Dear Doctor: I’m a tea drinker, and I like it best when it’s steaming hot. My sister says drinking liquids that hot is bad for you, and that they can cause cancer. Is she right? Should I be worried?

Dear Reader: About three years ago, a report that classified drinking very hot liquids as a probable carcinogen made headlines around the world. The warning came from the International Agency for Research on Cancer, an arm of the World Health Organization. The finding arose from several observational studies that linked drinking very hot liquids to an increased risk of cancer of the esophagus.

The most common hot beverage in those studies was mate, a tea widely consumed in South America, Africa and Asia. Mate is traditionally served quite hot, about 149 degrees Fahrenheit, which is scalding. Drinking the same liquids in the studies at cooler or cold temperatures was not associated with elevated cancer risk.

The report received some pushback, which included the criticism that the studies it cited did not include precise temperature data of the drinks consumed by the participants.

Since then, findings from two newer studies have made similar connections between very hot beverages and esophageal cancer. In a report published last year in the Annals of Internal Medicine, the increase in cancer risk was seen mostly in drinkers of very hot tea who also smoked or drank alcohol.

The study analyzed the tea consumption habits of 450,000 Chinese adults over the course of almost 10 years. When consumption of very hot tea was combined with smoking and drinking, cancer risk was 2 to 5 times greater. The alcohol use associated with the increased risk was one beer, glass of wine or shot of hard liquor per day. Smoking was defined as one or more cigarettes per day.

Another study of 50,000 adults in Iran, published in the International Journal of Cancer in March, found that drinking two large cups of tea per day hotter than 140 degrees Fahrenheit resulted in almost double the cancer risk.

Cancer of the esophagus, which is the eighth most common cancer worldwide, is responsible for 500,000 deaths per year. Researchers suspect that very hot liquids irritate or damage the lining of the esophagus. This type of repeated injury likely leads to increased inflammation and leaves the delicate tissues vulnerable to damage from other potential carcinogens, including those contained in tobacco products and alcohol. Tobacco and alcohol use, acid reflux and being over 55 are also considered to be risk factors for cancer of the esophagus. This type of cancer is more common in men than in women.

When it comes to preferences for beverage temperature, Americans and Europeans tend to be more moderate than tea drinkers in Asia, South America and Africa. Considering that 80 percent of tea in the United States is consumed as iced tea, we suspect that added sugar may be as much of a health concern here as the temperatures of hot tea. Still, we think it makes sense to opt for cooler temperatures with any hot beverages in order to protect the hard-working tissues of the esophagus.

(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: Our granddad went through a really hard time after our grandmother died last summer. He turned into a hermit. Now he’s set on getting a dog, which our mom thinks is a bad idea because of all the extra work. But my brothers and I think a pet will help him be active and make him feel better. Who’s right?

Dear Reader: We’re sorry to learn of your grandmother’s passing and of your grandfather’s struggles without her. The loss of a spouse can be devastating. It’s not unusual for people to deal with grief by withdrawing from the world, a reaction that can all too easily become an ongoing habit.

When it comes to sharing a home with a dog, both your mom and you kids have valid points. There is no question that properly caring for a dog takes time and effort, to say nothing of money for food, pet supplies and the inevitable vet bills. But you and your brothers have a persuasive body of research on your side. A number of studies have linked pet ownership to a range of physical and psychological benefits. These include a positive effect on stress, blood pressure, depression and loneliness, to name just a few.

Now the results of a new study are shedding light on the benefits of pet ownership for older adults. In response to a poll conducted by researchers at the University of Michigan’s School of Public Health, pet owners reported that the many challenges of aging are made easier due to the pets in their lives. Researchers sent the online poll to about 2,000 randomly selected adults between the ages of 50 and 80, and about 65 percent of the group completed the poll.

More than half of all respondents reported owning a pet, and 55 percent of those said they had two or more pets in their homes. The majority of those pets (68 percent) were dogs. Almost half of respondents lived with cats and 16 percent reported having a small pet such as a hamster, bird or fish.

More than three-quarters of the pet owners said their animal companions eased stress, kept them active and helped them to connect with people. The positive effects of pet ownership were particularly evident among those who rated their own physical health as poor or fair. Seventy percent of those reported that the presence of their pets helped them cope with the physical and emotional symptoms of illness, and almost half said their pets helped distract them from physical pain. Close to 90 percent of all pet owners said that their animals helped them to enjoy life and made them feel loved.

At the same time, it’s important be clear-eyed about the challenges of pet ownership. About 20 percent admitted to financial pressures due to pets. And 80 percent reported that they had help in caring for their animals, which means you and your mom may have to pitch in if your grandfather does get his dog.

The findings from this poll should give your mom, you kids and your grandfather plenty to consider as the dog decision gets made.

(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 granddaughters are absolutely crazy about soccer. They’re constantly trying to outdo each other with their maneuvers, and now one is trying to learn to "head" the ball. But isn’t that dangerous, especially for girls?

Dear Reader: We’ve long been aware of the risk of head injuries posed by activities like football, rugby, ice hockey and boxing, where jolting physical contact is literally built into the sport. Now soccer, long thought of primarily as a running game, is also getting a second look. Although collisions with other players (and with the occasional goalpost) have been the most visible potential sources of head injury on the soccer field, new research confirms what many have suspected -- heading the ball takes a toll on the brain.

A study published last spring found that heading the ball -- in which a player deliberately moves into the path of a speeding soccer ball in order to control its trajectory with his or her head -- is responsible for a greater number of concussions than is contact with elbows, knees or feet. And according to a study published last summer, the adverse physical effects of that signature move are more pronounced in female soccer players than in their male counterparts.

The earlier study, published last April in the journal Frontiers in Neurology, gathered data from 308 active amateur soccer players, 78 percent of them male. Each player self-reported head impacts and any resulting symptoms during a series of two-week intervals. Players also underwent an in-person neuropsychological assessment during each two-week period. With a total of 741 complete data sets collected over the course of three years, researchers were able to correlate frequency of heading with reductions in attention span and reaction time. They found that working memory was also affected, but to a lesser degree.

The other study, published last July in the journal Radiology, found that heading the ball resulted in alterations to white matter in the brain. When this finding was broken down by the sex of the players, it was revealed that these alterations were more pronounced in the brains of the women in the study than in the brains of the men. White matter, which accounts for half of the human brain, is made up of millions of bundles of nerve fibers. Located beneath the gray matter cortex, they connect the different regions of the brain. The white color is due to myelin, a type of electrical insulation that coats the nerve fibers. Damage to white matter can interfere with the high-speed transmission of electrical impulses in the brain, which can result in impairment to sensory, motor and cognitive function. The researchers refer to this damage as "subconcussive head impacts," meaning that though these injuries don’t produce immediate or measurable symptoms, as concussion does, the effect can be cumulative and long-term.

Because the impact forces of heading a soccer ball come close to matching a helmet-to-helmet football tackle, U.S. Youth Soccer has banned the practice for players younger than 11 years old. You didn’t specify the ages of your granddaughters, but considering what’s potentially at stake, it’s probably a good idea to check in with their parents on the topic of heading.

(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.)