How eating green potatoes, sprouting yam tubers poses health risks
Potatoes, a dietary staple for many Nigerians, are valued for their versatility and nutritional benefits.
However, not all potatoes are safe to consume, especially when they exhibit signs of greening or sprouting, experts have noted.
Understanding the factors contributing to these changes and the associated health risks is crucial for safeguarding public health.
Research has shown that the green discoloration of potatoes occurs when they are exposed to light, triggering the synthesis of chlorophyll in their skin.
This natural process, known as photomorphogenesis, occurs as a response to environmental stimuli and is essential for plant growth and development. However, in the case of potatoes, prolonged exposure to light, particularly sunlight, can lead to excessive chlorophyll production, resulting in the characteristic green hue. While chlorophyll itself is harmless, its presence in potatoes signifies the accumulation of potentially harmful compounds called glycoalkaloids.
Glycoalkaloids, the culprit
Glycoalkaloids, specifically solanine and chaconine, according to Medical News Today, are natural plant toxins found in various members of the Solanaceae family, including potatoes.
“These compounds serve as a defence mechanism against pests and predators, deterring consumption by imparting a bitter taste and causing gastrointestinal discomfort. While glycoalkaloids are present in all parts of the potato plant, their concentrations are highest in the green skin and sprouting eyes of potatoes. Solanine, in particular, is notorious for its toxicity and has been implicated in cases of potato poisoning worldwide,” the resource added.
A registered dietician-nutrition and Chief Nutritionist at the Geeky Nutritionist, Uju Onuorah, said eating green or sprouting potatoes could lead to health risks due to the presence of a toxic compound called solanine.
Solanine is a natural defence mechanism found in certain members of the nightshade family, including potatoes, tomatoes, and eggplants.
She added that when potatoes were exposed to light or when they started sprouting, they produced increased levels of solanine.
Ingestion of potatoes containing solanine, according to her, can lead to several health risks, including gastrointestinal distress, neurological symptoms, and cardiac effects, among others.
She said, “These GIT symptoms could include nausea, vomiting, diarrhea, and abdominal cramps. These symptoms typically occur within a few hours of ingestion.”
For neurological symptoms, she said, “In severe cases of solanine poisoning, individuals may experience neurological symptoms such as headache, dizziness, confusion, and hallucinations. These symptoms are often more pronounced in children and individuals with weakened immune systems.”
She also noted that consuming these potatoes could lead to respiratory issues.
In some persons, she noted, solanine poisoning can lead to respiratory distress, including difficulty breathing and shortness of breath.
“This is more common in individuals who consume large quantities of green potatoes. Solanine toxicity can also affect the heart, leading to an irregular heartbeat or even cardiac arrest in extreme cases,” she added.
Onuorah also noted that there was a risk of death from the poisoning caused by consuming these vegetables.
She added, “While fatalities from solanine poisoning are rare, severe cases can be life-threatening, especially if medical treatment is delayed. To prevent solanine poisoning, a key consideration is to store potatoes in a cool, dark place and discard any potatoes that have turned green or begun to sprout.
“People often cook these potatoes believing that cooking at high temperatures can destroy the solanine, however cooking at high temperature only partially degrades solanine, so it’s best to avoid consuming green potatoes altogether.”
The nutritionist further noted that in addition, peeling potatoes could help reduce solanine levels, as the majority of solanine was concentrated in the skin and sprouts.
“On the other hand, poisoning from green or sprouting yams is not caused by solanine ingestion.”
Also speaking, another registered dietitian-nutritionist based in Ibadan, Oyo State,, Mr Emmanuel Udoh, said potatoes and yams were starchy vegetables that provided dietary energy in the form of carbohydrates.
“They are also good sources of protein, fibre, vitamins, minerals, and phytochemicals,” he added.
He said the debate about whether sprouted potatoes or yams were harmful could be attributed to preventing food wastage.
“When people buy potatoes or yams from the market if they are not stored properly at the right temperature, it could result in sprouting. Therefore, the question of whether they are still edible or not arises.
“Sprouting is a result of physiological aging where the apical eye begins to grow and sprout, though there’s no known harm that could result from eating sprouted yams as long as the sprouted area has been cut off, which is the morphological base of the yam. However, research has shown that sprouted potatoes, especially Irish potatoes, could be toxic.”
He also noted that when potatoes are stored for too long, they begin to sprout.
Potatoes are a natural source of solanine and chaconine, which are glycoalkaloid compounds.
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“Although these glycoalkaloids have health benefits like lowering blood sugar and cholesterol and antibiotic properties, they could become toxic when consumed in excess. Now, when a potato sprouts, its glycoalkaloid content rises, and eating potatoes that have sprouted can cause one to ingest excessive amounts of these compounds, resulting in symptoms such as vomiting, diarrhoea, and abdominal pain, fever, headache, etc.
“At higher doses, the toxicity could result in more severe symptoms, like, rapid pulse, low blood pressure, rapid respiration, neurological disorders, and even death in extreme situations.”
