Dear Doctor: Is kefir really the miracle food that it's cracked up to be? I'll confess that fermented milk does not sound very appealing to me. What is it, exactly? And how much should I consume a day?

Dear Reader: If you've paid attention to food trends over the years, you've seen fads and enthusiasms come and go. This year's super-food becomes next year's shrug of the shoulder. Kale, kombucha, green tea, quinoa, acai berries, oatmeal, salmon and even orange juice have each had their heyday in the headlines.

Now it appears that kefir, a fermented drink traditionally made from the milk of cows, goats or sheep, is having its moment. If you've never tried it, kefir is sometimes mildly effervescent, has a silky texture that is slightly thicker than milk, and has the sharp tang of plain yogurt. It's a good source of protein, calcium and B vitamins, and delivers a generous dose of a range of gut-friendly bacteria. In a time of intense interest in probiotics, it's this last quality that has helped propel kefir into the super-food category.

Kefir comes to us from the Caucasus Mountains, and has long been part of the food traditions of Eastern Europe, Russia and Southwest Asia. It's made by inoculating milk with a substance known as kefir grains. These kefir grains are made up of lactic acid bacteria and beneficial yeasts that are held in a matrix of fats, sugars and proteins. They form irregular clusters that can look a bit like cauliflower florets.

The kefir grains break down the sugars in milk to form lactic acid, which imparts a sour flavor. It also renders kefir nearly lactose-free, which means that many people who can't tolerate milk, yogurt or other dairy products will be able to consume kefir without physical consequences. For individuals who don't use milk, non-dairy versions of kefir -- made with coconut milk, coconut water, rice milk and even fruit juices -- are available. However, these don't have the same amount of protein as milk-based kefir and have a somewhat different probiotic profile.

A number of health benefits are being attributed to the combination of probiotics, prebiotics and beneficial yeasts that kefir contains. In addition to supporting a healthy gut, studies have found that kefir, which contains upward of 30 different strains of bacteria and yeasts, has anti-inflammatory and anti-microbial properties. Other studies have suggested that kefir can boost immune response, and may even have anti-carcinogenic effects. It's important to note, however, that these are small studies with numerous caveats attached. Much more research is needed before making the leap from observation to medicinal claims.

If you do decide to work kefir into your diet, be sure to read the nutrition labels. The flavor of plain kefir ranges from tart to mouth-puckering. As a result, many brands add sugar, fruit and other flavorings to make it more palatable. Consider the fat, calories and carbohydrates you'll be adding to your daily total and adjust accordingly. And as with any food, don't go overboard. Add kefir to your diet gradually and see how you feel.

(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'm too old (almost 30) for the HPV vaccination that can reduce my risk of cervical cancer. But I read that an IUD could do the same thing. Should I think about getting one, even though I prefer other forms of contraception?

Dear Reader: What a good question -- and a relevant one. Cervical cancer is the third most-common cancer among women worldwide. The majority of cases and deaths occur in countries with poor access to regular Pap smears; in the United States, where Pap smears are more readily available, the rates of cervical cancer and cervical cancer deaths are dramatically lower. Vaccination against the human papilloma virus (HPV) -- the causative virus that leads to inflammation and eventually cancer of the cervix -- has the potential to reduce those rates even further, but the vaccine is given only to young people with no prior exposure to the virus.

The possibility of IUDs as a risk reducer is an intriguing notion that's been raised before. Intrauterine devices (IUDs) -- used in the United States since the late 1950s -- prevent sperm from joining with the egg by either damaging the sperm or creating a hostile environment for it. A 2011 study analyzed cervical cancer rates among women from 11 countries who had used an IUD and among women who hadn't. Women who had a history of IUD use had half the risk of developing cervical cancer as women with no IUD use, regardless of whether the use was for 10 years or only one year. There was no difference in HPV infection rates between the two groups, so obviously some other factor was involved.

