Trout: vitamin B12 and vitamin D in a low-mercury fish

The best trial of trout as a food comes from Shiraz. Of 106 adults with high blood lipids who were not on statins, 95 were analyzed after 8 weeks of either 8.8 oz (250 g) of farmed trout twice a week or 2 g a day of omega-3 capsules. LDL cholesterol fell by 22.75 mg/dL with trout and rose by 18.7 mg/dL with capsules. The trial was open-label, the groups started with different lipid levels, and the fish group also changed what it ate in place of the trout. The trout served there held 1.4 g of omega-3 per 3.5 oz (100 g), 280 mg of it EPA and 160 mg DHA, from one farm whose fish vary with feed. Outside trials, trout is a dense source of two vitamins. USDA puts raw mixed-species trout at 7.79 micrograms of vitamin B12 per 3.5 oz (100 g), 325% of the Daily Value, yet its seven trout records run from 2.77 to 7.79. A regular 90 g fillet in US survey data carries 10.9 micrograms of vitamin D, recalculated from 100 g, and farmed trout gets its vitamin D from feed.

The numbers, per 3.5 oz (100 g)

As people eat it, per 3.5 oz (100 g)

How much is actually in it

• USDA puts raw trout at 7.79 micrograms of vitamin B12 per 3.5 oz (100 g), 325% of the Daily Value, but its seven trout records range from 2.77 to 7.79. — USDA SR Legacy record Fish, trout, mixed species, raw, plus six rainbow (farmed, wild), brook and cooked trout records (n = 7 records) Evidence E source
  Vitamin B12 7.79 micrograms (325% DV), protein 20.77 g (42% DV), thiamin 0.35 mg (29% DV) per 3.5 oz (100 g) raw; across 7 records B12 2.77 to 7.79, protein 19.94 to 26.63, thiamin 0.12 to 0.426
• The UK table gives raw brown trout 19.4 g of protein, 3.8 g of fat and 25 micrograms of selenium per 3.5 oz (100 g), at 112 calories. — CoFID 2021 record 16-224, Trout, brown, raw (n = 1 record) Evidence E source
  Protein 19.4 g, fat 3.8 g, energy 112 calories, selenium 25 micrograms, sodium 56 mg per 3.5 oz (100 g); USDA mixed species protein 20.77 g
• In a survey of 3,257 Polish male teenagers, rainbow trout was among the richest vitamin D foods at 7 to 15 micrograms per 3.5 oz (100 g), alongside salmon, herring and eel. — 3,257 male adolescents aged 14 to 20 from all regions of Poland, food frequency questionnaire (n = 3257) Evidence C source
  Rainbow trout grouped with fish providing 7 to 15 micrograms vitamin D per 3.5 oz (100 g); brook trout among fish with 1.05 to 4 micrograms; median intake 4.36 micrograms a day, below 15 in almost 80%

What a real portion looks like

• One regular 90 g trout fillet in US survey data carries 10.9 micrograms of vitamin D and 15.4 g of protein. — FNDDS survey food Fish, trout, NFS (2706302) Evidence E source
  Vitamin D 12.1 micrograms per 3.5 oz (100 g); 90 g fillet 10.9 micrograms, 135 g large fillet 16.3 micrograms; protein 17.08 g per 3.5 oz (100 g), 15.4 g per 90 g fillet

What your body absorbs

• In a stable-isotope trial in 35 men using labeled trout, fish selenium was absorbed as well as selenate and retained better, with no difference between two processing methods. — 35 healthy men aged 18 to 50 in Norwich and Zeist eating biosynthetically labeled trout processed two ways, labeled yeast or selenate (n = 35) Evidence B source
  Apparent absorption from trout similar to selenate; retention significantly higher than selenate (P<0.001); no difference between two processing methods

What cooking and storage change

• FDA guidance says parasites in fish meant to be eaten raw are killed by freezing at -20°C (-4°F) or below for 7 days, or at -35°C (-31°F) until solid and then 15 hours, and that heating fish enough to kill bacteria also kills parasites. — fish intended to be eaten raw or undercooked (US seafood industry guidance) Evidence E source
  -4 °F (-20°C) for 7 days, or -31 °F (-35°C) until solid plus 15 hours at -31 °F (-35°C), or plus 24 hours at -4 °F (-20°C), kills parasites
• For finfish above 5% fat, the USDA retention table keeps 85% of vitamin B12 after baking without drippings and 75% after broiling or frying. — USDA retention factors for the Finfish and Shellfish Products group, finfish above 5% fat Evidence E source
  Vitamin B12 retained 85% baked without drippings (2451), 75% broiled without drippings (2455), 75% fried without coating (2459)

