It is mandatory to drink during the marathon itself, usually points of drinks every 5 km. Organizers often offer energy drinks and electrolytic drinks. Under extreme stress, you should study the reaction of your body to such things. You can limit yourself to plain water. Although if the weather is hot (from 30 degrees) and you run for a long time, then maybe they will help you. But you must drink before and during the marathon, especially in hot weather. Now there are a large number of nutritional gels that help replenish your body with minerals, electrolytes, energy and other substances. Their use helps to avoid clogging of the muscles during the distance and maintains your strength.

In principle, apples, bananas, citrus fruits, raisins, prunes, dried apricots, nuts will help you replenish your strength. It’s all individual. If you are determined to run 42 km 195 meters in about 3 hours, then due to intense loads, digestion will practically not work.
However, now even for long workouts, I use natural energy drinks and bars. You should choose what suits you, and then you are in a big plus. When preparing for a marathon, it is advisable to take the following vitamins in addition to nutrition: C, multivitamins, calcium-magnesium, vitamin B complex. This is when your mileage has increased, say, to 80 km per week.
There is a famous “protein” diet that you can try before a marathon. 6 days before the start, you stop eating all foods containing carbohydrates. In the diet only protein products. 3 days before the start, you change everything – exclude protein from the diet and eat only carbohydrate-containing foods. Usually, the last 3 days before the start, athletes no longer train (complete rest), and thus the liver can accumulate glycogen, which is so necessary during an intense load on a marathon distance. This diet only works for marathon races. On multi-day races, carbohydrates (glycogen) cease to be the leading fuel – there the picture changes. It is useful to drink – water or mineral water with a small amount of sugar 2-4 g / 100 g. dilute juice 1:3 or 1:2.

– Too much sugar – will slow down the absorption and leave the body without replenishing carbohydrates. Without carbohydrates, the decomposition of fat will not go.
Fats, meat in the stomach will slow down the absorption of everything, and specifically carbohydrates and water, which is important. Those. snickers, chocolate, fat – as a result, the energy will be only “tomorrow”, but you need “now”. Consider that you are going without food, although you are carrying weight in your stomach. In addition, the water will stop coming in.

– During the marathon – any white bread or unsweetened low-fat cookies. A little bit. Diluted juice.