How to make your own homemade isotonic drink

An isotonic drink is a sports drink intended for the rehydration of the athlete that helps replenish fluids and electrolytes to compensate for losses through sweating, which depend on the temperature and humidity of the environment. If the exercise is intense, the environment is hot or you sweat a lot, drinking an isotonic drink helps to replenish fluids, electrolytes and energy lost during exercise and helps to delay fatigue, avoid heat-related injuries(cramps, syncope...), improve performance and accelerate recovery.

Isotonic drinks contain the equivalent amount of salts in solution that are lost with sweat and usually contain simple sugars, with the consequent contribution of calories.

These sugars and electrolytes are at the same osmotic pressure as blood (330 milliosmoles/liter -mOsm/L-), so the liquid leaves the stomach, passes to the intestine where it is absorbed and from there goes into the bloodstream without difficulty, favoring a better and faster assimilation of its components and avoiding digestive problems.

Osmolarity is a way of measuring the total concentration of a solution in relation to the number of dissolved molecules. When molecules have a low molecular weight, their osmolarity is higher, and as the molecular weight increases, the osmolarity decreases. Osmolarity influences the speed of gastric emptying and conditions the passage of nutrients from the stomach to the intestine in order to be absorbed. The higher the osmolarity, i.e., the higher the concentration of solutes, the slower the gastric emptying rate.

The combination of different sugars (fructose + glucose, glucose + maltodextrin, glucose + fructose + maltodextrin) facilitates the availability of energy. In sports of long duration and medium/high intensity, preparations containing glucose polymers (maltodextrins), not only glucose or fructose, are recommended because of their better absorption and ability to ensure a sufficient energy supply without risk of digestive disorders.

Maltodextrin is a polymer formed by chains of linked D-glucose units. It has good solubility and low sweetening power. It is obtained by partial hydrolysis of starch, usually from corn, although it can also be from potato, tapioca or wheat. Maltodextrin is considered to have a high glycemic index, so it is recommended to replenish glycogen levels after training and also to maintain glycemia and energy during long duration exercises, avoiding fatigue. Maltodextrin has a higher molecular weight than other carbohydrates of high glycemic index, consequently its osmolarity is lower than the osmolarity of simple carbohydrates, which gives it a faster transit, a better availability before and a relatively high absorption speed of glucose into the bloodstream. Maltodextrin powder is available on the market (Nestlé Nessucar, Aptonia, Solé Graells, HSNraw, etc.).

In February 2001, the European Commission's Directorate-General for Health and Consumer Protection, through the Scientific Committee on Food, defined sports replenishment drinks as: "Flavored drinks that provide carbohydrates (60-80 g/L), sodium (10-25 mmol/L) and potassium3 mmol/L) to rapidly replenish fluids and energy during and after exercise". In other words: isotonic sports drinks should have the following composition:

• Between 80-350 kcal per liter.
• At least 75% of the calories should come from carbohydrates with a high glycemic index (glucose, sucrose, maltrodextrins).
• Between 6% and 9 carbohydrates (60-90 grams per liter).
• Between 460-1150 mg of sodium per liter (46-115 mg per 100 ml).
• The amount of potassium should range between 10-25 mg/100 ml, although it admits the addition of potassium up to 700 mg/L (70 mg/100ml).
• The sodium/potassium ratio is usually 4/1.
• Osmolarity between 200 mOsm/L of water.

Sports drinks may contain other electrolytes (e.g. magnesium, calcium). Drinks that include protein or branched amino acids are also commercially available. The taste and temperature of sports drinks are also important factors in achieving hydration goals. Flavored and cold drinks (10-15°C) are generally better tolerated by athletes.

General recommendations

It is important to remember that hydration should be adequate throughout the day, before, during and after exercise. Carbohydrates usually come from a mixture of glucose, fructose and maltrodextrins. However, the individuality of the athlete, tastes, etc. must be taken into account. It should also be taken into account that a high concentration of fructose can cause gastrointestinal discomfort. The ratio of fluids to carbohydrates may vary according to the environment, the athlete's preparation and exercise demands. If fluid needs are greater than carbohydrate needs, more dilute beverages can be used. In the opposite case, the greater the carbohydrate demand, other supplements such as gels or sports bars can be added.

From Burke et al. 2010.

