Vegetarian Society UK definition + EPIC-Oxford cohort framing

Pescatarian Is Not Vegetarian: What the Term Actually Means

Pescatarianism is a coherent and internally consistent diet, but it is not vegetarianism. The Vegetarian Society UK definition explicitly excludes fish and seafood. The academic literature on diet and disease treats pescatarians as a separate cohort. This page covers the definition, the nutrition profile, the environmental tradeoffs, and the practical fish-choice guidance, with the published sources to back it up.

The short answer. Pescatarians eat plants, dairy, eggs, fish, and seafood. They do not eat meat from land animals (no beef, pork, chicken, lamb, game). The Vegetarian Society UK and the Vegan Society both define vegetarian to exclude fish; pescatarian is therefore not a subset of vegetarian. The label is convenient social shorthand and useful at restaurants; the technical distinction matters when reading nutrition research or health claims.

The definitional disagreement, traced

The English word vegetarian was coined in 1842 by the Alcott House community at the Vegetarian Society's predecessor meetings, formally adopted by the Vegetarian Society at its 1847 founding. From the start the definition excluded all animal flesh, including fish. The current Vegetarian Society UK definition reads "someone who lives on a diet of grains, pulses, legumes, nuts, seeds, vegetables, fruits, fungi, algae, yeast, and other non-animal-based foods (e.g. salt) with, or without, dairy products, honey and eggs. A vegetarian does not eat foods that consist of, or have been produced with the aid of products consisting of or created from, any part of the body of a living or dead animal. This includes meat, poultry, fish, shellfish, insects, by-products of slaughter, or any food made with processing aids created from these."

The North American Vegetarian Society and the European Vegetarian Union both use compatible definitions. The Vegan Society's vegan definition extends further to exclude dairy, eggs, and honey, plus non-food animal-derived products. The academic public health literature follows these definitions when classifying cohort participants.

Where the confusion enters: many people who describe themselves casually as vegetarian do eat fish, treating the term loosely as "I don't eat red or white meat." This is colloquially common but technically conflates pescatarian with vegetarian. When the conflation matters (medical research, certified labelling, dietitian consultation), the precise terms should be used. When it does not matter (a friend choosing a restaurant), the colloquial usage is usually fine.

Why the research literature separates the groups

The EPIC-Oxford cohort recruited 65,000 UK adults from 1993 with deliberate over-representation of vegetarians, vegans, and fish-eaters. Their classification system has five groups: regular meat-eaters, low meat-eaters (under 50 g per day), fish-eaters (no meat but fish), vegetarians (no meat or fish but dairy and eggs), and vegans. The Adventist Health Study-2 cohort uses similar categories: non-vegetarian, semi-vegetarian, pescovegetarian, lacto-ovo vegetarian, and vegan. Both studies treat the fish-eating group as biologically distinct.

The separation matters because outcomes differ. The Tong 2019 EPIC-Oxford paper on ischaemic heart disease (BMJ 2019; 366: l4897) found that fish-eaters had 13% lower IHD risk than meat-eaters, vegetarians had 22% lower IHD risk, and vegans had 24% lower IHD risk (numbers vary slightly between adjusted models). The Adventist Health Study-2 found mortality patterns broadly similar across pesco-vegetarians and lacto-ovo vegetarians, both lower than non-vegetarians but the exact ordering varies by cause-of-death subgroup.

The biologically plausible reasons for the differences: fish-eaters get long-chain EPA and DHA omega-3 directly (cardiovascular benefit); vegans avoid all saturated fat from animal sources; vegetarians eat dairy fat but less than meat-eaters. The interactions are complex enough that lumping pescatarians with vegetarians would smear the data.

