Dear Doctor: I've been feeling a bit down lately, and I read that even one hour a week of exercise could reduce depression. How much exercise is optimal to reduce the likelihood of depression?

Dear Reader: We're very sorry to hear that you're struggling, but we are glad that you're open to the idea of physical exercise as a way to improve your mood. In addition to therapy and medication, a combination that offers relief to millions of Americans who suffer from depression or anxiety, studies continue to show that regular exercise can have a beneficial effect on mood and emotional well-being.

The idea of a sound body leading to a sound mind dates back to at least the ancient Greeks. In labs and think tanks throughout the world, scientists have been exploring the connection between exercise and mood for decades. Here in the United States, where health and fitness fads sweep through popular culture like clockwork, plain old exercise remains a constant among the more exotic (goat yoga) and outlandish (sauna suits) approaches that come and -- thankfully -- go.

The latest confirmation of the existence of the mind-body connection comes from a group of scientists who took a new look at data collected from more than 33,000 adults living in Norway. The study subjects, none of whom had mental health or physical issues, were followed for 11 years. During that time, researchers monitored the onset of depression or anxiety among members of the group. They also tracked physical activity.

Their finding that regular exercise had a positive effect on mood wasn't a big surprise. What was startling was just how little physical activity it took for the study participants to experience the mental health benefits.

According to the analysis of the 11 years of data, participants who exercised as little as one hour per week had a 44 percent lower risk of developing depression during the term of the study than the those who remained sedentary. On top of that, exercise intensity appeared not to play a role: Mild and moderate exercise was just as effective as strenuous workouts.

And while increased intensity and duration of physical activity do yield physical benefits, researchers concluded that when it came to protection against depression, mental health benefits leveled off beyond two hours of activity per week. The other interesting outcome of this second look at the data was that while exercise did offer a degree of protection against depression, it had no effect on anxiety.

If your next question is why just one hour of exercise a week can be beneficial to mental health, the authors of the study admit they don't know. But with such intriguing findings in an area of study that's important to millions of people worldwide, you can bet that follow-up research is already in the works.

In the meantime, the good news is that the data say we can benefit from as little as 10 minutes of exercise per day. That's a walk around the block, a couple of laps in the pool or a few flights of stairs at work instead of the elevator.

We hope you'll give it a try and, after a few months, will let us know how you're doing.

(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 friend of mine was diagnosed with, and treated for, anal cancer about two years ago. She never told me the location of her cancer until recently because she thought that "anus" and "anal" were shameful words. She also let the symptoms drag on for a year or so because she thought they were due to hemorrhoids. What are the symptoms, how is this type of cancer treated, and is it on the increase?

Dear Reader: In our everyday life, we focus on our usual responsibilities: our family, our job, paying our mortgage or rent, maintaining friendships, worrying about politics, etc. This complex existence often doesn't afford us time to deal with nagging symptoms. When those symptoms occur in a part of the body that people don't like to consider, like the anus, the likelihood of a delay in diagnosis increases.

Also, anal cancer is relatively uncommon, meaning people are unlikely to suspect the disease. Each year, it's diagnosed in approximately 8,200 people in the United States, leading to about 1,100 deaths; only about 0.2 percent of the population will be diagnosed with it over their lifetime. But to answer your last question: Even though the numbers are small, yes, the rate of anal cancer is increasing. Compared to diagnoses 40 years ago, the rate of anal cancer has increased three times in men and 1.7 times in women. As with cervical cancer, infection with the human papillomavirus (HPV) increases the risk, as does homosexuality (for men), anal sex and a history of anal warts.

As for symptoms, anal bleeding occurs in 45 percent of patients but, because hemorrhoids can similarly cause bleeding, people often can ignore this sign. Anal pain or a sensation of fullness in the rectum occurs in about 30 percent of patients, and 20 percent of patients have no symptoms at all.

In the 1960s, treatment consisted of the removal of the anus and the surrounding tissues, leading to a permanent colostomy, that is, a rerouting of the colon through an opening in the abdomen. Three percent of patients died from the procedure alone.

Today, treatment consists largely of radiation and chemotherapy. The radiation therapy is generally given in 25 treatments over a period of five weeks. The chemotherapy -- typically, 5-fluorouracil and Mitomycin (or cisplatin) -- is often given on the first and fifth weeks of radiation treatment. This combined approach has decreased not only the death rate from anal cancer, but also the need for a colostomy. Today, only 14 to 35 percent of patients need a colostomy after five years. Survival rates depend on the tumor size at diagnosis. The five-year survival rate ranges from 86 percent to 42 percent, depending on the severity of the disease.

Radiation, however, has side effects, potentially leading to more frequent bowel movements, flatulence and rectal incontinence -- as well as potential impotence in men and vaginal damage in women. Newer forms of radiation therapy using computer-controlled techniques and 3-D imaging can reduce some of these side effects.

It's a testament to your friendship that your friend was finally able to share her diagnosis with you. By seeking to learn more about anal cancer, you're not only showing concern, but also helping raise awareness.

(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 recently read that probiotic bacteria could protect newborns from sepsis. Does that mean I should be giving probiotics to my newborn?

Dear Reader: Sepsis occurs when the body's immune response to infection goes haywire and winds up injuring its own organs and tissues. The World Health Organization estimates that neonatal sepsis, a bloodstream infection in newborns, claims the lives of up to 1 million newborns each year. About 34,000 of these cases occur in the United States. Even among infants who are properly diagnosed and receive timely medical treatment with antibiotics, the mortality rate for sepsis can reach 60 percent.

In response to this heartbreaking health crisis, researchers in the U.S. and India looked to probiotic bacteria, which have proven effective in combating other types of infections in both infants and adults. Probiotics have been successful in treating necrotizing enterocolitis, a bacterial infection that results in the death of the tissues of the intestine. It's a condition that affects mostly newborns, and researchers hoped that probiotics could turn the tide of neonatal sepsis as well.

After screening and testing close to 300 strains of bacteria, the researchers settled on Lactobacillus plantarum, a microorganism with a well-documented history of safety in fermented foods. They combined the bacterium with food sources for its survival, known as prebiotics. The final product, known as a synbiotic, was fed for one week to the 4,500 or so healthy infants taking part in the trial. They were randomly selected from 149 villages in the state of Odisha in India, where sepsis is a major cause of infant death.

The idea was that by colonizing the newborns' intestines with these beneficial bacteria, the adverse organisms that cause sepsis would fail to flourish. Researchers then followed the medical histories of the inoculated babies, as well as a control group of healthy infants who did not get the synbiotic. The result was a 40 percent drop in the rate of sepsis and death from sepsis among the infants who ingested the synbiotic.

In addition, researchers noted that of the infants who took the synbiotic, infections of the lower respiratory tract were reduced by one-third. This exciting news suggests that synbiotics may promote immunity against infections other than those that arise within the gut.

While it took us just a few hundred words to sketch out the (very) basics of these studies, the trials themselves took a decade to complete. Now the scientists say they want to know whether these results can translate to premature infants, who face a host of medical challenges. They also want to expand the sepsis trial to other parts of the world.

As for whether you should begin giving probiotics to your own baby, the science is young and many outlandish claims are being made. The American Academy of Pediatrics has thus far weighed in with a "not yet." We believe this is something you need to discuss with your pediatrician, and move forward only with his or her guidance.

(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.)