Updated 02 February 2015

Should you be carbo-loading for a marathon?

There are countless tips on what you should eat in preparation for the Comrades, Two Oceans marathons and other ultra- and long-distance marathons around the world. With the new focus on low-carb diets, should you still be carbo-loading?


Preparation is the name of the game

As with all human endeavours there are probably hundreds of different tips and myths and superstitions that govern the months of preparation before a marathon and participation on the actual day of the event.

Noakes’s low-carbs or carbo-loading?

The rituals associated with dietary intake and hydration are legion and I would love to know how many athletes decided to follow Prof Tim Noakes new low-carb approach? Have you stopped eating a high carbohydrate diet, and have you banished carbo-loading before the race? Are you going to stock up on proteins and fats and drink only pure water? (Most energy drinks contain carbs.)

A balanced approach

In contrast to Prof Noakes's theories, I would like to introduce you to a more balanced dietary approach as suggested by my colleague G Attwell (2012). One of the major problems all endurance athletes, including the Comrades runners, have to cope with, is the increase in infections, particularly respiratory infections, associated with intense physical activity.

Research has shown that doing very intensive exercise tends to make the human body release stress hormones such as cortisol which can in turn reduce the body’s ability to fight off infections. A variety of studies conducted in the USA found that this challenge to the immune system can be prevented by ensuring adequate intakes of carbohydrate before, during and after intensive exercise - both during training and on the actual event day (Van Heerden, 2003).

According to Attwell (2012) and referring to the Comrades Marathon (the longest marathon event in the world that takes place in the South African winter) it makes it even more essential that runners prevent the stress-cortisol-immunity depletion-infection cycle.

Read: How Tim Noakes wants you to train?

She suggest that the following nutritional strategies can help all runners complete their marathon and also prevent them from falling ill with colds and flu afterwards:

a) A balanced diet

Use a balanced diet which provides adequate quantities of all the so-called macronutrients (proteins, fats and carbohydrates), plus micronutrients (minerals, vitamins and phytonutrients). Using a wide variety of different foods to achieve dietary diversity as recommended in the first and most important Food-Based Dietary Guideline (FBDG) for South Africans. If you eat a variety of foods you will achieve the balanced nutrition suggested above.

Athletes and runners who find it difficult to select an adequate diet which not only supplies them with sufficient energy, but also ensures an efficient immune system should consider consulting a registered dietician who specialises in Sport Nutrition. Visit the Association for Dietetics in SA (Adsa) website to find one near you.

b) Vitamin and mineral supplements

The use of a multivitamin and mineral supplement can be considered to boost immunity. Vitamins and minerals tend to work better in unison so ask your pharmacist for a complete vitamin and mineral supplement, such as Centrum or Supradyn (use Supradyn Forte if you are a female runner or if you tend to suffer from exercise-induced iron deficiency).

Once you start using a complete vitamin and mineral supplement, do not add all kinds of additional sources of vitamins and minerals to your regimen. For example, check your protein shakes and carbo-boosting powders for added micronutrients and just for fun add up how much vitamin A you ingest per day - you may be in for a big surprise.

Do not exceed the RDAs (Recommended Daily Allowances) or NRVs (Nutrient Reference Values) for any of these nutrients, because excessive intakes can cause harm (e.g. too much vitamin A can permanently damage your joints and muscles) and even detract from your performance. This is one situation where “more of a good thing is not better”!

c) Avoid alcohol

Alcohol is not a good idea when you are training intensively because it can aggravate dehydration (Attwell, 2012). Rather wait till you have completed the race and recovered before you have that glass of champagne!

d) Boost carbohydrate intake

Paying attention to your carbohydrate intake is key to boosting your energy reserves and preventing post-race infections.

Include at least 1-2 servings of carbohydrates at each meal and before, during and after your training sessions and the actual race. Attwell (2012) suggests that athletes should consume 30-60 g of carbohydrates per hour when training or participating for long periods (i.e. those exceeding 90 minutes), to reduce stress hormones and prevent fatigue.

Sources of carbohydrate that are useful during exercise include:

  • Sports drinks such as Energade, Powerade, EnerG, and PeptoSport® (the latter also contains protein hydrolysate to improve performance and recovery)
  • Sports gels
  • Sweets
  • Dried fruit (test to see what type of dried fruit does not induce diarrhoea which is undesirable during events!)
  • Energy bars with a low fat content
  • Low-fat, sweetened drinking yoghurts

(Attwell, 2012)

Don’t neglect recovery

Most runners are aware of the fact that they need to replenish their energy stores after a mega-strenuous event such as the Comrades Marathon, but they may be too tired to give attention to this vital part of their dietary programme. The golden rule is that you need to stock up on carbohydrates and fluids (rehydration) immediately after the race (or heavy training session).

Attwell (2012) suggests the following:

  • Sports drinks ( Energade, Powerade, EnerG, and PeptoSport®)
  • Soft chewable sweets
  • Fruit such as bananas, apples, etc - fresh, cooked or canned
  • Liquid meal replacements (e.g. Ensure, Peptamen, etc) if the athlete cannot face eating solid foods
  • Sandwiches and rolls with high GI toppings like jam
  • Smoothies made with fruits, low-fat milk and honey
  • Low-fat drinking yoghurt

The combination of carbohydrates and proteins found in drinking yoghurt, and sports drinks such as PeptoSport® may assist in preventing immunosuppression linked to heavy training and/or participation in events.

If you apply these dietary suggestions the chances are that you will have a successful Comrades Marathon this year, and also not develop debilitating respiratory tract infections afterwards. 

(Photo of marathon runners from Shutterstock)                   


(Attwell, G (2012). A healthy immune system for the Comrades Marathon. ADSA Advertorial -14 May 2012; Van Heerden, IV (2003). Sugar and immunity with special reference to HIV/AIDS. Paper presented at the Sugar & Health Symposium, Potchefstroom University, 22 Aug 2003)

Any questions? Ask DietDoc

Read more:

Top 10 tips for the Comrades
The lowdown on carbo-loading
Fluid: how much do you need?
Tim Noakes on carbohydrates
Life after the finish line

Dr Ingrid van Heerden is a registered dietician and holds a doctoral degree in Nutrition and Biochemistry. She believes that "we are what we eat" and offers free nutrition and weight loss advice via her DietDoc service on Read more of her articles.




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