The recent study you mention was a review of 16 studies exploring the link between cervical cancer and IUDs. The studies were from the 1980s and 1990s, and three of them were performed in the United States. Overall, cervical cancer rates were 30 percent lower among women using the device compared to nonusers. Keep in mind that the finding was a correlation and so does not prove that IUDs actually lower the rate of cervical cancer. But the authors surmised that the reason IUDs could potentially reduce the risk of cervical cancer is because insertion of an IUD causes an inflammatory reaction that increases the immune response in the cervix. This could lead to the clearance of the human papilloma virus.

The results of another study, one that followed 676 sexually active women in San Francisco from 2000 to 2014, conflict with this theory. The average age of the women at the beginning of the study was about 18. The women were routinely tested for HPV, and 85 of them used an IUD at some point during the study. No benefit was seen in either the acquisition or the clearance of HPV in women using an IUD. The authors of this study wondered if IUDs decreased the incidence of cervical cancer by somehow clearing precancerous lesions in the cervix.

In conclusion, I'm not certain that getting an IUD for the purpose of decreasing cervical cancer risk is necessary. It seems even less necessary if you have had multiple negative HPV tests and Pap smears. Nonetheless, for women making an initial birth control choice who are weighing the risks and benefits of an IUD, these studies may be an influencing factor.

(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.)

Welcome to part two of our discussion about high blood pressure. For those who missed it, a previous column examined new blood pressure guidelines released by the American Heart Association and the American College of Cardiology, in which normal is now a range below 120/80. It's a conservative definition that puts people with blood pressure in the range of 120-129/80 into the "elevated" category. This is not a diagnosis of high blood pressure, or hypertension. Rather, it's a warning sign that, without certain lifestyle changes, hypertension may well be in your future.

Now we'd like to expand on the techniques that can be helpful in getting better numbers.

-- Lose weight: Weight gain increases body mass, which means the heart has to pump harder to deliver blood throughout the body. At the same time, that increase in body mass offers greater resistance and results in elevated blood pressure. Studies show that a weight gain of even 5 pounds can cause blood pressure to rise.

-- Stop smoking: Not only do smokers face double the risk for stroke and heart attack as nonsmokers, they are also at increased risk of a range of cancers. In addition, the nicotine and other substances in cigarettes and other tobacco products make blood pressure go up.

-- Exercise regularly: Exercise strengthens the heart and makes it more efficient. Regular physical activity like brisk walks, cycling, swimming, dancing, hiking or active sports can lower your top (systolic) blood pressure number by four points. That's on par with what blood pressure medications will do. Aim for 150 minutes per week of moderate aerobic activity, or 75 minutes of vigorous activity.

-- Watch your diet: When it comes to food, the DASH diet (Dietary Approaches to Stop Hypertension) is a good guide. Not only does it naturally limit salt intake, but it also incorporates a healthful range of foods into your life. These include fresh fruits and vegetables, whole grains, legumes, nuts, lean proteins, limited saturated fats and limited amounts of sugar. You can get full details at: https://www.nhlbi.nih.gov/health-topics/dash-eating-plan.

-- Cut back on salt: New research suggests the relationship between salt and blood pressure is more complex than previously understood. Still, hidden salt in processed food means many Americans are getting far too much sodium. Switching to fresh foods and the rest of the DASH diet recommendations can make a difference.

-- Limit alcohol: Although we still don't know exactly how or why, drinking alcohol raises blood pressure. If you're a regular drinker, quitting can lower your top blood pressure number by several points.

-- Cut back on caffeine: As with alcohol, the mechanism behind the brief blood pressure spike that accompanies caffeine intake isn't fully understood. If you're looking to lower your blood pressure, though, we recommend cutting back on or quitting caffeine.

-- Reduce stress: Easier said than done, we know. But regular exercise, meditation, breathing exercises, yoga, a daily nap or just a bit of quiet time to yourself can help relieve tension.

-- Keep track: Make note of your blood pressure readings to track which direction you're trending. The American Heart Association supports self-monitoring, which can be done with a home blood pressure monitor and in partnership with your primary care physician.

(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.)