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Food and Nutrition

Glycoalkaloids in Foods

The Issue

Glycoalkaloids are a group of nitrogen-containing compounds that are naturally produced in various cultivated and ornamental plant species of the Solanaceae family. This large family of plants includes commonly consumed vegetables such as potatoes, tomatoes, eggplants, and peppers. Examples of non-food plants in the Solanaceae family include tobacco, petunia, and climbing or bittersweet nightshade.

Glycoalkaloids are toxic to humans if consumed in high concentrations. Canadians are rarely exposed to levels of glycoalkaloids that cause serious health effects. However, there are occasional reports of short-term adverse symptoms, usually from eating potatoes that contain elevated concentrations of glycoalkaloids or from consuming a non-food plant in the Solanaceae family.

Background

Glycoalkaloids may have evolved in selected plant species to protect against predators and pathogens such as bacteria, fungi, viruses, insects, and animals. Glycoalkaloids also impart certain flavours in some plants. For example, low levels of glycoalkaloids produce desirable flavours in potatoes.

Different species of plants contain different glycoalkaloids that vary in their toxicity to humans. For example, tomatoes contain the glycoalkaloids alpha-tomatine and dehydrotomatine whereas potatoes contain alpha-chaconine and alpha-solanine. The glycoalkaloids found in potatoes are more toxic than those in tomatoes and tomato plants.

Health Effects

Canadians are exposed to low levels of naturally occurring glycoalkaloids through certain foods in their diet. Consumption of these low levels glycoalkaloids do not pose a safety concern to humans, however, undesirable health effects can result from intakes of higher levels of glylcoalkaloids.

Adverse health effects from higher intakes of glycoalkaloids are usually related to consumption of potatoes that show signs of physical change or damage (e.g. sprouting, greening, bruising). Symptoms associated with glycoalkaloid poisoning from potatoes include a bitter or burning sensation in the mouth and flu-like symptoms such as nausea, vomiting, stomach and abdominal cramps, and diarrhea. More severe cases of glycoalkaloid poisoning may be accompanied by a variety of neurological effects (i.e. drowsiness, apathy, restlessness, shaking, confusion, weakness, and disturbed vision). There are a few reports of deaths being attributed to glycoalkaloid exposure from the consumption of potatoes, potato leaves, and potato berries.

Limited information is available on which to assess the health impacts of long-term exposure to low levels of glycoalkaloids. However, the fact that potatoes have been consumed regularly by millions of people worldwide suggests that the low levels of glycoalkaloids normally found in properly stored and handled potatoes are not a concern.

What is the Government of Canada Doing?

Health Canada has established a health-based maximum level of 20 mg total glycoalkaloids per 100 g (fresh weight) of potato tuber. This maximum level is applicable to all potatoes that are commercially sold in Canada.

What Can You Do?

Do not consume plants, particularly those growing in the wild, if you do not know their identity or if they are safe for human consumption.

Cooking (i.e. baking, boiling, frying, microwaving) does not significantly reduce the levels of glycoalkaloids in foods. However, there are some practices that you can follow to minimize exposure to glycoalkaloids in food plants. The advice below is specific to potatoes and tomatoes as these foods are consumed in relatively greater quantities than other food plants that contain glycoalkaloids.

Minimizing Exposure to Glycoalkaloids in Potatoes

  • Store potatoes in a cool, dry, dark environment to minimize glycoalkaloid formation.
  • Cut away any parts of a potato that show signs of greening, physical damage (cuts or bruises), rotting, or sprouting. In severe cases, discard the entire potato.
  • Peel the skin from potatoes to reduce glycoalkaloid levels.
  • Do not assume that the concentration of glycoalkaloids in a potato have decreased if the green colour diminishes after storage in a dark environment.
  • Avoid the consumption of potato sprouts, flowers, and the area around the eyes.
  • Do not eat raw or cooked potatoes that taste bitter or cause a burning sensation in the mouth.

Minimizing Exposure to Glycoalkaloids in Tomatoes

  • Consume ripe tomatoes; glycoalkaloid levels decrease as the fruit matures and ripens.
  • Consume green tomatoes and products made with green tomatoes in moderation (i.e. green tomato chow chow, fried green tomatoes, green tomato relish).
  • Do not consume the green parts of tomato plants (i.e. stem, leaves).

Health Canada recommends that Canadians consume a variety of foods from each food group according to Eating Well with Canadas Food Guide.

For More Information:

Canadian Standards (Maximum Levels) for Various Chemicals in Retail Foods (Health Canada)

Next link will take you to another Web site Natural Toxins in Fresh Fruit and Vegetables (CFIA)

Eating Well with Canadas Food Guide