Dear Doctor: I just read that full-fat milk isn't actually bad for you, and that it may even reduce the risk of stroke. That's just so different from what we've been taught. What's the deal?

Dear Reader: The results of emerging research in recent years suggest that some of what had been taken as fact regarding the adverse health effects of a range of dietary fats was incorrect. Among the tenets recently called into question is the theory that full-fat dairy products have a direct link to heart disease and stroke.

To understand how deeply this idea has taken root, just take a look at the cheese and dairy cases of your local grocery store. Offerings of nonfat and low-fat milk far outnumber those of whole milk. Ditto for the cream and half-and-half section, which is often dwarfed by a wide selection of fat-free creamlike products. The de-fatting trend has transferred to the cheese and ice cream aisles as well. It's fascinating to read ingredient labels and see the culinary (and chemical) gymnastics used to arrive at some of these low-fat products.

Heart disease is the leading cause of death for both men and women in the United States each year. Small wonder then that the study you're referring to, which disputes the long-held idea that dairy fat raises cardiovascular risk, made such a splash. What added to the collective double-take is that researchers from the Friedman School of Nutrition Science and Policy at Tufts University in Medford, Massachusetts, went on to report that in some instances, full-fat dairy products may even offer health benefits.

Published last summer in The American Journal of Clinical Nutrition, the study contradicts the most recent Dietary Guidelines for Americans. The current guidelines, which are issued by the federal Office of Disease Prevention and Health Promotion, urge Americans to choose dairy products that are low-fat or fat-free.

The study analyzed health data from more than 2,900 women and men aged 65 and older. Researchers began in 1992, with baseline measurements of participants' blood plasma levels of three fatty acids that are contained in dairy products. They followed the study participants for the next 22 years, including periodic rechecks of blood plasma levels. By 2014, a total of 2,428 of the study participants had died. Of those deaths, 833 were attributed to heart disease. However, according to the final analysis of the data, none of the three fatty acids that were the focus of the study were linked to the risk of total mortality. Even more surprising were results that showed participants with higher levels of fatty acids, which suggested higher levels of consumption of whole-fat dairy products, had a 42 percent lower risk of death from stroke.

As the study's authors point out, low-fat dairy products tend to have higher levels of simple sugars, which are now getting a closer look as a factor in cardiovascular disease. It will be interesting to see whether federal dietary guidelines shift as a result of this study, which was funded by the National Institutes of Health.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: My daughter is 16 weeks pregnant with her second child. Her father and I can tell that she's really feeling down, even though she's been trying to hide it. I thought that women get the baby blues after giving birth, not during pregnancy. Is there anything I can do to help her?

Dear Reader: We read and hear a lot about postpartum depression, a form of clinical depression related to the physical, emotional and hormonal changes that accompany childbirth. However, the changes to mood that take place during pregnancy itself, known as perinatal depression, are not nearly as well known. That's unfortunate because an estimated 14 to 23 percent of pregnant women experience some level of depression during pregnancy.

For most of them, it will go unaddressed. Some women say that having symptoms of depression during pregnancy, a time that popular culture associates with joy and anticipation, causes them to feel shame. For many, the physical changes that take place while carrying a baby can obscure the bigger picture of their mental health. That's because a surprising number of symptoms that are common to pregnancy, such as changes to sleep patterns, decreased energy levels, a loss of appetite and a drop in libido, are also common to pregnancy.

Whether it's due to a reluctance to admit to depression, or that the symptoms of the condition have been obscured, the end result is that a significant percentage of women who experience depression during pregnancy don't get help. This can be dangerous to the mother and her baby, and it can adversely affect her family as well. Regular prenatal care is important to the well-being of both mother and child. When someone is depressed, though, making and keeping a series of appointments can be overwhelming. The same goes for eating a healthful diet and getting proper exercise, both of which can take more attention and planning than someone who is depressed can muster on a daily basis. Depression during pregnancy can adversely affect existing relationships, such as with children and spouses. It can interfere with a mother's ability to bond with her new infant after birth, and it is linked to an increased risk of going on to develop postpartum depression.

The American College of Obstetricians and Gynecologists recommends that women get screened for depression at least once during pregnancy. However, anyone who suspects she is experiencing perinatal depression shouldn't wait for her health care provider to take the lead. In the case of your daughter, the fact that she hasn't been successful at hiding her underlying distress from the family makes it likely she realizes something is amiss.

One of the things you can do to help is start talking to her about it. Urge her to open up to her doctor, and if possible, offer to take her to the visit. When people are depressed, necessary self-care can often fall by the wayside.

Should depression be diagnosed, her doctor will discuss treatment options. These include individual psychotherapy, support groups, bright light therapy and, in certain cases, medication. The important thing is to start the conversation and let her know she won't be going through this alone.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: I am an 86-year-old female, and sometimes, about an hour after eating a meal, my blood pressure drops significantly, from a normal of 123/74 to as low as 93/47. When it happens, my lips tingle and get dry, and I feel "zonked" out, like I'm in some kind of a trance. What causes this? What can I do?

Dear Reader: What you've described is known as postprandial hypotension, which means that someone's blood pressure drops measurably in response to eating. (Postprandial refers to the time after a meal, and the "hypo" in hypotension refers to low blood pressure.) The condition is common in older adults and is estimated to be present to some degree in up to 30 to 40 percent of the elderly. It is also often found in people living with Parkinson's disease. Because the condition can lead to dizziness, falls and fainting, and in some cases can result in angina, stroke or heart attack, it's important that it be diagnosed and addressed.

Each time we eat, we require our circulatory system to reorganize and recalibrate its activities. That's because the tasks of digestion and absorption create the need for additional blood flow to the stomach, particularly the small intestine. To accommodate that need, blood vessels throughout the body that are not involved in the digestive system begin to narrow. This allows blood to be redirected to the stomach and small intestine, while still maintaining consistent blood pressure throughout the body. To aid in those dual goals, the heart beats faster. As the stomach and intestines complete their work, blood vessels dilate again, and the heartbeat returns to normal.

In people with postprandial hypotension, blood flows as needed to the digestive organs. However, the circulatory system doesn't respond with the appropriate measures. For reasons that aren't yet clear, the heart rate doesn't increase enough, and blood vessels do not narrow enough to compensate for the redirected blood flow. That results in a drop in blood pressure and the symptoms you described.

Since low blood pressure can lead to a loss of consciousness and a fall, as well as the more serious complications we mentioned earlier, it's important that you address this with your family doctor. It sounds as though you've been tracking your blood pressure with a home monitor, and your doctor will want to see those readings. She or he will also want to follow up with a definitive diagnosis, which entails a baseline blood pressure reading before a meal, and then up to two hours of post-meal blood pressure monitoring.

People who take blood pressure medications may be asked to make changes to how and when they take the drug. But please don't make any changes without your physician's input.

Lifestyle changes may include a pre-meal cup of coffee, as caffeine can cause an increase in blood pressure. A large glass of water before a meal has also been shown to be helpful. Diet may play a role too, as postprandial hypotension has been linked to meals high in carbohydrates. It's a good idea to track what you're eating and see if the food correlates to episodes of low blood pressure.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)