Dear Doctors: As a former NASA mission planner, I would signal a “no-go” for human colonization of the moon and Mars. The human body's functions cannot tolerate the long-term effects of a low-gravity environment. I assume, from your column about the effects of low gravity, you agree?

Dear Reader: You are referring to a column prompted by a reader's son, who became fascinated by the drama of two U.S. astronauts last spring. Their mission aboard the International Space Station (ISS) encountered technical difficulties, and their eight-day mission stretched into an unplanned nine-month stay. In that column, we explored how prolonged microgravity interferes with biological systems. It affects bone remodeling, fluid balance, circulation, red blood cell metabolism, vestibular systems and even going to the bathroom.

Space tourism -- and the technologies that make it possible -- have had rapid advances recently. So it’s more relevant than ever to study the health effects of space travel on the human body. Your own question happens to coincide with the release of new findings about the potential effects of spending extended time in microgravity. The journal Proceedings of the National Academy of Sciences published the study earlier this year. The study found that, following spaceflight, the brain shifts position in the skull.

In this new study, researchers used health data collected from 26 astronauts. Of those 26, 15 underwent preflight and postflight measurements of their brains. The study used existing preflight and postflight brain measurements for the other 11 astronauts. Brain scans showed that, absent gravity, the brain shifts upward and back in the skull. The researchers also noted that different regions of the brain migrated, independent of each other. These changes to the brain were in mere millimeters, but they still impacted both the motor and sensory regions of the brain.

Not surprisingly, astronauts with the longest stays in microgravity underwent the greatest changes. However, measurable brain movement was seen even in those who spent two weeks on the ISS. These shifts led to what the researchers referred to as “sensory conflicts.” For example, astronauts in space could have brief bouts of motion sickness or spatial disorientation. Back on Earth, balance issues could arise. Continued monitoring showed that the brain orientation of the astronauts in the study slowly returned to normal. For those with the longest stays, recovery could take up to six months.

As for a decision on colonizing the moon or Mars, we are relieved this decision isn't up to us. But experts like yourself appear to agree about several important things. One is that we need more research to understand how the human body responds to the rigors of space. The other is that the technology to keep people healthy so far from Earth is not yet in place. This includes things like artificial gravity and radiation shielding. We would also need autonomous medical care, mental health support and on-demand evacuation procedures. Experts in the field agree that until those gaps are closed, deep space missions, including long-term stays on the moon or Mars, will remain out of reach.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10960 Wilshire Blvd., Suite 1955, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

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Dear Doctors: When I was young, it seemed to be a regular practice that you would get your tonsils removed, though I still have mine. Why was that? Is it still the same now? What are the pros and cons of having your tonsils removed as a child?

Dear Reader: You are correct. From the early 1900s through the 1960s, tonsillectomies were common preventive care. As a frontline organ of the immune system, tonsils are prone to repeated infection. Before antibiotics and when antibiotics were still new, these infections were seen as a danger to health. To avoid repeated throat infections in children, surgery to remove tonsils became the go-to answer. The trend peaked in the late 1950s, with more than 1.4 million tonsillectomies done in a single year.

Tonsillectomies still take place today, but for more selective reasons. Part of the reason for the decline is that we now understand the role of tonsils in good health. Tonsils are two oval mounds, perched on either side of the throat. They are an important part of the immune system and lymphatic system. They guard the entrance to the respiratory system, trapping viruses and bacteria. They also act as a filing system to help guide the body’s future immune responses. They contain immune cells that sample incoming microbes and help build long-term immune memory. This is very important during childhood, when the immune system is on a steep learning curve. As antibiotics became more widespread and doctors grew more comfortable using them, medication clearly became less extreme than surgery.

Today, people have tonsillectomies for specific reasons, unlike in the past when they were almost a childhood rite of passage. In some cases, the tonsils can be too large for the throat and can interfere with breathing, particularly at night. This can lead to snoring and to obstructive sleep apnea. Sleep apnea is when breathing repeatedly stops and starts during sleep. It can be a potentially dangerous condition. Children who have frequent throat infections across multiple years may benefit from tonsillectomy. People who experience serious complications, such as infections that lead to abscesses, may also be referred for surgery.

Providers now evaluate the pros and cons of tonsillectomy on a case-by-case basis. The wide-ranging immune benefits of the organs often outweigh the difficulties of an occasional infection. Surgery itself carries risks, including pain and bleeding. Complications from anesthesia are also possible, though these are rare. The surgery has an uncomfortable recovery period. Depending on insurance, it can also be costly. Children with severe and frequent throat infections may experience stress from illness and miss school days. They can also have other problems from repeated antibiotics use. These may be cases where tonsillectomy is the best path forward.

The bottom line is we no longer view tonsils as useless, nuisance organs. But for some people in specific circumstances, tonsillectomy is still a solid and well-supported treatment.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10960 Wilshire Blvd., Suite 1955, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctors: I had always heard that it takes three weeks to get a new habit to stick, but now people are saying it's more like three months. Is that right? Last year, I made a resolution to stop eating sugar, and I'm still fighting (and losing) that battle. What makes new habits so hard?

Dear Reader: You have asked two very interesting questions that will take us in two somewhat different directions. The first is about the length of time it takes to lock into a new habit. We have an updated answer from newer research. The second opens a discussion of the differences between a habit and a behavior. That may seem like splitting hairs, but the definitions hold key clues to common roadblocks as well as strategies that can lead to success.

Let's start with the three-week timeline. It comes from an observation made in a 1960 self-help book. In this book, a plastic surgeon said that's how long it took for his patients to get used to their altered appearances. Not surprisingly, subsequent studies have found the time frame to be both longer and more fluid. That includes conclusions from researchers in Australia, who analyzed data from 20 studies conducted between 2008 and 2023. In those studies, 2,601 people between the ages of 21 and 73 reported their progress in trying to acquire new habits. These goals included exercising, flossing, taking vitamins, drinking more water and eating healthier. The researchers found it took between two and five months to develop a new habit, and that the actual time frame ranged from four days to nearly a year.

That brings us to an important distinction. A habit, such as flossing, is a single, repeatable action. Behavior change, like the one you are struggling with in quitting sugar, is more complex. When you look at it closely, a new behavior often requires a collection of new habits, which helps explain why it can be hard to adopt. Flossing, for example, is triggered by the clear cue of brushing your teeth. But reducing sugar means making a series of choices throughout the day. That creates many decision points where, depending on mood, stress level or social setting, it can be easy to relax or abandon the guidelines you have set.

With your goal to eat less sugar, it can be helpful to analyze your daily routine and pinpoint the potential stumbling blocks. These might include a morning coffee break, lunch with co-workers or late-night snacking. Choose the situation that feels easiest to change, and decide in advance on a different response. If you've been having a cookie with lunch, consider a baked good made with less sugar. Gradually reducing the portion size of a sweet treat also works. Break complex behavior into smaller habits, and then tackle those one by one. This makes change more manageable. Be sure to give yourself plenty of time, and grace if you falter, for a new behavior to become your new habit.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10960 Wilshire Blvd., Suite 1955, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)