Halibut: lean protein, and not a vitamin D fish

In a meta-analysis of randomized trials with 640 people, lean fish raised blood vitamin D by 1.9 nmol/L, a difference that did not reach significance (95% CI -2.3 to 6.0), while fatty fish raised it by 6.8 nmol/L. Halibut is a lean fish, with 1.9 g of fat per 3.5 oz (100 g) raw in UK data, so these trials give no reason to expect it to raise your vitamin D. A meta-analysis of 18 to 21 trials with 1,392 to 1,456 people found that lean fish lowered blood triglycerides compared with no fish and did not change cholesterol. Its abstract gives no size for that drop, and the authors ask for larger and longer trials before the lipid question is settled. What halibut reliably gives is protein. A typical 140 g fillet carries about 29 g in US survey data.

The numbers, per 3.5 oz (100 g)

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

How much is actually in it

• Across 6 US samples of frozen wild halibut, selenium ran from 36.4 to 66.7 mcg and sodium from 41.9 to 187 mg per 3.5 oz (100 g). — USDA Foundation Foods, Halibut, frozen, wild caught (FDC 2747656), 6 samples (n = 6 samples) Evidence E source
  Selenium mean 53.68 mcg (36.4 to 66.7); protein 19.06 g (17.0 to 20.9); potassium 430.2 mg (390 to 462); sodium 108.3 mg (41.9 to 187) per 3.5 oz (100 g)
• Grilling halibut raises its values per 3.5 oz (100 g) from 103 to 121 calories and from 21.5 to 25.3 g protein as water cooks out, in UK data. — CoFID 2021 Halibut, flesh only, raw (16-073) and grilled (16-074) (n = 2 records) Evidence E source
  Raw 103 calories, protein 21.5 g, fat 1.9 g, iodine 40 mcg; grilled 121 calories, 25.3 g, 2.2 g, 47 mcg per 3.5 oz (100 g)

What a real portion looks like

• A typical 140 g halibut fillet provides about 29 g of protein in US survey data. — US household measures, FNDDS 26118010 Fish, halibut (n = 1 food code) Evidence E source
  Protein 20.73 g/100 g; fillet 140 g: 29.0 g; steak 210 g

What your body absorbs

• In a 4-week crossover RCT in 20 adults, a lean-seafood diet raised urinary iodine from 70 to 135 mcg/L and also raised plasma selenium and arsenic. — 20 adults, mean age 50.6, two 4-week diets (n = 20) Evidence B source
  UIC median 70 to 135 mcg/L vs 58 mcg/L on non-seafood diet, P < 0.001; plasma Se up; urinary and plasma As up
• In an 8-week RCT in 63 adults with overweight, 750 g a week of lean cod raised serum selenium and lowered the immune marker neopterin by 2.65 nmol/L. — 63 adults with overweight or obesity, 8 weeks (n = 63) Evidence B source
  Neopterin median change -2.65 nmol/L, P = 0.018; serum selenium up vs control, P = 0.017

What cooking and storage change

• By the USDA table for lean finfish broiled without drippings, about 90% of vitamin B12, B6 and folate and 95% of niacin are retained. — USDA retention factors, group Finfish and Shellfish Products, <5% fat, broiled (n = 1 method code) Evidence E source
  Retained: vitamin B12 90%, B6 90%, folate 90%, thiamin 90%, niacin 95%, riboflavin 95%, minerals 100%

What it does to your health

• A meta-analysis of 18 to 21 RCTs with about 1,400 people found lean fish lowered blood triglycerides versus no fish, with no change in cholesterol. — 18 to 21 crossover and parallel RCTs, 1392 to 1456 participants (n = 1456) Evidence A source
  Triacylglycerol lowered; no significant change in total cholesterol or lipoproteins; pooled size not given in abstract

Safety, limits and interactions

• In a randomized dinner study in 9 adults, a halibut maki meal without seaweed raised urinary iodine by 59%, and only briefly. — 9 euthyroid adults, single sushi meal, followed 1 week (n = 9) Evidence B source
  UIE +59% without seaweed, +385% with fresh Greenlandic seaweed; back to baseline by day 2

What people believe that the data does not support

• In a meta-analysis of RCTs, lean fish raised blood vitamin D by a non-significant 1.9 nmol/L, while fatty fish raised it by 6.8 nmol/L. — 9 RCT data sets, 640 subjects (n = 640) Evidence A source
  Lean fish MD 1.9 nmol/L (95% CI -2.3 to 6.0); fatty fish MD 6.8 nmol/L (95% CI 3.7 to 9.9)

