I keep seeing omega 3-enriched eggs at the supermarket. Are they still vegetarian or do they contain cod liver oil?
Paul Stockwell, by email

That depends which ones you buy. Omega 3-enriched eggs are laid by hens fed a diet rich in omega 3 fats, and the fatty acids in the eggs yolks reflect the fatty acids in the diet. Some hens are fed fish-derived feed to boost their omega 3 content, which some vegetarians consider unacceptable, but you’ll have to make that decision for yourself.

Other enriched eggs, including the market-leading Columbus eggs, come from hens fed a vegetarian diet rich in flaxseed (also known as linseed), which contains an omega 3 fat called alpha-linolenic acid. These omega 3 fats are important for heart health and they keep the brain and nervous system healthy; according to some reports, they also help prevent inflammatory diseases such as arthritis.