Nutrition Do’s and Don’ts When Preparing for a Marathon (or any endurance event)

That is it. You wanted to help cancer patients and you chose to join Team for Life to support Lazarex Cancer Foundation by participating in an endurance event. And now the big day is approaching. What can you do in these last few days to ensure that you’re ready? You've spent the last few months diligently training your body and watching what you eat and drink. You are right because your food and drink intake strongly influences your performance, and now, a few days before your big day, it must be optimal. You may already have specific plans, but let’s review some nutrition Do’s and Don’ts.

Mistake # 1: Eating too much fiber
As a general rule, it is essential to consume enough dietary fiber to ensure the proper functioning of the bowel. But fibers are non-digestible food that increase intestinal transit and may cause digestive discomfort or bloating.
Therefore, you should reduce your fiber intake before a race by reducing your consumption of pulses (peas, lentils...), cruciferous (cabbage family...), oilseeds (almonds, walnuts...) and whole grains (brown bread, rye, wholemeal pasta...) and focusing on raw fruits and vegetables.

Mistake # 2: Changing your habits
Do not suddenly change your eating habits a few days before the event. Any specific diet for the pre-competition period must have been tested previously (in the context of competition preparation) to avoid any intestinal disorders or various intolerances.

Mistake No. 3: Stuffing yourself with starch
There is a widespread belief that one should eat large quantities of carbohydrates one or two days before an endurance event, especially during the traditional pasta party the night before.
Urban legend or truth?
Well, you read or heard that you needed to store up glycogen prior to running a marathon. However, excessive amounts of carbohydrates can cause intestinal fermentation with the proliferation of saccharolytic bacteria (which feeds on sugars). This intestinal dysbiosis can causes gas, bloating and even diarrhea and is also involved in the development of functional disorders, including some of inflammatory origin. So, if your diet in the days leading up to an endurance event must obviously be rich in carbohydrates, you must limit your daily intake to 4-5g of carbohydrate per lbs of body weight. It is useless to go beyond. These carbs will mostly come from your intake of foods with low glycemic index (cereals such as rice, semolina, pasta, and fruit ...). Healthy snacks also ensure an adequate intake of carbohydrates and thus avoid having too large portions of starches during the main meals. You should start this high-carbohydrate diet three days before the competition. Finally, the final dinner should be relatively frugal rather than gargantuan, to allow time for the digestive system to digest and store those carbs in the muscles and liver (glycogen) without causing nausea and other sensations of “heaviness” when you stand on the starting line.

Mistake No. 4: Not hydrating properly
Hydration is essential to ensure the daily maintenance of body density and prevent injuries especially at the tendon level, a frequent injury when running on asphalt. However, like for the carbs, it’s all about balance. Be careful to not fall into hyper-hydration. Drinking large quantities of water may indeed lead to true water intoxication by diluting the blood volume. For example, serum sodium, which is the concentration of sodium in the blood, decreases sharply following the ingestion of a large volume of water. During an endurance effort, this can even lead to the phenomenon of hyponatremia (i.e. when the concentration of sodium in the blood is too low).
The symptoms of hyponatremia may be mistaken for dehydration: apathy, nausea, headache, and cramps. If you also present signs of incoordination, confusion and other neurological disorders, consult a doctor and tell him about your fluid intake.
However, you need to increase your water consumption during the days leading up to the event to account for the increased amounts of carbohydrates ingested. Indeed, it is necessary to store 2.7 g water for 1 g of carbohydrate. Consider drinking different sort of waters to supply your body with all the elements essential to metabolism.

So we have reviewed the most common mistakes to avoid when preparing for a marathon, now let’s see what you should eat before and during the event:
The nutritional preparation for a competition goes far beyond the simple dish of pasta the night before. An intense effort like running a marathon leads to severe functional demands on the body. So you need to ensure that your body functions at 100% of its potential. Having high reserves of glycogen is one aspect of it. The acid-base balance, the fight against free radicals and the prevention of intestinal disorders are also essential elements and should begin well before the eve of the competition. It's daily, throughout the season leading up to the event, that you should pay close attention to your diet.

