What are the disadvantages of the pescatarian diet?

December 17, 2025 •

3 min read

While often lauded for its health benefits, research shows that a pescatarian diet is not without its drawbacks. Before adopting this eating style, it is crucial to understand what are the disadvantages of the pescatarian diet, including potential mercury toxicity and sustainability issues.

Quick Summary

Several considerations are associated with the pescatarian diet, such as the risk of mercury toxicity from certain fish, potential nutrient deficiencies, environmental concerns related to overfishing, and higher costs for quality seafood.

Key Points

Mercury Exposure: Larger predatory fish can contain high levels of mercury, a neurotoxin that poses risks, especially to pregnant women and children.
Nutrient Gaps: A poorly planned pescatarian diet might lack sufficient iron, vitamin B12, and zinc, nutrients primarily found in red meat.
Environmental Damage: The fishing industry contributes to overfishing, habitat destruction, and significant bycatch, challenging the diet's sustainability claims.
Higher Food Costs: Quality fresh seafood can be a more expensive protein source compared to meat or plant-based alternatives.
Ethical Considerations: Concerns exist regarding the welfare of fish, as commercial fishing practices often involve crowded conditions and inhumane slaughter methods.
Risk of Processed Foods: Focusing only on fish and omitting meat doesn't guarantee a healthy diet if processed, unhealthy foods are still consumed.

Health Risks and Contaminants

One of the most frequently cited drawbacks of a pescatarian diet is the potential for consuming elevated levels of contaminants, especially mercury. Mercury is a neurotoxin that can accumulate in fish, particularly larger predatory species like swordfish, shark, and king mackerel. For most people, the health benefits of eating fish outweigh the risks, but high exposure can lead to neurological damage. Pregnant women, breastfeeding mothers, and young children are particularly vulnerable and must be cautious about their seafood choices. Pollution in our oceans also means microplastics are a growing concern, as these tiny particles can be ingested by marine life and potentially transferred to humans.

Mercury Levels and Fish Selection

Not all fish carry the same level of risk. The FDA and EPA provide guidance to help consumers make safer choices.

High-Mercury Fish to Limit or Avoid:
- Shark
- Swordfish
- King Mackerel
- Tilefish
- Bigeye Tuna
Low-Mercury Fish (Best Choices):
- Salmon
- Sardines
- Shrimp
- Catfish
- Canned Light Tuna

Potential Nutritional Deficiencies

While adding fish to a vegetarian diet helps provide nutrients like omega-3s, a poorly planned pescatarian diet can still result in deficiencies. Nutrients commonly found in red meat, such as vitamin B12, iron, and zinc, may be harder to obtain consistently. While many pescatarians consume dairy and eggs, those who rely heavily on just fish and plant-based foods must be diligent in their meal planning. It is important to remember that simply adding fish to a diet of processed snacks and refined carbohydrates does not make it healthy. Focusing on whole foods is key to a truly balanced diet.

Environmental and Ethical Concerns

Despite being considered more eco-friendly than a red meat-based diet, pescetarianism is not without its own set of environmental issues. Overfishing has led to the depletion of fish stocks and can disrupt entire marine ecosystems. Unsustainable fishing practices, including destructive gear and overfishing, harm ocean habitats and can result in significant bycatch, the unintentional killing of non-target species. While efforts like the Monterey Bay Aquarium's Seafood Watch guide help consumers make better choices, industrial-scale fishing remains a problem. Ethical concerns are also a point of debate, with research suggesting fish can feel pain and suffer in the intensive conditions of commercial fish farms, which are often crowded and unsanitary.

Higher Costs

For many, fresh fish and high-quality seafood are a more expensive protein source compared to less processed red meat or plant-based proteins like legumes and grains. Studies, such as one from Oxford University, suggest that while vegetarian and vegan diets can reduce food costs, a pescatarian diet may slightly increase them. The price of fresh seafood can also fluctuate significantly based on seasonal availability. While cheaper alternatives like canned fish exist, they may not always meet the demand for variety or taste that some dieters seek.

Comparison: Pescatarian vs. Omnivore Diet Disadvantages


Disadvantage	Pescatarian Diet	Omnivore Diet
Mercury Risk	Present in certain fish, especially large predators. Requires careful selection.	Generally low, though mercury from fish consumption can still be a factor if seafood is included.
Nutrient Deficiencies	Possible if not well-planned, especially for iron and B12.	Less common due to diverse food sources, but still possible with poor planning.
Environmental Impact	Risks associated with overfishing, bycatch, and habitat destruction. Lower overall carbon footprint than red meat diets.	High greenhouse gas emissions and land use, especially with red meat production.
Cost	Potentially higher due to the cost of fresh, quality seafood.	Can be less expensive, but cost varies widely based on food choices.
Ethical Concerns	Debates exist regarding the pain perception and welfare of fish in commercial fishing.	Well-documented ethical issues related to animal welfare in large-scale farming.

Conclusion

While a pescatarian diet offers numerous health advantages, including increased intake of omega-3 fatty acids, it is not without its faults. Individuals must navigate the risks of mercury and other contaminants by making informed seafood choices, especially those who are pregnant or breastfeeding. Careful planning is essential to avoid nutritional deficiencies in iron and vitamin B12. Moreover, pescatarians must consider the environmental impact of their food choices and opt for sustainable seafood to mitigate issues like overfishing and habitat destruction. The higher cost of high-quality fish can also be a barrier for some. Ultimately, a balanced pescatarian diet requires proactive education and conscientious sourcing to minimize its inherent disadvantages and maximize its benefits. For further information on seafood sustainability, consider consulting the Monterey Bay Aquarium Seafood Watch guide.

Frequently Asked Questions

The primary health risk is exposure to mercury and other contaminants found in certain fish. Larger, predatory fish tend to have higher levels of mercury, which can cause serious health issues with excessive consumption.

While often less impactful than a red meat-heavy diet, a pescatarian diet can harm the environment through issues like overfishing, which depletes marine resources, and destructive fishing practices that damage ocean habitats.

If not carefully planned, a pescatarian diet may be low in nutrients such as iron, vitamin B12, and zinc, which are more abundant in red meat. Shellfish, dairy, and fortified foods can help fill these gaps.

Yes, adopting a pescatarian diet can be more expensive, as high-quality fresh seafood generally costs more than many plant-based proteins or less-processed meats. The price can also vary seasonally.

While rare, mercury poisoning is a possibility with very high consumption of specific high-mercury fish. It is crucial to vary your fish intake and prioritize low-mercury options to minimize risk.

Yes, ethical debates surround commercial fishing due to concerns about animal welfare. Research suggests fish can feel pain, and intensive fish farming and capture methods can cause significant stress and suffering.

Pregnant and breastfeeding women should be cautious with a pescatarian diet. The FDA recommends they limit fish intake to low-mercury options and avoid high-mercury species entirely to protect against developmental issues.