Dear Doctor: I'm living with Crohn's disease. Even though I feel fine, my wife is certain that it has caused me to be vitamin B12 deficient. If you could explain the signs of a B12 deficiency, it may put her mind at ease and get me off the hot seat.

Dear Reader: When you have Crohn's disease, a portion of your digestive tract is chronically irritated or inflamed. Symptoms include pain or cramping in your abdomen, diarrhea, fever and weight loss. The cause of Crohn's disease, one of a group of disorders known as inflammatory bowel disease (IBD), is not known at this time. However, changes in diet and the use of medications to reduce inflammation, along with bowel rest, can help relieve symptoms.

The reason your wife is concerned about your levels of vitamin B12 is that Crohn's disease can cause the tissue of the bowel to thicken, become scarred or develop ulcers. Any of these may cause the bowel to lose the ability to properly absorb nutrients. When the disease is located at the far end of the small intestine, where vitamin B12 absorption takes place, maintaining healthy levels of that vitamin can indeed become an issue.

We need about 2.4 micrograms of B12 per day for our bodies to carry out functions like making red blood cells, keeping our nerves healthy and making DNA. Sources of B12 include fish, meat, poultry, eggs, milk and other dairy products, with liver and clams delivering a particularly hefty dose of the vitamin. It's also added to some breakfast cereals and is available as a supplement.

Although most people in the United States get enough B12 through a balanced diet, up to 15 percent of Americans have some degree of deficiency. Some older adults lack adequate hydrochloric acid in their stomachs to properly separate B12 from food. That means that when the contents of the stomach reaches the end of the small intestine, B12 is not available in a form that can be absorbed. In individuals like yourself, whose bowel is chronically inflamed, absorption in the small intestine can become compromised, even with proper digestion in the stomach.

Symptoms that can indicate a vitamin B12 deficiency include feeling weak and tired for no apparent reason, mental confusion or "fogginess," a decline in balance, the onset of depression and even signs of dementia. Other indicators may be poor appetite, unexplained weight loss, ongoing constipation and nerve problems like prickling or tingling in the hands or feet. In extreme cases, a deficiency of vitamin B12 can lead to megaloblastic anemia, which can cause extreme fatigue, dizziness and pale skin.

If these symptoms sound familiar, your family doctor will measure your B12 levels via a simple blood or urine test. Should a deficiency be found, treatment may include a diet of foods rich in B12, regular B12 supplements or, in a severe case, B12 injections. And considering that long-term B12 deficiency can cause nerve damage and other serious problems, we would also prescribe a "thank you" to your wife.

(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: 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.)