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Research · Food and drink

Fish and seafood

Pooled cohorts link eating more fish to lower coronary heart disease, stroke, dementia and death, with the heart links driven by fatty fish. Two diet-advice trials in men disagreed. Seafood in pregnancy is linked to better child development scores. Mercury is the main documented harm, and shellfish and fish allergy affect about 3% and 1% of US adults.

Add to Bio HackChecked 2026-11-13
Status
A food, not a regulated health product. The FDA and EPA advise people who are or might become pregnant or are breastfeeding to eat 2 to 3 servings a week from their list of fish lowest in mercury, and list king mackerel, marlin, orange roughy, shark, swordfish, Gulf of Mexico tilefish and bigeye tuna as "Choices to Avoid" for them and for children [1]. The Dietary Guidelines for Americans, 2025-2030 list seafood among protein foods and name low-mercury omega-3-rich seafood for pregnancy [2]. Fish and crustacean shellfish are among the nine major food allergens under US law [3].
Also called
fish, seafood, oily fish, fatty fish, lean fish, white fish, salmon, sardines, mackerel, herring, trout, tuna, canned tuna, cod, shellfish, shrimp, oysters, crab
Studied for
heart health, heart attack and stroke, longer life, brain health, memory, focus, dementia, depression, mood, pregnancy, baby brain development, omega-3

Strong several reviews agree · Moderate one review or consistent trials · Limited one or a few small studies · Untested no study in people, listed with what it rests on

Shown to help6

Reported risks4

What it was studied for, and what was found

Shown to help6

Strong

Death from any cause

Linked to 6% lower death from any cause at the highest fish intake than the lowest, and 12% lower at 60 g a day than none, in pooled cohorts.

Compared with the lowest category of fish intake, or people who never ate fish [4]; 20 g a day less fish, in a dose-response model [5]; the lowest fatty fish intake [6]

The numbers and sources
Effect
Across 12 cohorts, the highest category of fish intake was linked to lower death from any cause than the lowest (RR 0.94, 95% CI 0.90 to 0.98), and 60 g of fish a day to 12% lower death than never eating fish (RR 0.88, 95% CI 0.83 to 0.93) [4]. In a second review, each extra 20 g a day was marginally linked to lower death (RR 0.98, 95% CI 0.97 to 1.00, I² 81.9%). The link was significant only in Asian studies, and Western studies suggested a U-shaped curve with the lowest risk near 20 g a day [5]. Fatty fish was linked to lower total death (RR 0.97, 95% CI 0.94 to 0.99), and lean fish was not [6].
Population
672,389 participants and 57,641 deaths in 12 cohorts [4]. 911,348 participants and 75,451 deaths in 14 cohorts [5]. 104,763 deaths in the cohorts of fatty fish [6].
Sources
[4], [5], [6]
Caveats
Observational. People who eat more fish may differ in income, diet and other habits (confounding), and people who fall ill may change what they eat, which can run the link backward (reverse causation). The regional differences may reflect the type of fish and how it is cooked [5].
Strong

Coronary heart disease

Linked to 9% lower coronary heart disease and 15% lower coronary death at the highest fish intake than the lowest, in pooled cohorts, with lean fish showing no link.

Compared with the lowest fish intake category [7][6]; 20 g a day less fish, in a dose-response model [7][5]

The numbers and sources
Effect
Across 22 cohorts, the highest fish intake was linked to lower coronary heart disease than the lowest (RR 0.91, 95% CI 0.84 to 0.97), and across 27 cohorts to lower coronary death (RR 0.85, 95% CI 0.77 to 0.94). Each extra 20 g a day was linked to 4% lower incidence and 4% lower death [7]. Each extra 20 g a day was also linked to lower cardiovascular death (RR 0.96, 95% CI 0.94 to 0.98) across 8 cohorts [5]. Fatty fish was linked to lower coronary heart disease (RR 0.92, 95% CI 0.86 to 0.97) and coronary death (RR 0.83, 95% CI 0.70 to 0.98). Lean fish was not, and neither type was significantly linked to overall cardiovascular disease [6].
Population
918,783 participants and 28,261 coronary cases, and 1,139,553 participants and 10,568 coronary deaths, in 40 cohorts [7]. 8 cohorts for cardiovascular death [5]. 20,531 coronary cases in the fatty fish cohorts and 21,636 in the lean fish cohorts [6].
Sources
[7], [5], [6]
Caveats
Observational, with moderate heterogeneity (I² 47.4% for incidence and 51.3% for death) [7]. Confounding by other habits and reverse causation are possible. Trials of advice to eat fish disagree (see the next block but one).
Strong

Stroke

Linked to 10% lower stroke at the highest fish intake than the lowest, and 6% lower for each 3 extra servings a week, in pooled cohorts.

