Dietary fiber is a type of complex carbohydrate that is almost totally indigestible.
Although it does not supply energy, its physical nature contributes to health and well-being. Dietary fiber is not a single substance but a complex mixture of substances which varies in different foods. The best sources of fiber are grains, legumes, fruits, vegetables, and seaweed. Methods of measuring fiber have improved in recent years and are being standardized for accuracy throughout the food industry. Dietary fibers can be classified according to water solubility in an extraction process.