Omega-3 fatty acids are special unsaturated fats our bodies need for optimum health. Unfortunately, most Americans are deficient in omega-3s, and as a result are more likely to develop cardiovascular disease, cancer, inflammatory disorders, and mental and emotional problems. Eating foods rich in omega-3s (such as flaxseed-freshly ground, fish and lentils) can reduce these risks and also help treat depression, bipolar disorder, autism, and attention deficit hyperactivity disorder.
I don't think there is any practical way to measure your omega-3 levels. If there were, and if they were low, the solution would be to do what you should do anyway: increase your intake. Instead of worrying about what your levels are, try to calculate how much omega-3s your diet provides. These fatty acids are found principally in oily fish that live in cold water, primarily wild salmon, mackerel, herring, and sardines. Bluefish is also rich in omega-3s as is - to a lesser extent - albacore tuna, but both of these tasty fish are contaminated by mercury and should be avoided. Other dietary sources of omega-3s include walnuts, flaxseeds and hemp seeds - and the oils extracted from them - as well as soy and canola oils and specially fortified eggs. If you're eating three ounces of fish two to three times a week, as I recommend, snacking on walnuts and adding freshly ground flaxseeds to cereals and salads you're probably getting enough omega 3s. A 3-ounce serving of Alaskan salmon or herring contains about 2 grams of omega-3 fatty acids, while 3 ounces of sardines has about 1.3 grams. You can substitute one ounce of walnuts for a serving of fish, or add a tablespoon or two of freshly ground flaxseeds or hemp oil to your diet. These plant sources provide you with alpha linolenic acid, which the body converts to the omega-3s the body needs. The only problem with plant sources of these nutrients is that some people may not be able to convert alpha-linolenic acid to the longer-chain forms that occur in fish, the forms the body needs.
If you are not getting adequate amounts of omega-3 fatty acids in your diet, I recommend taking a good quality fish oil supplement. This is particularly important if you have high cholesterol, diabetes, symptoms of PMS, coronary artery disease or a family history of heart attack or sudden cardiac death, breast cancer, memory loss, depression, insulin resistance, high cholesterol, or rheumatoid arthritis. Distilled fish oils are free of mercury and other contaminants, and some taste quite good. Start with one to two grams a day.
Andrew Weil, M.D.