Sports nutrition is no longer just for professional sportsmen and gym obsessives. The various powders and supplements that (legally) help to boost muscle growth or make it easier to exercise longer are moving into the mainstream.

GlaxoSmithKline, which has a healthy sideline in Lucozade, has paid Darwin Private Equity £162 million for Maxinutrition, the protein drinks company that makes Maximuscle, the UK’s bestselling sports nutrition product according to Euromonitor.

Bright Food Group, the Chinese company that was in talks to buy United Biscuits this year, is working on a near-$3 billion bid for General Nutrition Centers. They are motivated by double-digit annual sales growth in a market that is still fragmented, with the top three players — including GNC — accounting for less than a quarter of global sales, which makes it ripe for consolidation by bigger players.

GSK is buying Maxinutrition, which made £36 million in sales in the year to April 2010, from Darwin Private Equity to grow its consumer healthcare business. It expanded into sports nutrition through Lucozade-branded energy bars.

Peter Boddy, the chief executive of Maxinutrition, said: “We’ve been working on making it mainstream for a number of years by trying to simplify and normalise it. We’re stocked in Tesco, Boots and Argos, which is all part of trying to make this an everyday product.”

Andrew Witty, the chief executive of GSK, said: “If you think about GSK now, we have a carbohydrates nutrition business with Lucozade, we have a calcium micronutrients business which is Horlicks, and now we have a protein nutritional business.”