Dear Doctor: For years now, I've been trying to eat more fruits and vegetables, less meat and a whole lot of olive oil and mixed nuts. Now I'm seeing that one of the studies supporting this has been retracted. Can I go back to hamburgers and fries?

Dear Reader: The Mediterranean diet has been the focus of all sorts of attention in the decades (yes, decades) since it was first introduced. Based on the eating habits of people living in southern Italy, Spain and Greece in the 1940s and '50s, it's just as you outlined -- a fruit- and vegetable-forward diet with lean proteins, whole grains, and plenty of nuts, legumes and olive oil. First publicized in the mid-1970s, the diet really entered the public consciousness in the 1990s. That's when a spate of studies looking into the eating plan got a lot of ink, and diet books devoted to the concept began to hit best-seller lists.

In 2013, a large study in Spain randomly assigned 7,447 individuals to either the Mediterranean diet or to a low-fat diet. All were overweight, and all had risk factors for heart disease, such as smoking and diabetes. Although the study participants assigned to the Mediterranean diet faithfully followed the plan, those assigned to the low-fat diet tended to return to their normal eating habits. As a result, the study turned out to be as much a referendum on the modern diet as it was about the Mediterranean plan. After five years, researchers concluded that the Mediterranean diet lowered heart disease by 30 percent.

But did it? According to a recent analysis of the study by a scientist in England, it's impossible to know. That's because of two extremely important words in the description of the 2013 study -- randomly assigned. For the results of these types of studies to be free from bias, participants must be randomly assigned to the treatment option they will follow. Without absolute randomization, you can't be confident the resulting data is the effect of the treatment. And as you've probably already guessed, the English scientist discovered that the 2013 study did not, in fact, use absolute randomization. In some cases, entire villages were assigned to the Mediterranean diet. Although those participants all followed the same food rules, they also shared other important environmental factors that could affect their health outcomes. This was sufficient to derail the claim of randomization for the 2013 study, and to merit both a retraction and a rewrite by the New England Journal of Medicine in June.

The original takeaway of the 2013 study was that several thousand people had fewer heart attacks and strokes because they followed the Mediterranean diet. The new conclusion is several thousand people had fewer heart attacks and strokes and they followed the Mediterranean diet. In this study, the diet can no longer be cited as the specific reason for the health benefits.

Finally, regarding your question about burgers and fries, the answer is moderation. As an occasional treat? Probably fine if you're in good health. But as a dietary staple? Please don't.

(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 often do flashing lights cause seizures? Does it happen only in people with epilepsy? I ask because I recently saw a warning about flashing lights in the new "Incredibles 2" movie.

Dear Reader: While the idea that the makers of an animated children's film would issue a health alert to potential viewers sounds like an urban legend, that is indeed what happened with "Incredibles 2," the long-awaited sequel to "The Incredibles" from Disney. Specifically, several sequences -- in which the film's villain uses a strobelike weapon -- can act as triggers for a seizure for some people. The issue emerged the same day the film opened as discussions of the specific scenes spread on social media. Several blog posts written by people susceptible to seizures due to strobing lights also helped move the issue into the mainstream. According to one blogger, whose post on the topic went viral, "After last night, I can say that the movie is unlike anything I have ever seen before, in that the villain's weapon of choice can hurt not only characters on screen, but can also hurt the people in the audience as well. The weapon? Continuous sequences of rapidly flashing/strobing lights."

The condition is known as photosensitive epilepsy. It affects about 3 percent of those living with epilepsy, which is a disorder of the brain in which abnormal electrical activity can lead to a range of different types of seizures. In photosensitive epilepsy, lights that flash at certain intensities, in certain visual patterns, or with contrasting light and dark patterns, can act as triggers for a seizure. According to the Epilepsy Foundation, photosensitive epilepsy tends to be more common among children and adolescents, particularly those with generalized epilepsy and a type known as juvenile myoclonic epilepsy.

But other populations can be adversely affected by strobing lights and patterns as well. These include anyone who is prone to migraine or other headache disorders, people with vertigo, individuals with autism or ADHD, and those living with non-epilepsy seizure disorders. For these populations, the sequences of the film with the flashing lights -- one scene reportedly lasts for more than a minute -- may not cause seizures, but can lead to headache, nausea, balance issues, light sensitivity, loss of bladder control or general physical discomfort.

There is no cure for photosensitive epilepsy, and once a seizure or other physical reaction has started, there is no way to stop it. Therefore, it's to Disney's credit that, as soon as the issue with the strobe lights emerged, the studio sent out an advisory to all theaters showing the film. The theaters then posted prominent signs, and some even had their ticket takers issue verbal warnings regarding the potentially disruptive scenes.

If this sounds a bit familiar, it may be because back in 1997, an episode of a "Pokemon" cartoon that featured similarly strobing lights adversely affected nearly 700 children in Japan. Many of them wound up in hospitals, and the issue of photosensitive epilepsy moved from medical books to the front pages of newspapers.

(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: My husband and I are terrible at remembering to wear sunscreen. I don't like how it feels, and he just plain forgets. I recently saw an ad for sunscreen pills. Could they be an option?

Dear Reader: We hate to be the bearers of bad news, but no, sunscreen pills don't work. They have been marketed as dietary supplements that will allow your skin to (magically, it would have to be) ward off sunburn, reduce sun-related aging and even shield you from skin cancer. To paraphrase the Food and Drug Administration, there's no such thing as a sunscreen pill. The risks posed by unprotected sun exposure are serious enough that the FDA put out a statement in May debunking the claims of sunscreen pill manufacturers. It also sent out warning letters demanding that the companies hawking these pills stop their false advertising, which it said violates federal law. The specific companies mentioned in the FDA's announcement are Advanced Skin Brightening Formula, Sunsafe Rx, Solaricare and Sunergetic.

You're right to be concerned that you and your husband have been lax in the sunscreen department. From the instant the sun rises to the moment it sets, amid the spectrum of light that it emits is ultraviolet radiation. The wavelengths of UV rays are shorter than those of visible light, which makes them invisible to the naked eye. But the potential damage they can cause to unprotected skin is considerable.

UV radiation is broken down into UVA, UVB and UVC rays. (We don't hear much about UVC, the shortest of the three, because it gets absorbed by the Earth's ozone layer.) But UVA rays, which are the longest of the three and account for 95 percent of the UV radiation that reaches us on Earth, and UVB rays, which are slightly shorter, do a real number on our skin. UVA, in addition to causing the physiological changes that we call a suntan, penetrates the deepest. It plays a big role in premature aging, and more recent research shows that it plays a part in skin cancers as well. The shorter UVB rays give us sunburns and play a significant role in a range of skin cancers. Both types of UV rays can damage the skin's cellular DNA and thus give rise to genetic mutations that can lead to cancer.

All of this bad news about UV rays would be far more alarming if it weren't for the existence of sunscreens. Legitimate sunscreens are all applied topically. Each contains a mix of certain types of organic and/or inorganic chemicals, which either deflect, reflect, scatter or absorb the UV rays. All types of sunscreens need to be reapplied throughout the day because they either wear off through contact or perspiration, or, if they're absorbing the UV rays, their chemical bonds break down. The array of legitimate sunscreen products is vast.

We think that if you're willing to experiment, you'll find one you don't hate. Just be sure to choose a full-spectrum product that absorbs both UVA and UVB rays and choose an SPF of at least 30. Use sunscreen liberally and reapply often.

(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.)