Dear Doctor: I love ham sandwiches -- and have one almost every day. I also have asthma, and just read that processed meats can increase the risk of asthma. How can this be?

Dear Reader: Meats have been cured -- that is, preserved and flavored -- since ancient times, largely through salting or smoking. Potassium nitrate and sodium nitrite salts were used to some degree in the Middle Ages, though the practice was not widespread. In the United States, these salts have been used to cure meat since 1925, and are highly effective in decreasing the incidence of bacterial disease. However, ingested nitrates and nitrites can form nitrosamines, which are carcinogenic.

Now comes a study, published last year in the journal Thorax, concluding that cured meats like ham increase the risk of asthma. The study enrolled 971 male and female participants from five cities in France. The enrollees -- not all of whom had asthma -- filled out a 118-item food-frequency questionnaire. Cured items included ham, sausage and dried sausage. Exposure was categorized as less than 1 serving a week; 1 to 3 servings per week; or greater than 4 servings per week. Participants reported the severity of their asthma over a 12-month period and scored this from 0 to 5, with 5 being waking up from sleep with an asthma attack.

At the beginning of the study, those who consumed more than 4 servings of cured meat per week were more likely to be men, were slightly more likely to smoke, were slightly more obese and had slightly lower educational levels. Those who ate more than 4 servings per week of cured meat were also more likely to be asthmatic and have more severe asthma at the beginning of the study.

After seven years, the participants filled out another survey regarding their level of asthma. Among those who ate less than 1 serving of cured meat per week, 14 percent reported increased asthma symptoms; among those who ate more than 4 servings of cured meat per week, 22 percent reported increased asthma symptoms. Noting that increased weight is also a factor for worsening asthma symptoms, the researchers adjusted for weight, smoking and educational levels -- and still found a correlation between worsening asthma and cured meat.

Oddly enough, two U.S studies have found that people newly diagnosed with chronic obstructive pulmonary disease were more likely to eat cured meats four to six times per week, but they did not find an increase in asthma risk. The cured meats here also included hot dogs and bacon.

As for why eating cured meat might worsen asthma, theoretically, nitrites can cause oxidative stress within the lungs and lead to more inflammation within the body, which can worsen asthma. While nitrates and nitrites may worsen asthma, I am not certain that they create asthma.

In addition, these studies did not separate meats cured by nitrites or nitrates and those cured by other means.

The take-home message: Stay away from meats cured with sodium nitrite or potassium nitrate. Not only are cured meats associated with greater obesity and increased asthma, meats cured with nitrites and nitrates increase the risk of cancer. If you don't have asthma and you don't smoke cigarettes, cured meats without nitrites and nitrates should be safe, but still, it's better to limit them. When you're shopping for smoked meats, make a close read of the food labels part of your pre-purchase 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 Readers: When we first began writing this column, we wondered how we would know if we were reaching anyone. The answer came almost immediately, via your letters, all of which are read. It has been heartwarming to learn that we have helped many of you, delightful to discover how studious and curious you are about science and medicine, and humbling to have you engage us at such a personal level about your health issues and your lives.

We quickly learned that some of our columns, in which we answer a specific question or discuss a particular topic, give rise to a host of new questions. Many of these can and will be answered in future columns. Some of the letters we receive are, unfortunately, so personal and specific that we are unable to address them. But even in these letters we often find a more universal question that can be useful to discuss in the future.

So far, the columns about veganism, shingles, postpartum depression, vitamin B12 and toenail fungus have sparked the liveliest discussions. Regarding the column about the specific nutritional needs of vegans, we received appreciative notes from families who are considering the move to a vegan diet. We were also taken to task for not congratulating the potential vegans who wrote to us for advice regarding their new direction.

The truth is, we are deeply appreciative of how engaged you, the readers, are in living the healthiest lifestyle possible. We celebrate every query that reveals an interest in a better life. We're thrilled when we can help and do our best to offer the most useful, well-rounded explanations and information.

In the future, we will revisit the question of shingles as well as the vaccine, delve deeper into the importance of vitamin B12, and explore the causes and cures of various types of anemia. An excellent question we received asked for advice on how to get the most out of the relationship with one's family physician. In an upcoming column, we will discuss what we do to create the most useful relationships with our patients, and how we strive to serve them.

Finally, the other category of letter we get is from individuals sharing some interesting and surprising solutions to the problems many of us face. This one came from a 94-year-old gentleman who was diagnosed with sleep apnea, which occurs only when he sleeps on his back. How to assure you don't roll over onto your back once you're asleep? His family doctor had an ingenious solution:

"As suggested by my doctor, my wife sewed a pocket on the back of my pajamas to hold an everyday tennis ball. It was easily removable for washing. Since then, I have slept very comfortably, but only on one side or the other. And no longer do I snore."

So thank you again for making this column part of your lives and for taking the time to write to us. We, in turn, will make responding to your letters part of ours.

(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: A new study said that working out too much could ruin your sex life. I like to be in shape -- but not at that high a price. What's the deal?

Dear Reader: Exercise is unequivocally good for men's libido. Compared with sedentary individuals, men who exercise regularly have higher testosterone levels, greater libido and greater fertility. But extreme exercise is not without risks. Hormones are complex, and although the body is adept at regulating them through feedback mechanisms -- a finely tuned system known as the hormonal axis -- that feedback can be disrupted. In women, chronic endurance exercise training can lead to disruption of the hormonal axis, which can affect their menstrual cycle and fertility. It can similarly disrupt men's hormonal axis, leading to testosterone levels at the lower end of normal. The question is: What degree of exercise leads to this disruption, and does the disruption lead to decreased libido?

The study you mentioned, published earlier this year in Medicine and Science in Sports and Exercise, attempted to answer this question -- at least among men. Male subjects filled out online surveys about their level of exercise and their level of libido. Data were gathered from participants who were healthy, free of hormonal disorders, not taking prescription medications, older than 18 and involved in sporting activities. The researchers' primary focus was those men involved in organizations associated with endurance running, biking or triathlons.

Of the men who filled out online surveys, 1,077 men met the overall criteria, with respondents answering questions about the total number of hours exercised per week and the level of exercise intensity. The researchers also separated the men into two groups: low libido and normal-to-high libido. Notably, there were considerably fewer men in the low-libido group: only 60 compared to 1,017 in the normal-to-high libido group.

In men reporting normal-to-high libido, 33.1 percent exercised 4 to 6 hours per week; 35 percent exercised 7 to 10 hours per week; and 22.2 percent exercised more than 10 hours per week. Conversely, in the low-libido group, 10 percent exercised 4 to 6 hours per week; 23.3 percent exercised 7 to 10 hours per week; and 65 percent exercised more than 10 hours per week.

Researchers also assessed level of intensity and how many years the participant had been exercising at that intensity. In the low-libido group, there were three times as many intense/prolonged exercisers than there were moderate intensity/duration exercisers.

So, yes, this study shows that males who exercised at a high intensity for many years had a lower libido than those with a more moderate track record. But keep two things in mind. One, the low-libido group consisted of only 60 people, so the power of the data is not strong. Two, 22.2 percent of men in the normal-to-high libido group exercised more than 10 hours a week; 65 percent in the low-libido group exercised that much. Unless you exercise more than 10 hours per week, every week, I wouldn't be concerned.

That said, if you're finding that your libido is low and you're exercising more than 10 hours per week, you might want to reconsider your priorities.

(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.)