Compared with the lowest fish intake category [8]; 3 fewer servings a week, in a dose-response model [9]

The numbers and sources
Effect
Across 33 cohorts, the highest against the lowest fish intake was linked to lower stroke (HR 0.90, 95% CI 0.85 to 0.96), with stronger links for hemorrhagic stroke (HR 0.88), women (HR 0.83) and Asia-Pacific cohorts (HR 0.87). Risk was 2% to 12% lower with intakes up to 100 to 700 g a week [8]. Across 15 cohorts, 3 extra servings a week were linked to 6% lower total stroke (RR 0.94, 95% CI 0.89 to 0.99), 0.90 (95% CI 0.84 to 0.97) for ischemic stroke and 0.90 (95% CI 0.76 to 1.06) for hemorrhagic stroke [9].
Population
33 prospective cohorts [8]. 383,838 participants and 9,360 strokes in 15 cohorts [9].
Sources
[8], [9]
Caveats
Observational. One review rated its evidence moderate by NutriGrade [8], and the other described the link as weak [9]. The two reviews differ on hemorrhagic stroke.
ModerateStudied in pregnancy

Child development after seafood in pregnancy

Linked to better social-emotional, behavioral and overall development scores in children whose mothers ate more seafood in pregnancy, with inconsistent results for overall cognition.

Compared with children whose mothers ate less seafood in pregnancy [13]

The numbers and sources
Effect
Across 40 articles (1 randomized trial, 24 prospective cohorts and 1 retrospective cohort), higher seafood intake in pregnancy was related to better social-emotional and behavioral development from birth to 18 years and better aggregate development scores before age 4. Evidence for overall cognitive development was inconsistent, with possible links to attention, reasoning and problem-solving, and verbal intelligence. Results were inconsistent for movement and language, and few studies covered ADHD and autism [13]. The FDA states that moderate scientific evidence shows fish intake in pregnancy can help a baby's cognitive development [1].
Population
Pregnant women and their children aged 0 to 18 years. No studies of seafood during breastfeeding were found [13].
Sources
[13], [1]
Caveats
Certainty was very low to moderate because of the lack of randomized trials [13]. Families who eat more seafood may differ in income and education, which the cohorts may not fully adjust for.
Strong

Memory, cognitive decline and dementia

Linked to 18% lower cognitive impairment and 18% lower dementia at the highest fish intake than the lowest, in pooled observational studies of adults.

Compared with the lowest fish intake [14]; one fewer serving a week, in a dose-response model [15]

The numbers and sources
Effect
Across 35 studies, the highest against the lowest fish intake was linked to lower cognitive impairment or decline (RR 0.82, 95% CI 0.75 to 0.90), dementia (RR 0.82, 95% CI 0.73 to 0.93) and Alzheimer disease (RR 0.80, 95% CI 0.67 to 0.96). Risk of cognitive impairment was up to 30% lower at 150 g a day (RR 0.70, 95% CI 0.52 to 0.95) [14]. Across 21 cohorts, each extra weekly serving of fish was linked to 5% lower dementia (RR 0.95, 95% CI 0.90 to 0.99) and 7% lower Alzheimer disease (RR 0.93, 95% CI 0.90 to 0.95) [15].
Population
35 observational studies [14]. 181,580 participants and 4,438 cases followed 2.1 to 21 years [15].
Sources
[14], [15]
Caveats
Observational, with heterogeneity up to I² 61.1% [14] and 74.8% [15]. The authors of the newer review call for further studies on dementia and Alzheimer disease [14]. People with early memory loss may change their diet, which can run the link backward. Day-to-day focus and attention in adults were not the outcomes measured.
Strong

Depression

Linked to 17% to 22% lower risk of depression at the highest fish intake than the lowest, in pooled observational studies.

Compared with the lowest fish consumption [16][17]

The numbers and sources
Effect
Across 26 studies, the pooled relative risk of depression for the highest against the lowest fish consumption was 0.83 (95% CI 0.74 to 0.93), and 0.84 (95% CI 0.75 to 0.94) in the 10 cohort studies [16]. Across 21 datasets, it was 0.78 (95% CI 0.69 to 0.89), with a linear dose-response [17].
Population
150,278 participants in 26 studies [16]. 255,076 individuals and over 20,000 cases of depression in 31 studies [17].
Sources
[16], [17]
Caveats
Observational, and 16 of the 26 studies in one review were cross-sectional [16]. The other review notes possible confounding from variables the studies did not adjust for [17]. Low mood can change diet, which can run the link backward.

