When Suzanne Martignoni skips her Vitamin D, she can tell.

With historically low levels of the vitamin in her body, plus the impact on her of seasonal affective disorder (SAD), the 48-year-old from Newton, Massachusetts, finds herself lacking the vigor she usually has during the sunnier months of the year.

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“Taking my supplements helps a lot and, within a few days, I feel better,” the food marketing exec told LifeZette. “There’s a significant difference in my energy level. This weekend, I started them again, and I ended up getting a lot of big projects done and didn’t need a nap.”

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Martignoni’s extra energy falls right in line with vitamin D’s M.O. It boosts mood and boasts a laundry list of other health benefits, which may include a little extra “oomph” in exercise.

New research has found vitamin D supplements boost exercise performance.

A recent trial study presented by the Society for Endocrinology at its annual conference in Edinburgh, Scotland, found an increase in exercise performance and a lowered risk of heart disease through the use of vitamin D supplements.

Researchers from Queen Margaret University gave 13 healthy adults either daily doses of vitamin D or a placebo over a period of two weeks. The supplementing group ended up with lower blood pressure and lower levels of cortisol (the stress hormone) in the urine.

The group taking vitamin D also increased its stamina by cycling 30 percent further in an allotted 20 minutes, compared to a first go-around on the bike at the start of the experiment. As a bonus side effect, there were fewer signs of physical exertion.

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Vitamin D is considered the DIY of vitamins. It’s actually a hormone, which is created in response to sunlight by the skin. Of course, with sunlight coming in shorter quantities during winter months, we need other ways to get it. We get some through diets rich in oily fish, eggs, and enriched dairy products, but a supplement still is the best choice for many.

Before you pop extra D on the way to boot camp, though, there’s still work to be done about the study’s efficacy. Jeanett Tapia in San Diego, California, said this small pilot investigation is on the right track, but isn’t quite there yet.

“I’m glad more studies have been published on the role of vitamin D on muscle function,” she told LifeZette. “Muscle power increases significantly when vitamin D is supplemented. Individuals deficient in vitamin D have significantly lower voluntary muscle contractions, as well as lower electrically stimulated muscle twitching and muscle relaxation rates.”

Translation into layman’s terms, vitamin D is necessary for maintaining adequate muscle function during daily activities, never mind during a hard workout. The concept of its benefiting your cardiovascular system is also a no-brainer.

“Of course vitamin D levels affect heart health. The heart is a powerful muscle,” Tapia said. “Vitamin D deficiency is a risk factor for heart attacks, congestive heart failure, strokes, and conditions associated with cardiovascular disease, such as high blood pressure and diabetes from prior studies.”

But she stressed that until larger clinical trials are performed, health care professionals can’t claim that supplementing actually prevents a heart attack or heart disease.

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Rene Ficek, a registered dietitian and lead dietitian nutritionist at Seattle Sutton’s Healthy Eating, agreed.

“The research pointed out that vitamin D may reduce circulating levels of cortisol. Therefore, it could theoretically improve exercise performance and lower cardiovascular risk factors,” she told LifeZette.com.

High levels of cortisol have been known to raise blood pressure by restricting arteries, narrowing blood vessels, and stimulating the kidneys to retain water.

“Researchers set out to test this hypothesis, but this piece of research doesn’t hold much weight due to the size of the study. It’s hopeful this small study opens the door to other similar larger studies, so that a cause and effect can be detected,” she said.

With or without the controversial concept of improving exercise performance, there are still a number of benefits to vitamin D. When you need a boost, supplementation is the best route.