American Health & Medical Research Association
Practical guide

Fish eaters fared best in a big U.S. study of vegetarian eating

Vegetarian, pescatarian and flexitarian patterns each have research behind them, and a British study complicates the story. This guide covers what the evidence shows, plus a four-step plan to eat less meat.

By the Health Research USA editorial team

Published Last updated October 2026

Written from the sources listed below; links checked October 2026. It touches on medicines, doses or health conditions and has not yet been reviewed by a licensed clinician, so use it to prepare for a conversation with yours. How we research and review

Sources15, listed below Reading time15 minutes

Where the evidence stands

  • Strong evidence People who skip meat, poultry and seafood need more iron
  • Promising but early Vegetarian and pescatarian eating lowers death ratesAdding fish gives an extra survival edge over vegetarian eatingFlexitarian eating helps weight and blood sugarTargeting red and processed meat works better than targeting all meatLow-mercury fish in pregnancy supports a child's development
  • Not enough evidence The planetary health diet, eaten worldwide, would prevent about 15 million deaths a year
  • Evidence says no, or unsafe Persuasion campaigns substantially cut meat intake

Each use is rated separately, from the scorecard in this guide. Safety cautions are spelled out in the guide itself. How we grade

On this page
  1. Four patterns, sorted by how often meat and fish show up
  2. Two big studies, two different answers
  3. Flexitarian research is young, small and partly industry-funded
  4. The planetary health diet is a flexitarian plan with numbers
  5. Campaigns rarely change what people eat. Your kitchen can
  6. A four-step plan from omnivore to flexitarian
  7. What changes on your plate when meat leaves it
  8. A pattern that fits natural-health values without demanding purity
  9. How the evidence stacks up
  10. Questions readers ask
  11. The bottom line

Key takeaways

  • In a study of 73,308 Seventh-day Adventists, people who ate fish but rarely other meat had 19% lower death rates over about six years than regular meat eaters1.
  • A British analysis of 60,310 people found no difference in overall death rates among vegetarians, fish eaters and comparable meat eaters3.
  • “Flexitarian” has no formal definition, and a 2017 review of 25 studies, paid for by a meat-substitute maker, found only early signs of benefit4.
  • In 41 randomized trials, campaigns to cut meat and other animal foods barely changed what people ate, so build changes into your own kitchen instead8.
  • If you eat fish while pregnant or breastfeeding, FDA and EPA advise 2 to 3 weekly servings from its “Best Choices” list and none of the high-mercury fish such as swordfish and king mackerel10.

In a major U.S. study of vegetarian diets, the group with the lowest death rate wasn’t the vegans. It was the people who ate fish.

Researchers at Loma Linda University in California followed 73,308 Seventh-day Adventists in the U.S. and Canada for an average of almost six years12. Compared with people who ate meat more than once a week, pesco-vegetarians had a 19% lower death rate1.

Vegans came in 15% lower and lacto-ovo vegetarians 9% lower, though neither result was statistically firm1.

Then a British team looked at a similar question and found no difference in overall death rates at all3. That clash is the most useful lesson in this field.

It also matters because few people quit meat entirely. About 4% of U.S. adults call themselves vegetarian and 1% vegan, according to a 2023 Gallup poll cited by the Academy of Nutrition and Dietetics5. In Britain, 29% of people told a 2016 national survey that they had cut back on meat in the past year4.

This guide weighs each pattern and ends with a four-step plan to eat less meat without relying on willpower.

Four patterns, sorted by how often meat and fish show up

The Adventist study defined each pattern by how often people ate animal foods over the past year1.

Pattern Eggs and dairy Fish Other meat
Lacto-ovo vegetarian At least monthly Less than once a month Less than once a month
Pescatarian (pesco-vegetarian) Any amount At least monthly Less than once a month
Semi-vegetarian (flexitarian) Any amount Meat and fish combined no more than once a week Meat at least monthly
Nonvegetarian Any amount Meat and fish combined more than once a week At least monthly

“Flexitarian” is the fuzziest of these labels. A 2017 review in Frontiers in Nutrition described it as mostly vegetarian with occasional meat or fish, and found no agreed definition4.

