Optimum Nutrition for Sport

  • 11 Apr 2013
  • Reading time 18 mins
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Sports nutritionist Jacky Hems, answers your questions.
Sports nutrition has changed in recent years and the days of carbohydrate-loading for endurance sports and high-protein diets for strength/resistance exercise is being replaced with the recognition of the need for a more balanced approach in both types of exercise. Many of the principles of good health and optimum nutrition can be applied to sports nutrition. The key additional element is adjusting these to achieve maximum performance, regardless of the level you are at when it comes to fitness and exercise. You may find that some of these adjustments conflict with what you have come to understand about healthy eating, particularly around the consumption of carbohydrates and insulin release. However, I will explain why these adjustments are important and help you to achieve the maximum benefits from your exercise programme. The requirements for sports nutrition will vary from person to person depending on the type, intensity and frequency of sport/exercise you do, your personal goals and biochemical individuality. So the following answers to our most frequently asked questions are based on general principles, with some examples to give you more guidance.

When and what to eat before and after exercise.
As well as knowing what and how much to eat, one of the most powerful differences you can make to your training regime is knowing ‘when’ to eat around your programme. Two of the leading authors on this subject are Ivy and Portman and in their book Nutrient Timing: the Future of Sports Nutrition (1) they describe three key nutrient timing phases – the Energy, Anabolic and Growth Phases. These are primarily focused on strength training but with a few adaptations can be applied to endurance training. Understanding the role of some key hormones released during and after exercise is important, as it alters what is best to eat, and when.

The Energy Phase – during a workout
This covers the period of a workout. During this ‘catabolic’ phase, when you are burning a high amount of energy, the main objective is to spare muscle glycogen (which is the muscle’s energy reserve) and protein to help reduce muscle fatigue and damage and enable faster recovery post-workout. If you’re exercising for an hour or more (e.g. intense strength training, marathon, triathlon, cycling), at around 10-20 minutes before you start have a drink/gel consisting of 30-60g high GI carbohydrate (glucose, sucrose or maltodextrin - fructose can cause digestive problems for some people) and add around one third of that amount whey protein (see Benefits of Whey Protein below for alternatives) for strength training. During exercise, for both strength and endurance training, continue with a ratio of around 3:1 carbohydrate to protein per hour of exercise (if you’re exercising for less time than this you shouldn’t need to supplement), with added electrolyte rehydration salts, vitamins C and E and magnesium. The amounts needed vary from person to person depending on the duration of your workout and your caloric needs. The following amounts are recommended by Ivy and Portman (1) High GI carbohydrate 20-26g Whey protein 5-6g Leucine 1g Vitamin C 30-120mg Vitamin E 20-60IU Sodium 100-250IU Potassium 60-120mg Magnesium 60-120mg with these quantities doubled for athletes over 75kg (Table 1: Ivy and Portman, Recommended Supplements for the Nutrient Timing System Energy Phase) On a practical level, unless you have time to make up your own formula, try a pre-made product available from specialist sports shops, health food shops and online. Obviously ratios and ingredients in bought formulas will vary and you may need to experiment to find a product that suits you. Not all contain vitamins and magnesium so you may want to add these. Some formulas contain creatine, which is crucial for powering muscle contraction. Look for natural products and avoid those that include artificial colours, flavours and sweeteners. Some ranges include soya, pea and hemp protein powders, as alternatives to whey. Having a combination of carbohydrate and protein during a workout has been, and still is, hotly debated, particularly for endurance athletes. However, in a study of a small group of cyclists given a placebo, carbohydrate-only or carbohydrate-protein combination drink every 20 minutes during various exercises to exhaustion, those given the carbohydrate-protein combination achieved the highest level of aerobic endurance performance. In another small study looking at the effects of carbohydrate with and without protein during resistance exercise, the combination of carbohydrate and protein together lowered the rate of muscle protein breakdown compared to carbohydrate on its own, so I would recommend having a combination of both during exercise.

If you’re just starting out and haven’t tried drinks or gels before, an alternative is to eat a banana and a few nuts (around 30g) about an hour before you exercise. A note on the consumption of high GI carbohydrates and in liquid form – while in other aspects of nutrition I would not usually recommend this type of carbohydrate and would err on the side of caution with using liquid foods on a regular basis, sports nutrition is different. Simple carbohydrates are needed for faster absorption and delivery to the muscles and use less energy to do this than eating whole foods Moving on to hormones, here’s why they are important. Glucose is an essential energy source during this phase and the hormones glucagon and cortisol are responsible for increasing blood glucose through the breakdown of fat, carbohydrate and protein. Amino acids are also used up (particularly glutamine, and the branch-chained amino acids (BCAAs) leucine, isoleucine and valine). The ......

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