A pescatarian (sometimes spelled “pescetarian”) is someone who eats fish and shellfish but avoids meat and poultry. It’s essentially a vegetarian diet with seafood added back in. Most pescatarians also eat dairy, eggs, fruits, vegetables, grains, legumes, nuts, and seeds, making it one of the more flexible plant-leaning diets.
What Pescatarians Eat and Don’t Eat
The core rule is simple: no meat from land animals. That means no beef, pork, chicken, turkey, lamb, or game. Everything else is generally on the table. Fish, shrimp, crab, scallops, mussels, oysters, and all other seafood are included. Dairy and eggs stay in the diet, which distinguishes a standard pescatarian from the less common “pescavegan” (sometimes called “seagan”), who eats fish but skips dairy and eggs entirely.
There’s no single authority that defines exact rules, so people adapt the diet to fit their lives. Some pescatarians eat fish daily, others only a few times a week. The USDA’s dietary modeling for a pescatarian pattern recommends 8 to 10 ounces of seafood per week at a 2,000-calorie level, alongside 3 cups of dairy and about 3 ounces of eggs weekly. That gives you a rough sense of what a balanced version looks like, though individual needs vary.
Why People Choose This Diet
Motivations tend to fall into three categories: health, environment, and ethics. Some people want the nutritional benefits of seafood (particularly omega-3 fats) without the health risks linked to red and processed meat. Others are uncomfortable with factory farming of land animals but feel differently about fishing. And some are drawn by the lower environmental footprint.
On the carbon front, the numbers are striking. A pescatarian diet produces about 1.66 kg of CO₂ equivalent per 1,000 calories consumed. That’s 25% lower than an omnivore diet (2.23 kg), 43% lower than keto (2.91 kg), and 37% lower than paleo (2.62 kg). It’s still higher than vegetarian (1.16 kg) and vegan (0.69 kg) diets, but for people who aren’t ready to give up animal protein entirely, it represents a meaningful reduction.
Heart Health and Longevity Benefits
The cardiovascular data for pescatarians is encouraging. A large study published in The BMJ found that pescatarians had a 13% lower risk of ischemic heart disease compared to meat eaters. Vegetarians did slightly better at 22% lower risk, but both groups showed meaningful protection.
Longevity research tells a similar story. The Adventist Health Study 2, which followed over 73,000 people, found that pescatarians had a 19% lower risk of dying from any cause compared to nonvegetarians. The effect was especially pronounced in men, who showed a 27% reduction in all-cause mortality. For women, the trend pointed in the same direction but was less statistically certain.
Omega-3s and Brain Health
The biggest nutritional advantage pescatarians have over vegetarians is direct access to EPA and DHA, the long-chain omega-3 fatty acids found in fish. Your body can convert plant-based omega-3s (from flaxseed or walnuts, for example) into EPA and DHA, but the conversion rate is poor. Eating fish skips that bottleneck entirely.
These fats play a meaningful role in brain function. A systematic review in Cureus found that omega-3 intake improves learning, memory, cognitive well-being, and blood flow in the brain. In one trial, people taking 900 mg of DHA daily for 24 weeks made significantly fewer memory errors and showed improved recognition memory compared to a placebo group. Another study found that omega-3 supplementation improved executive function by 26% in older adults over a 26-week period. Higher DHA consumption has also been linked to reduced risk of dementia and age-related cognitive decline. While these studies used supplements rather than whole fish, fish is the primary dietary source of these same compounds.
Potential Nutritional Gaps
Because pescatarians eat fish, dairy, and eggs, they’re less vulnerable to the nutrient deficiencies that sometimes affect vegans and strict vegetarians. Vitamin B12, which is only found naturally in animal foods, is well-supplied by fish, eggs, and dairy. Iron is sometimes flagged as a concern for plant-heavy diets, but a Norwegian study comparing vegans, vegetarians, and pescatarians found no significant difference in iron status between the groups, and median levels for all groups fell within normal reference ranges. About 8% of women across all three diet groups had low iron stores, which reflects the general challenge women of reproductive age face regardless of diet.
The nutrients to pay attention to are the ones that depend on variety. If you eat the same type of fish repeatedly, you may miss out on the broader range of minerals that comes from rotating your protein sources. Zinc, iodine, and selenium all vary significantly by species. Shellfish like oysters are exceptionally rich in zinc, while ocean fish tend to be better sources of iodine and selenium than freshwater varieties.
Mercury: Which Fish to Prioritize
Mercury is the main safety concern for anyone eating fish regularly. The EPA and FDA recommend eating 2 to 3 servings per week from their “Best Choices” list, or 1 serving per week from the “Good Choices” list. For people who are pregnant or breastfeeding, the recommendation is 8 to 12 ounces per week of lower-mercury varieties.
The lowest-mercury options include salmon, sardines, anchovies, shrimp, tilapia, pollock, catfish, trout, haddock, flounder, sole, oysters, clams, crab, crawfish, scallops, and Atlantic mackerel. These are the fish you can eat most freely. High-mercury species to avoid entirely include king mackerel, shark, swordfish, tilefish from the Gulf of Mexico, bigeye tuna, and marlin. If you’re eating fish several times a week as a pescatarian, rotating through the low-mercury options is the simplest way to keep exposure in check.
Weight and BMI Differences
A study of nearly 38,000 participants in the EPIC-Oxford cohort found that fish eaters had significantly lower BMI than meat eaters. Average BMI for meat-eating men was 24.41, compared to a lower intermediate value for fish eaters. Women showed the same pattern, with meat eaters averaging 23.52 and fish eaters falling below that. Vegans had the lowest BMI of all groups, and fish eaters and vegetarians clustered together in the middle.
This doesn’t necessarily mean switching to a pescatarian diet causes weight loss. People who choose plant-forward diets may also differ in other habits like exercise, cooking at home, or overall calorie awareness. But the association is consistent across large studies, and replacing calorie-dense red meat with leaner fish and more vegetables can shift the balance for many people.
Making the Transition
If you currently eat meat, switching to a pescatarian diet doesn’t require an overnight overhaul. Many people start by replacing their least-favorite meat meals with fish or plant-based alternatives and gradually phasing out the rest. A practical weekly framework might include two or three fish-based dinners, a couple of egg or dairy-based meals, and the rest built around beans, lentils, tofu, or whole grains.
Canned fish (sardines, salmon, tuna) is inexpensive, shelf-stable, and nutritionally comparable to fresh. Frozen fish fillets are another affordable option that keeps well. The diet doesn’t have to revolve around expensive sushi-grade seafood to deliver its benefits. The key is consistency: regular fish intake for omega-3s, plenty of vegetables and whole grains for fiber and micronutrients, and enough variety to cover your nutritional bases without overthinking every meal.