Wednesday, May 4, 2011

Watch Those Glycoalkaloids!

No one I know has gotten sick--much less died--from eating potatoes that have sprouted or turned green. However, there is a slight risk from eating potatoes in this condition, so I just thought I'd bring it to everyone's attention.

Potatoes belong to the Solanaceae, or "nightshade" family, which all contain varying amounts of glycoalkaloids. These are natural toxins that serve as the plant's defense against fungi and creatures that might want to eat them (including us). Now before we get all freaked out and swear off potatoes, let me add that tomatoes and eggplants are also members of this family, and if they were all that lethal, every Italian would be dead (not to mention the Irish). Apparently, tomatoes and eggplants contain much lower levels of glycoalkaloids than potatoes, so we can go ahead and take them off the terror watch list now.

There are some varieties of potato that tend to have dangerously high levels of glycoalkaloids in any condition, and these have been identified over the years and removed from cultivation and distribution. The potatoes we pick up at the market are only potentially harmful when they're sprouting, and when they begin to turn green.

There are a few factors that stimulate the potato to produce these toxins, including periods of high metabolic activity (such as sprouting), extremely low temperature, exposure to light, and stress conditions (such as rough handling). These are all the plant's defense reaction to "attack."  However, the most common one in potatoes that look fine when we buy them and then turn green a while later is exposure to light. As a precaution, it's a good practice to store potatoes in a dark place.

If you happen to notice a greenish color on or just under the skin (see the picture below, with a section of skin scraped away), the affected area can generally be peeled away. Simply take it down to where the green color is gone. But once the green color has spread well into the interior of the potato, it's best to consider it too toxic to eat.

The most common symptoms resulting from eating potatoes with high concentrations of glycoalkaloids are mainly a mild gastrointestinal discomfort, although some cases have also included nausea, vomiting, diarrhea, stomach cramps, and headaches. In some rare instances where people ate the sprouts and flowers, or very green potatoes, the results were much more serious, with reports of hallucinations, paralysis, and even deaths. Again, these cases are very rare, and the data is anecdotal, so I wouldn't panic and stop eating potatoes altogether.

I know this post may be a little alarming, but consider that we've all been eating a ton of potatoes over the years with none of the more severe symptoms. I'm just putting the information out there so people can be aware and avoid eating green potatoes. Also, cooking potatoes at high temperature (roughly 350F and above) will lower the concentration of glycoalkaloids, so those who enjoy their "freedom fries" and baked potatoes can generally continue doing so without undue worry (beyond the normal concern regarding fried food).

Bon appétit, everyone!

1 comment:

  1. Dr. Greger mentioned in one of his yearly DVDs that white potatoes should probably be avoided altogether and definitely peeled if eaten. I haven't given them up, but I will be sure to not eat ones which have sprouted or turned green.