Who this works differently for

• In an RCT in 133 pregnant women, 7.1 oz (200 g) of cod twice weekly for 16 weeks did not change infants' general development in the first year. — 133 pregnant women from 19 weeks of gestation or earlier, 16 weeks (n = 133) Evidence B source
  ASQ-2 no difference (P = 0.633); ASQ:SE favored intervention (P = 0.020)
• US federal fish advice puts halibut among Good Choices, meaning one serving a week for pregnant people and children, not two to three. — people who are or might become pregnant, breastfeeding, and children Evidence E source
  Good Choices: 1 serving a week; Best Choices: 2 to 3
• A case report describes a 68-year-old man whose fish allergy resolved and who then tolerated halibut, salmon and cod for 8 months. — 1 man aged 68 with past fish-induced anaphylaxis (n = 1) Evidence D source
  Negative skin tests and tolerated open halibut challenge

What is still unknown

• The authors of the 24-study lean fish meta-analysis call for larger and longer RCTs before lipid effects can be settled. — 24 studies of lean fish and fish-derived protein (n = 24 studies) Evidence A source
  Evidence judged inconclusive for lipid profile

The bottom line

Six US samples of frozen wild halibut ran from 36.4 to 66.7 mcg of selenium and from 41.9 to 187 mg of sodium per 3.5 oz (100 g), a wide spread between samples. Grilling raises the values per 3.5 oz (100 g), from 103 to 121 calories and from 21.5 to 25.3 g of protein in UK data, because water cooks out. By a 1975 USDA factor for lean fish broiled without drippings, about 90 percent of vitamin B12, B6 and folate survive, a figure for the whole group and never measured on halibut. In a 4-week crossover trial in 20 adults, a lean seafood diet raised median urinary iodine from 70 to 135 mcg/L and raised plasma selenium, with lean seafood in general and not halibut alone. In 63 adults with overweight, 26 oz (750 g) of cod a week for 8 weeks raised serum selenium and lowered the immune marker neopterin by a median 2.65 nmol/L. For anyone pregnant, breastfeeding or feeding children, US federal fish advice lists halibut among Good Choices, one serving a week instead of the two to three allowed from Best Choices, a grouping based on mercury. The same lean seafood diet that raised iodine also raised arsenic in blood and urine. A halibut maki meal without seaweed raised urinary iodine by 59 percent in 9 adults, back to baseline by day 2, in a tiny single-meal study. In 133 pregnant women, 7.1 oz (200 g) of cod twice a week for 16 weeks did not change infants' overall development at one year (P = 0.633), while a social and emotional score favored the cod group (P = 0.020), in a secondary analysis. One case report describes a 68-year-old man with past fish anaphylaxis whose allergy resolved and who then ate halibut, salmon and cod for 8 months. It tells you nothing about anyone else's fish allergy.