Mixed results1

LimitedStudied in men

Death after a heart attack and in angina, in diet-advice trials

Mixed results: advice to eat fatty fish cut 2-year death 29% in men after a heart attack in one trial, while another found more cardiac death in men with angina.

Compared with men given no advice to eat fish [10][11][12]

The numbers and sources
Effect
In DART, men recovering from a heart attack who were advised to eat more fatty fish had 29% lower all-cause death over 2 years [10] (unadjusted HR 0.70, 95% CI 0.54 to 0.92), followed by higher risk over the next 3 years (HR 1.31, 95% CI 1.01 to 1.70), and no substantial long-term survival benefit [11]. In DART-2, men with angina advised to eat two portions of oily fish a week or take fish oil capsules had no fall in all-cause death, and higher cardiac death (adjusted HR 1.26, 95% CI 1.00 to 1.58) and sudden cardiac death (HR 1.54, 95% CI 1.06 to 2.23), largely in the group given capsules [12].
Population
2,033 men, mean age 56.5, recovering from a heart attack [10]. 3,114 men under 70 with angina, followed 3 to 9 years [12].
Sources
[10], [11], [12]
Caveats
Trials of dietary advice, so the fish actually eaten varied. DART-2 combined fish and capsule advice, and its authors call the excess cardiac death unexplained [12]. Trials of fish oil supplements are on the fish-oil page.

Amounts studied

Cohort reviews compared the highest with the lowest intake category, or modeled risk per 20 g a day [5][7], per serving a week [15] or per 3 servings a week [9]. Death from any cause was 12% lower at 60 g a day than none in one review [4], and in Western studies lowest near 20 g a day in another [5]. The stroke review modeled intakes up to 100 to 700 g a week [8]. In DART-2, men were advised to eat two portions of oily fish a week [12]. The FDA and EPA advice for pregnancy and breastfeeding uses 4-ounce servings, 2 to 3 a week from the lower-mercury list. The FDA cites the Dietary Guidelines figure of at least 8 ounces of seafood a week on a 2,000 calorie diet, and 8 to 12 ounces in pregnancy and breastfeeding [1].

Risks

Reported risks2

LimitedCommon

Shellfish and fish allergy

A national survey estimated convincing shellfish allergy in 2.9% and fin fish allergy in 0.9% of US adults. Studies using food challenges found lower figures.

The numbers and sources
How common
Common: between 1 in 100 and 1 in 10 people.
Effect
Among 40,443 US adults, convincing shellfish allergy was estimated at 2.9% (95% CI 2.7 to 3.1) and fin fish allergy at 0.9% (95% CI 0.8 to 1.0) [22]. A systematic review of 61 studies found fish allergy prevalence from 0% to 7% and shellfish allergy from 0% to 10.3%, depending on how it was diagnosed, and 0% to 0.3% and 0% to 0.9% where food challenges were used [23]. Fish and crustacean shellfish are among the nine major food allergens under US law [3].
Population
40,443 US adults surveyed in 2015 and 2016 [22]. 61 population-based studies worldwide [23].
Sources
[22], [23], [3]
Caveats
Surveys give higher figures than food challenge testing [23]. The survey estimate rests on reported symptoms [22].
ModerateHow often is not known

Mercury and the developing brain

FDA and EPA advise limiting mercury in pregnancy and childhood. In newer cohorts at lower exposure, pooled IQ loss per unit of mercury did not reach significance.

The numbers and sources
How common
How often is not known: the sources give no rate.
Effect
The FDA and EPA state it is important to limit mercury in the diets of those who are pregnant or breastfeeding and of children, and grade fish by mercury level [1]. A 2026 meta-analysis reports that an earlier pooling of three highly exposed cohorts (16.8 to 27.2 µg/L methylmercury in maternal blood) found IQ decrements. Pooling five newer cohorts at 0.60 to 12.8 µg/L, it found a change of -0.407 IQ points per µg/L of maternal blood (95% CI -0.962 to 0.147) [18]. A review of low-level exposure found possible effects on fetal growth in susceptible subgroups and on infant growth, and neurologic effects that may differ by age, sex and timing of exposure [19]. Another review found that DHA appears beneficial for, and low-level methylmercury may adversely affect, early neurodevelopment [20].
Population
7 populations from 5 cohorts, children tested at 3.5 to 12 years [18]. Human studies with a biomarker of mercury exposure, excluding very highly exposed groups [19].
Sources
[1], [18], [19], [20]
Caveats
Exposure was measured as mercury in blood or hair, not as fish eaten. Nutrients in the same fish may offset the effect or confound the studies [19].

