The pescatarian diet has a lot in common with a Mediterranean-style diet. Both eating patterns encourage the consumption of fruits, vegetables, nuts, whole grains, etc. But the difference is that pescetarianism excludes meat, which makes seafood their main source of animal protein.

One of the common problems faced by vegetarians and vegans is the deficiency of vitamin B12, which is mostly available in the form of animal protein. However, even a single serving of fish will help pescatarians meet their daily requirements for B12.

You may also be aware that seafood is an excellent source of omega-3 fatty acids which are linked to improved heart health. "Omega-3 fatty acids may decrease inflammation in the body and lower both blood pressure and triglycerides," registered dietitian Georgia Rounder told Women's Health Mag.

Salmon, mackerel, herring, lake trout, sardines, and albacore tuna are high in these fatty acids. As noted by the National Institutes of Health, people who eat seafood one to four times a week have a lower chance of dying from heart disease.

This may be attributed to the fact that fish contain unsaturated fats, which have a place in a heart-healthy diet. On the other hand, those who primarily get their protein from meat — especially processed meat — are at risk of high cholesterol because they consume more saturated fat.  

In a 2015 study, the pescatarian diet was associated with a 43 percent lower risk of colorectal cancer compared to meat eaters. More research is needed to know whether meat consumption itself raises our cancer risk. However, we do know that high-temperature cooking methods like grilling and barbecuing can produce cancer-causing chemicals.

As for the potential downside in this diet, you may need to watch out for the risk of contamination. This particularly applies to pregnant women, nursing mothers, and young children according to Eric Rimm of Harvard T.H. Chan School of Public Health.

These groups are advised to avoid larger fish with longer lifespans — some examples include tuna, shark, and swordfish — as they are more likely to contain toxins such as mercury.

Furthermore, it is important to make sure that the fish you buy is sustainably sourced. Monterey Bay Aquarium’s Seafood Watch is highly recommended to make choices that reduce any negative impact on the environment as much as possible.

"I think it's important to educate clients that a pescetarian diet does not mean they must eat fish at every meal," said registered dietitian Sharon Palmer, nutrition editor of Today's Dietitian.

"It means that a person enjoys lots of plant-based meals — vegetarian lasagna, veggie chili with cornbread, tofu vegetable stir-fry with brown rice — in addition to a few meals during the week based on fish."