The thickeners are modified food starch or certain vegetable gums. When these thickeners are added to the beverage, they absorb the fluid and the fluid thickens. Breaking down the starches reverses the thickening action and almost all water in the beverage is available as free fluid for absorption by the body. If the thickening agent is vegetable gum, it will continue to hold water even during digestion. Thus a vegetable based thickening agent may reduce fluid availability to the body. Commonly used thickening agents are pectin, agar-agar, lignin, algin, and gums.

All gums are polysaccharides, that is similar to sugars but with many sugar units making up a large molecule. They are bland in taste, odour less and tasteless. They may have a nutritional quality besides the primary function but they certainly help in digestion and may be used as laxatives.