Mixed results2

ModerateHow often is not known

Mercury and heart disease in adults

Mixed results: a meta-analysis linked higher mercury exposure to 68% higher cardiovascular death, while two reviews found no clear pattern for heart disease at low exposure.

The numbers and sources
How common
How often is not known: the sources give no rate.
Effect
Across 14 studies, mercury exposure was linked to higher cardiovascular death (RR 1.68, 95% CI 1.15 to 2.45) and death from other heart diseases (RR 1.50, 95% CI 1.07 to 2.11). Links with nonfatal ischemic heart disease (RR 1.21, 95% CI 0.98 to 1.50) and death from any cause (RR 1.21, 95% CI 0.90 to 1.62) did not reach significance, and stroke was not linked. Risk rose consistently from a hair mercury level of 2 µg/g [21]. A review of low-level exposure found no clear pattern for cardiovascular disease across populations [19]. Another found the effects of low-level methylmercury in adults not clearly established, while it may modestly reduce the cardiovascular benefits of fish [20].
Population
More than 34,000 participants in 17 countries, including people exposed to inorganic mercury at work [21].
Sources
[21], [19], [20]
Caveats
Observational. Some studies measured mercury from work, not from fish [21].
ModerateHow often is not known

Type 2 diabetes

Mixed results: in pooled cohorts, each extra 100 g of fish weekly was linked to 2% more type 2 diabetes in women, mainly in the Americas, and none in men.

The numbers and sources
How common
How often is not known: the sources give no rate.
Effect
In women, each extra 100 g of fish a week was linked to higher type 2 diabetes (IRR 1.02, 95% CI 1.01 to 1.03) for total fish, 1.04 for fatty fish and 1.02 for lean fish. In men, all associations were null. In women the link appeared in the Americas (IRR 1.03, 95% CI 1.02 to 1.04) and not in other regions [24].
Population
956,122 participants and 48,084 cases in 28 cohorts from the Americas, Europe, the Western Pacific and the Eastern Mediterranean [24].
Sources
[24]
Caveats
Observational, with heterogeneity (I² 61% for total fish in women). The authors point to cooking methods, accompanying foods and pollutants as possible explanations [24].

Claims tested and not found

  1. That lean fish carries the same heart links as fatty fish. In pooled cohorts, lean fish was not linked to coronary heart disease, coronary death or total death, while fatty fish was [6].
  2. That advice to eat oily fish lowers death in men with angina. In DART-2, all-cause death did not fall, and cardiac death was higher in men advised to eat oily fish or take fish oil [12].
  3. That fish lowers type 2 diabetes. A pooled analysis of 28 cohorts found no link in men and a small rise in women [24].

