Many children are engaged in sport and some are very talented young athletes. Nutrition is important especially in growing children but are their needs further increased when in training?
Do children need sports nutrition?
A question I get asked very often is: “do children need sports nutrition”. As always the answer of the scientists is "it depends"... but let’s break down this question into a number of smaller questions:
Is the physiology of children fundamentally (or significantly) different from adults?
Do children have different nutrition requirements?
Should recommendations for children be different from adults?
Once we have answered those questions it should be possible to get to an evidence based judgement.
To start with the short answers:
Is the physiology of children fundamentally (or significantly) different from adults? No.
Do children have different nutrition requirements? Yes, especially protein requirements may be increased.
Should recommendations for children be different from adults? Largely no, the recommendations we have for adults are appropriate for children. Some of the advice is expressed per kilogram body weight and some take into account individual sweat rates and therefore any differences are already taken into account in the current recommendations.
Carbohydrate and fat
There may be differences in substrate use (preference for carbohydrate or fat as a fuel) between children and adults. Young children preferentially use fat as a fuel and the capacity to use carbohydrate tends to be lower. These differences in metabolism diminish throughout adolescence, especially in boys. Therefore, it appears that children may be less carbohydrate dependent, but the differences are probably to impact the practical recommendations. During prolonged exercise in adults, carbohydrate feedings has been shown to improve exercise performance and studies suggest that this is no different in children. The delivery of carbohydrates requires a gastro-intestinal system that can absorb carbohydrate well. During the early years of development, the gastro-intestinal system grows and the capacity to absorb carbohydrate improves. At the age of 5 good absorptive capacity is usually in place. Carbohydrate intake recommendations during exercise are dependent on exercise duration (as well as intensity). Children typically exercise for shorter durations and lower absolute exercise intensities, reducing the need for carbohydrate during exercise.
There may be differences in substrate use (preference for carbohydrate or fat as a fuel) between children and adults.
One of the main ways that children and adults lose heat is through the evaporation of sweat from the skin. As children have a higher ratio of body surface area to body mass (at the age of 8 years it is approximately 50% higher than that of an adult) it has been suggested that exercising children should be able to get rid of heat quicker than adults. On the other hand, sweat glands are less developed and therefore it may be difficult for children to sweat and get rid of heat. In practice, adults and active children seem to experience similar core temperatures, even when exercising at high temperatures.
The current guidelines for adults take into account sweat rate. If sweat losses are high and result in body weight loss that exceeds 2% body weight it is generally recommended to drink. Drinking behaviour should aim to reduce body weight loss to between 0 and 2%. Both weight gain and excessive weight loss should be avoided.