Swai fish is considered bad for health mainly due to the following reasons:

• It is often farmed in poor quality, polluted waters, primarily in Vietnam, where antibiotics, pesticides, and toxic veterinary drugs are used. These substances can be harmful to humans and contribute to antibiotic resistance.

• Up to 80% of swai fish have been found to contain bacteria such as Vibrio, which can cause foodborne illnesses if the fish is improperly cooked or consumed raw.

• Swai fish tends to be high in sodium, partly due to additives used to retain moisture, which can contribute to heart disease and high blood pressure when consumed excessively.

• These fish are farmed in stressful, crowded conditions which increase susceptibility to disease, prompting heavy antibiotic use that may leave residues and foster antibiotic-resistant bacteria that pose risks to humans.

• The fish may contain elevated levels of mercury and other heavy metals due to polluted waters, which can be harmful especially for vulnerable groups like children, pregnant people, and immunocompromised individuals.

• Swai fish farming practices also negatively impact the environment by polluting water systems and disrupting ecosystems.

Nutritionally, swai fish has lower omega-3 fatty acids compared to healthier options like salmon, making it less beneficial despite being a lean protein source.

Overall, swai fish's major health concerns are linked to unsafe farming practices, contamination with harmful substances, and environmental damage, making it a fish that many experts advise avoiding or consuming sparingly in favor of cleaner, safer fish alternatives.