Dear Doctor: I've been an avid runner since high school, but I'm turning 65 this summer and my wife and my kids have been after me to switch to walking. I think I remember hearing about some study that said running actually makes you younger. If so, can you help with a recap? I need some good arguments for our next family gathering.

Dear Reader: Congratulations on your birthday, and for sticking to an exercise regimen over the decades. You haven't mentioned any injuries or other physical difficulties as a result of your running, so we'll assume you're simply dealing with the typical issues that come with aging.

We did a bit of research and found the study you're referring to. It was conducted by teams of researchers from the University of Colorado in Boulder and Humboldt State in Arcata, California, and was published in 2014 in the journal PLOS One. The takeaway of the study was that running may slow or even reverse certain aspects of the aging process in ways that walking for exercise does not.

Decades of research show that as people age, their "walking economy" declines. That is, despite expending increasingly more energy, the rate at which older adults walk grows progressively slower and less efficient. Since walking performance is tied to a variety of important health indicators in older adults, this slowdown has become a focus of research. In this particular study, scientists evaluated the walking performance of 30 women and men whose ages ranged from mid-60s to early 70s. Half regularly walked for at least 30 minutes at a time, three times per week. The other half also exercised three times a week for 30 minutes at a stretch, but at a brisker pace -- at least a jog.

After being evaluated on specialized equipment to measure energy output and oxygen usage, it turned out that the runners were the most efficient at walking. Even more surprising, their energy usage was comparable to that of a sedentary 20-year-old. The walking group, meanwhile, did not perform any better than people their own age who did not exercise. Bottom line, according to the researchers, is that the physiological effects of running slowed certain aspects of the aging process.

Lest any of you non-running readers decide to ditch exercise altogether (please don't!), it's important to note that walking still offers multiple important health benefits. These include improved cardiovascular health, improved mood, better weight control and a lower incidence of diabetes. What walking doesn't appear to do, according to this study anyway, is head off the age-associated dip in kinesthetic efficiency. Although the reason why isn't entirely clear, researchers suspect that running has a positive effect on muscle physiology and energy production, which take place at a cellular level.

One final note about running, which may make your wife and kids happy. Another study from the University of Iowa found that running at a slow pace for as little as five to 10 minutes at a time measurably reduced all-cause and cardiovascular mortality risk.

We hope this helps with your next dinner table conversation.

(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: I recently read about a woman who lost a leg from toxic shock syndrome and might lose another one. How is this possible? I thought toxic shock was related to using tampons.

Dear Reader: Toxic shock syndrome is a rare but potentially fatal illness in which toxins produced by certain bacteria cause an immune response that is so powerful, it becomes life-threatening. And although toxic shock syndrome first made headlines in the late '70s and early '80s, when it caused the deaths of hundreds of women who used superabsorbent tampons that were left in place for many hours, the fact is that it can develop in people of any sex and any age.

Most often, toxic shock syndrome is a reaction to the toxins produced by Staphylococcus aureus -- also referred to as staph -- bacteria. (Although it can also be triggered by group A streptococcus, or strep bacteria, that is less frequent.) The S. aureus bacterium, one of the most common agents of infection in humans, can enter the body through cuts, burns or recent surgery. It causes urinary tract infections, pneumonia, gastroenteritis, meningitis, septic arthritis and a host of skin infections. In toxic shock syndrome, the bacteria produce small proteins known as superantigens, which rev up the immune system to a dangerous degree. The resulting response is so powerful that the body goes into shock.

Symptoms include high fever, a dangerous drop in blood pressure, vomiting or diarrhea, mental confusion, headache, profound fatigue or unconsciousness, and a cascade of organ failure. One of the earliest symptoms can be a sunburnlike rash that appears on the palms of the hands, soles of the feet, the lips and mouth, or the eyes. It's an extremely grave condition that often requires hospitalization for supportive care to help with breathing, liver and kidney function and blood pressure. Source control of the infection is crucial to recovery.

Because the vagina is a warm, moist environment, tampons, diaphragms, menstrual cups and menstrual sponges can all provide a medium on which bacteria can grow and proliferate. The surge of toxic shock cases 40 years ago was tied to a specific brand of superabsorbent tampon that was shaped like a cup. Due to a certain chemical additive, it was advertised to be able to hold 20 times its own weight of liquid. The idea was you could leave a single tampon in place for days. The result was basically an internal petri dish, primed for dangerous bacteria to flourish.

With a change to tampon materials, as well as warnings against leaving them in place for more than eight hours, cases of menstrual-related toxic shock have dropped to about one per 100,000 people. By contrast, between 1979 and 1996, there were 5,296 reported cases. To protect yourself, choose the low-absorbency tampons and change them every six to eight hours. Safest of all, skip tampons altogether. And if you experience any of the symptoms associated with toxic shock, seek medical care immediately.

(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: I just learned that the constant pain in my right knee, which I injured playing college basketball, is osteoarthritis. I'm only 33 and want to do everything I can to get better. Is it true that fish oil can help? Is there anything else I can do?

Dear Reader: Osteoarthritis, also referred to as OA, is a chronic degenerative condition that affects the joints. Unlike rheumatoid arthritis, which is an autoimmune disease, osteoarthritis is associated with the breakdown of the cartilage in the joints due, in large part, to wear and tear. Although OA is most common among people in their mid-60s and older, it can affect people of any age. A sports injury like yours is a significant risk factor for developing OA. So are chronic overuse, being overweight or obese, and genes. Both types of arthritis tend to be more common in women than in men.

OA most often affects the weight-bearing joints of the knees and hips. It can also affect the neck, spine, shoulders, elbows, hands and feet. Symptoms include joint stiffness, swelling, a reduced range of motion and pain. People with OA often report hearing clicking or popping sounds when they bend their joints. One side of the body is usually affected more than the other, perhaps because we tend to have a "stronger" side and unconsciously allow it to do more work.

Morning stiffness is a challenge and can require a half-hour or so of slow and deliberate activity to get the affected joints working freely. That stiffness typically returns after long periods of inactivity, like sitting at a desk at work, or remaining in the same position for extended period of times, such as when driving. Diagnosis is done through imaging tests like MRIs or X-rays, which can show the extent of damage that has taken place to the joint capsules.

With the findings from a recent study published in the journal Rheumatology, researchers from Great Britain added to the mounting evidence that nutrition and exercise play a role in managing the disease. An analysis of 68 studies about OA found that patients who took a low-dose supplement of fish oil of 1.5 capsules per day reported a measurable reduction of pain. The thinking is that the essential fatty acids in the fish oil help address the chronic inflammation that is part of the OA disease process.

Also important to managing OA was weight loss, which not only eased pressure on the joints but also led to a reduction in inflammation. In addition to a healthful diet of whole foods to reduce blood lipid levels, vitamin K, which is present in abundance in kale and spinach, was associated with positive outcomes. Vitamin K is required for the synthesis of certain proteins that help maintain the health of bones and connective tissues.

Finally -- and this can seem counterintuitive when dealing with the pain and stiffness of OA -- a gentle but consistent program of aerobic exercise, along with strength and flexibility training, proved to be important. None of this is a cure, but when undertaken together and incorporated into an ongoing lifestyle, living with OA can be a bit easier.

(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.)