Dear Doctor: I'm hearing a lot about the health benefits of a ketogenic diet, that it's great for weight loss and can even reverse diabetes. What is the diet, exactly? Are the claims true?

Dear Reader: The ketogenic diet, widely known as "keto," is an eating plan that switches an individual's main energy source from carbohydrates to fat. In its strictest form, 80 percent of calories come from fat, 15 percent from protein, and carbohydrates are limited to 5 percent of the total daily food intake. Considering that most Americans get about half of their daily calories from carbohydrates, 15 percent from protein, and about one-third from fat, keto basically flips the typical American diet on its head.

The name comes from the word "ketosis," the metabolic state that arises from this particular distribution of nutrients. When adequate carbohydrates are available, the body turns them into glucose, which it uses for energy. With carbs missing in action, the body switches to Plan B -- its stored fat. Burning that fat creates an energy source known as ketones. This shift takes place over the course of the first few days of limiting carbs to the 20- to 50-gram range. (Some dieters opt to jump-start the process with a 24- or 36-hour fast.)

People on a ketogenic diet eat mainly meat, fish, eggs, full-fat dairy, oils and low-carb vegetables, like leafy greens. Because of their high carb count, fruit, root vegetables, corn, grains, cereals and legumes don't make it onto the plate. Needless to say, pasta, rice, bread, and sweets become a thing of the past. In fact, with carbs restricted to about 20 grams per day, a single apple or banana will blow your carbohydrate budget.

While the extreme nature of the keto diet makes it sound like a fad, it was actually introduced in the 1920s to help children with medication-resistant epilepsy. Ongoing research suggests the diet may be neuroprotective, and scientists are looking into its potential to help patients with neurodegenerative diseases like Parkinson's and Alzheimer's disease.

You're right that the keto diet has been shown to improve glycemic control in people with Type 2 diabetes. Some patients do go on to reduce or even discontinue their medication. However, the diet's effect on blood chemistry can be extreme enough to require rapid adjustments in medication levels. People with Type 2 diabetes should not attempt it without a doctor's supervision. The diet is not recommended for people with Type 1 diabetes.

And while those on the keto diet experience rapid weight loss, they're also subject to constipation, electrolyte imbalances, nutritional deficiencies, poor mood and just plain boredom. Our main concern is the high fat content. Despite a dieter's best intentions to stick to good fats, the focus on high fat inevitably leads to excessive bad fat consumption. One of our patients wound up with LDL levels that doubled, which is never a good thing.

You've heard this from us before, but seriously, please check with your doctor before going keto. And if you do decide to give it a try, it would be wise to work with a nutritionist to craft the most well-rounded version of the diet possible.

(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 a 76-year-old woman who had a complete hysterectomy when I was 50. My daughters insist that I should still be seeing a gynecologist for cervical cancer screenings, including pelvic exams. Is this really necessary? I already see my family physician every six months for a checkup and blood work.

Dear Reader: Your daughters' confidence in this screening is understandable. Pap smears are an important part of primary care medicine, proven to decrease the rates of cervical cancer and related deaths. Years ago, physicians recommended annual Pap smears for every woman over the age of 21. Now, with the knowledge that cervical cancer is directly linked to HPV infection, doctors understand that screening intervals for Pap smears no longer have to be yearly. The U.S. Preventive Services Task Force now recommends Pap smears every three years for women ages 21 to 30, and both Pap smears and HPV tests every five years for those ages 30 to 65. These recommendations include shorter intervals if the Pap smear shows abnormalities or if the HPV test is positive.

Women who haven't had an abnormal Pap smear and whose HPV tests have been negative have a very low risk of developing cervical cancer after the age of 65. One reason for this is the low likelihood of acquiring a new HPV infection past that age. Many doctors -- including myself -- don't normally recommend Pap smears for women over age 65.

Women who have had a total hysterectomy, in which the cervix is removed, are even less likely to need a Pap smear. Some hysterectomies remove the uterus and leave the cervix, but that would have been highly unlikely 26 years ago. For that reason, I'm assuming that your cervix was removed. If so, you cannot develop a new cervical cancer. If your cervix showed cervical cancer before it was removed, then a Pap smear is reasonable to assess whether the cancer may have returned.

