Sports nutrition is a constantly evolving field – we understand it better because of the outpouring of results from thousands of research studies that are conducted annually. Finding sports nutrition products and ingredients that have proven studies to support claims of performance enhancement and energy in this field can be challenging, as unsubstantiated claims typically cloud the marketplace. We will list and discuss products in this review that have human clinical trial data at improving energy, endurance and other sports nutrition goals.
Sports nutrition supplements typically contain carbohydrates, fats, proteins, vitamins, minerals, herbs, and sometimes plant extracts. Supplements can generally be classified as convenience supplements such as ready to drink supplements, energy bars and meal replacement powders. They provide a convenient means of meeting caloric needs, while also delivering performance enhancement supplements.
Performance enhancement supplements that have science behind them include ergogenic agents such as caffeine, guarana, creatine, green tea extracts, willow bark, Kola nut, Sida cordifolia, Citrus aurantium (bitter orange), calcium and sodium phosphate, thyroid stimulators, including guggulsterones, black pepper extracts, and ginger root.
Plant-based supplements that are used in formulations include Tribulus terrestris (puncture weed or caltrops) and Fenugreek seed extract (Trigonella foenum-graecum), extracts that stimulate the natural production or release of bound testosterone to free testosterone. Free testosterone is the only metabolically active form of testosterone.
Both Tribulus and Fenugreek seed extracts have been marketed to promote greater gains in strength and muscle mass during weight training with sufficient clinical trial data to prove their efficacy.
Dietary calcium has been shown to suppress fat metabolism and weight gain during periods of high caloric intake. Further, increasing calcium intake has been shown to increase fat metabolism and preserve thermogenesis during caloric restriction.
The role of sodium and calcium phosphate on energy metabolism and exercise performance has been studied over several decades of research. Phosphate supplementation may influence metabolic rate possibly by affecting thyroid hormone levels. Phosphates could serve as potential thermogenic nutrients in supplement formulations.
Phosphates are formed during the Krebs cycle for energy production. Each turn of the Krebs or Citric acid cycle generates one guanosine triphosphate molecule which has a high-energy phosphate bond, stored energy that can then be broken to release energy for the cell.
Other Krebs cycle intermediates that have been used in sports nutrition include creatine phosphate, alpha-keto glutarate (AKG), sodium pyruvate and ethyl pyruvate. Creatine supplementation has, by far, the largest clinical trial documentation at increasing energy and enhancing athletic performance, although there is evidence that it loses its efficacy after long term use.
Green tea is believed to increase energy expenditure by stimulating brown fat (adipose) tissue thermogenesis. Green tea supplementation in combination with caffeine increased 24-hour energy expenditure and fat utilization in humans. The thermogenic effects of green tea supplementation depend on the synergistic effects of the caffeine and EGCG (epigallocatechin gallate) contents.
Other reported sports nutrition extracts include Rhodiola rosea, Eleutherococcus senticosus (formerly called Siberian ginseng) and Schizandra chinensis (Schizandra dried berries or extracts). These are all classified as adaptogens, since they allow the plants that produce them to survive in the Siberian tundra, where freezing and drought conditions occur on a regular basis.
These extracts are also called Russian adaptogens. The clinical trial data was compiled by Russian scientists beginning in 1947 through the 1970’s, but Western clinical double-blind or placebo-controlled standards were not used, which makes the data obtained from the studies of questionable value.
Schizandra chinensis does have the most compelling clinical data – it acts as a central nervous system stimulant or ergogenic agent. The effects after two months of use diminish, according to some of the Russian studies.
Forskolin is a plant native to India that has been used for centuries in traditional Ayurvedic medicine primarily to treat skin disorders and respiratory problems. A considerable amount of research has evaluated the physiological and potential medical applications of Forskolin over the past 25 years. Forskolin has been reported to increase cyclic AMP and thereby stimulate fat metabolism and is used in some sports nutrition formulas.
St. John’s Wart, Kava, Ginkgo Biloba, Ginseng, and L-Tyrosine are believed to serve as naturally occurring antidepressants, relaxants, and mental stimulants and are often included in sports nutrition formulas.
Garcinia cambogia dried fruit rind contains between 10% to 50% Hydroxycitric Acid (HCA), a nutrient that increases fat oxidation by inhibiting citrate lyase and new fat cell formation (lipogenesis).
There is sufficient clinical trial data to support its inclusion in sports nutrition formulas, the calcium salt being the most metabolically active form of HCA.
New products are continually being introduced and marketed in the sports nutrition arena, which is rapidly growing because of health awareness and other factors. The consumer needs to be aware if the new or existing sports nutrition products are based on human clinical data to support their energy or performance enhancement claims.
