Green Potatoes/Steroidal Glycoalkaloids (SGAs)

Green potatoes, creeping eyes – is something wrong with my potatoes?

Have you ever wondered if they are safe to eat?

We see few foods on special buys, and we tend to save money. Nothing wrong in that, after all, it is our hard-earned money. But, if we will not store certain foods properly, they can become toxic.

One such food is potato.

Potatoes (Solanum tuberosum L.) are eaten widely as staple food across the globe [1]. Potatoes can be consumed after baking, boiling, steaming and frying. Potatoes are good source of carbohydrates, fibre (if consumed with the skin) and also, contain some essential amino acids, vitamins, minerals, and polyphenols such as chlorogenic acid [2].

Steroidal glycoalkaloids (SGAs) are found generally in low levels in potatoes and are beneficial. These are produced as a defence mechanism to protect the potato tubers from pathogens [3]. Mechanical damage and microbial infections also induce the synthesis of SGAs [4].

Potatoes turn green or start sprouting on prolonged exposure of natural or any source of light. The light induces the chlorophyll and steroidal glycoalkaloids (SGAs mainly alpha-solanine and alpha-chaconine) biosynthesis and thus the skin of potato become green in colour [5].

Chlorophyll is not a health concern, but greening or sprouting is the sign that SGAs content is also increased along with chlorophyll. Solanine and chaconine become toxic at high doses [6]. SGAs at high doses adversely affect central nervous system, cause liver damage, disrupt cell membranes in the gut and can adversely affect metabolism [7]. Severe poisoning may even lead to respiratory issues, paralysis, cardiac failure and coma [8]. Unfortunately heating also does not reduce the levels of SGAs however, frying may reduce little amount [7]. But discarding the sprouts, green skin and bruised parts may be the safest thing to do.

So next time you buy a bag of potatoes, store them in a cool dark place, in your cupboard or drawers covered with a cotton cloth.

Be wise, be safe!

References:

  1. Camire ME, Kubow S, Donnelly DJ (2009) Potatoes and Human Health. Critical Reviews in Food Science and Nutrition 49: 823-840.
  2. Singh J, Kaur L (2016) Advances in potato chemistry and technology: Academic press.
  3. Dao L, Friedman M (1994) Chlorophyll, chlorogenic acid, glycoalkaloid, and protease inhibitor content of fresh and green potatoes. Journal of agricultural and food chemistry 42: 633-639.
  4. Osman SF (1983) Glycoalkaloids in potatoes. Food Chemistry 11: 235-247.
  5. AD P (2016) G1437 green potatoes: The problems and the solution.
  6. Knuthsen P, Jensen U, Schmidt B, et al. (2009) Glycoalkaloids in potatoes: Content of glycoalkaloids in potatoes for consumption. Journal of Food Composition and Analysis 22: 577-581.
  7. Smith DB, Roddick JG, Jones JL (1996) Potato glycoalkaloids: Some unanswered questions. Trends in Food Science & Technology 7: 126-131.
  8. Mensinga TT, Sips AJAM, Rompelberg CJM, et al. (2005) Potato glycoalkaloids and adverse effects in humans: an ascending dose study. Regulatory Toxicology and Pharmacology 41: 66-72.