In the early years of the twentieth century, William Hay introduced the notion of food combining. Hay believed that disease was caused by toxins and waste accumulating in our bodies. The Hay diet advocated the avoidance of "foods that fight". For example, carbohydrates should not be combined with proteins in the same meal and foods should be consumed that restore the "natural" acid / alkali balance in our bodies. At its inception, no scientific evidence existed to support his theory. This situation is no different today, but this has not stopped the Hay Diet from being dusted off and re-invented on numerous occasions throughout the last century. It experienced particularly high profile resurgence in 1991, when it was widely reported that the Duchess of Kent had been adhering to it.