Table 2.
Carbohydrate-electrolyte beverage composition and factors known to influence intestinal absorption
| Factor | Effect |
|---|---|
| Osmolality |
Ingested beverages < 270 mOsmol L−1 may aid water absorption as a result of a favourable osmotic gradient encouraging water movement from the proximal small intestine across the mucosa [29] Electrolytes (sodium) will aid water absorption in the duodenum but will slow the rate of water absorption in the jejunum due to movement of sodium into the lumen of the jejunum down concentration gradients, reducing effectiveness of water absorption [101] Hypertonic drinks result in net efflux of water from the body into the intestinal lumen, causing a net negative effect on water absorption and plasma volume [102] Hypotonic beverages are more effective than isotonic beverages for maximal water absorption [32, 103–106] |
| Carbohydrate concentration and type |
Active co-transport of glucose and sodium facilitates the absorption of glucose and promotes the osmotic gradients that aid water absorption in the jejunum [39] Multiple transportable carbohydrate (e.g., glucose and fructose) in the jejunum creates a favourable osmotic gradient improving water absorption through solvent drag [39] Maltodextrin reduces osmolality when compared to glucose monomer potentially facilitating an increasing water uptake [1] |
| Sodium concentration |
In the jejunum sodium is coactively transported with carbohydrates, amino acids, organic acids and bile salts [29] The role of sodium in active nutrient transport and water absorption is considered necessary in oral hydration solutions for clinical dehydration [107], but most evidence suggests negligible impact on absorption, plasma volume and retention during exercise [23, 32, 33] Solutions containing multiple carbohydrate types produce the greatest sodium absorption rates in the duodenojejunum and jejunum [1] |
| pH |
Most beverages are acidic to maintain shelf life and palatability Acidosis may enhance water and sodium transport but not glucose [29] |
| Temperature |
Ingested fluid is equilibrated to body temperature and at the level of the intestine [98] Temperature of the ingested fluid is likely to have minimal influence on intestinal absorption [98] |
| Sex | Limited research in gender differences and intestinal absorption |
mOsmol L−1 osmolarity