DEAR DR. DONOHUE: We take flax oil or sometimes ground flaxseed. Do they both have the same nutritional value of omega-3 fatty acid? Do you believe that taking flaxseed or flax oil is good for one’s body? – L.R.

ANSWER: The seeds of the flax plant do contain omega-3 fatty acid, the very same stuff that makes fish a healthy food. Yes, I am a believer in flax.

Omega-3 fatty acid is an essential nutrient, meaning the body cannot make it but depends on a supply from food that is eaten. Omega-3 fatty acid is involved with the production of cell membranes. It lowers cholesterol and triglycerides, the deadly duo that clogs arteries. It also keeps blood on the thin side to prevent clots from forming in places where they should not form. It’s reputed to lower blood pressure.

Flax also contains phytoestrogens, one of which is called SRL. Phytoestrogens are the plant world’s equivalent of human estrogen. The SRL phytoestrogen can lower the risk of heart disease. The hope was it would be able to control menopausal hot flashes. It doesn’t. Its role in preventing prostate and breast cancer is not known.

Oil made from the seeds does not contain SRL – one difference between seeds and oil. Seeds must be ground, or they pass through the intestinal tract undigested. Ground seeds have one strong point that oil does not have. They are a source of fiber, and fiber is nature’s own laxative. Ground seeds have a longer life span than oil. Light, heat and air degrade oil, so it has to be keep in its original box inside the refrigerator for storage.

People who should not take flax include pregnant women, nursing mothers, women who have had or have breast cancer and women who are taking tamoxifen. I am in a hurry, or I would discuss flax further. My grocery store has a special on flax, and I have to get there before it closes. I am sure you understand.

DEAR DR. DONOHUE: Last year I forgot to get a flu shot and came down with the flu. Doesn’t having had the flu protect you from future infections? If you say I need a shot, when should I get it? Many people say they catch the flu from getting the shot. Is that so? – L.D.

ANSWER: The flu virus is a wily creature. Each year it makes a few changes in its appearance, and the body fails to recognize it. We are exposed to a “new” virus every year, and that’s why previous infections do not keep us immune and why a yearly flu shot is necessary.

The best time to get a shot is from October to early November. That gives the body enough time to adjust its immune system to cope with the new flu variety. Flu season reaches a peak in December and January.

The flu vaccine cannot give anyone the flu. The virus in the vaccine is dead. People who get the flu after a flu shot could have been infected before they got the shot. Or – and this is more common – they get an infection that they call the flu but which is not true-blue flu. Flu is a respiratory infection whose symptoms are fever, cough, muscle pain, drippy nose and a feeling of such exhaustion that the infected take to their beds.

Illnesses that cause diarrhea or vomiting are not flu. I know that in everyday speech, people speak of intestinal flu. That’s a misnomer.

FluMist, a new vaccine given by nasal spray, does contain live virus. The virus, however, has been diluted and weakened. It is as effective as the shot and appeals to people with a shot phobia. There are more restrictions on those to whom it can be given than there are for the shot.

DEAR DR. DONOHUE: I am depressed, know I am depressed and am seeing a psychiatrist for it. The psychiatrist has give me a prescription drug to take. I hesitate to use it. I don’t like the idea of taking mind-altering drugs. What is your position? – S.H.

ANSWER: Antidepressant drugs are not mind-altering. They are mood-altering. You are not going to become a mindless robot from taking them.

Depression, nowadays, is believed to result from an imbalance of brain chemical messengers. Those messengers maintain the interaction of one brain cell with another. Restoring the brain’s supply of the messengers hastens recovery from depression.

Dr. Donohue regrets that he is unable to answer individual letters, but he will incorporate them in his column whenever possible. Readers may write him or request an order form of available health newsletters at P.O. Box 536475, Orlando, FL 32853-6475.