Studies in that review defined it in very different ways. One allowed red meat, poultry or fish no more than once a week. Another counted anyone who skipped only red meat4.

Two big studies, two different answers

The Adventist health study-2 (AHS-2) tracked 2,570 deaths1. Vegetarians as a whole had a 12% lower death rate than nonvegetarians after adjusting for lifestyle and demographic factors12.

The benefit was clearer in men. Vegetarian men had an 18% lower death rate and fewer deaths from heart disease. In women, the 7% difference could have been chance1.

The researchers noted that vegetarians in the study were also more likely to exercise, less likely to smoke or drink, and thinner2. They adjusted for those habits, but no observational study can fully separate diet from the life around it. A commentary published with the paper made that point, and the authors themselves noted that a British study had found no survival edge1.

The British study pooled two long-running British studies, analyzed by Oxford researchers who include members of the EPIC-Oxford team. It covered 60,310 people: regular meat eaters, people who ate meat less than five times a week, fish eaters and vegetarians3. Over more than a million person-years, 5,294 people died before age 903.

Overall death rates were statistically the same across all four groups3. The details were mixed. Fish eaters had 18% fewer cancer deaths but 22% more deaths from circulatory disease, which includes heart attacks and strokes. Vegetarians had fewer deaths from pancreatic and blood cancers3.

Why the gap between countries? No one knows for sure. The Adventist team called the difference interesting and worth careful study1.

Still, both studies agree on one thing: neither found that swapping meat for fish or plants shortened lives. Our article on faith and health decisions covers the Adventist community behind AHS-2.

Flexitarian research is young, small and partly industry-funded

The 2017 review gathered 25 studies, 21 of them observational and only 4 clinical trials4. Semi-vegetarians tended to have lower body weight than meat eaters in snapshot surveys. Some studies tied the pattern to lower blood sugar and less diabetes4.

In one six-month trial, which had just 13 semi-vegetarians, vegans lost 7.5% of their body weight and semi-vegetarians 3.2%4. The review found no clear cancer benefit for semi-vegetarians4.

Two cautions apply. In four of the studies, about 70% of self-described flexitarians were educated women, so the results may not fit everyone4. And the review was funded by the maker of Quorn, a meat-substitute brand, though the company had no role in writing it4.

The big cohorts offer only hints. In AHS-2, semi-vegetarians had an 8% lower death rate, a result that could be chance1. In Britain, people who ate meat less than five times a week came in 7% lower, right at the edge of statistical significance3.

The planetary health diet is a flexitarian plan with numbers

On October 3, 2025, the EAT-Lancet Commission, 70 experts from 35 countries, published an update of its 2019 “planetary health diet” in The Lancet6. The diet itself was broadly unchanged from 2019, and Line Gordon of Stockholm University, one of the report’s lead authors, described it as flexitarian7.

What it suggests per day for an adult eating about 2,400 calories6:

  • Plants as the base: about 210 grams of whole grains, 300 grams of vegetables, 200 grams of fruit, 75 grams of legumes and 50 grams of nuts.
  • Animal foods as accents: about 250 grams of milk or its equivalent, 30 grams each of poultry and fish, 15 grams of eggs and 15 grams of red meat.

In practice, that’s roughly one portion of red meat a week6. The ranges are wide. Red meat can run from zero to 30 grams a day, and dairy from zero to 500 grams6.

By the commission’s math, if the world ate this way, roughly 15 million deaths a year could be avoided, more than a quarter of the global total6. That’s a projection, not the result of a trial of people eating the diet.

Critics from the livestock side pushed back. The Animal Agriculture Alliance told Western Livestock Journal, a livestock news outlet, that the plan was a “near-vegan” diet that would put people at risk of nutrient deficiencies9.

The British Nutrition Foundation struck a more measured note. Some British diets already run short on iron, zinc, calcium, iodine and B12, especially among children, teens, pregnant women and older adults, and animal foods are key sources of all five, it said. In its view, eating plant-rich doesn’t require giving up animal foods6.

