Dear Doctors: My boyfriend has been lifting weights at his gym. He’s working on getting stronger, and one of the trainers there suggested he start taking creatine as a supplement. I’ve never heard of that before. What is creatine, and what is it made out of? How does it affect your body?

Dear Reader: Creatine is a naturally occurring compound that our bodies use to help power the skeletal muscles. About half of our daily requirement is produced by the liver and kidneys. The other half is derived from dietary sources, primarily red meat, seafood and chicken, and to a lesser extent, dairy products.

Creatine is stored in the skeletal muscles, then used to help power high bursts of physical activity. It appears to be particularly effective in boosting anaerobic performance, including weightlifting and resistance training. It can also help the muscles and muscle groups that are used during a specific type of exercise to grow larger and stronger.

Numerous studies have shown that adding a creatine supplement to the daily diet can enhance an individual’s natural store of the compound. This can lead to modest, but still measurable, improvements to both athletic performance and endurance when engaged in high-intensity exercise. Research into creatine supplements also suggests they may play a role in helping to prevent use-related muscle injuries, support or even speed post-exercise recovery, and help the body to regulate temperature during exercise. All of this has led to creatine quickly becoming one of the most popular dietary supplements among athletes and others hoping to improve physical performance.

Another interesting aspect of research into creatine is the discovery that the supplement doesn’t produce the same effects in all populations. Instead, studies have found that people who are younger and in good health derive the greatest benefits. Also, these benefits, including muscle growth, were seen only when the individual followed a targeted and sustained training program.

Outside of the gym, creatine may have some useful clinical applications. Studies are looking into whether supplementation with creatine can help to slow disease progression in people living with Parkinson’s or Huntington’s diseases, aid in recovery from spinal cord injury, ease the effects of fibromyalgia and perhaps play a role in blood-glucose management, including in people living with diabetes.

If your boyfriend eats a well-rounded diet that includes a wide range of animal-based sources of lean, high-quality protein, he is quite likely getting enough creatine. However, because increases in intramuscular creatine concentrations can benefit athletic training, many athletes find it to be an attractive option. When used appropriately, creatine supplementation has proven to be safe and well-tolerated by individuals who are healthy and in good physical condition. Some people report experiencing water retention. Others, particularly those using it in large amounts, have occasional gastric distress. As with all supplements, it’s important to use a high-quality product, and to follow the guidelines for use. We always think it’s a good idea to check with your healthcare provider or a licensed dietician before adding any type of supplement to your daily diet.

(Send your questions to askthedoctors@mednet.ucla.edu. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctors: I am 84 years old and just got a new doctor. When I asked her about the prostate exam my previous doctor did every few years, she seemed dismissive, saying, “Oh, we don't do that anymore.” Is this a personal choice by the physician? I worry about missing an important diagnosis.

Dear Reader: The exam you are referring to is known as a digital rectal exam, or DRE. In men, it is used to examine the prostate gland. The prostate, which supplies seminal fluid, is part of the male reproductive system. It also plays a role in urine flow and helps in hormone production. Roughly the size of an unshelled walnut, the prostate sits in front of the rectum, just below the bladder. A healthy prostate is smooth and symmetrical, with a springy surface. Due to its location, it cannot be felt from outside the body.

During a DRE, the doctor feels the gland for possible anomalies. This includes areas that are hard or lumpy, the presence of nodules, areas of tenderness and evidence of enlargement. The procedure typically lasts less than a minute and, while it can cause discomfort, it should not be painful.

Due to the positioning of the prostate, a digital rectal examination only allows access to the back wall of the gland. Any abnormalities that are present in the central or forward portions of the organ cannot be felt via this method. For that reason, a blood test, called a PSA test, is also used as part of prostate screening.

PSA is short for prostate-specific antigen. That’s a type of protein that is produced by several types of tissues in the human body, including by the prostate gland. Elevated PSA levels can indicate the presence of cancer. However, advancing age, inflammation, infection and an enlarged prostate can also result in higher PSA readings. So can recent ejaculation and certain medications. For this reason, elevated PSA levels are not considered to be an automatic indicator of prostate cancer. Rather, they signal the need for further investigation to determine the potential causes for the reading.

Although a PSA test can flag the presence of cancer that may not be discovered in a digital rectal exam, the opposite is also true. Some types of prostate cancer don’t cause a rise in PSA, and if they are located at the back of the gland, may be detected during a DRE. That has led some doctors to always use both types of screening.

It’s disappointing your new doctor failed to fully explain her position regarding the use of DRE. It left you feeling dismissed, which damages the patient-doctor relationship. However, we don’t think she was acting on her personal preferences, but rather on her understanding of the latest screening guidelines. We urge you to broach the subject with her again. Keeping in mind important factors such as your age, general health, medical history and family history of cancer, the two of you can find the best prostate cancer screening for your specific situation.

(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’m a 33-year-old woman in good health. The problem is that I got into some bad habits during the pandemic and gained weight. I’m back on track with diet, and now I am adding exercise. I remember reading that the time of day that women exercise makes a difference. Is that true?

Dear Reader: We think you’re referring to the results of a study that made headlines last spring. The findings are intriguing in that they suggest that the optimal time of day to exercise may be different for women than it is for men.

The 12-week study, which was published in the journal Frontiers in Physiology, included results from 27 women and 20 men between the ages of 25 and 55. All were in good health, had comparable body mass indexes and were already physically active when the study began. The participants were randomly divided into two groups. Each group followed the same exercise regimen, which included stretching, endurance exercises, resistance training and interval sprints. They also all ate the same diet, and at the same times of day.

The only difference between the two groups was the time of day at which they were asked to exercise. The morning group worked out for an hour and ended their sessions by 8:30 a.m. The evening group also exercised for one hour, but between 6 and 8 p.m. Over the course of the study, the researchers took regular blood pressure readings and measured changes in body fat percentage. An assessment of each person’s strength, aerobic capacity and flexibility was made at the start and the conclusion of the study.

At the end of 12 weeks, each of the participants saw an increase in athletic performance, as well as improvements to measures of general health, including body fat percentage and blood pressure. But the results included a surprise. It turned out that the women in the group who completed their one-hour exercise sessions before 8:30 a.m. burned more body fat, particularly around the abdominal region, than did those whose workouts took place in the evening. The opposite proved to be true for the men. Those whose exercise sessions took place between 6 and 8 p.m. burned more body fat than their early-morning counterparts. Meanwhile, the women with the late-day exercise schedule saw greater gains in upper-body strength. They also reported improvements to mood, as well as to hunger and satiety, that were not seen in the morning group. For the men, improvements to mood occurred no matter when they exercised.

These results bolster the idea that time of day has an impact on exercise for women and men. However, this is a small study and can’t be considered conclusive. With such a fascinating outcome, we can count on seeing future research into the topic. What we do know for sure, thanks to numerous studies over the years, is that regular exercise is beneficial to both physical and mental health. That means the best time to exercise is whenever it fits into your day.

(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.)