The pros and cons of munching on raw potatoesQUESTION: I grew up on a farm in Minnesota, and I always used to like eating raw potatoes like apples. I still like them better raw than cooked, with a little salt on them. My mother always said they were healthier that way. Was she right?
â€“ RLL, via e-mail
ANSWER: Although not a common component in the American diet, the eating of raw potatoes has footing in some family traditions. There are some considerations and interesting science regarding eating them this way.
The potato plant produces a number of defensive (toxic) substances in the upper plant (leaves, stems and above-ground fruit), but they are not in the below-ground tubers, which are the â€śpotatoesâ€ť we're familiar with. However, a potato (tuber) that's been injured, exposed to sunlight or stored for an extended period of time might begin to sprout or develop patches of green. The green is chlorophyll, produced by photosynthesis.
Chlorophyll is not toxic, but if photosynthesis has begun, it means that toxic alkaloids, such as solanine, will be also present. Green potatoes and especially potato sprouts, should never be eaten. Cooking does not deactivate these toxins.
The raw potato also contains antinutrients that act as enzyme (protease) inhibitors. This might be a consideration if you don't eat well and crunching on raw spuds is a regular part of your diet.
The August 2006 issue of the Journal of Food Science looked at three of the enzyme inhibitors found in raw potatoes and how they decreased during cooking. These substances tend to be in the peel, so you might consider removing the peel. You'll also lose some of the nutrients, but it's a reasonable trade.
Unlike cooked potatoes, some of the starch in raw potatoes is digested poorly. Called â€śresistant starch,â€ť it passes through the small intestine into the large intestine, where it ends up being fermented by the flora that live there.
Similar to what happens when we eat legumes, this can result in increased fecal bulk, bloating and possibly some undesirable gastrointestinal effects. All this has a positive side in that the fermentation of resistant starches increases the production of butyrate, a fatty acid that is associated with favorable effects on diseases in the colon.
A study in the March 2009 issue of Gut reported how resistant starch had positive effects in colon cancer patients. Another benefit is that raw potatoes don't increase blood sugar like their cooked counterpart.
Interestingly, a study in the November 2005 issue of the European Journal of Clinical Nutrition reported that if you chill a cooked potato, you regain some of this effect. (In that study, they served the chilled potatoes with a vinegar dressing.)
The bottom line is that if you want to eat raw potatoes, aside from peeling them, look for fresh, unblemished, unsprouted potatoes with no hint of green. If you have a choice, opt for potatoes that are grown organically.
There is a complete list of potato nutrients at tinyurl.com/dyerf5. This list represents the nutrients in the raw potato. Cooked potatoes have less vitamin C, thiamine and riboflavin. When eating cooked potatoes, include the skin if you can.
Ed Blonz, Ph.D., is a nutritional scientist based in Northern California. General-interest questions about nutrition can be mailed to: Ed Blonz, Focus on Nutrition, P.O. Box 120191, San Diego, CA 92112-0191, or sent via e-mail to UTFood@blonz.com