Once a niche segment concerning serious exercisers, the market for these functional beverages has now expanded to cover anyone who exercises or wants to lead a more healthy lifestyle.

Growth in this segment has been due to a number of factors including technological advances, changes in lifestyle, and the improved taste/texture of products.

RTD protein beverages now come in water, juice and milk-based variants, as well as an increasing number of smoothies.

Recent research has suggested that a diet rich in protein can have benefits for a number of different groups. For example, protein has been found to affect satiety meaning that companies have created beverages targeted specifically at the weight management market.

Other new potential segments for RTD protein beverages are the elderly, young children, hospital patients, along with the existing sports nutrition consumers.

Potential challenges include public scepticism of scientific studies and claims made, and a congested functional drinks market.

The transformation from niche to the mass-market segment has certainly begun but there is still unfulfilled potential - it's possible that once a big player enters the market, the global reach it could bring would launch the segment into the mainstream.

Once just viewed as a by-product of cheese making which was often just thrown away or used for animal feed, whey is now currently the most popular form of supplementary protein. Other sources of protein include casein, milk, soy, egg whites and legumes.