Research in high altitude climbers has suggested that supplementation with the amino acid leucine can help to boost fat burning whilst preventing loss of muscle tissue.
High altitude climbing can take its toll on the body, leading to muscle wastage as we burn energy.
The study, which was conducted on Mt. Everest climbers, adds to the evidence that the amino acid – which is found in many foods, dietary supplements, and energy bars – could help people to burn fat while sustaining muscle tissue during periods of food restriction.
Foods High in Leucine
Leucine is one of the 8 essential amino acids that needs to be supplied from dietary sources.
Evidences from several studies, on rats, suggest that leucine is involved in protein synthesis in the skeletal muscles. Leucine can also inhibit protein degradation in skeletal muscle and liver. Leucine is an important component of hemoglobin.
Leucine rich food sources include legumes such as cowpea and animal products such as beef and fish. Below are some food sources that contain leucine and estimates of their leucine content. The foods are ordered high to low leucine content.
- Mature Seeds, Raw
Beef, Top Round
- Peanuts, all types, Raw
Fish, Salmon, Pink, Raw
- Crustaceans, Shrimp, Mixed Species, Raw
- Nuts, Almonds
- Egg, Yolk, Raw, Fresh
- Chickpeas (garbanzo beans, bengal gram), mature seeds, Raw
The researchers, led by Dr Wayne Askew from the University of Utah, USA, pointed out that the findings could also help people at lower altitudes who want to lose weight while preserving their lean body mass, or who are elderly and don't eat or exercise enough to maintain strength.
Askew also predicted that consumers might one day see leucine-rich bars on grocery store shelves, especially at high-altitude locations, where high-altitude skiing and climbing activities are popular.
The research was reported at the 242nd National Meeting & Exposition of the American Chemical Society (ACS) in Denver.
The researchers explained that the extreme weather conditions, low oxygen levels, treacherous terrain and strenuous exercise during such climbs create a huge nutritional challenge.
Askew and co-workers explained that weight loss at high altitude is exactly the opposite problem that is on the minds of millions of people in the United States and other countries, who are trying to shed excess weight.
Climbers often cannot or do not eat enough calories, failing to replenish their bodies with important nutrients. They therefore lose both fat and muscle during climbs, which can endanger their strength and coordination.
"The significant part about this weight loss is that a disproportionate amount comes from the muscle mass," said Askew.
"This can be a problem on long expeditions at high altitude because the longer climbers are there and the higher they go, the weaker they get. The body breaks down the muscle for energy, so climbers don't have it available for moving up the mountain," he added.
In a pilot study of the feasibility of supplementing the diet of climbers with leucine, the research team studied 10 climbers for six to eight weeks as they ascended Mt. Everest to assess physiological benefits of adding leucine to the climbers' diets.
"We knew that leucine has been shown to help people on very low-calorie, or so-called 'calorie-restricted diets', stay healthy at sea level," said Askew.
"It's one of the components, the building blocks, of protein. But no one had tested whether leucine would help people stay healthy and strong at high altitudes, so we added leucine to specially prepared food bars that we gave to the climbers."
From base camp on Everest members of the research team measured expedition members' fat and muscle by using an ultrasound device placed on the skin.
The research suggested that the additional leucine may help to prevent the body from breaking down muscle tissue by promoting fat burning when the body was in short supply of energy.
The authors said that one finding that was apparent early on in the study was that the food item in which the leucine was delivered was critically important, noting that the climbers had difficulties consuming the three food bars per day that contained the additional leucine.
Askew stressed that the current findings are from a small pilot study to test the feasibility of leucine supplementation at altitude, so definitive conclusions of its benefits at altitude must await the results of more controlled clinical tests.
The researchers also said that they plan to improve the palatability of the leucine food vehicle in consultation with US military food product developers at Natick Research Development and Engineering Center and conduct a more controlled study at high altitude, possibly with the U.S. Army Institute of Environmental Medicine.