Related

Fish oilOmega-3 indexMediterranean diet

Sources

  1. US Food and Drug Administration. Advice about Eating Fish: For Those Who Might Become or Are Pregnant or Breastfeeding and Children Ages 1 to 11 Years. FDA. Content current as of 2024-03-05. https://www.fda.gov/food/consumers/advice-about-eating-fish
  2. US Department of Agriculture and US Department of Health and Human Services. Dietary Guidelines for Americans, 2025-2030. realfood.gov. 2026. https://cdn.realfood.gov/DGA.pdf
  3. US Food and Drug Administration. Food Allergies. FDA. Content current as of 2026-03-11. https://www.fda.gov/food/nutrition-food-labeling-and-critical-foods/food-allergies
  4. Zhao LG, Sun JW, Yang Y, et al. Fish consumption and all-cause mortality: a meta-analysis of cohort studies. European Journal of Clinical Nutrition. 2016. https://doi.org/10.1038/ejcn.2015.72
  5. Jayedi A, Shab-Bidar S, Eimeri S, Djafarian K. Fish consumption and risk of all-cause and cardiovascular mortality: a dose-response meta-analysis of prospective observational studies. Public Health Nutrition. 2018. https://doi.org/10.1017/s1368980017003834
  6. Giosuè A, Calabrese I, Lupoli R, et al. Relations between the Consumption of Fatty or Lean Fish and Risk of Cardiovascular Disease and All-Cause Mortality: A Systematic Review and Meta-Analysis. Advances in Nutrition. 2022. https://doi.org/10.1093/advances/nmac006
  7. Zhang B, Xiong K, Cai J, Ma A. Fish Consumption and Coronary Heart Disease: A Meta-Analysis. Nutrients. 2020. https://doi.org/10.3390/nu12082278
  8. Zhao W, Tang H, Yang X, et al. Fish Consumption and Stroke Risk: A Meta-Analysis of Prospective Cohort Studies. Journal of Stroke and Cerebrovascular Diseases. 2019. https://doi.org/10.1016/j.jstrokecerebrovasdis.2018.10.036
  9. Larsson SC, Orsini N. Fish consumption and the risk of stroke: a dose-response meta-analysis. Stroke. 2011. https://doi.org/10.1161/strokeaha.111.630319
  10. Burr ML. Secondary prevention of CHD in UK men: the Diet and Reinfarction Trial and its sequel. Proceedings of the Nutrition Society. 2007. https://doi.org/10.1017/s0029665107005241
  11. Ness AR, Hughes J, Elwood PC, et al. The long-term effect of dietary advice in men with coronary disease: follow-up of the Diet and Reinfarction trial (DART). European Journal of Clinical Nutrition. 2002. https://doi.org/10.1038/sj.ejcn.1601342
  12. Burr ML, Ashfield-Watt PA, Dunstan FD, et al. Lack of benefit of dietary advice to men with angina: results of a controlled trial. European Journal of Clinical Nutrition. 2003. https://doi.org/10.1038/sj.ejcn.1601539
  13. O'Connor LE, Spill MK, Saha S, et al. Seafood During Pregnancy and Lactation and Child Neurocognitive Development: A Systematic Review. Advances in Nutrition. 2025. https://doi.org/10.1016/j.advnut.2025.100414
  14. Godos J, Micek A, Currenti W, et al. Fish consumption, cognitive impairment and dementia: an updated dose-response meta-analysis of observational studies. Aging Clinical and Experimental Research. 2024. https://doi.org/10.1007/s40520-024-02823-6
  15. Zhang Y, Chen J, Qiu J, et al. Intakes of fish and polyunsaturated fatty acids and mild-to-severe cognitive impairment risks: a dose-response meta-analysis of 21 cohort studies. The American Journal of Clinical Nutrition. 2016. https://doi.org/10.3945/ajcn.115.124081
  16. Li F, Liu X, Zhang D. Fish consumption and risk of depression: a meta-analysis. Journal of Epidemiology and Community Health. 2016. https://doi.org/10.1136/jech-2015-206278
  17. Grosso G, Micek A, Marventano S, et al. Dietary n-3 PUFA, fish consumption and depression: A systematic review and meta-analysis of observational studies. Journal of Affective Disorders. 2016. https://doi.org/10.1016/j.jad.2016.08.011
  18. Kopylev L, Dzierlenga M, Lin YS, et al. Relationship Between Prenatal Methylmercury Exposure and IQ: A Meta-analysis. Exposure and Health. 2026. https://doi.org/10.1007/s12403-026-00781-0
  19. Karagas MR, Choi AL, Oken E, et al. Evidence on the human health effects of low-level methylmercury exposure. Environmental Health Perspectives. 2012. https://doi.org/10.1289/ehp.1104494
  20. Mozaffarian D, Rimm EB. Fish intake, contaminants, and human health: evaluating the risks and the benefits. JAMA. 2006. https://doi.org/10.1001/jama.296.15.1885
  21. Hu XF, Lowe M, Chan HM. Mercury exposure, cardiovascular disease, and mortality: A systematic review and dose-response meta-analysis. Environmental Research. 2021. https://doi.org/10.1016/j.envres.2020.110538
  22. Gupta RS, Warren CM, Smith BM, et al. Prevalence and Severity of Food Allergies Among US Adults. JAMA Network Open. 2019. https://doi.org/10.1001/jamanetworkopen.2018.5630
  23. Moonesinghe H, Mackenzie H, Venter C, et al. Prevalence of fish and shellfish allergy: A systematic review. Annals of Allergy, Asthma and Immunology. 2016. https://doi.org/10.1016/j.anai.2016.07.015
  24. Pastorino S, Bishop T, Sharp SJ, et al. Heterogeneity of Associations between Total and Types of Fish Intake and the Incidence of Type 2 Diabetes: Federated Meta-Analysis of 28 Prospective Studies Including 956,122 Participants. Nutrients. 2021. https://doi.org/10.3390/nu13041223

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