Space nutrition: Resveratrol could be key to preventing muscle loss in astronauts exploring Mars

19 Jul 2019 --- As the pioneering space race hurtles forward, a NASA-funded study conducted by Harvard researchers is proposing supplementing astronauts with a nutritional compound commonly found in grape skin and blueberries, resveratrol, as a means of preserving muscle mass and strength. Published in Frontiers in Physiology, their study shows that resveratrol substantially preserves both muscular attributes in rats exposed to the wasting effects of simulated Mars gravity.

Mars is about nine months from Earth with today's tech, NASA believes. To allow astronauts to operate safely on long missions to Mars - whose gravitational pull is just 40 percent of Earth's - mitigating strategies will be needed to prevent muscle deconditioning.

Out in space, unchallenged by gravity, muscles and bones are prone to significant weakening. Weight-bearing muscles, such as the soleus muscle in the calf, are hit first and worst, the researchers note. “After just three weeks in space, the human soleus muscle shrinks by a third,” Dr. Marie Mortreux, lead author of the study at the laboratory of Dr. Seward Rutkove, Beth Israel Deaconess Medical Center, Harvard Medical School, tells NutritionInsight. “This is accompanied by a loss of slow-twitch muscle fibers, which are needed for endurance.”

The calf muscles are especially prone to significant weakening in space. Dietary strategies could be key, especially since astronauts travelling to Mars will not have access to the type of exercise machines deployed on the ISS, adds Dr. Mortreux. 

Resveratrol has been widely investigated for its anti-inflammatory, anti-oxidative, and anti-diabetic effects. "Resveratrol has been shown to preserve bone and muscle mass in rats during complete unloading, analogous to microgravity during spaceflight. So, we hypothesized that a moderate daily dose would help mitigate muscle deconditioning in a Mars gravity analogue, too."

Galactic space rats
To mimic Mars gravity, the researchers used an approach in which rats were fitted with a full-body harness and suspended by a chain from their cage ceiling. "Resveratrol has been shown to preserve bone and muscle mass in rats during complete unloading, analogous to microgravity during spaceflight. We hypothesized that a moderate daily dose would help mitigate muscle deconditioning in a Mars gravity analogue too," says Dr. Montreux.

A total of 24 male rats were exposed to normal “Earth” loading or 40 percent “Mars” loading for 14 days. In each group, half received resveratrol (150mg/kg/day) in water, while the other group was given only water. Both groups were prescribed the same food diet.

Calf circumference and front and rear paw grip force were measured weekly, and at 14 days the calf muscles were analyzed. Results of the experiment were as expected, the researchers note. The “Mars” condition was found to have weakened the rats’ gripping power and shrank their calf circumference, muscle weight and slow-twitch fiber content.

Notably, resveratrol supplementation almost entirely rescued front and rear paw grip in the Mars rats, to the level of the non-supplemented Earth rats. Furthermore, resveratrol completely protected muscle mass (soleus and gastrocnemius) in the Mars rats, and also reduced the loss of slow-twitch muscle fibers, which sustain endurance. 

Resveratrol was not found to have affected food intake or total body weight of the rats.

The researchers acknowledge that further consideration must be given to the differences in the physiological makeup of rats and humans, which was not a focus of the study. “Rodents, and particularly rats, are a good physiological model to study humans but they are not perfect,” says Dr. Montreux. “However, previous research highlights that in both humans and in rats, hypokinesia led to insulin resistance, and microgravity or unloading yielded similar results.”

Perfecting the doseResveratrol supplements are usually in doses of 500 or 1000mg. 
When asked about adequate dosing strategy for resveratrol, Dr. Monteux notes that natural sources of resveratrol are good but not sufficiently concentrated to provide the same benefits outlined in the study. “The dose given to my animals is equivalent to a dose short of 1500mg/day for a 60kg human. However, since resveratrol has been around for quite a while, you can find it over-the-counter in the form of dietary supplements. Most of the pills are dosed at 500 or 1000mg, so the nutrient is very easy to obtain using this source,” she explains.

“In red wine, the effects of alcohol would outweigh the benefits of resveratrol and we can’t solely rely on that, unfortunately,” she concedes.

Previous research on the impact of resveratrol on insulin can partially explain the benefits of resveratrol, says Dr. Mortreux. "A likely factor here is insulin sensitivity. Resveratrol treatment promotes muscle growth in diabetic or unloaded animals by increasing insulin sensitivity and glucose uptake in the muscle fibers. This is relevant for astronauts, who are known to develop reduced insulin sensitivity during spaceflight."

The anti-inflammatory effects of resveratrol could be a factor in conserving muscles and bones, and other antioxidant sources such as dried plums are being used to test this, she adds.

"Further studies are needed to explore the mechanisms involved, as well as the effects of different doses of resveratrol (up to 700 mg/kg/day) in both males and females. In addition, it will be important to confirm the lack of any potentially harmful interactions of resveratrol with other drugs administered to astronauts during space missions,” she concludes.

By Benjamin Ferrer