A later article in this series compares the environmental footprints of major diets.

Campaigns rarely change what people eat, but your kitchen can

Meatless Monday and similar campaigns ask people to skip meat for a day or a meal. Do such messages work?

In a meta-analysis in the journal Appetite (2026 volume), researchers pooled 41 randomized trials with about 87,000 participants8. The team kept only trials that checked people’s eating at least a day after the intervention. Persuasion, delivered through documentaries, leaflets and opinion pieces, was the most common approach8.

The pooled effect was tiny. For every 50 or so people who got an intervention, about one ate fewer animal foods8. The authors titled their paper with a blunt verdict: meaningfully reducing meat and animal-food intake is an “unsolved problem”8.

Two findings point to what may help. Messages that targeted only red and processed meat worked better, with effects over three times the overall average8. Changing the setting itself, such as making a vegetarian dish the default at university events, has sometimes shown large effects, but only two such studies met the authors’ standards, and next-day effects are mostly unknown15.

There’s a catch: cutting red meat may just send people toward chicken or fish8.

The practical lesson, in our reading: don’t rely on a pledge or a film. Change what’s in your fridge, what’s on your weekly menu, and what your family’s default dinner is.

A four-step plan from omnivore to flexitarian

Move to the next step when the current one feels normal, not when the calendar says so.

  1. Weeks 1 to 2: Count, then cut processed meat first. Tally your meat meals for one week without changing anything. Then replace deli meat, bacon and hot dogs with eggs, beans, hummus or fish. Our protein guide explains why processed meat is the first target.
  2. Weeks 3 to 6: Add two plant-based dinners a week and stretch the rest. Pick two fixed nights. On meat nights, make half the ground meat lentils, beans or chopped mushrooms.
  3. Weeks 7 to 10: Make meat a side and bring in fish. Serve smaller meat portions over grains and vegetables. Eat fish twice a week from FDA’s “Best Choices” list, such as salmon, sardines, cod or canned light tuna10.
  4. Week 11 on: Choose your landing spot. Settle where you’re comfortable: a flexitarian week like the one below, with fish once or twice and meat once at most; pescatarian; or lacto-ovo vegetarian. The Adventist study’s semi-vegetarians went further, eating meat and fish together no more than once a week1.

Two sample weeks of dinners:

Day Step 2 week Step 4 flexitarian week
Monday Black bean and sweet potato tacos Lentil soup with whole-grain bread
Tuesday Half-beef, half-lentil chili Tofu and vegetable stir-fry
Wednesday Baked chicken, roasted vegetables Baked salmon, brown rice, greens
Thursday Chickpea curry with rice Bean-and-cheese enchiladas
Friday Fish tacos Vegetable pizza on a whole-wheat crust
Saturday Burgers, half beef and half mushroom Chicken and vegetable kebabs, a small portion
Sunday Pasta with marinara and white beans Egg and vegetable frittata

Swaps that keep the flavor:

Instead of Try Why it works
Ground beef in tacos or chili Half lentils or black beans Similar texture; spices carry the flavor
Ham or turkey sandwich Hummus, egg salad or bean spread Cuts processed meat, the top priority
Bacon in beans or greens Smoked paprika or a little smoked salt Keeps the smoky taste
Steak night Salmon or sardines Brings omega-3 fats from a low-mercury fish10
Chicken stir-fry Tofu, tempeh or edamame Absorbs the sauce the same way

What changes on your plate when meat leaves it

Iron needs nearly double. People who eat no meat, poultry or seafood need almost twice the iron listed in standard recommendations, because the body absorbs plant iron less well, says the NIH Office of Dietary Supplements12. For women 19 to 50, the standard amount is 18 mg a day12.

The Academy of Nutrition and Dietetics reports high rates of iron deficiency among vegetarian women who still have periods and says some may benefit from a supplement5. Ask your clinician before taking one. Flexitarians and pescatarians have a built-in help: eating beans or greens with a little fish or meat boosts absorption of the plant iron12.

