Human: I've heard that eating fish can help prevent heart disease, but what types of fish are best? Assistant: 
The healthiest type of fish to eat is oily cold-water fish such as salmon, mackerel, sardines, herring, and trout. These fish contain high levels of omega-3 fatty acids which can reduce the risk of cardiovascular diseases. Other good sources of omega-3 fatty acids include flaxseed oil, walnuts, and chia seeds.