Sweet-Potato Diet to Fight Cancer? Beware Bowel Obstruction

Once people have an incurable disease, they easily believe all kinds of extreme views. Eating a sweet-potato diet to fight cancer is one of them. Quite a few cancer patients have asked me whether sweet potatoes are an anticancer food and whether they should persistently eat large amounts of them to fight cancer.

I grew up in the countryside, where sweet potatoes are a staple crop. From childhood our elders told us not to eat too many sweet potatoes — they cause gas. This is the most basic common sense of rural people. But I do not know when the absurd notion began circulating in cancer circles that a sweet-potato diet fights cancer and that eating lots of sweet potatoes treats cancer. I have never seen anyone successfully fight cancer by eating sweet potatoes, but there are plenty who, after eating too many, suffer gas, stomachache, and constipation; some patients have even ended up with bowel obstruction.

Sweet potatoes are a common food; eaten in normal moderation they are not very harmful. But eaten in excess they stimulate massive gastric acid secretion; acid refluxing into the esophagus causes acid regurgitation, heartburn, stomachache, and constipation. Sweet potatoes contain large amounts of starch and sugar and are not an easy food to digest. They contain gas-forming enzymes; eating too many easily produces carbon dioxide in the gut, causing intestinal gas, belching, and flatulence. Some patients, after overeating sweet potatoes, develop cracked tongue coating, bad breath, and poor appetite. The starch in sweet potatoes is rich in sugars; excess sugar the body cannot absorb and metabolize turns to fat and is stored, so eating too many sweet potatoes easily makes you fat.

Eating sweet potatoes in moderation may indeed help prevent digestive-tract tumors, but once cancer has developed, relying on sweet potatoes is useless. For many patients with weak digestion and a tendency to gas, sweet potatoes, glutinous rice, and beans — hard-to-digest or gas-producing foods — should be on the prohibited list. Such patients, eating sweet potatoes, not only fail to get anticancer effect but harm their quality of life and shorten their survival.

There are many similar extreme views — the ketogenic diet, wheatgrass juice for cancer, raw potato juice for cancer — too many to rebut one by one. As a patient, remember one rule: if a so-called anticancer notion has no doctor's recommendation, or only one or two isolated doctors recommend it, keep your distance. Cancer is an ancient disease; every multicellular organism gets it, and enormous numbers of doctors study it. If a dietary therapy actually worked, a great many doctors would have observed it; it would not be found only by a tiny handful. It is like a valuable scientific experiment: it must be repeatable by other scientists in their own labs.