What Sunita Williams learned about health while in space

Image courtesy of NASA

For Sunita L. Williams and her fellow astronauts aboard the International Space Station, daily exercise was not only good for general health – it was essential to prevent their bones and muscles from deteriorating.

Without the constant pull of Earth’s gravity, Williams said, “your body says it doesn’t need this anymore, and bone density and muscle mass start to go away,” with the body going into “advanced osteoporosis.”

According to NASA, for every month in space, an astronaut’s weight-bearing bones lose 1 percent of density unless counteractive steps are taken. Muscles that constantly work against the force of gravity on Earth start atrophying in space. Even on Earth, lack of exercise can cause muscles to quickly waste away. Healthy young people can lose 0.5 percent of leg muscle mass daily during a short stay in bed, and hospitalized severely sick or comatose patients can shed 15 percent or more daily, according to an August 13, 2025 article in Current Opinion in Critical Nutrition and Metabolic Care.

Williams knows about the effects of zero-gravity on the body. She has spent a total of 608 days in space over the course of three missions and over 62 hours of space walking, a record for a female astronaut, according to her NASA biography. Her last trip to the International Space Station (ISS) launched on June 5, 2024, and lasted about 10 months, when NASA opted to have the Starliner craft that brought her and Butch Wilmore to the station return to Earth without a crew. The pair ended up staying until March 2025, and, as a result, Williams and Wilmore tied for sixth place for the longest time on a single space flight by a NASA astronaut.

Other Space Effects

Williams retired from NASA after 27 years on December 27, 2025. She spoke to Cape Cod Health News recently from a family member’s home in Falmouth.

On the ISS, Williams used a treadmill, stationary bike and weights for workouts – weights every day and the bike or treadmill every other day. “The bike is really good for cardiovascular health,” she said.

Even so, she said she struggled with agility, somewhat, after returning to Earth. “We don’t exercise every bit of our muscles” in space, she said, and the smaller muscles contribute to walking and daily activities.

“I’m still a little bit slow,” which, she joked, may be due to getting older. She’s 60, however, age didn’t keep her from running the Boston Marathon on Patriots Day (April 20) this year. She’s run the race before, including in 2007, when she completed the same 26-mile length aboard the space station, according to an April 18, 2026 story in Runner’s World.

Planned space flights to establish a base on the moon likely won’t have room for big exercise equipment as she used on the ISS, Williams said, but “when you get to the moon and Mars, you’ll have some gravity.”

In addition to exercise, Williams said she and her fellow astronauts took a daily multivitamin and vitamin D supplement while in space, which is essential for absorption of calcium to build bones. The body can make vitamin D when exposed to sunlight, but that wasn’t an option in the space station. They didn’t take calcium supplements, which are often suggested along with vitamin D to help strengthen bones, because she didn’t want to develop kidney stones. Medical treatment for that possibility wasn’t available in space.

Lessons for Earth People

While Williams and her fellow astronauts made an extra effort to maintain bone integrity while in gravity-less space, everyone here on Earth needs exercise to maintain healthy muscle and bone, said internal medicine specialist Sarita Bajracharya, MD, in a separate interview. She said the practice is essential for some people, including:

• Post-menopausal women and those with premature menopause or certain hormonal conditions.
• Older men.
• People with rheumatoid arthritis, osteoarthritis, etc.
• Those taking corticosteroids.
• Anyone “limited in their ability to move around.”

Although 150 minutes of exercise spread throughout a week is advised for most adults, the duration and intensity should be tailored to an individual’s ability, said Dr. Bajracharya, who practices at Primary Care Internists in Hyannis. Workouts should begin with light or moderate effort to avoid injury and gradually increase in intensity. Gait and balance exercises can be very beneficial for anyone at risk of falling, she said. People with cardiovascular disease, COPD (chronic obstructive pulmonary disease) or other chronic conditions should first check with their doctor. They may need medical clearance and may benefit from cardiac rehabilitation programs or pulmonary rehabilitation programs before beginning an unsupervised exercise program.

“Also make smart goals. Are you going to walk the dog? Walk with a neighbor? How many times a week? How long will you walk each day?” she said.

The main point is to move as much as is safely possible, she said. “Younger patients can get in the regimen of exercising every day” to lower their risk of obesity, diabetes and high cholesterol, she said.

Getting outside has other health benefits, such as enjoying the weather and improving mood, Dr. Bajracharya said. Going to a gym, YMCA, community center or senior center for regular exercise classes two to three times weekly can boost physical and mental health, as it provides opportunities to socialize. These facilities may offer special classes such as water aerobics or tai chi, she noted. Even some area hotels open their pools in the off-season for residents to exercise.

For more information on exercise, she recommends patients check the American College of Sports Medicine website. Its Rx for Health Series lists appropriate exercise programs for various age groups and health conditions.

Proper nutrition is necessary to ensure adequate intake of calcium and vitamin D to limit bone loss as people age. Dr. Bajracharya recommends that adults get 1,200 mg of calcium and 800-1,000 mg of vitamin D daily, both of which can be obtained through a healthy diet as well as through over the counter supplement if dietary intake is inadequate.

“It’s always better to get it from natural sources,” she said.

She urges patients to go onto the Bone Health and Osteoporosis Foundation’s website, which lists food sources of these two nutrients, as well as tips to help people determine if they’re getting enough in their diet, such as checking food labels. Don’t go overboard with calcium supplements, she cautioned, because excess calcium could possibly deposit in cardiac blood vessels or form kidney stones.

Williams’ Next Mission

In retirement, Williams said she plans to spend time speaking to school children to promote STEM (science, technology, engineering and mathematics) education and related careers that will be needed for the future of space flight. She also wants to push the idea of collaboration across borders to solve problems.

“Kids all over the world are connecting” through the internet, Williams said.

The former astronaut said she became familiar with Cape Cod when her family traveled through Falmouth on their way from Needham to vacation on Martha’s Vineyard. Her parents later moved to Falmouth when she was finishing high school.

During a brief question and answer session at the end of a Feb. 20, 2026 Falmouth Forum presentation she gave in Woods Hole, a young woman gushed how all of her classmates in her native India learned about Williams in school. Williams also has an elementary school named after her in Needham. Such recognition and fandom are “super humbling,” she said.