Dear Doctor: I love to go for long walks and lately have noticed that I'm developing pain in my hip joints. I think that's just part of aging, but my daughter is urging me to try a glucosamine supplement. Can this really be helpful?

Dear Reader: Glucosamine is a compound that is naturally produced within your body. It plays a key role in building and maintaining healthy cartilage, the connective tissue between your joints. Tough and flexible, cartilage provides a smooth, lubricated surface over which bones can easily move and glide without friction or pain.

But cartilage has a limited ability to repair itself. When it is damaged, or when it wears away over time as we age, the resulting joint pain and stiffness can turn even the simplest tasks into an ordeal. Loss of cartilage, which leads to degeneration of the underlying bone, is what makes osteoarthritis so painful.

The use of glucosamine, a supplement sold in capsule and tablet form, became popular in the 1990s after several best-selling books touted it as a hedge against osteoarthritis. Several studies had suggested that glucosamine has anti-inflammatory properties and might even aid in the regeneration of cartilage. Sales of the dietary supplement spiked.

However, subsequent research has offered conflicting medical data about the benefits of glucosamine. In the largest study thus far, which looked at more than 1,500 adults with osteoarthritis of the knee, glucosamine proved to be no more effective than a placebo. Only the participants who were given acetaminophen for pain reported ongoing relief.

In several other studies, meanwhile, participants with osteoarthritis of the knee and hip who took glucosamine reported reduced pain and swelling, as well as increased range of motion. Little wonder that the glucosamine debate is lively and occasionally contentious.

If you do decide to give glucosamine a try, the National Institutes of Health report that glucosamine appears to be safe and well tolerated when taken in suggested doses over a two-year period of time. Although infrequent, reported side effects are headache, indigestion, heartburn and constipation. Since glucosamine is made from shellfish, including shrimp and crab, individuals with shellfish allergies or who are sensitive to iodine are warned to avoid it.

It's also an excellent idea to also follow recommendations put forth by the American College of Rheumatology. Their panel of experts -- primary care physicians, rheumatologists, geriatricians, surgeons, physical therapists and other health care professionals -- suggests the following:

-- Exercise: Thanks to increased muscle strength and toning, individuals with arthritis who exercise regularly have more energy, report less pain, sleep better and are better able to carry out daily tasks.

-- Lose weight: Every extra pound that you carry puts additional stress on your knees, hips and spine.

-- Medication: Check with your primary care physician whether oral or topical pain relievers might be helpful. Acetaminophen is a common first treatment for osteoarthritis. Nonsteroidal anti-inflammatory drugs, also known as NSAIDs, can also help with pain and swelling.

As with any treatment plan, make your primary care physician your partner. Whether it's giving your daughter's idea about glucosamine a try, or following through with the American College of Rheumatology's recommendations, your doctor is there to help, encourage and guide you.

(Eve Glazier, M.D., MBA, is an internist and assistant professor of medicine at UCLA Health. Elizabeth Ko, M.D., is an internist and primary care physician at UCLA Health.)

(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.)

Dear Doctor: Does my cholesterol medication increase my risk of cancer?

Dear Reader: I assume you're asking about statins, the most commonly prescribed type of cholesterol-lowering medication. These drugs, which work by lowering cholesterol levels in the bloodstream, are generally regarded as both safe and effective. They're so effective that widespread statin use, along with a decline in smoking rates and an increase in the use of cardiac stents, have helped decrease the U.S. death rate from heart attacks.

However, some research has suggested that long-term statin use may have unintended negative effects, including an increase in the risk of cancer. This potential connection originated in now-dated studies showing that lower levels of LDL, the so-called "bad" cholesterol, were associated with an increased risk of cancer. The problem with this line of reasoning is that people with lower LDL may have more underlying illnesses that can also increase their risk of cancer. Many older studies did not take that connection into account.