What it does to your health

• In 95 adults with high cholesterol, 8.8 oz (250 g) of trout twice a week for 8 weeks cut LDL by 22.75 mg/dL, while 2 g a day of omega-3 capsules raised it by 18.7. — 95 analyzed of 106 hyperlipidemic adults in Shiraz, not on statins, randomized to farmed trout 250 g twice weekly or 2 g/day omega-3 capsules for 8 weeks (n = 95) Evidence B source
  LDL -22.75 mg/dL with trout versus +18.7 with capsules (P<0.001); HDL +8.51 versus +4.47 (P=0.022); total cholesterol, non-HDL and triglycerides fell in both, more with trout
• The farmed trout used in that trial held 1.4 g of omega-3 per 3.5 oz (100 g), including 280 mg EPA and 160 mg DHA, so two 8.8 oz (250 g) meals supplied about 14 g a week. — farmed trout served to the dietary-fish arm of a Shiraz lipid trial, 250 g twice a week for 2 months (n = 53) Evidence B source
  1.4 g omega-3 per 3.5 oz (100 g) (280 mg EPA, 160 mg DHA); about 14 g omega-3 per week, 2.8 g EPA and 1.6 g DHA

Safety, limits and interactions

• A 19-year-old in Japan passed a fish tapeworm two months after eating raw trout, with falling vitamin B12 that recovered after treatment. — one 19-year-old man in Japan with molecularly confirmed Dibothriocephalus nihonkaiensis infection (n = 1) Evidence D source
  Tapeworm excretion 2 months after raw trout; vitamin B12 slightly low, then lower two months later, normal after anthelmintic treatment; no anemia

What people believe that the data does not support

• Coral trout, a reef grouper and not a true trout, gave a Queensland family of four including a pregnant woman ciguatera poisoning, and all recovered. — one family of four in Queensland, including a woman in the first trimester of pregnancy (n = 4) Evidence D source
  Ciguatera confirmed by bioassay of the fish; all four recovered with intravenous mannitol; infant showed no adverse effects at birth

Who this works differently for

• FDA advises pregnant women to avoid refrigerated smoked seafood, trout included, unless it is in a cooked dish such as a casserole. Canned or shelf-stable smoked seafood is okay. — Pregnant women (n = -) Evidence E source
  Avoid refrigerated smoked seafood unless in a cooked dish, canned or shelf-stable is okay
• FDA testing of 35 freshwater trout samples found mean mercury of 0.071 ppm and median 0.025, though single fish reached 0.678. — 35 freshwater trout samples in FDA monitoring, 1991 to 2008 (n = 35) Evidence E source
  Mercury mean 0.071 ppm, median 0.025, standard deviation 0.141, minimum not detected, maximum 0.678
• Among 240 fresh rainbow trout from farms and shops in western Iran, 9.16% carried Listeria monocytogenes. — 240 fresh rainbow trout, 120 from farms and 120 from retail outlets, Kurdistan province, Iran (n = 240) Evidence C source
  Listeria spp. in 35.83%; L. monocytogenes 9.16%; L. ivanovii 6.66%; most isolates resistant to tetracycline (62.79%)
• Among First Nations adults in Ontario, trout was one of the fish supplying methylmercury, yet 97.8% stayed below Health Canada reference values. — 1,429 adult First Nations participants living on-reserve in Ontario, total diet study with 744 hair samples (n = 1429) Evidence C source
  Average methylmercury exposure 0.039 micrograms/kg/day, 1.6 times the general Canadian population; 97.8% below reference values; 1.3% of women of childbearing age above 2 micrograms/g hair

What is still unknown

• In a crossover of 44 obese Colombians, 8 weeks of a diet built on fruit, avocado, whole grains and trout lowered fasting insulin, VLDL and HOMA-IR and blunted post-meal triglyceride rises. — 44 obese adults aged 45 to 60, BMI 30 or more, 8 weeks on a fruit, avocado, whole grain and trout diet versus a usual high saturated fat diet, 2-week washout (n = 44) Evidence B source
  Fasting insulin, VLDL and HOMA-IR lower after 8 weeks (P<0.05); smaller postprandial rise in triglycerides, VLDL and insulin; sizes not in the abstract

