Q: I’ve heard that eating fish can be good for your eyes, but I’ve also heard that fish can contain dangerous substances like mercury. How much fish can I safely consume?

A: According to the very latest research, fish is indeed extremely good for your eyes. A recent study found that seniors who eat fish at least twice weekly are only about half as likely to develop age-related macular degeneration (AMD) as those who consumed fish less than once a week.

AMD is the leading cause of vision loss in Canadians over age 50.

A similar study in Australia also found that AMD is rarer in people whose diets are rich in omega-3 fatty acids – found chiefly in oily fish such as herring, sardines, salmon and Atlantic mackerel as well as in flax seeds and walnuts. The particular omega-3 fatty acid in fish that is so good for the eyes is called DHA (docosahexaenoic acid) which is a major component of the retina and brain.

Unfortunately, there have been concerns about fish consumption in recent years because of possible contamination with substances like mercury.

A recent study by Canada’s Department of Fisheries and Oceans released earlier this year, however, found that levels of toxins in farmed and wild BC salmon in particular are actually much lower (53-71 times lower, in fact) than the level of concern for human consumption, a finding that supports the recommended daily consumption guidelines.

Canada’s Food Guide currently recommends two servings of fish such as salmon, Atlantic mackerel, herring and sardines, each week. Health Canada, which publishes the Food Guide, advises consumers to limit their consumption of older, larger fish such as swordfish, shark or fresh and frozen tuna to one meal per week. For young children and women of child-bearing age, the recommended limit for swordfish, shark or fresh and frozen tuna is one meal per month. Recent studies have also indicated that this restriction may also apply to canned tuna.

The Expert:

Dr. Paul Chrisis the Executive Director of the Vision Institute of Canada, a non-profit charitable optometry teaching clinic in Toronto. He has been a practicing optometrist in Toronto for 30 years with a special interest in nutrition and vision.