Dear Doctor: I'm only 22 and already I've gotten whiplash from all the studies about coffee. First it's bad for you, then it's good. Then, oops, no -- it's actually bad. My girlfriend's a serious coffee drinker, and she's thrilled about another new study that says coffee's going to help her live longer. Is that right? How do we know what to believe?

Dear Reader: We agree that the back-and-forth about coffee over the decades has been confusing and for coffee drinkers who want a final answer, frustrating. Part of this is because of the nature of ongoing research, which, as it asks new questions, incorporates the newest data. Add enough variables to any line of inquiry, and chances are quite good that the conclusions will shift, if not change.

Another factor that plays a role is the study itself. Many of the coffee studies, including this latest one, have been observational studies. That means that researchers gather data from large populations, identify and account for lifestyle or environmental factors that could sway results, then analyze the resulting data to draw conclusions. When they're finished they have a correlation, but not a definitive cause. That doesn't mean such studies should be discounted. Far from it. It was through observational studies that researchers first linked smoking to lung cancer. This in turn led to the more rigorous and targeted research that revolutionized how we view tobacco and tobacco products.

We suspect that coffee is the subject of so many studies for a couple of reasons. First, it's so widely consumed. Here in the United States, it's our favorite beverage. We drink more coffee than soda, tea and juice combined. Plus, thanks to its caffeine content, coffee is a stimulant. In fact, caffeine is the most widely consumed physiological stimulant in the world. That's why, with regular use, it can result in a mild form of physical dependence. In addition, caffeine has been associated with adverse side effects in some individuals, such as temporary spikes in blood pressure. All of this -- widespread use, potential physiological effects, as well as the numerous bioactive compounds that it contains -- have made coffee a prime target for research. Which brings us to the new study now making headlines.

Researchers in Britain looked at a decade's worth of health data for about 500,000 adults who regularly drank from one to eight cups of coffee per day. This included brewed and instant coffee, as well as decaf. According to their analysis, those who drank coffee regularly had a slightly (emphasis is ours) lower risk of death than did non-coffee drinkers. Although the study didn't address questions of how or why, the researchers have cited coffee's complexity.

In addition to the caffeine that reels us in, coffee contains over 1,000 different chemical compounds, including B vitamins, potassium, magnesium, as well as hundreds of phytochemicals with antioxidant and anti-inflammatory properties. However -- and this is important -- if you're not already a regular or heavy coffee drinker, don't dive into the deep end with a multi-cup habit. And when it comes to pregnant women, the consensus is clear -- severely limit (or quit) coffee. That's because the enzyme needed to metabolize caffeine is not present in the fetus.

(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’ve never really enjoyed exercise and have managed to get to a fairly healthy 58 without doing very much of it at all. But I just got remarried and my husband, who is pretty active, wants me to start some kind of fitness program. Really, at my age, what good will it do?

Dear Reader: We’re sorry to rain on your no-exercise parade, but your husband is on the right track. (Congratulations on your marriage!) It’s never too late to start to reap the benefits of a fitness program. It’s not that we don’t understand your wish to avoid it. Even the most ardent workout enthusiast has been faced with the twin challenges of physical discomfort and boredom. But we think half the battle when easing into a fitness program is choosing the right activities, then setting modest goals. Exercise comes in many guises and with some creative thinking and a bit of grit, we believe you can find an activity or two that you’ll enjoy enough that you’ll stick with it. But first let’s talk about why it’s a good idea.

We’ve all heard a lot about the psychological boost that exercise imparts, which is no small thing in this stressful day and age. Staying active also helps regulate body weight and contributes to overall good health. Now, new research shows that for people over the age of 50, a time of life when blood vessels start to stiffen up and hearts gradually begin to get less efficient, regular exercise can reverse these effects.

In a study published in January, researchers in Texas evaluated the hearts of middle-age adults, looking at how stiff the cardiac muscles had become. When the study participants were sorted by their degree of physical activity, it emerged that the heart muscles of regular exercisers were stronger and more supple -- and therefore effectively younger -- than those of either the sedentary individuals or those who exercised only occasionally.

Next, the researchers wanted to know what effect starting an exercise program later in life might have on the heart. To that end, they tracked two groups of previously sedentary individuals. One group began exercising for 30 minutes at least four times per week. The other started a program of balance and stretching. Two years later, tests showed that the hearts of the exercise group had become not just stronger but also more supple. The stretch-and-balance group did not reap the same cardiac benefits.

The idea that we can return our hearts to a more youthful state, even later in life, is an exciting one. The challenge is to find an activity (or activities) you’re willing to do at least four times per week and will stick with over the years. Brisk walks or hikes require only a pair of decent shoes. Mix it up with activities you may have enjoyed as a child, such as cycling, swimming, trampolining or skating. Working out with friends, your husband, or with music and books on tape helps make it all more interesting. Just be sure to start slow and take the time you need to ease into your new routine.

(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 love salty foods, always have, and I don’t have high blood pressure or heart disease or anything like that. But I did see a story recently that said high-salt diets can affect the brain. How worried should I be?

Dear Reader: Our attraction to salt -- researchers refer to it as “sodium appetite” -- has long fascinated everyone from scientists to philosophers to poets. At a physiological level, our bodies require sodium, which plays a key role in fluid balance, and in nerve and muscle function. As cooks (and eaters) know, adding salt to almost any food makes it taste better. And scientists in Australia recently identified specific pathways in the brain’s emotional center, which light up when salt is consumed, a reward system of sorts.

Yet as your question acknowledges, and as research has shown, too much salt in the diet puts you at risk of high blood pressure and heart disease. Now, a recent study from Weill Cornell Medical College, the research unit and medical school of Cornell University, has added the potential for cognitive impairment to woes caused by too much dietary salt.

When scientists fed mice a high-salt diet, the flow of blood to their brains declined, and the vessels that carried that blood were adversely affected. The mice also began to perform poorly on cognitive tests that, before this change to their diets, they had aced. What was particularly interesting was that, rather than this decline arising from a spike in blood pressure, it appeared to be tied to chemical changes in the brain that were prompted by an immune response in the gut. When the mice were returned to a normal diet, they regained the cognitive ground that they had lost. Whether this same scenario will translate to humans is not yet clear.

As for your own sodium consumption, we believe that even absent physical symptoms like high blood pressure, overdoing it with salt is not a good idea. And if you don’t really know how much salt you’re eating, then you’re like the majority of Americans. That may be why, according to the American Heart Association, most adults consume more than 3,400 milligrams of sodium per day, which is 30 percent more than the organization’s recommended maximum of 2,300 milligrams per day. A whopping 70 percent of that sodium comes from prepared and packaged foods and from restaurant meals. The rest comes out of the salt shaker.

We think it would be wise for you to begin to keep track of your daily sodium intake. Packaged and processed foods will have the numbers you need on their nutritional labels. To be accurate, be sure to pay attention to serving size as well. As of May 7, restaurants with 20 or more locations have been required by the Food and Drug Administration to provide customers with a range of nutritional information, including calorie counts and sodium content. And if you’re a home cook, track the sodium levels -- both in the ingredients you’re using as well as the salt you’re adding. Your body and maybe even your brain will thank you.

(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.)