A study of 4400 North American men and women, ages 45 to 79, followed for eight years, showed that those who ate fried potatoes two or more times a week were at increased risk for dying during the study period, compared to those who ate fried potatoes occasionally. Those who ate potatoes that were not fried had no increased risk of death (Am J Clin Nutr, Jul, 2017;106(1):162-167).
I can find no data to show that eating French fries on occasion, such as once a week, increases risk for any disease. However, several studies have shown that people who eat fried potatoes frequently are at increased risk for:
• obesity (Am J Clin Nutr, Aug 2016;104(2):489-98)
• high blood pressure (BMJ, May 7, 2016;353:i2351)
• colon cancer (Nutr Cancer, May-Jun, 2017;69(4):564-572
• diabetes (Diabetes Care, Mar 2016;39(3):376-84; Am J Clin Nutr, Feb 2006;83(2):284-90). Replacing potatoes with whole grains was associated with reduced diabetes risk.
One study showed no association between eating potatoes and heart attacks (Am J Clin Nutr, Nov 2016;104(5):1245-1252).
Potatoes are Healthful
Potatoes are the fourth most important staple food crop in the world, behind wheat, corn and rice. They are a healthful food and are good sources of resistant starch, a type of soluble fiber. Humans lack the necessary enzymes to break down resistant starches, so they cannot be absorbed in the upper intestinal tract and pass to the colon where certain bacteria do have the enzymes to break them down so that they can be absorbed there. Your colon contains healthful and harmful bacteria and what you eat determines which types of bacteria grow in your colon. Colon bacteria eat what you eat, and eating a plant-based diet encourages the growth of bacteria species that help to break down resistant starches and other soluble fiber that:
• help make the vitamins biotin, folate and vitamin K
• stimulate your immunity to protect you against infections
• help prevent diabetes by lowering blood levels of sugar and insulin
• lower blood levels of cholesterol and triglycerides
• produce butyrate that may help to reduce your chances of developing cancer or inflammatory bowel disease
How Soluble Fiber Promotes Good Gut Bacteria
Anti-Inflammatory and Pro-Inflammatory Foods
How Frying Turns Healthful Foods into Unhealthful Ones
When you cook a potato with water, such as boiling, steaming or stewing, the sugar in it combines with the water to produce energy, carbon dioxide and water as the end products of digestion, all of which are safe and healthful. (Baked potatoes are “steamed”, cooked in the water trapped inside their skins). On the other hand, when you cook without water, such as frying, the sugar combines with protein to form advanced glycation end products (AGEs) that have been linked to cancers in animals and may increase cancer risk in humans. Eating a lot of foods that are high in AGEs can also prevent cells from responding to insulin, which can lead to diabetes or make it harder to control existing diabetes (Diabetes Care, January, 2014;37:88-95).