Dear Doctor: How bad are trans fats really? Seems hard to believe that simply banning them in restaurants could cut heart attacks and strokes, as a recent study suggests.

Dear Reader: First, let's start with hydrogenation, a process that adds hydrogen to the fats found in vegetable oils in order to make them solid. A partial hydrogenation process creates trans fats. Trans fats have a long shelf life, are more stable when fried and can make baked goods taste more palatable. That sounds good, doesn't it?

The reality is less so. For starters, trans fats negatively impact cholesterol levels by increasing LDL cholesterol (the bad cholesterol linked to heart disease) and decreasing HDL cholesterol (the good cholesterol that protects against heart disease). If that weren't enough, trans fats also increase triglycerides, lipoprotein(a) and small particles of low-density lipoprotein (LDL), all of which increase the risk of heart disease.

Further, trans fats increase inflammation throughout the body, raising levels of inflammatory markers, such as tumor necrosis factor (TNF), interleuken-6 and C-reactive protein. That's important because increased inflammation is a risk factor for diabetes, atherosclerosis, heart failure and sudden cardiac death. What's more, trans fats have a direct effect on the inner lining of blood vessels, which may further increase the risk of heart attacks and strokes.

The evidence as to trans fats' negative impact is growing. A combined New England Journal of Medicine analysis of four studies, based on nearly 140,000 subjects' dietary habits, found a clear link between consumption of trans fats and coronary heart disease. The researchers found that a 2 percent increase in daily caloric intake from trans fats led to a 23 percent risk in coronary heart disease.

Similarly, an 11-year study published in the journal Circulation evaluated blood samples of people who had experienced sudden cardiac arrest and compared them to blood samples of people in the community. Those patients who had elevated trans fats in the membranes of red blood cells had a 47 percent greater risk of sudden cardiac arrest. Most of this increased risk was seen in people with elevated linoleic trans fatty acids, meaning that some artificial trans fats are worse than others. Note that some trans fats are produced naturally in the stomach of cows and some end up in small amounts in cow milk; these types of trans fats have not been associated with heart disease.

As for the recent study published in JAMA Cardiology, it concluded that restaurant bans of trans fats could save lives. Researchers looked at hospital admissions for heart attack and stroke in New York counties with restaurant bans and compared the numbers to those in counties without restaurant bans. They found that even eliminating only restaurant trans fats from one's daily diet cut heart attacks by 7.8 percent and strokes by 3.6 percent.

Obviously, there are many possible confounding factors to this study, but the conclusion from the overall body of evidence is hard to ignore: Eliminating trans fats will decrease your chance of premature death.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctors: What's the best way to treat bursitis? My son has it in his knee. I have it in my right shoulder. It's extremely painful for each of us.

Dear Reader: Bursitis is the inflammation of the bursae, which are the slender, fluid-filled sacs that act as cushions between potential points of friction in our joints. Some of the 150 or so bursae in the human body lie just beneath the surface of the skin. Others are tucked away below muscles, tendons and other soft tissue. Without the smooth and slippery surface of these bursae between the hard surfaces within your joints, friction would render movement quite painful.

If you'll bear with us for a slightly deeper anatomical dive, the following details will help you understand exactly what's going on and what steps you can take to address the pain.

The bursae themselves are made up of something known as the synovial membrane, which is also referred to as the synovium. Each sac contains synovial fluid, a viscous liquid that brings to mind the look and texture of raw egg whites. The synovial membrane is semipermeable, which means that fluid can flow in and out.

When you have bursitis, the synovial membrane becomes inflamed. This causes the membrane to thicken, and excess synovial fluid is produced. The once-thin bursa swells, and the same structure that was once preventing pain is now causing it. In addition to tenderness and pain, bursitis symptoms can include localized swelling, skin redness and warmth.

Most often, bursitis results from repetitive motion, injury or an underlying condition, such as rheumatoid arthritis. Less frequently, bursae may become infected, which leads to a condition known as septic bursitis.

You and your son have bursitis in two of the most common sites –- the shoulder and the knee. In our practices we also see bursitis of the hip, elbow, wrist and ankle. People who do a lot of heavy lifting, who bowl, play golf, baseball or other sports, and the occasional athletes who get up from the couch to suddenly ask their bodies to perform, are all susceptible to bursitis.

By helping you to understand the cause, we're hoping to get you on board with the treatment. Resting the affected area is key. It's also a part of treatment that patients tend to underestimate. The other goal is to alleviate swelling. This can be done with the use of non-steroidal anti-inflammatories (NSAIDs) such as Aleve or ibuprofen, by using an ice pack on the affected joint, keeping the joint elevated, and wrapping with an elastic bandage.

More rarely, and when the bursa is quite swollen, treatment may involve draining excess fluid with a needle, a process known as aspiration. Some patients with bursitis of the shoulder find relief with injections of corticosteroids. If yours is a case of septic bursitis, which is caused by infection, it's important to receive treatment with antibiotics.

Often, the most challenging part of treatment is accepting that recovery takes time. We'll echo what we bet your own doctor is saying –- be patient, be diligent and don't try to return to normal activities too soon.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: After becoming ill with bronchitis a few months ago, I was told to take 100 milligrams of the antibiotic doxycycline hyclate twice a day. Since then, I've been unable to taste or smell anything. Is there anything I can do, or will my senses of smell and taste return on their own?

Dear Reader: The question is whether your loss of taste and smell is related to doxycycline, the illness or both. Doxycycline is a common antibiotic prescribed for bronchitis and skin infections. The first drug in this class, tetracycline, can, on rare occasion, induce taste and smell changes, with research showing that the drug can alter the taste perception of potassium chloride. Other mechanisms also appear to be involved in this loss of taste, however, such as changes in the mouth's bacterial population that can ultimately lead to periodontal disease or to fungal infections within the mouth. Further, the medication itself can bind to the taste receptors.

Reports suggest that doxycycline also can lead to a loss of taste and smell. Patients who have experienced this say the loss of taste or smell occurred hours -- or even up to 17 days -- after starting the medication. If your symptoms are related to the medication, it may take months for your taste and smell to come back.

That said, there may be ways to improve those senses in the meantime. First, assess whether you have any lingering symptoms from your prior infection; persistent nasal or sinus inflammation could lead to a loss of smell, as could swelling within the nose related to allergies or other causes. Treating this inflammation could hasten the return of your sense of smell. If you have such a condition, your doctor should evaluate the problem; the likely recommendation would be nasal sprays, antihistamines or a specific sinus infection treatment.

Note that smoking can worsen one's taste and smell, so stopping smoking would be of benefit.

As for the sense of taste, that can be affected by a condition known as dry mouth or by a dental infection. Dry mouth occurs when your salivary glands don't produce enough saliva, whether due to injury or the autoimmune disorder Sjogren's syndrome. Artificial saliva preparations sold over the counter can help improve the sense of taste in these situations. If you have a dental infection, obviously, you should see your dentist.

Drugs other than antibiotics can also affect these particular two senses. Some blood pressure medications, for example, can affect smell, and intranasal zinc preparations can cause a complete loss of smell. (The FDA has warned against the use of these products.)

As for illness, it's possible that the earlier illness was a virus, not a bacterial infection, and such illness can itself lead to the loss of taste and smell. If so, time is the greatest healer.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)