True, other cancers can sometimes be found on a pelvic exam, such as ovarian cancers, uterine and vaginal cancers, but not very reliably -- meaning pelvic exams yield little benefit. For instance, although the only good screening test for vaginal cancer is a visual exam of the area, because the incidence is low (1 in 100,000 women), the yield for screening is also low. Ovarian cancer is much more common, but has no good screening tests. A pelvic exam can sometimes detect an ovarian cancer, but not easily; the tumors are generally small and the ovaries' location makes finding them difficult. As for uterine cancers, they're typically found when a woman notes abnormal bleeding from the uterus.

When I started medical school, many physicians did yearly Pap smears and pelvic exams on women over age 65. As the science became clearer, the medical community has altered its thinking. Although some physicians still recommend yearly Pap smears and pelvic exams regardless of a woman's age, the practice is becoming increasingly less prevalent.

Unless you have one of the signs of cancer in the pelvic region, such as vaginal/uterine bleeding, abdominal bloating or pain or vaginal pain, you're correct: There's little use for a routine pelvic exam.

(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: How should chocolate be processed to preserve its healthful properties? I've read that a non-alkalizing process is better than an alkalizing process, but I don't understand the difference.

Dear Reader: Ever since studies revealed that chocolate can convey health benefits, a certain segment of the population (hello, fellow chocolate lovers) has been doing a happy dance. Researchers have found that biologically active compounds in chocolate, known as flavonoids, can lower cholesterol, prevent memory decline and reduce the risk of developing heart disease. (Cocoa is also a good source of potassium, magnesium and phosphorus.) But while the headlines simplified the findings to just plain "chocolate," the facts of the matter are a bit more complex.

Chocolate is the end product of a multistep process that begins with the colorful, podlike fruit of the cacao tree. Farmers harvest the cacao pods and separate the seeds from the fleshy (one reference we read used the word "mucilaginous") white pulp via a multiweek process of fermentation and drying. The seeds are then roasted and ground into chocolate liquor, a thick liquid comprised of cocoa butter and cocoa solids. From there, it's up to each manufacturer how this liquid will be manipulated, and how much sugar and other ingredients will be added to create the final product that we call chocolate.

Which brings us back to those flavonoids. They are a class of plant nutrient contained in most fruit and vegetables. Not only do they give our fresh food those bright colors, they're also powerful antioxidants that help boost the immune system and act as anti-inflammatories. One of the subgroups of flavonoids are flavanols, which are found in grapes, apples, berries, tea, red wine and -- here's why they're important to this discussion -- cocoa. And like many micronutrients, they can be damaged during cooking or processing.

Cocoa is naturally acidic, which can give the natural products a rough edge. Natural cocoa powder is basically a cocoa bean concentrate. It's light brown, slightly fruity and has a penetrating and bitter flavor. To take the edge off that bitterness, some manufacturers treat the cocoa with an alkalizing agent. Cocoa that has been alkalized is also known as Dutch-process.

This type of processing makes the cocoa powder darker, decreases the bitterness, and makes it smell and taste more "chocolatey." However, it does have a negative effect on flavanol levels. In some analyses, cocoa that had been alkalized had half of the amount of flavanols as did natural cocoa. So, if your chocolate intake is specifically for its health effects, then natural cocoas are the way to go.

Whether alkalized or not, pure cocoa is extremely bitter. To make it palatable, chocolate products are highly processed. In addition to fermenting, roasting and alkalization, all of which can reduce flavanol levels, cocoa is combined with sugar, fat and various milk products. The result are foods whose fat and sugar levels may outweigh whatever advantages the flavanols would confer.

Bottom line? Despite its purported health benefits, chocolate is not a food group. (Sorry, chocoholics.) Instead, think of it as a condiment. Go for the darker, less processed varieties, and just enjoy a square or two at a time.

(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.)