Man Eating Nothing But Potatoes for 2 Months

by Christopher Wanjek

Chris Voigt loves his job. And, it seems, he loves potatoes, too. As executive director of the Washington State Potato Commission, Voigt has pledged to eat nothing but potatoes for two months.

No toppings. No sides. Just the wholesome goodness of 20 potatoes a day to meet his caloric needs, from Oct. 1 to Nov. 29.

"I want to show the world that the potato is so healthy that you could live off them alone for an extended period of time without any negative impact to your health," Voigt explained on his website.

You don't get that kind of commitment from the scallion commissioner, that no-good lackey. But to paraphrase the announcer before any Evel Knievel stunt, "Kids, don't try this at home."

Potatoes or nuts?

Much research has been conducted on potatoes, and the conclusion drawn by every medical doctor and nutritionist on the planet is that you have to be nuts to think you can live off of potatoes.

To Voigt's credit, his lighthearted stunt will educate the public about many healthy aspects of the potato: a decent and inexpensive source of vitamin C, vitamin B₆, potassium, magnesium and, with the skin left on, dietary fiber.

Also, low-carb advocates are harsher on the potato than science allows them to be. Some potato varieties, prepared correctly, can be as healthy as the much-lauded whole grains. 

Voigt didn't enter this diet blindly. He told LiveScience he first consulted with a doctor and dietician to confirm he could go 60 days on just potatoes. You need healthy kidneys to process the excess potassium delivered by 20 potatoes a day. You also need a store of nutrients potatoes lack, such as vitamin A for proper vision, or else exit this diet blindly.

Potato vs. the world

The potato's charm is its mediocrity: It is a decent famine food, because it has modest amounts of many nutrients, as opposed to the so-called healthy orange, which just delivers vitamin C and some fiber. The United Nations has promoted the potato as a means to eliminate world hunger.

The problem is that potatoes have a high glycemic index, a measure of how quickly carbohydrates are absorbed into the bloodstream. Foods with a higher glycemic index — most notoriously, processed foods — are associated with weight gain, insulin resistance and diabetes.

Potatoes get worse with the typical preparation: mashed and served with butter or gravy, or fried and salted.

"Potatoes can be an excellent part of a healthy diet, but are not a healthy single source diet," said Barry Swanson, regents professor and interim director of the School of Food Science at Washington State University and University of Idaho, a guy who traverses the two states that produce about half of North America's potatoes. "The glucose release in the body is pretty large for most potato products since the starch is readily digestible."

This means the potato initially satisfies energy needs but, if that's your primary food source, leaves you hungry and tired a few hours later, Swanson said. Like all starches, the potato is most healthful when eaten with other vegetables.

A baked Russet has a glycemic index of 76. Most starches have a lower glycemic index, such as white rice (64), brown rice (55), lentils and beans (under 30) and barley (25), according to the Linus Pauling Institute at Oregon State University. Vinegar and cold storage lowers the glycemic index. A cold, boiled red potato has a glycemic index of 55.

For the record, Voigt told LiveScience his blood sugar level is in the mid-90s, slightly high but within normal range and actually lower than his pre-diet measurement.

Man doth not live by bread only

Can humans survive on any single food? A whale or other marine mammal might do the trick. Some Inuit have survived long periods entirely on meat, attaining vitamin C in muktuk, the skin and blubber of whales.

Surprisingly, potatoes offer a complete protein if you eat enough, over 10 per day. But you would ultimately encounter deficiencies in vitamins A, B₁₂ and E, and calcium and selenium if you keep to just potatoes. Potatoes are slightly toxic, too. The poison is in the stem and leaves, but trace amounts can be in greenish spots on the potato itself and can cause serious illness if you eat enough.

In eating any single vegetable, you are sacrificing nutrients. Soybeans, chickpeas, lentils, or carrots also provide a good range of nutrients. Subjective, yes. I welcome your suggestions.