Let food be thy medicine and medicine be thy food is a phrase credited to Hippocrates, an ancient Greek physician thought to be the father of medicine. In other words, the notion is nothing new.

But its hold over us is as strong as ever.

The way health influencers and diet gurus talk about certain trendy health foods, youd think they could cure cancer. In fact, there are people who say that certain foods can cure cancer and other illnesses. Anthony William, known as the Medical Medium, published a book about celery juice and told Goop that he has seen thousands of people who suffer from chronic and mystery illnesses restore their health by drinking sixteen ounces of celery juice daily on an empty stomach. Dr. Oz has promoted certain foods as having cancer-starving benefits , suggesting that eating them in particular quantities may literally prevent cancer from spreading in your body.

Though at first glance these claims might seem hopeful, or harmless, thinking of food as medicine can actually be dangerous. For one thing, it downplays the importance of actual medicine in the treatment of diseases. Not to mention its manipulative (and sometimes insulting) to suggest that a person could solve their health problems with a simple diet change.

Food does play a central role in the treatment of a few diseases, but these are relatively rare.

In the case of certain diseases, the effect of diet is well supported by evidence. People with diabetes need to be mindful of how food affects their blood sugar levels, and children with epilepsy might benefit from following a ketogenic diet .