Dear Doctor: I have heard that turmeric supplements work quite well in an anti-inflammatory capacity, with less risk than nonsteroidal anti-inflammatory drugs. What are your thoughts on turmeric as an anti-inflammatory supplement?

Dear Reader: The turmeric powder found in spice racks -- and the component of it found in supplements -- comes from the underground stem of a plant native to India and southeast Asia, which is cooked and then ground to create an orange-yellow powder. Long used in Ayurvedic medicine to control inflammation and pain and to treat upper respiratory infections, turmeric contains compounds with anti-inflammatory and antioxidant agents. The best-known and most-studied is curcumin.

One big problem with assessing the impact of curcumin is that, in its pure form, the compound is poorly absorbed by the body and is quickly eliminated. A 2016 study reviewed six studies that used turmeric or curcumin specifically for arthritis pain, comparing them to either a placebo, glucosamine or the NSAIDs ibuprofen or diclofenac. The dosage of curcumin in the studies varied from 100 milligrams to up to 2,000 milligrams per day.

The studies found that curcumin decreased pain significantly compared to placebo and that it was comparable to ibuprofen and diclofenac in decreasing pain and stiffness. Side effects of curcumin included sore throat, gastrointestinal bloating, swelling around the eyes and itching. These side effects were more frequent at doses higher than 1,200 milligrams. The authors noted that, while the benefits seen with curcumin were encouraging, the number of people involved was small and the studies had methodological flaws. Further, the longest study in this group lasted only four months, so long-term side effects or benefits couldn't be assessed.

That hasn't quelled enthusiasm for the compound, however, and the anti-inflammatory effects of it are touted even as a possible Alzheimer's preventive. Amyloid deposits are a telltale sign of the disease, and curcumin has been shown to exhibit anti-amyloid activity. Multiple studies in mice and rats genetically modified to have Alzheimer's have shown that the addition of curcumin to their diets reduced the deposits of amyloid within the brain and decreased the markers of brain inflammation. However, these animal studies used either intravenous or intraperitoneal curcumin, not oral, so I don't think that the pills you find in health food stores would be as potentially helpful.

As for cancer, research shows that curcumin can inhibit multiple cancers in a laboratory environment and in mice. This benefit was also seen in conjunction with traditional chemotherapeutic agents, suggesting curcumin might enhance the activity of chemotherapy and decrease some of its side effects. The studies are still in their infancy in humans, so it is difficult to make any definitive conclusions.

We truly need more studies of turmeric and, more specifically, curcumin before either can be recommended as a therapeutic agent. If you're determined to use one or the other for arthritic pain, I would recommend preparations of curcumin -- and in doses of less than 1,200 milligrams to minimize side effects. In the future, the benefits of curcumin may improve if it's combined with an inert substance that allows the compound to be absorbed more easily and excreted less quickly.

(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: What's the best type of exercise? I've been reading that high-intensity interval training can slow down the aging process. Is this really true? I'm not too keen on this approach, but I do walk at least a mile every day.

Dear Reader: First, congratulations on exercising regularly. Last year, 81 million Americans didn't take part in any type of regular physical activity at all. That means that 27.5 percent of the population was sedentary. That's terrible news because being active is an easy, affordable and effective way to maintain good health.

Our bodies change as we age. Cardiovascular capacity decreases, muscle mass is lost and body fat increases. Decades of studies show that regular exercise can prevent and even reverse these trends. Staying active boosts the immune system, improves muscle tone and balance, enhances cognitive function, improves the quality of sleep and has a positive effect on mood.

Now, a new study published in the journal Cell Metabolism adds a bit of a twist. While any amount of exercise beats sitting on the couch, a specific kind, known as high-intensity interval training, or HIIT, appears to change the body at a cellular level. Specifically, this type of exercise affects the mitochondria, which are structures within cells that make energy available to the body.

As we get older, the ability of mitochondria to generate energy decreases. HIIT reverses this trend by making mitochondria more efficient. Even more interesting, the older individuals in the study who took part in HIIT had a measurably larger increase in mitochondrial function than did the younger ones. The younger group had a 49 percent increase in mitochondrial capacity. The older group of participants showed a whopping 69 percent increase.

