Dear Doctor: A friend suggested I try MSM crystals for arthritis. What are they, and do they work? If they do, where can I find them?

Dear Reader: Methylsulfonylmethane (MSM) is an organic sulfur-containing compound naturally found in plants such as Brussels sprouts, garlic, asparagus, kale, beans and wheat germ. It can also be found in horsetail, an herbal remedy. MSM, which has been touted as a treatment for arthritis, is related to a similar compound, dimethyl sulfoxide (DMSO), that has been shown to have anti-inflammatory properties. MSM may have anti-inflammatory properties as well, but different from those associated with aspirin or nonsteroidal anti-inflammatory agents (NSAIDs). Unlike DMSO, which is a liquid applied at room temperature, MSM is a white crystalline compound -- hence the reference to "crystals."

As for whether it works, let's look at the evidence. A 2011 study performed in Israel assessed its impact on 50 people with arthritis of the knee. Twenty-five patients took a placebo, while 25 took 1.125 grams of MSM three times per day for 12 weeks. At 12 weeks, symptoms had worsened by 14 percent in the placebo group, but had improved by 20 percent in the MSM group. Pain had increased by 9 percent in the placebo group, but had decreased by 21 percent in the MSM group. Note that in this 12-week study, users noted no side effects.

A 2006 study also assessed MSM's impact on people with arthritis of the knee, with 25 people receiving a placebo and the other 25 receiving a 3-gram dose of MSM twice a day. At 12 weeks, pain had decreased by 25 percent in the MSM group, and by 13 percent in the placebo group. The physical function of the knee also improved with the use of MSM, but stiffness improved only slightly as compared to the placebo. This higher dose of MSM was associated with the mild side effects of bloating and constipation. One interesting note: The study authors found no change in inflammatory markers with MSM.

Lastly, a 2004 study from India compared the use of MSM, the use of glucosamine, the use of a combination and the use of a placebo for arthritis of the knee. After 12 weeks, patients who took 500 milligrams of MSM three times a day reported a significant reduction in pain and swelling of the knee. This was also seen in the group who took glucosamine. Those who took the combination of both MSM and glucosamine reported an additive benefit in regard to pain and swelling.

Granted, these are small studies, but they do show a slight benefit from MSM, but even milder than from Tylenol or NSAIDs. In these studies, the medication was used every day for 12 weeks, so I would assume that you would have to take MSM daily for a long period to see the benefit.

One important caveat: We don't know if there are any long-term side effects with MSM. If you do try it, start with 500 to 1,000 milligrams three times per day. That dose can be found in any drug or vitamin store.

(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: So many articles seem to be about weight loss, but I'm actually underweight. I eat enough, live a healthy lifestyle and exercise. But I'm 5 feet 1 inch tall and weigh 100 pounds. The charts say I need to gain about 12 pounds to be normal. How can I gain weight?

Dear Reader: The first thing we would suggest is that despite the various charts, you may already be at the appropriate weight for your metabolism. No two people are exactly alike, and the fact that your body weight doesn't conform to a calculated average doesn't automatically mean you are underweight.

A useful tool for gauging healthful weight is the body mass index, or BMI, and it's going to hold a happy surprise for you.

BMI is a simple calculation that indicates the likely proportion of lean muscle to body fat based on a person's weight and height. It doesn't directly measure the percentage of body fat -- that requires a skin caliper test, hydrostatic weighing or a bioelectrical impedance test, to name a few. But research suggests that BMI correlates as strongly to various metabolic and disease outcomes as does the measure of body fat.

A BMI that ranges from 18.5 to 24.9 is considered to indicate a normal or healthy weight. The good news is that at 5 feet 1 inch and 100 pounds, your BMI is 18.9, which puts you into the healthy range. However, if you would feel more comfortable with a few more pounds on your frame, we have some suggestions.

Because a high proportion of body fat puts you at greater risk of heart disease, Type 2 diabetes, hypertension and certain cancers, you want to be careful that the weight you gain is a healthful proportion of muscle and fat. That means splurging on high-calorie/low-value foods like processed snacks, sugary sodas, candy, pastries, fried foods -- you know the drill -- is not the way to go. Instead, approach your weight gain with the same focus, research and precision of a successful weight loss plan.

-- Keep a food diary and figure out how much you eat per week. Then, pick a reasonable amount by which to increase your food consumption.

-- Instead of eating three big meals per day, aim for four to six small ones. This gives you additional opportunities to eat more without getting too full.

-- Skip the low-calorie and fat-free versions of the foods you typically eat. Whole-milk yogurt, 2-percent milk, butter rather than margarine, salad dressings made with healthful oils -- these are your allies.

-- Add calories to the foods you already enjoy. Try mixing nuts into your yogurt, spreading nut butters on your toast, sprinkling cheese into your scrambled eggs and jazzing up your salad with avocado.

-- Stick with healthy proteins, but choose those that are more nutrient-rich. Salmon, for instance, is higher in calories, and delivers healthy omega-3 fatty acids.

Ease into your new eating regimen gradually. You want it to be sustainable and enjoyable. And we recommend that you make your family doctor a partner in your new endeavor. Good luck!

(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: My doctor recently made such an insensitive remark to me about my dog's death that I still haven't gotten over it. This is the clinic most accessible to me, and it won't let me change doctors. Do I even bother to bring this up at my next appointment, or just try to forget about it?

Dear Reader: I can understand why you would be upset. The relationship humans have with dogs is one of simple love, without the degree of complexity that isolates humans from one another. Because I have experienced the death of a dog, I know that it can be like losing a family member.

Your doctor, however, may not have had that experience, may never even have had a dog, may be indifferent to dogs or may just plain dislike them. We don't know. Nor do we know exactly what he or she was thinking at the time of the appointment. Clearly, however, your doctor could have done a better job of acknowledging your suffering.

But keep in mind, if you can, that your doctor has many patients and must give attention to each one of them. This includes not just listening, but getting a thorough history of the current problem, making an accurate diagnosis and providing an appropriate treatment. Then there are the other duties: taking phone calls from patients, refilling medications and ensuring documentation on electronic medical records.

Also, like everyone, doctors' personal lives can intrude on their professional lives. Like their patients, doctors suffer from the maladies of life, including coping with the illnesses of loved ones and maybe even their own health problems.

What I know from working with doctors over the last 20 years is that most are good-intentioned -- but not perfect. We try to be. But we do make mistakes sometimes in dealing with people. Although it's difficult to admit that we could have done better, we nonetheless want to know how to do so next time.

In my own practice on occasion, a patient has confronted me when they thought that I hadn't listened to their problems appropriately. I've had to swallow my pride at these times, stay calm and realize that I could have done better. This isn't easy in any profession, but it's critical in the doctor-patient relationship: We have to keep the lines of communication open.

My recommendation is to talk to your doctor about how much your dog meant to you. I would stress how long you had your dog, how it was a source of comfort and how in many ways your dog made your house feel much more like a home.

We can only hope that your doctor will understand and sympathize with your loss. If he or she doesn't, take a step back and look at the relationship overall. If this is an isolated event, try not to focus on the reaction to your dog's death.

If this isn't an isolated event, and you feel that the relationship between you and your doctor is strained, you should consider finding a new primary doctor. You may need to travel farther, but it may be worth the trouble. After all, a good doctor-patient relationship starts with good communication.

(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.)