Mariah Carey's purple pledge Mariah Carey will only eat purple food. The pop diva is convinced mauve-coloured foods like red grapes and plums - known for their anti-ageing benefits - will stop her developing wrinkles. The songstress, who devised the diet with her nutritionist, now munches purple meals three days a week. A source is quoted in Britain's The Sun newspaper as saying: "It sounds off-the-wall but it's a huge injection of healthy food in one go. Purple products are nature's best weapons in the battle against ageing. There's a saying that 'a plum a day keeps a facelift away'." "Purple food can prevent breakdown of collagen and slow the wasting of muscles." It isn't the first time Mariah has tried a bizarre diet.