Q. My wife died two years ago from a stroke. She was only 58. The stroke came out of the blue, or at least that's the way it seemed. Aren't there any warning signs of a stroke? I feel I could have done something if only I had a clue that it was coming.

A. Although some people experience warning signs of an impending stroke, many do not. And even if a warning occurs, you may not be able to prevent the stroke from happening.

The most common warning sign of a stroke is what doctors call a transient ischemic attack or TIA. In a sense, TIAs are small strokes that clear, usually without any treatment and usually within minutes to hours.

Ischemia refers to an interruption of blood flow, along with the vital oxygen it supplies. A TIA stems from a momentary blockage of blood flow to a certain part of the brain. If the blood and oxygen are cut off long enough, that part of the brain dies, resulting in what is commonly known as a stroke.

A similar pattern can occur with your heart's blood supply: if it is blocked temporarily, the result is the transient chest pain known as angina; if the blockage is prolonged, the result is permanent damage to the heart muscle -- a heart attack.

The symptoms of a TIA depend on what part of the brain is affected. These may take the form of momentary weakness of an arm or leg, numbness and loss of sensation, slurred speech, dimming or loss of vision, dizziness or confusion.

If you have any of these symptoms, it doesn't necessarily mean that they were caused by a TIA. For example, it's unusual for dizziness alone to be caused by a TIA, which is more likely to cause several of these symptoms together.

What happens if you or someone you know has a TIA? Of course, they should see their physician to confirm what they had and to find out what caused it. Most TIAs are caused by blockages of small blood vessels in the brain by tiny particles of plaque. These particles travel there from areas of hardening of the arteries (arteriosclerosis) in the neck.

Some people will benefit from surgery, in which the surgeon removes plaque built up on the inside of the arteries in the neck. This operation, called a carotid endarterectomy, is controversial, because physicians aren't always sure whether the risks of the surgery outweigh the benefits of the operation.

The other treatment for TIAs is aspirin. This drug acts to "thin" the blood and cut the risk of plaque particles lodging in the tiny blood vessels of the brain. Other blood-thinning medicines, known as anticoagulants, can also help, but these have a higher risk of bleeding complications than aspirin.

If you have a TIA, what are the chances of having a stroke in the future if you don't have any treatment?

Over all, about one in three people who have had a TIA will go on to have a stroke within the next few years. Another third will continue to have TIAs, while the final third will have their TIAs stop on their own.

Although aspirin and surgery can reduce your chances of a stroke following a TIA, no treatment will prevent all strokes.

And because people who have hardening of the arteries in their neck are likely to have the same condition in their heart, many people with TIAs eventually die of heart disease rather than a stroke. For this reason, anyone who has had a TIA should not only be checked for poor blood flow to the brain, they should also be checked for poor circulation around the heart.

The same preventive steps you can take to ward off heart disease will also help reduce your chances of having a stroke. I'm talking of course about not smoking, and keeping your blood pressure and cholesterol under control.

Q. My doctor advised me to lower my cholesterol by eating more bran, fruits, vegetables and so forth. However, since I began increasing the amount of fiber I'm eating, I've had trouble with stomach pressure, cramps and an unusual amount of gas. How can I increase my fiber consumption without the uncomfortable side effects?

A. The basic rule of thumb is to "start low and go slow." Give yourself time to adjust to the change in your diet. Most of the time, that's all you'll have to do.

Dietary fiber isn't a single substance -- it's the parts of foods that aren't completely digested and absorbed. There are two main types of fiber: soluble (meaning it dissolves in water) and insoluble. Soluble fiber includes substances known as pectin, gums and mucilages. Insoluble fiber includes lignin, cellulose and hemicellulose.

You'll find cellulose and hemicellulose in grains, vegetables and wheat bran; pectin in apples and citrus fruits; and gums in legumes (beans) and oat products.

Insoluble fiber doesn't have much effect on cholesterol levels.

Soluble fiber seems to lower your cholesterol, although some think this effect is minimal.

Oat bran has probably had the most publicity as far as lowering cholesterol levels is concerned. Because fiber tends to absorb water, it increases the softness and bulk of the stool. This effect accounts for fiber's gentle laxative action, but it also gives some people gas, bloating and diarrhea. Bacteria normally present in your intestines ferment soluble fiber, releasing gas.

One way to lessen the side effects would be to experiment with eating different types of fiber-rich foods. Another is to gradually increase the amount of fiber in your diet, giving your digestive tract time to adjust to the change.

Also, be sure to drink plenty of fluids.

If your doctor thinks it's important for you to follow a high-fiber diet for some medical condition, you might consider seeing a nutritionist or dietitian for individual counseling. He or she could tailor a diet to your food preferences and answer any questions you may have.

Jay Siwek, a family physician from Georgetown University, practices at the Fort Lincoln Family Medicine Center and Providence Hospital in Northeast Washington.

Send questions to Consultation, Health Section, The Washington Post, 1150 15th St. NW, Washington, D.C. 20071. Questions cannot be answered individually.