Fish Is a Nutrient-Rich Food — But Eating It the Wrong Way Can Turn Its Benefits Into Health Risks

Fish is a nutrient-dense food that’s great for the heart, brain, and immune system. However, if you eat it incorrectly or choose the wrong types, its health benefits can be completely “reversed” — even increasing your risk of cancer and other serious diseases.

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Fish is a familiar ingredient used to make many delicious and nutritious dishes. Thanks to its high-quality protein and essential vitamins and minerals, fish provides tremendous health benefits. However, not all fish are good for you. Some types, when eaten too often, can actually harm your body and raise your risk of dangerous diseases.

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1. Fish High in Mercury

Mercury is a toxic heavy metal that can persist in soil, water, and air. When it accumulates in the body — especially through mercury-contaminated fish — it can damage the nervous system, impair memory, and increase the risk of conditions such as depression, Alzheimer’s, Parkinson’s disease, and liver disorders. Pregnant women and young children are particularly sensitive to mercury exposure.

Fish that are high in mercury and should be limited include bigeye tuna, mackerel, swordfish, grouper, shark, eel, catfish, tilapia, pangasius (basa fish), and Chilean sea bass.
Instead, opt for safer seafood choices such as salmon, sardines, shrimp, or herring — all rich in nutrients but low in heavy metal contamination.

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2. Grilled or Fried Fish at High Temperatures

Grilled or fried fish often tastes delicious thanks to its rich flavor, but cooking at high temperatures can produce carcinogenic substances like benzopyrene and heterocyclic amines. Moreover, frying can destroy beneficial amino acids, significantly reducing the fish’s nutritional value.

Therefore, you should limit eating fish that’s charred, burnt, or deeply fried. Healthier cooking methods include steaming, boiling, making soup, or stewing — all of which preserve nutrients and support digestion and heart health.

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3. Salted or Pickled Fish

Salted, pickled, or fermented fish is a traditional favorite for many people, but it carries notable health risks.

The first danger is food poisoning, which can occur if the preparation process is unhygienic, packaging is unsafe, or the fish isn’t salted or fermented long enough. When the pH level isn’t low enough, harmful bacteria like Clostridium botulinum can thrive, leading to severe poisoning. Mild cases may cause abdominal pain, nausea, or diarrhea; severe cases can damage multiple organs or even become life-threatening.

In addition to the poisoning risk, eating salted fish frequently may increase the risk of nasopharyngeal (throat) and nasal cancers. This is because during fermentation, nitrites can form in the fish. These compounds react with protein breakdown products to create nitrosamines — carcinogenic substances linked to stomach and colon cancers. For this reason, salted fish should be eaten only occasionally, not regularly.

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4. Fish With Unusual Odors

An unusual or pungent smell is a common sign that fish is spoiled and unsafe to eat. However, some dishonest vendors use formaldehyde (a known carcinogen) or pesticides to soak fish, masking the rotten smell and extending shelf life.

If you detect a strange, sharp, or eye-irritating odor, do not buy it. Choose fish that’s fresh — firm flesh, elastic texture, clear eyes, bright red gills, and a mild natural scent. Always buy from reliable sources that store fish properly.

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So How Should You Eat Fish Safely for Optimal Health?

• Eat fish in moderation: About two servings per week (around 340 g total) is ideal. For oily fish, the recommended amount is 140–560 g per week. Pregnant or breastfeeding women should limit intake to 280 g per week to minimize mercury exposure.

• Choose fresh fish: Fresh fish should have firm flesh, red gills, clear eyes, and a light natural smell. Avoid fish with strange odors or mushy texture.

• Cook it healthily: Always cook fish thoroughly by steaming, boiling, or making soup. Avoid fried, grilled, or salted fish to reduce harmful compounds.

• Eat a variety: Combine different types of fish with vegetables, fruits, whole grains, and healthy fats for a balanced diet.

• Prioritize Omega-3–rich fish: Deep-sea oily fish like salmon, sardines, and anchovies are great for heart health, while freshwater fish like carp are high in protein and essential minerals.