Sources

1. hlbt-r5-01 · food composition dataset
   Halibut, frozen, wild caught: Selenium 53.68 UG (36.4–66.7, n 6) · Protein 19.0625 G (17.0–20.875) · Potassium 430.2 MG (390.0–462.0, n 6) · Sodium 108.3 MG (41.9–187.0, n 6)
   USDA FoodData Central, Foundation Foods, release 2026-04-30, FDC 2747656 Halibut, frozen, wild caught · checked 2026-09-30
2. hlbt-r5-02 · food composition dataset
   Halibut, flesh only, raw (16-073): Energy 103 kcal | Protein 21.5 g | Fat 1.9 g | Iodine 40 µg · Halibut, flesh only, grilled (16-074): Energy 121 kcal | Protein 25.3 g | Fat 2.2 g | Iodine 47 µg
   CoFID 2021 (Public Health England, OGL v3.0), codes 16-073 and 16-074 Halibut · checked 2026-09-30
3. hlbt-r5-04 · reference dataset
   FNDDS 2706260 Fish, halibut (26118010): 1 fillet, any size 140 g · 1 steak 210 g · Protein 20.73 g/100 g, 1 fillet 29.0 g
   USDA FNDDS 2021-2023, food code 26118010 · checked 2026-09-30
4. hlbt-r5-08 · crossover RCT
   UIC increased after 4 weeks of the lean-seafood intervention to 135 (110, 278) µg/L, but not after the non-seafood intervention [58 (33, 91) µg/L] (P diet-effect < 0.001). Fasting plasma Se increased in the lean-seafood intervention and decreased in the non-seafood intervention (P diet-effect = 0.001). Fasting urinary and plasma As increased in the lean-seafood intervention and was unchanged in the non-seafood intervention (P diet-effect < 0.001).
   Eur J Nutr, 2021 · checked 2026-09-30
5. hlbt-r5-09 · RCT
   In this randomised clinical trial, 63 participants with overweight/obesity consumed 750 g/week of either Atlantic cod (N = 22) or Atlantic salmon (N = 22) or were instructed to continue their normal eating habits but avoid fish intake (Control group, N = 19) for 8 weeks. ... Serum total neopterin concentration was reduced in the Cod group (median change - 2.65 (25th, 75th percentiles - 3.68, - 0.45) nmol/l, P = 0.018) ... Increased serum concentration of selenium was observed only after cod intake when compared to the Control group (P = 0.017).
   Eur J Nutr, 2021 · checked 2026-09-30
6. hlbt-r5-03 · reference dataset
   USDA-RETN-R6:2305 FINFISH,<5%FAT,BROILED,WO/DRIPPINGS: vitamin_b12_ug 90% · vitamin_b6_mg 90% · folate_total_ug 90% · thiamin_mg 90% · niacin_mg 95% · riboflavin_mg 95% · minerals 100%
   USDA Table of Nutrient Retention Factors, Release 6 (2007), code 2305 FINFISH,<5%FAT,BROILED,WO/DRIPPINGS · checked 2026-09-30
7. hlbt-r5-05 · meta-analysis of RCTs
   Meta-analysis of data from 18 to 21 eligible crossover and parallel-design RCTs with a total of 1392 to 1456 participants found triacylglycerol-lowering effects for lean fish compared with no fish consumption. Lean fish intake showed no significant differences related to total cholesterol or lipoprotein levels.
   Nutr Rev, 2021 · checked 2026-09-30
8. hlbt-r5-11 · RCT
   Nine euthyroid participants were randomized into three groups: Halibut maki roll with either (A) newly harvested Greenlandic seaweed salad, (B) no seaweed salad on the side, or (C) Japanese seaweed salad purchased at a local store. ... UIE rose (p < 0.001) by 385%, 59% and 43% for groups A, B, and C, peaked in the 6-h spot urine sample at 393, 120, and 109 µg/g, and was down to pre-meal values by day 2.
   J Endocrinol Invest, 2020 · checked 2026-09-30
9. hlbt-r5-07 · meta-analysis of RCTs
   The type of the fish also played a key role: the consumption of fatty fish resulted in a mean difference of 6.8 nmol/L (95% CI: 3.7, 9.9 nmol/L; P < 0.0001, I(2) = 0%; 7 study groups), whereas for lean fish the mean difference was 1.9 nmol/L (95% CI: -2.3, 6.0 nmol/L; P < 0.38, I(2) = 37%; 7 study groups).
   Am J Clin Nutr, 2015 · checked 2026-09-30
10. hlbt-r5-10 · RCT
    In an RCT, 133 pregnant women (≤19 weeks of gestation) were randomly assigned to receive 200 g cod fillet twice weekly (intervention) or to continue with their habitual diet (control) for 16 wk. ... We found no difference between infants in the intervention and control groups on total ASQ-2 scores (P = 0.633)
    J Nutr, 2021 · checked 2026-09-30
11. hlbt-r5-12 · regulatory advice
    Eat 2 to 3 servings a week from the "Best Choices" list (OR 1 serving from the "Good Choices" list).
    US FDA and EPA, Advice about Eating Fish, updated 2024 · checked 2026-09-30
12. hlbt-r5-13 · case report
    Subsequently, he underwent an open challenge with halibut. ... In the ensuing 8 months, he has regularly ingested salmon, cod, and halibut without experiencing any allergic reactions.
    Ann Allergy Asthma Immunol, 2003 · checked 2026-09-30
13. hlbt-r5-06 · meta-analysis of RCTs
    Additional better-designed, longer, and larger RCTs, particularly crossover RCTs, are needed to clarify the impact of lean fish and fish proteins on the serum/plasma lipid profile.
    Nutr Rev, 2021 · checked 2026-09-30