US scientists have found that a nutrient found in shellfish and beets can boost athleticperformance when added to a sports drink.

Prior research from Exeter University in the UK has already linked beetroot juice with enhancing performance, thanks to its potent levels of nitrates, but now scientists are looking into a nutrient known as betaine.

Researchers at Ithaca College in New York found it can improve performance by nearly six percent when added to a sports drink, in either powder or tablet form.

"Betaine may contribute to creatine synthesis, which improves strength, power and short-term performance," said study lead Thomas Swensen. "Future research should elucidate the mechanism of how betaine supplementation improves performance."

Researchers recruited 16 university-aged cyclists, men and women, who were tested three times to measure how the sports drink and betaine beverage affected performance variables, such as maximum peak power.

Findings showed that one week of betaine supplementation increased peak and mean anaerobic power by 5.5 percent compared to baseline measures.

The team used the following recipe: dissolve 2.5 grams of betaine in a 20-ounce (591 milliliters) sports drink and drink half in the morning and half in the afternoon.

The study, announced last week, is published online in the Journal of the International Society of Sports Nutrition.

Another natural sports enhancer could be bananas. Last year, researchers found that snacking on bananas can boost endurance just as well as sports drinks.

The study was published in the journal PLoS ONE.