B12 may run short even with eggs and dairy. Milk, dairy and eggs can supply the recommended amount of B12, but the Academy says some vegetarians may need more than that to avoid running low5. Our vegan guide covers B12 sources and supplements in detail.

Omega-3s come from fish or algae. Fish supply the long-chain omega-3 fats DHA and EPA, along with iodine, vitamin D and selenium, FDA notes10. Experts haven’t set a recommended amount for DHA and EPA, and vegetarians who want them can choose algal oil, made from algae13.

Choose low-mercury fish. FDA and EPA’s advice, last revised in October 2021, is written for people who are or may become pregnant or breastfeeding, and for children 1 to 1110. It recommends 2 to 3 servings a week from the “Best Choices” list, or 1 from “Good Choices.” For adults, a serving is 4 ounces, and FDA suggests the palm of your hand as a guide10.

Skip the “Choices to Avoid”: king mackerel, marlin, orange roughy, shark, swordfish, bigeye tuna and tilefish from the Gulf of Mexico10. For young children, servings run about 1 ounce at ages 1 to 3 and 2 ounces at ages 4 to 710. If a friend hands you a fish from a local lake, look up the fish advisory for that water. With no advisory, eat just that one serving and no other fish that week10.

In 2017, EPA reported that fish on the “Best Choices” list make up nearly 90% of the fish Americans eat14. A 2024 National Academies report found too little evidence to change how much seafood people are advised to eat, and FDA says it is weighing the report as it considers the joint FDA and EPA advice11.

Talk with your clinician first if you’re pregnant or take medicine for diabetes or blood pressure. In people with type 2 diabetes, vegetarian diets likely lower HbA1c, a long-term blood sugar measure, the Academy reports5. That’s welcome, but your doses may need to change, and our article on healthy habits that clash with medicines explains how to plan that talk.

A pattern that fits natural-health values without demanding purity

Many natural-health readers already eat this way: home-cooked meals, beans and grains, garden vegetables, and meat from a farmer they know. Flexitarian eating honors that. It treats meat as food to savor, not a daily habit, and it leaves room for family recipes and holidays.

The research supports moving in that direction, though it can’t say how far you need to go. Judge every sponsor evenly, whether a meat-substitute maker or a cattle group.

How the evidence stacks up

This is how the main claims rate on our four-level scale.

Claim Evidence rating What it rests on
Vegetarian and pescatarian eating lowers death rates Promising but early Lower rates in AHS-2; no difference in the British study13
Adding fish gives an extra survival edge over vegetarian eating Promising but early Favored in one U.S. cohort; no edge, and more circulatory deaths, in the British one13
Flexitarian eating helps weight and blood sugar Promising but early Mostly observational; loose definitions; industry-funded review4
The planetary health diet, eaten worldwide, would prevent about 15 million deaths a year Not enough evidence A modeled estimate; no trial has tested it6
Persuasion campaigns substantially cut meat intake Evidence says no 41 trials; average effect very small8
Targeting red and processed meat works better than targeting all meat Promising but early Larger effect in the same meta-analysis8
People who skip meat, poultry and seafood need more iron Strong evidence Plant iron is absorbed less well, per NIH12
Low-mercury fish in pregnancy supports a child’s development Promising but early FDA rates the evidence moderate10

Questions readers ask

Is a pescatarian diet healthier than a vegetarian one?

Maybe, but one study can’t settle it. Pesco-vegetarians had the lowest death rate in AHS-2, while British fish eaters and vegetarians both matched comparable meat eaters13. Fish does add DHA and EPA, omega-3 fats that otherwise come mainly from algae-based supplements1013.

Do vegetarians need supplements?

Not automatically. The Academy says decisions should be made person by person, though some vegetarians need more B12 than eggs and dairy provide, and iron deficiency is common in vegetarian women who still have periods5.

Do I have to give up meat completely to see a benefit?

The research can’t say exactly where benefits begin. Lighter meat eaters trended slightly better in both big studies, but those results could be chance13. A steady flexitarian pattern you enjoy beats a strict one you abandon.