Your nutrition during this last week should be divided into two periods (assuming that your marathon takes place on a Sunday):
- Monday through Thursday: eat mostly vegetables, legumes, nuts and fatty fish to fill up with omega 3, vitamins and fiber.
- Thursday to Saturday night: your daily intake should include 4 to 5 grams of carbohydrates and 0.5 to 0.75 grams of fat per lbs. of body weight. Each meal consists of a large portion (150 g) of cereals or equivalent (wheat, rice, buckwheat, quinoa, etc.), one or two fruits and / or a sweet dessert (two or three slices of spice bread, 150 g of soy dessert, etc.). Avoid cheese because they have a high acid content while dairy products like yogurt and white cheeses are neutral. In addition, you must completely eliminate dairy products in these final days of preparation if you have lactose intolerance causing intestinal problems (bloating, gas, diarrhea). You can use milk by substitute if needed. (Oat milk, rice, soy...)

What about the Scandinavian Dissociated Diet for athletes?
The Scandinavian Dissociated Diet (SDD) was born in Scandinavia in the 60s. The principle is simple: it is a way to work the overcompensation in order to raise the amount of stored sugar in the muscles just before a big competition. It's based on the dissociation of nutrients and it's made out of 2 steps, the first is a low carbohydrate period and the second is a high carbohydrate period.

Day 7 to Day 3 (the 7th day before the competition until the 3rd day): Training is long and intense in order to run out of your sugar stocks, while your diet is low in carbohydrates but rich in lipids and proteins. The objective is the gradual depletion of glycogen reserves (limited to 500 g). So you need to reduce the part of your carbohydrated food down to 10% (fat: 55% and proteins: 35%).

Day 3 to D-Day: Now it's time to fill up with carbohydrates (sugar). So you must increase the part of your carbohydrated food, up to 80% (fat: 8% and protein: 12%). And of course, the training must be reduced in order to save the sugar saturation.
For many years, endurance athletes have strictly applied the SDD rules. Currently it is alleged to be too demanding mentally and cause digestive problems and risks of injury. However, some tests showed that this diet allows multiplying by 2 or 3 the amount of sugar contained in muscles.

In-flight refueling
When done correctly, drink intake during the effort definitely improves performance. This external supply of water, electrolytes and carbohydrates can indeed delay the onset of fatigue by maintaining proper blood sugar levels. But to benefit fully from these beverages you should drink at regular intervals, every 15 minutes, in small quantities (150ml = 2 full sips) and the liquid should contain between 4 and 8% of carbohydrate for a total of 40 to 80 g of carbohydrate per hour. Following these practices will facilitate the passage of nutrients from the intestinal lumen into the blood compartment and prevent possible intestinal disorders.

"Repair" drinks
Not only do sports drinks improve performance, but they also promote recovery and facilitate the repletion of carbohydrates reserves in the body (muscle and liver glycogen), which are greatly reduced after a long and intense exercise. The carbohydrate intake during exercise can also minimize muscle damage caused by exercise. The magnitude of muscle damage depends on the level of closely glycogen stored. The pursuit of physical activity with low reserves of carbohydrates increases the production and release of substances involved in the inflammatory process (cytokines, etc.).
Carbohydrates are obviously the essential nutrient for physical effort. They must be the main component of your effort food. But proteins should not be neglected, as they are key nutrients for enterocytes, immune defences and the anabolic factor. The protein concentration is directly linked to carbohydrate levels and environmental conditions. Don’t forget to use these drinks during your training so that your body is used to them when the time for the marathon arrives.

Last advice: slide an energy gel in your pocket. Swallow it with some water in the last 5 miles to get an extra boost to reach the finish line.

For more resources about cancer treatments and patients’ wellbeing, visit our website: www.teamforlifelcf.org

By Fabienne Der Hagopian
Lazarex Senior Writer
Paris, France