was caught. Farmed salmon, by comparison, typically contains 2.3 to 7.3 mcg per 100 grams. That means wild salmon can deliver two to four times more vitamin D than its farmed counterpart.
The difference comes down to diet. Wild salmon eat smaller fish and zooplankton rich in vitamin D, while farmed salmon get their nutrients from commercial feed. Studies on farmed Atlantic salmon show that vitamin D content in the fillet directly corresponds to the amount of vitamin D in the feed. When researchers increased feed levels from 270 to 1,440 mcg per kilogram, fillet concentrations rose from 2.9 to 9.5 mcg per 100 grams. Even at the highest feed level, farmed salmon only matched wild salmon from the North Sea and fell well short of wild Baltic Sea salmon.
Farmed fish still provides a worthwhile amount of vitamin D. But if maximizing this nutrient is your goal, wild-caught is the better choice.
How Cooking Affects Vitamin Content
Cooking fish reduces some of its vitamin content, particularly B12. Research on herring found that grilling, boiling, frying, steaming, and microwaving all decreased B12 levels by up to 62%. That’s a significant loss. However, vacuum-sealed pouch cooking (similar to sous vide) preserved B12 completely, with no measurable loss regardless of temperature.
If you’re baking or pan-frying your fish, you’ll still absorb a meaningful amount of B12 since fish starts with such high concentrations. But choosing gentler cooking methods helps you retain more of what’s there.
How Freezing Affects Vitamins
Freezing fish is common, and it does affect certain vitamins over time. A study on frozen herring, mackerel, and capelin stored at standard freezer temperature found that vitamins A, D3, and E all declined significantly over six months. Water-soluble nutrients like B1 and minerals like iron, zinc, and selenium remained stable during the same period.
The takeaway: eating frozen fish within a few months preserves more of the fat-soluble vitamins. If your fish has been in the freezer for half a year or longer, expect reduced levels of vitamins A, D, and E, though the protein, minerals, and B vitamins will still be intact.
Quick Comparison by Fish Type
- Wild salmon: Highest vitamin D of any common fish (roughly 988 IU per 3.5 oz), strong B12 (about 5 mcg per 100 g canned), good B6 and niacin.
- Tuna: Excellent B12 (10.9 mcg per 100 g for bluefin), solid vitamin D (around 404 IU per 3.5 oz for fresh ahi), good niacin.
- Cod: Moderate vitamin D (104 IU per 3.5 oz), reliable B12 (2.31 mcg per 100 g), lower in fat-soluble vitamins than fatty fish.
- Farmed salmon: Moderate vitamin D (roughly 240 IU per 3.5 oz), similar B-vitamin profile to wild salmon.
- Tilapia: Lower in fat-soluble vitamins, but still provides 1.83 mcg B12 per fillet.
- Farmed trout: Good vitamin D (388 IU per 3.5 oz), solid B-vitamin content.