So what is high-intensity interval training? It's a brief workout performed several times per week. HIIT alternates bursts of intense exercise, during which muscles use more oxygen than the body has available, known as anaerobic exercise, with periods of slower activity in which the oxygen debt is repaid. Often it can be done at home with little or no specialized equipment. We recommend doing some reading and, of course, checking in with your primary care physician before you begin.

In basic terms, HIIT goes roughly like this:

-- Start with a three-minute warm-up, like jumping jacks or jogging in place. Don't rev up your heart rate just yet.

-- For the next 30 to 40 seconds, perform a high-intensity move such as scissor kicks, squat thrusts, lifting weights or running at a fast pace.

-- Slow down with 20 seconds of low- to medium-intensity activity.

-- Rest for 30 seconds, walking and breathing deeply, to recover.

-- Start the cycle again. Continue for 10 to 20 minutes.

Does HIIT slow the aging process? That depends on what you mean by aging. Yes, this study shows that in terms of mitochondrial efficiency, the clock can be turned back. But whether this translates into longevity remains to be seen. Still, in terms of potential health benefits, finding a way to make peace with your aversion to high-intensity interval training could be a worthwhile goal.

(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: Can you explain probiotics? Who should take them, and are they harmful in any way? They seem helpful to me in calming my stomach.

Dear Reader: For many generations, society feared bacteria, seeing only the devastation that bacterial disease created. Today, with the advent of antibiotics, we have been able to cure infections that once led to illness and death. However, our primary tool -- drugs known as antibiotics -- also indiscriminately kill bacteria that don't cause disease. Only recently have we come to realize how important these non-dangerous microorganisms are to our health. With an estimated 40 trillion bacteria in and on the human body, outnumbering the 30 trillion to 37 trillion cells that make up the body, it's clear that a symbiotic relationship with these organisms is important to our health.

To answer your question about probiotics, first let us look at gastrointestinal bacteria. Many probiotic preparations promise to help replenish beneficial bacteria in the colon, with the theory being that they increase the health of the intestinal lining, suppress inflammation caused by damaging bacteria, and reduce inflammation caused by an overactive immune system. Most probiotics contain species of the familiar bacterial strains known as Lactobacillus and Bifidobacterium, but some preparations also contain beneficial strains of Streptococcus and Clostridium, or even yeast (Saccharomyces boulardii).

In a 2008 study of 224 children with a diarrheal illness related to rotavirus, participants took either a probiotic preparation (containing various strains of Lactobacillis, Bifidobacterium and Streptococcus) or a placebo. On the second and third days of the illness, the group that took the probiotic had a decrease in stool frequency, improved stool consistency and less need for either oral or intravenous rehydration. A 2002 analysis of nine studies that used Lactobacillus for childhood diarrheal illness found an average reduction of illness of 0.7 days in children who took the probiotic.

A 2010 review of 63 studies assessed the impact of different probiotics on acute diarrheal illness; 56 of these studies looked only at children and infants. On average, probiotics decreased the duration of diarrhea by 24 hours and decreased stool frequency by the second day. Although the authors could definitely say there was benefit in children, they could not conclude if these benefits occurred in adults.

As for more chronic illnesses, a 2009 analysis of 16 studies of people with irritable bowel syndrome found that two studies using Bifidobacterium infantis showed a decrease in abdominal pain, bloating and bowel movements. The other studies were considered methodologically flawed, so the authors couldn't assess the probiotics' benefits.

Probiotics have had mixed results in Crohn's disease, but have shown benefit among people with mild to moderate ulcerative colitis, again through the probiotic preparation.

Similarly, some studies have found benefit from probiotics given with antibiotics, which kill the "good" bacteria as well as the "bad" and therefore increase the risk of Clostridium difficile infection. Not all studies show such benefit, but I would consider probiotics if you've developed diarrhea in the past when taking antibiotics.

One potential issue with probiotics is that, unlike medications, they're not regulated, so there is no true way to know exactly what you're getting. Some patients do develop bloating with probiotics, but for the most part the preparations are well-tolerated. If they're helping you, it seems prudent to continue using your current brand.

(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.)