The bottom line

Selenium from trout is well used. In a stable-isotope trial in 35 healthy men, selenium from labeled trout was absorbed about as well as selenate and retained significantly better, with no difference between two processing methods. Cooking costs some B12. USDA group factors for finfish above 5% fat keep 85% after baking and 75% after broiling or frying, set for the group and not measured on trout. The UK table gives raw brown trout 112 calories, 3.8 g of fat and 25 micrograms of selenium per 3.5 oz (100 g). Polish food tables put rainbow trout at 7 to 15 micrograms of vitamin D per 3.5 oz (100 g) and brook trout at 1.05 to 4. Whether trout helps blood sugar is unclear. In a crossover of 44 obese adults in Colombia, 8 weeks on a diet built on fruit, avocado, whole grains and trout lowered fasting insulin, VLDL and HOMA-IR against a usual high saturated fat diet. Trout was one part of a whole pattern, so its own share cannot be separated, and the abstract gives no sizes. Commercial trout tested low in mercury on average. FDA testing of 35 freshwater trout samples found a mean of 0.071 ppm and a median of 0.025, though one fish reached 0.678, and trout caught by family and friends can fall under state advisories. Among 1,429 First Nations adults in Ontario eating lake fish, trout was one of the species supplying methylmercury, and 97.8% stayed below Health Canada reference values. Raw trout carries germs and parasites. In 240 fresh rainbow trout from farms and shops in one Iranian province, 9.16% carried Listeria monocytogenes, which matters for pregnant, older and immunocompromised people eating trout raw or smoked. We hold no card on how those groups should handle smoked trout, so they should ask whoever treats them before eating it raw or smoked. A 19-year-old in Japan passed a fish tapeworm two months after eating raw trout, a single case that shows the risk and says nothing about how often it happens. We hold no card on the cooking temperature or the freezing that make fish safe to eat raw, so this page cannot tell you that raw, cured or marinated trout made at home is safe. Coral trout is a tropical reef grouper and not a true trout. One Queensland family of four, a pregnant woman among them, got ciguatera poisoning from it, and all four recovered.

