Are green potatoes dangerous to eat?

Peeling potatoes before cooking reduces the toxins. PHOTO | PROMISE TWINAMUKYE

What you need to know:

  • Sometimes we leave potatoes to sit out too long and they turn a green colour. What does it mean when potatoes turn green and are they still safe to eat?

Potatoes are commonly referred to as starchy vegetables rich in vitamins, especially vitamin C, Vitamin B6, minerals such as potassium, iron, phosphorus, and carbohydrates. Franka Piloya, a dietician, says potatoes have low calories which makes them healthy to eat.

Potatoes are one of the foods that are greatly filling due to their starch, according to Piloya. Filling foods are known to help in regulating weight gain since they reduce cravings, especially for junk and fast foods.

Potatoes are also an excellent source of vitamin C and according to, they have more vitamin C than one medium tomato or sweet potato.

An excerpt from states that the addition of raw potatoes and vinegar to the sailor’s diet did a lot to eradicate scurvy from the maritime scene.

Blood sugar control

“Research has linked resistant starch to many health benefits, including reducing insulin resistance, which, in turn improves blood sugar control,” a article states.  The article reveals that one can also increase the resistant starch content of potatoes by storing boiled potatoes in the fridge overnight and consuming them cold.

When they turn green

According to, potatoes contain two types of glycoalkaloids, which are natural toxins:

● Solanine 

● Chaconine

When your potatoes are exposed to light, these toxins form at a rapid pace. The appearance of green colour is called "greening" and it indicates the formation of chlorophyll. While chlorophyll is not necessarily harmful for human consumption, its presence indicates that tubers have increased their production of a glycoalkaloid known as solanine, which causes a bitter taste, thus making them unsuitable for consumption.

Felista Nakasiita, a nutritionist, says this substance is also toxic to the body since its consumption can lead to symptoms such as headache, stomach pain and diarrhoea. 

“Symptoms usually occur eight to 12 hours after ingestion, but may also occur as rapidly as 10 minutes after eating high-solanine foods,” Nakasiita says.

According to Food Security Authority of Ireland (fsai), there are a number of reports suggesting that ingestion of potatoes containing high levels of glycoalkaloids has led to poisoning incidents where the main symptoms displayed are irritation of the gut and drowsiness. 

Piloya advises one to avoid eating green, sprouted, and damaged potatoes since glycoalkaloids cannot be destroyed by cooking.

What to do

It is recommended that potatoes are stored in a cool, dry, and dark place as exposure to warm and bright conditions enhances the growth of these stem tubers. Nakasiita says since cooking methods such as boiling and frying have been shown to have minimal effects on solanine levels, green potatoes are best thrown away. 

She, however, says peeling potatoes before cooking them reduces the solanine intake from potato consumption as the majority (30-80 percent) of the solanine in potatoes is found in the outer layer of the potato.

This, however, should not be the case if the potato still remains bitter even after peeling. 

“If the green colour has spread throughout the potato, it is not possible to cut away enough of the solanine material to make it safe to eat,” MedicalNewsToday states.