Pescatarian nutrient profile vs vegetarian

Nutrient	Pescatarian	Lacto-Ovo Vegetarian	Vegan
Vitamin B12	Excellent (fish + dairy + eggs)	Good (dairy + eggs)	Requires supplement
Vitamin D	Good (oily fish)	Borderline (eggs only)	Requires supplement
Omega-3 EPA, DHA	Excellent (oily fish)	Modest (eggs only)	Requires algae oil
Iodine	Good (white fish + dairy)	Adequate (dairy)	Requires supplement or seaweed
Iron	Some heme from fish	Non-heme only	Non-heme only
Calcium	Good (dairy + bony fish)	Good (dairy)	Needs fortified milks or tofu
Choline	Excellent (eggs + fish)	Excellent (eggs)	Needs deliberate planning
Selenium	Excellent (fish)	Adequate	Brazil nuts essential

On nutrient adequacy alone, pescatarian is the easiest plant-forward diet to plan. The flip side is that it carries the environmental and ethical considerations of fishing, which a strictly vegetarian diet does not.

Fish choice: sustainability and contaminants

The Marine Conservation Society UK Good Fish Guide and Monterey Bay Aquarium Seafood Watch in the US are the two leading consumer-facing sustainability ratings. Both classify species and source on a green (eat freely), amber (think carefully), red (avoid) scale. Common examples for 2026 ratings:

Fish or seafood	MCS rating typical	Mercury level	Pregnancy guidance
Anchovies (wild)	Green	Very low	Eat freely
Sardines (wild)	Green	Very low	Eat freely
Mackerel (wild)	Green or amber by source	Low	Once a week max
Salmon (wild, MSC-certified Alaska)	Green	Low	Twice a week
Salmon (farmed Scotland, RSPCA Assured)	Amber	Low	Twice a week
Mussels (rope-grown)	Green	Very low	Eat freely
Oysters (farmed)	Green	Very low	Avoid raw during pregnancy
Pollock (Alaska)	Green	Low	Eat freely
Cod (Atlantic, Iceland or Barents)	Amber to green by source	Low	Eat freely
Tuna (skipjack, pole-caught)	Amber	Moderate	2 cans per week
Tuna (bluefin)	Red	High	Avoid
Swordfish	Red	Very high	Avoid in pregnancy
Shark	Red	Very high	Avoid in pregnancy
Prawns (UK farmed or MSC)	Amber to green	Low	Eat freely
Prawns (warm-water imported)	Often red	Low	Eat freely

Use the MCS Good Fish Guide in the UK or Monterey Bay Seafood Watch in the US to look up specific species and sources. Ratings change as fisheries are managed differently year by year, so the snapshot above will drift.

Environmental footprint compared

The Poore and Nemecek 2018 Science meta-analysis (a database of 38,700 farms and 1,600 processors across 119 countries) provides the most comprehensive comparison of greenhouse gas emissions per gram of protein across food categories. Beef sits at 50 kg CO2e per kg of protein. Dairy beef at 17 kg. Lamb at 20 kg. Pork at 8 kg. Chicken at 6 kg. Wild-caught small pelagic fish (anchovies, sardines) at 2 to 4 kg. Cheese at 11 kg. Eggs at 4.5 kg. Farmed Atlantic salmon at 6 kg. Farmed warm-water prawns at 26 kg (high because of mangrove clearing and feed). Tofu at 2 kg. Legumes at 0.8 kg.

The implication: a pescatarian who eats sardines and mussels has a markedly lower footprint than a vegetarian who eats cheese and eggs. A pescatarian who eats farmed salmon and prawns has a comparable or higher footprint than a vegetarian. The category label does not determine the footprint; the specific choices within the category do.

Pregnancy specifics. Pregnant pescatarians should follow standard UK or US fish-during-pregnancy guidance: avoid shark, swordfish, marlin, tilefish, king mackerel. Limit tuna to 2 cans per week or 1 fresh steak. Avoid raw fish (sushi sashimi, raw oysters) due to listeria and parasites. Otherwise the omega-3 contribution of oily fish during pregnancy is positive for fetal neural development. See pregnancy nutrition for the detailed walkthrough.

Related diet-type pages

Keep reading

Frequently asked questions about pescatarianism

Are pescatarians considered vegetarian?

By the Vegetarian Society UK definition and the Vegan Society definition, no. Vegetarians do not eat any animal flesh, including fish, shellfish, or crustaceans. Pescatarians eat fish and other seafood while avoiding meat from land animals. The academic literature on diet and health (EPIC-Oxford, Adventist Health Study-2, NutriNet-Sante) consistently separates pescatarians into their own cohort rather than grouping them with vegetarians, because their nutrient profile, environmental footprint, and disease outcome data all differ meaningfully. The colloquial label vegetarian sometimes gets stretched to include pescatarians, but it is not technically correct.