Sources

1. trt-r4-01 · USDA FoodData Central SR Legacy, dataset
   Fish, trout, mixed species, raw (FDC 175153, SR Legacy, Finfish and Shellfish Products): vitamin B12 7.79 ug per 100 g = 325% DV; protein 20.77 g = 42% DV; thiamin 0.35 mg = 29% DV; range over 7 records: B12 2.77-7.79, protein 19.94-26.63, thiamin 0.12-0.426; Foundation samples 0
   USDA FoodData Central, SR Legacy, FDC 175153 · checked 2026-09-29
2. trt-r4-02 · CoFID 2021 dataset
   Trout, brown, raw (CoFID 2021, code 16-224): Energy 112 kcal; Fat 3.8 g; Protein 19.4 g; Selenium 25 ug; Sodium 56 mg per 100 g
   CoFID 2021, Public Health England / OGL v3.0, code 16-224 · checked 2026-09-29
3. trt-r4-12 · cross-sectional study in humans
   The highest amounts of vitamin D were provided by salmon, rainbow trout, herring, and eel (fish species containing 7-15 µg of vitamin D in 100 g of product), and halibut, mackerel, brook trout, sole, and tuna (fish species containing 1.05-4 µg of vitamin D in 100 g of product), and these fish were consumed in the largest quantities by male adolescents.
   Nutrients, 2025 · checked 2026-09-29
4. trt-r4-03 · USDA FNDDS, dataset
   Fish, trout, NFS (fdc_id 2706302): Vitamin D (D2 + D3) 12.1 ug per 100 g; 1 small/regular fillet 90 g = 10.9 ug; 1 large fillet 135 g = 16.3 ug; Protein 17.08 g per 100 g; 1 small/regular fillet 90 g = 15.4 g
   USDA FNDDS, FoodData Central survey food 2706302 · checked 2026-09-29
5. trt-r4-05 · randomized controlled trial in humans
   Apparent absorption of selenium from fish was similar to selenate and there was no difference between the two processing methods used. However, retention of fish selenium was significantly higher than selenate (P<0.001).
   Eur J Clin Nutr, 2004 · checked 2026-09-29
6. sf-fpf-r1-9 · agency advice
   Freezing and storing at an ambient temperature of -4°F (-20°C) or below for 7 days (total time), or freezing at an ambient temperature of -31°F (-35°C) or below until solid and storing at an ambient temperature of -31°F (-35°C) or below for 15 hours, or freezing at an ambient temperature of -31°F (-35°C) or below until solid and storing at an ambient temperature of -4°F (-20°C) or below for 24 hours are sufficient to kill parasites. ... The process of heating raw fish sufficiently to kill bacterial pathogens is also sufficient to kill parasites.
   FDA, Fish and Fishery Products Hazards and Controls Guidance, Chapter 5: Parasites · checked 2026-10-08
7. trt-r4-04 · USDA Table of Nutrient Retention Factors, Release 6, dataset
   USDA-RETN-R6:2451 FINFISH,>5%FAT,BAKED,WO/DRIPPINGS vitamin B12 85%; USDA-RETN-R6:2455 FINFISH,>5%FAT,BROILED,WO/DRIPPNG 75%; USDA-RETN-R6:2459 FINFISH,>5%FAT,FRIED,WO/COATING 75%
   USDA Table of Nutrient Retention Factors, Release 6, 2007, codes 2451, 2455, 2459 · checked 2026-09-29
8. trt-r4-06 · randomized controlled trial in humans
   LDL level was increased in the supplementation group, while it was significantly reduced in the dietary-fish group (+18.7 ± 24.97 vs. -22.75 ± 27.28, P < 0.001).
   Nutr Diabetes, 2017 · checked 2026-09-29
9. trt-r4-07 · randomized controlled trial in humans
   Patients of the dietary-fish group were asked to consume 250 g farmed trout fish (which contained 1.4 g omega-3 (280 mg EPA and 160 mg DHA) per 100 g) two times a week for dinner and lunch for 2 months (Equal to consumption of 14 g of omega-3 [2.8 g EPA and 1.6 g DHA] per week) while they were advised not to consume fish oil supplement during the intervention period.
   Nutr Diabetes, 2017 · checked 2026-09-29
10. trt-r4-11 · case report
    The patient presented with tapeworm excretion at 2 months following raw trout fish consumption.
    J Infect Chemother, 2025 · checked 2026-09-29
11. trt-r4-13 · case report
    We describe a Queensland family of four (including a pregnant woman) with ciguatera, confirmed by bioassay of the implicated fish for ciguatoxin. All four recovered, illustrating the effectiveness of treatment with intravenous mannitol.
    Med J Aust, 1997 · checked 2026-09-29
12. sf-lrs-r3-2 · agency advice
    Refrigerated smoked seafood - unless it's in a cooked dish, such as a casserole. Refrigerated smoked seafood, such as salmon, trout, whitefish, cod, tuna, or mackerel, is most often labeled as "nova-style," "lox," "kippered," "smoked," or "jerky." ... Canned or shelf-stable smoked seafood.
    US FDA, Listeria (Food Safety for Moms-to-Be) · checked 2026-10-08
13. trt-r4-09 · agency monitoring data
    TROUT (FRESHWATER) | 0.071 | 0.025 | 0.141 | ND | 0.678 | 35 | FDA 1991-2008
    US FDA, Mercury Levels in Commercial Fish and Shellfish (1990-2012) · checked 2026-09-29
14. trt-r4-10 · cross-sectional contaminant survey of food samples
    The prevalence among the 240 samples was 9.16% (22 samples) for L. monocytogenes, 6.66% (16 samples) for L. ivanovii, 3.75% (9 samples) for L. welshimeri, 4.99% (12 samples) for L. grayi, 7.5% (18 samples) for L. innocua, and 3.75% (9 samples) for L. seeligeri.
    J Food Prot, 2018 · checked 2026-09-29
15. trt-r4-14 · cross-sectional exposure study
    Fish species contributing to the MeHg intake included pickerel-walleye, pike, perch and trout.
    Environ Res, 2017 · checked 2026-09-29
16. trt-r4-08 · randomized controlled trial in humans
    The FAWGT diet reduced fasting insulin, VLDL, and HOMA-IR after 8 weeks (p < 0.05), while there was a lower postprandial increase in TG, VLDL, and insulin levels after both acute and chronic intake of FAWGT diet (p < 0.05).
    Nutrients, 2021 · checked 2026-09-29