What’s the easiest fish to eat often?

Canned light tuna, salmon, sardines, shrimp and cod are all on FDA’s “Best Choices” list10. Albacore tuna sits one tier down, in “Good Choices,” so limit it to one serving a week if you’re pregnant or breastfeeding10.

The bottom line

You don’t have to go vegan to eat in a more plant-based way, and the evidence for vegetarian and pescatarian patterns is encouraging, though not airtight. The two big cohorts disagree on overall survival, and the flexitarian middle ground is barely studied.

Lean on structure, not willpower: cut processed meat first, set meatless nights, stretch the meat you eat, and choose low-mercury fish. Plan for iron and B12, and check with a clinician if you’re pregnant or on diabetes or blood pressure medicine.

About this article

This article was researched using FDA, EPA and NIH Office of Dietary Supplements sources, an Academy of Nutrition and Dietetics position paper, and peer-reviewed studies and reviews, listed below. It was reviewed in October 2026. It is general education, not medical, legal or financial advice..

Sources

  1. Orlich MJ, Singh PN, Sabaté J, et al. “Vegetarian Dietary Patterns and Mortality in Adventist Health Study 2.” JAMA Internal Medicine, June 2013 (abstract and commentary reproduced by NATAP). natap.org
  2. JAMA Network. “Vegetarian diets associated with lower risk of death.” News release via Newswise, June 3, 2013. newswise.com
  3. Appleby PN, Crowe FL, Bradbury KE, Travis RC, Key TJ. “Mortality in vegetarians and comparable nonvegetarians in the United Kingdom.” American Journal of Clinical Nutrition, 2016;103(1):218–230 (abstract via University of Oxford). ora.ox.ac.uk
  4. Derbyshire EJ. “Flexitarian Diets and Health: A Review of the Evidence-Based Literature.” Frontiers in Nutrition, 2017;3:55. frontiersin.org
  5. Raj S, Guest NS, Landry MJ, Mangels AR, Pawlak R, Rozga M. “Vegetarian Dietary Patterns for Adults: A Position Paper of the Academy of Nutrition and Dietetics.” Journal of the Academy of Nutrition and Dietetics, 2025. andeal.org
  6. British Nutrition Foundation. “EAT-Lancet Commission report calls for healthy, sustainable and just food systems.” October 24, 2025. nutrition.org.uk
  7. Stockholm University. “Global food transition needed to reduce pressure on the planet and to save millions of lives.” October 3, 2025. su.se
  8. Faunalytics. Summary of Green SA, Smith B, Mathur MB, “Meaningfully reducing consumption of meat and animal products is an unsolved problem: A meta-analysis,” Appetite, 2026;216:108233. December 3, 2025. faunalytics.org
  9. Wallace C. “EAT-Lancet report reaffirms call to cut red meat.” Western Livestock Journal, October 17, 2025. wlj.net
  10. U.S. Food and Drug Administration. “Advice about Eating Fish.” Revised October 2021; content current as of March 5, 2024. fda.gov
  11. U.S. Food and Drug Administration. “Technical Information on Development of FDA/EPA Advice about Eating Fish for Those Who Might Become or Are Pregnant or Breastfeeding and Children Ages 1–11 Years.” Content current as of June 7, 2024. fda.gov
  12. NIH Office of Dietary Supplements. “Iron: Fact Sheet for Consumers.” Updated August 17, 2023. ods.od.nih.gov
  13. NIH Office of Dietary Supplements. “Omega-3 Fatty Acids: Fact Sheet for Consumers.” Updated July 18, 2022. ods.od.nih.gov
  14. U.S. Environmental Protection Agency. “EPA and FDA Issue Final Fish Consumption Advice.” News release, January 18, 2017 (archived). epa.gov
  15. Humane and Sustainable Food Lab. “Meaningfully reducing meat consumption is an unsolved problem: meta-analysis.” Research summary, EA Forum, 2025. forum.effectivealtruism.org