Where does the word pescatarian come from?

The word combines the Italian pesce (fish) with the suffix -atarian (one who eats), formed by analogy with vegetarian. It enters English in the early 1990s and gains widespread use after about 2010 as plant-forward eating becomes more mainstream. The spelling pescetarian is the more etymologically consistent form (matching the Italian pesce-) but pescatarian is now the dominant spelling in US and UK English, and both major dictionaries (Merriam-Webster, Oxford) list pescatarian as the headword.

Why do researchers separate pescatarians from vegetarians?

The nutrient profiles differ substantially. Pescatarians get long-chain omega-3 EPA and DHA directly from oily fish, vitamin B12 from fish and shellfish, vitamin D from oily fish, iodine from white fish and seaweed, and high-quality complete protein from fish. Vegetarians get B12 from dairy and eggs but not omega-3 EPA or DHA reliably. The disease outcome data also differ: EPIC-Oxford finds pescatarians have lower all-cause mortality than vegetarians or vegans in some subgroups, plausibly because of the omega-3 contribution. Mixing the groups into a single category would obscure these effects.

Is a pescatarian diet better for the environment than a vegetarian one?

Depends on which fish and which dairy. The Poore and Nemecek 2018 Science paper places wild-caught small pelagic fish (anchovies, sardines, herring, mackerel) at a lower greenhouse gas footprint per gram of protein than dairy, which sits between fish and beef. Farmed Atlantic salmon and prawns are higher footprint than dairy due to feed inputs and the carbon cost of clearing land for fishmeal soy. Wild-caught cod, haddock, and pollock are roughly comparable to or lower than dairy footprint. A pescatarian eating sardines, mackerel, and mussels has a markedly lower footprint than a vegetarian eating cheese and yogurt. A pescatarian eating king prawns and farmed salmon has a comparable or higher footprint.

Should pescatarians worry about mercury and contaminants in fish?

Yes, particularly during pregnancy and for women planning pregnancy. The UK FSA and US FDA both advise limiting intake of high-mercury fish (shark, swordfish, marlin, king mackerel, tilefish) to one portion per week or less, and avoiding them entirely during pregnancy. Tuna falls in a middle category: two cans of light tuna or one fresh tuna steak per week. Low-mercury fish (salmon, sardines, anchovies, mackerel, mussels, oysters, cod, pollock) can be eaten more freely. The mercury risk in normally consumed fish for non-pregnant adults is modest; the published health benefits of regular oily fish consumption outweigh the contaminant risk per the AHA 2017 scientific statement.

Why do some people choose pescatarian over vegetarian?

Common reasons: ease of getting omega-3 EPA and DHA directly rather than relying on algae oil; cultural and family food traditions where fish is central (Mediterranean, Japanese, Scandinavian); environmental reasoning that small wild-caught fish are lower footprint than land animal farming; ethical frameworks that distinguish between sentient mammals and birds vs fish (a position not universally accepted; the ethics of fish consciousness is debated); and pragmatic transition logic where someone reducing land animal consumption finds fish an easier first step. The Vegan Society and Vegetarian Society both note that pescatarianism is a position with internal consistency, even if it does not meet their definitions of vegetarian.

Sources cited. Vegetarian Society UK definition; Tong TY et al. Risks of ischaemic heart disease and stroke in meat eaters, fish eaters, and vegetarians over 18 years of follow-up: results from the prospective EPIC-Oxford study, BMJ 2019; 366: l4897; Orlich MJ et al. Vegetarian dietary patterns and mortality in Adventist Health Study 2, JAMA Intern Med 2013; 173: 1230-1238; Poore J, Nemecek T. Reducing food's environmental impacts through producers and consumers, Science 2018; 360: 987-992; Marine Conservation Society UK Good Fish Guide; Monterey Bay Aquarium Seafood Watch; UK FSA fish and shellfish advice for pregnant women; US FDA Advice About Eating Fish 2021 update. All values as of May 2026.