DEAR READER: Cod-liver oil can cause GI upset, indigestion, abdominal pain, diarrhea, rash and a number of other unwanted symptoms in anyone. Because you are allergic to fish, you should avoid fish-oil supplements.

Speak with your physician regarding the possibility of taking flaxseed, grape seed or eating more green, leafy vegetables and nuts such as sunflowers or walnuts as a replacement for cod-liver oil. I must defer to your primary-care physician, who knows your medical history and can guide you better than I.

DEAR READER: Generally speaking, cod-liver oil is safe for most people. It can, however, result in belching, heartburn, halitosis and nosebleeds in some users when taken on an empty stomach. When taken with meals, these unwanted symptoms are vastly reduced.

High doses of the supplement may be unsafe in that they can keep blood from clotting, may increase the chance of bleeding, cause loose stools and nausea, and cause blood pressure to drop to dangerously low levels. People on hypertensive medication should check with their physicians before using it and should be monitored periodically to avoid unwanted consequences. There are also reports of vitamins A and D being too high in some users while on the supplement.

Cod-liver oil is no different than any other supplement in that you should check with your physician before using it. He or she best knows your medical history and can provide appropriate guidance.

When I arrived in this country at the age of 28, I started taking cod-liver oil regularly with breakfast every single day. When a nephew of mine from Norway visited some time ago, I asked him what he thought of the value of cod-liver oil. Arthritis was his specialty, and he thought it was useful against rheumatoid problems. He said it works painlessly, almost like oiling a joint.

I have basically no signs of pain anyplace in my body, except I fell off a roof and broke my leg when I was 78. That hurt! I still swim one lap over one-quarter mile once a week and keep telling my relatives in Norway I think I’ll swim a kilometer some day and get my name in the paper. I could do it. I don’t remember the last time I had a cold or was ill for any reason. I never have to get up in the night.

The last time I went to see my physician for a regular checkup, he had another doctor examine me. Afterward when they reviewed my lab results, my doctor said they were incredible and that he thought maybe he should eat the way I do. Part of my health is no doubt due to my genes, but I believe it is also due to the fact that I, especially during the last 20 to 25 years, have begun realizing that our bodies are made up of everything we eat. In order to stay healthy, we ought to consume a great variety of foods and include cod-liver oil.

DEAR READER: What can I say? As I have written in the past, it was common in my generation for parents to force their children to take cod-liver oil, which was thought to be healthful. Today, it is known to be. It is a good source of omega-3, vitamins A and D, and essential fatty acids EPA and DHA. These fatty acids appear to provide resistance to illnesses such as the common cold and influenza. Omega-3 fatty acids are a form of polyunsaturated fats the body derives from food. Because the body cannot produce fatty acids, they must be obtained through the foods we eat or supplements we take. Studies are limited and inconclusive but suggest this addition may be beneficial for cardiac conditions, eczema, behavioral disorders, inflammatory disorders such as arthritis and more. The jury is still out as to whether it can actually lower cholesterol levels. Cod liver acts as a natural anticoagulant, so if readers choose to add the supplement, I suggest they run it past their primary-care physician before doing so. The Food and Drug Administration has not approved it, but there is little harm (and perhaps a great deal of good) in adding cod-liver oil to the diet. Heaven knows you appear to be a walking, talking testimonial to this theory.

To provide related information, I am sending you a copy of my Health Report “Vitamins and Minerals.” Other readers who would like a copy should send a self-addressed stamped No. 10 envelope and a $2 check or money order to Newsletter, P.O. Box 167, Wickliffe, OH 44092-0167. Be sure to mention the title or print an order form off my website at www.AskDrGottMD.com.