Homemade isotonic drink

An isotonic drink can easily be made at home, which will be cheaper and provide the same benefits as a commercial isotonic drink.

The homemade formula consists of mixing salts and sugars and adding water or other liquid to make up to 1000 ml (1 liter) of drink.

In case of celiac disease and, if maltodextrins are used, their origin must be taken into account. In this case, choose corn, potato or tapioca maltodextrins.

The resulting values are approximate, since, when working with small quantities, it is very difficult to make it exact.

Remember to test during training sessions and adapt the drink to the taste and needs of each person.

Oral serum

It is sold in pharmacies, in powder form for reconstitution. It should be prepared in advance and slightly refrigerated. It is a solution consisting of water, glucose, salts and bicarbonate. According to the WHO formula, for 1 L of drinking water, add the contents of the sachet:

• 35 g of sodium chloride (NaCl) = 1400 mg Na (1 g of NaCL = 0.4 g of Na).
• 15 g of potassium chloride (KCl) = 780 mg K (1 g of KCL= 0.52 g of Na)
• 25 g of Sodium Bicarbonate (NaHCO3) = 685 mg Na (1 g of NaHCO3 = 0.27 g of Na)
• 20 g of Glucose
• Citrate

In total we have, in 100 ml of water, 2085 mg of Na, 78 mg of K and 2 g of carbohydrates. If we do it this way and compare it with the EFSA recommendation, we see that it has too much Na and K and not enough carbohydrates.
To make it an isotonic drink we should add a heaping tablespoon of maltodextrin powder (30 g) and a tablespoon of honey (20 g) and complete with water up to 2 liters. Thus we would have, in 100 ml of drink, 104'25 mg of Na, 39 mg of K and 7 g of carbohydrates.

Drink based on water soft drink and fruit juice

• 500 mg of sodium bicarbonate (equivalent to the empty blister pack of an aspirin) = 260 mg of Na
• 500 mg of salt (equivalent to the empty blister pack of an aspirin) = 200 mg Na
• 100 mg of potassium chloride (in pharmacies) = 52 mg of K
• 1 heaping tablespoonful of sugar = 30 g carbohydrates
• 1 heaping tablespoonful of maltodextrin powder = 30 g carbohydrates
• 100 ml fruit juice (half a glass): 146 mg K, 3 mg Na, 107 g carbohydrates
• Water up to 1000 ml of drink

Total for 100 ml: 463 mg Na, 19.8 mg K and 7.07 g carbohydrates.

Homemade alkaline lemonade

• œ level teaspoon of mocha (1 g) of salt = 400 mg Na
• œ level teaspoon of mocha (1 g) of sodium bicarbonate = 520 mg Na
• 1 heaping tablespoonful of sugar = 30 g carbohydrates
• 1 heaping tablespoonful of maltodextrin powder = 30 g carbohydrates
• Juice of two lemons (100 ml = half a glass) = 1 mg Na, 103 mg K, 6 g carbohydrates
• Water up to 1000 ml of drink

Total for 100 ml: 92'1 mg Na, 103 mg K, 6'6 g carbohydrates.

We can replace the lemon juice with grapefruit juice (100 ml = half a glass): 13 mg Na, 149 mg K, 10 carbohydrates

Total for 100 ml: 92'13 mg Na, 14'9 mg K, 7 g carbohydrates.

Coconut water based drink

• 1 L of coconut water: 230 mg of Na, 197 mg of K, 40 g carbohydrates
• 500 mg of sodium bicarbonate = 260 mg of Na
• 1 level tablespoonful of maltodextrin powder = 20 g carbohydrates
• 1 level tablespoon of honey = 20 g carbohydrates

Total for 100 ml: 49 mg Na, 197 mg K, 8 g carbohydrates.

Cola-based beverage

• 1 can of Coca-Cola (330 ml)
• 1 pinch of salt (100 mg of Na)
• 1 pinch of sodium bicarbonate (130 mg of Na)
• 100 ml of lemon juice = 1 mg of Na, 103 mg of K, 6 g carbohydrates
• 70 ml of water
• 500 ml = 435 g carbohydrates, 231 mg Na, 103 mg K

Total for 100 ml: 462 mg Na, 20.6 mg K, 87 g carbohydrates.

NutritionalValor of different beverages used in the preparation of homemade isotonic beverages