He said that because these glycoalkaloids were mostly found in the green or sprouted areas, and in addition to the damage done physically to the potatoes, it was often a sign of spoilage which also left a bitter taste in the mouth when eaten.
“However, discarding the sprouted area, and green skin by peeling and cutting it off, or frying it may help reduce the risk of toxicity by reducing the glycoalkaloid level,” he stated.
Hidden dangers
Several medical doctors have also noted that consuming green or sprouting potatoes poses significant health risks due to the presence of glycoalkaloids.
“Solanine and chaconine have been associated with a range of adverse effects, including gastrointestinal disturbances, such as nausea, vomiting, diarrhea, and abdominal pain,” Dr Oluwatosin Odeinde, a medical officer based in the United States of America, said.
He added, “In severe cases, ingestion of large quantities of these toxins can lead to more serious symptoms, including headache, dizziness, confusion, and respiratory paralysis. Furthermore, prolonged exposure to high levels of glycoalkaloids may increase the risk of chronic health conditions, such as neurological disorders and digestive problems.”
Preventing harm
To mitigate the risk of potato poisoning, he said it was essential to take proactive measures when handling and storing potatoes.
He said, “Store potatoes in a cool, dark place away from direct sunlight to prevent them from turning green or sprouting prematurely. Additionally, avoid storing potatoes near ethylene-producing fruits, such as apples and bananas, as ethylene exposure can accelerate sprouting.
“If you notice any green patches or sprouting eyes on potatoes, discard them immediately. Cutting away the affected areas may reduce the toxin content, but it is not guaranteed to eliminate the risk entirely.
“Cooking potatoes at high temperatures (above 170°C/340°F) can significantly reduce the levels of glycoalkaloids, rendering them safer to consume. Boiling, baking, or frying potatoes can effectively deactivate the toxins, making them suitable for consumption.
“While potatoes are a nutritious and versatile food source, it is essential to be vigilant when selecting and preparing them for consumption. Green or sprouting potatoes should be avoided, as they may contain elevated levels of glycoalkaloids, which can pose significant health risks.”
Same for yams?
While potatoes and yams share some similarities, such as starchy tuberous vegetables, they belong to different botanical families and have distinct characteristics. Unlike potatoes, which belong to the Solanaceae family, yams belong to the Dioscoreaceae family. As a result, the mechanisms and risks associated with green or sprouting yams differ from those of potatoes.
Udoh noted that greening in yams is less common compared to potatoes, as yams typically have a thicker, tougher skin that provides better protection against light exposure.
“However, if yams are exposed to prolonged sunlight or artificial light, they may develop green patches similar to potatoes. The green coloration in yams indicates the presence of chlorophyll, which may be accompanied by increased levels of glycoalkaloids, albeit at lower concentrations compared to potatoes,” he said.
Onuorah also noted that in the case of yams, glycoalkaloids, such as solanine and chaconine, are primarily concentrated in the skin and sprouting eyes, similar to potatoes.
“While the toxicity of green or sprouting yams is generally lower than that of potatoes, consumption of large quantities of these toxins can still lead to adverse health effects, such as gastrointestinal discomfort and nausea. To minimise the risk of consuming green or sprouting yams, it is advisable to follow similar precautions as with potatoes.
“Store yams in a cool, dark place away from direct sunlight to prevent them from greening or sprouting prematurely. If you notice any green patches or signs of sprouting on yams, discard them to avoid potential exposure to glycoalkaloids.
“Cooking yams at high temperatures can help reduce the levels of glycoalkaloids, making them safer to consume. Boiling, baking, or roasting yams until tender can help deactivate toxins and ensure food safety,” she stated.
Also, several public health experts have noted that while yams may pose a lower risk of toxicity compared to potatoes, it is still important to exercise caution and practice proper food handling and preparation techniques to minimise the risk of adverse health effects.
By being aware of the potential dangers associated with green or sprouting yams and taking appropriate preventive measures, individuals can enjoy yams as part of a healthy diet while reducing the risk of foodborne illness.
Onuorah added that though yams are not members of the nightshade family like potatoes, they contain similar compounds called dioscorine alkaloids when there are green sprouts.
She explained that dioscorine alkaloids, found in yams, could have similar effects to solanine if consumed in large quantities or if the yams were improperly prepared. She, however, said the levels of dioscorine alkaloids in yams were generally lower compared to the levels of solanine in potatoes.
“Proper cooking and preparation methods, such as peeling and boiling, can help reduce the risk of consuming harmful levels of dioscorine alkaloids in yams. Solanine poisoning is a concern primarily with potatoes.
“As a rule of thumb, handling, storing, and preparing all foods properly to minimise the risk of consuming toxic compounds is important.
“Potatoes and yams are a nutritious staple in many diets in Nigeria, so it’s important to be aware of the risks associated with consuming green or sprouting potatoes and yams to avoid food poisoning and its associated health complications,” she added.