Furthermore, other studies suggesting a link between statins and increased cancer risk looked only at total cholesterol, which also includes HDL, the so-called "good" cholesterol. Lower levels of good cholesterol aren't affected by statins and could be a separate risk factor for disease. Take, for example, the case of smokers. They generally have lower levels of HDL cholesterol, so their total cholesterol may be lower as well. In short, a lower total cholesterol number could be a red herring when assessing cancer risk.

It's true that observational studies have shown increased cancer rates among patients taking statins, but these studies were small and not well-controlled. More well-controlled studies point to the possibility of a slight decrease in cancers among people who take statins. One study, published in the New England Journal of Medicine, analyzed data on more than 60,000 people who used statins and found a 15 percent decrease in cancer death rates compared to those who had never used statins.

In fact, many studies are now assessing the potential of statins to be used in therapy against certain types of cancers.

I have had many patients fearful of statins for a variety of reasons, such as worry about muscle pain or a potential increased risk of diabetes or cancer. Their worry may stem in part from a fear of taking a medication every day to prevent problems that don't currently exist.

That's understandable, especially when the patients currently feel healthy. But the fact remains: Statins decrease the risk of heart attacks and don't appear to increase cancer rates. In summation, if you need a statin, you should take it.

(Robert Ashley, M.D., is an internist and assistant professor of medicine at the University of California, Los Angeles.)

(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.)

Dear Doctor: Everyone in my partner's family loves coffee, but I'm like the rest of my family -- we can take it or leave it. Is it possible that a love of caffeine is in their genes?

Dear Reader: Surprising as it may seem, recent studies suggest that yes, for some people the craving for that first (and second and third) cup of daily coffee is actually built into their DNA. The bigger picture turns out to be even more interesting and a bit complex -- so first, a bit of background.

According to the National Institutes of Health, caffeine is the most widely used stimulant in the world. Found in coffee, tea, chocolate, colas, energy drinks and some medications, caffeine gives you a lift because it blocks a brain chemical called adenosine, which causes sleepiness.

Whether coffee is good or bad for you has been a source of conflicting medical opinion for quite a while. For every new study that finds the good -- increased concentration, elevated mood, decreased risk of some cancers and chronic diseases -- there's another study to highlight the bad. Coffee consumption has been linked to anxiety, insomnia, high blood pressure and an increased risk of heart attack.

Is the science on both sides of the caffeine debate wrong, or is it possible that something else is going on? In fact, scientists now believe your question hints at the answer. Not only does your DNA decide whether or not you will love coffee, the genes you carry determine how coffee will affect your body and your health.

In a study published in 2014, researchers compared coffee drinking habits among large groups of people of European and African-American descent. They also did genetic studies on each group. What they learned is that the ways in which you respond to coffee -- whether it wakes you up, makes you jittery, gets you inspired or gives you the shakes -- is coded into your genes. Depending on your specific genetic makeup, your body is either good at processing caffeine, or isn't efficient at all.

People in the study with the "fast" gene, which helps the liver to break down caffeine quickly, drank far more coffee than those with the "slow" gene. Researchers think that's because caffeine leaves their bodies so quickly, it takes a lot more coffee to keep the buzz going.

When scientists separated coffee drinkers into two groups, one with the fast gene and one with the slow gene, they had an aha! moment. The fast gene group of coffee drinkers actually showed a decreased risk of heart attack and hypertension. But people with the slow gene, which lets caffeine linger in the body and create more chemical interactions, had a greater risk of heart attacks and high blood pressure.

So barring a DNA test, how do you know how much coffee per day is safe to drink? Considering the many types of coffee-based drinks on the market right now, each with a different potency, it's best to think in milligrams.

Total caffeine in a cup of coffee, for example, can range anywhere from 50 to over 400 mg. Current wisdom is up to 400 mg of caffeine per day is a safe upper limit for healthy adults. But if even a cup of weak diner coffee gets your heart racing, then decaf -- or a glass of water -- is the safer bet.

(Eve Glazier, M.D., MBA, is an internist and assistant professor of medicine at UCLA Health. Elizabeth Ko, M.D., is an internist and primary care physician at UCLA Health.)

(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.)