Diet meal-replacement drinks are a concentrated food source with a balanced ratio of vitamins, minerals, and other nutrients. They were originally designed as a weight-loss aid, but can also be a fast and easy meal replacement when used occasionally, and in moderation. Diet drinks are usually soya-protein based, and may contain other ingredients, such as soluble fibre, antioxidants, phytonutrients, and herbs and supplements purported to promote weight loss.