Green Under Potato Skin: Safety Facts & Handling Guide

Green discoloration under potato skin indicates chlorophyll development and potentially harmful solanine accumulation. While small green spots can be safely removed by cutting away generously, heavily green potatoes should be discarded entirely as solanine cannot be destroyed by cooking and may cause food poisoning.

Why Potatoes Develop Green Spots Under the Skin

When potatoes are exposed to light—whether natural sunlight or artificial lighting—their skin begins producing chlorophyll, the green pigment found in all plants. This harmless photosynthetic process signals a more concerning development: the simultaneous production of solanine, a natural defense compound.

Solanine belongs to a class of compounds called glycoalkaloids that act as the potato plant's natural pesticide. Unlike chlorophyll, solanine isn't visible to the naked eye but concentrates in the same areas where greening occurs. The greening serves as nature's warning sign that potentially harmful compounds are present.

Understanding Solanine: The Real Concern Behind Green Spots

While chlorophyll itself is completely harmless (and actually nutritious), solanine requires careful attention. This naturally occurring toxin protects potato plants from insects and fungi but can cause adverse effects in humans when consumed in sufficient quantities.

Solanine Level	Visible Indication	Recommended Action
Normal (0.5-1.0 mg/g)	No visible greening	Safe to eat without concern
Moderate (1-5 mg/g)	Small green spots under skin	Cut away generously (1/8 inch minimum)
High (5-10 mg/g)	Extensive greening throughout	Discard entire potato
Dangerous (>10 mg/g)	Severe greening with bitter taste	Immediately discard; potential health risk

According to research published by the U.S. Food and Drug Administration, solanine levels above 20 mg per 100 g of potato may cause symptoms of poisoning. The bitter taste often accompanying green spots is your natural warning system that solanine concentration has increased.

Health Implications of Consuming Green Potatoes

Solanine affects the nervous system and can cause gastrointestinal distress. Symptoms of solanine poisoning typically appear 8-12 hours after consumption and may include:

• Nausea and vomiting
• Stomach cramps and diarrhea
• Headache and dizziness
• In severe cases: fever, rapid pulse, and neurological symptoms

Vulnerable populations including children, pregnant women, and individuals with compromised immune systems face higher risks from solanine exposure. The Centers for Disease Control and Prevention notes that while fatal cases are extremely rare in modern times, significant discomfort can occur from consuming heavily greened potatoes.

Practical Handling Guide: What to Do With Green Potatoes

When you discover green spots under potato skin, follow these evidence-based steps:

1. Assess the extent: Small, isolated green spots (less than 10% of surface) can be safely removed
2. Cut generously: Remove green areas with at least 1/8 inch of surrounding tissue, as solanine extends beyond visible discoloration
3. Check for bitterness: If the potato tastes bitter after cooking, discard it immediately
4. Discard severely affected potatoes: If greening covers more than 25% of the potato or penetrates deeply, throw it away

Important note: Cooking does not eliminate solanine. Boiling, baking, or frying only reduces solanine content by 2-4% according to studies from the USDA Agricultural Research Service. The compound remains stable through normal cooking temperatures.

Preventing Potatoes From Turning Green

Proper storage is your best defense against greening potatoes. Follow these science-backed recommendations:

• Store potatoes in a cool, dark place between 45-50°F (7-10°C)
• Use opaque containers or paper bags to block all light exposure
• Maintain good ventilation to prevent moisture buildup
• Never store potatoes in refrigerators (cold temperatures convert starch to sugar)
• Keep potatoes away from onions, which release gases that accelerate sprouting

The University of Minnesota Extension confirms that properly stored potatoes can maintain quality for 2-3 months. When purchasing potatoes, examine them carefully for any signs of greening, even in areas that might be covered by packaging.

When Green Potatoes Become a Food Safety Emergency

While most cases of green potato consumption result in minor discomfort, certain situations require medical attention. Seek professional help if you experience:

• Persistent vomiting or diarrhea lasting more than 24 hours
• Neurological symptoms like confusion or vision changes
• Heart palpitations or irregular heartbeat
• Symptoms in children, who are more vulnerable to solanine's effects

Remember that individual sensitivity to solanine varies significantly. What might cause mild discomfort in one person could trigger stronger reactions in another, particularly those with pre-existing gastrointestinal conditions.

Common Misconceptions About Green Potatoes

Several myths persist about green potatoes that deserve clarification:

• "The green part is just chlorophyll and perfectly safe" - While chlorophyll is harmless, it co-occurs with solanine
• "Cooking destroys the toxins" - Solanine remains stable through normal cooking temperatures
• "Only the green spots matter" - Toxins extend beyond visible discoloration
• "Organic potatoes don't turn green" - All potato varieties develop solanine when exposed to light

Is it safe to eat potatoes with green spots under the skin?

Small green spots can be safely eaten after cutting away generously (at least 1/8 inch around the affected area). However, potatoes with extensive greening throughout should be discarded entirely as solanine cannot be destroyed by cooking and may cause food poisoning.

Why do potatoes turn green under the skin?

Potatoes turn green under the skin when exposed to light, triggering chlorophyll production. This visible greening signals the simultaneous development of solanine, a natural defense compound the plant produces as protection against pests and disease.

Can cooking remove solanine from green potatoes?

No, cooking does not eliminate solanine. Boiling, baking, or frying only reduces solanine content by 2-4% according to USDA research. The compound remains stable through normal cooking temperatures, which is why cutting away green areas or discarding affected potatoes is necessary.

How much green potato would cause solanine poisoning?

Symptoms may occur when consuming potatoes with solanine levels above 20 mg per 100 g. For a 200-pound adult, this would require eating approximately 10 pounds of heavily greened potatoes at one sitting. However, children and sensitive individuals may experience symptoms from much smaller amounts.

How should I store potatoes to prevent greening?

Store potatoes in a cool (45-50°F), dark, well-ventilated place using opaque containers or paper bags. Never store potatoes in refrigerators, as cold temperatures convert starch to sugar. Keep them away from onions, which release gases that accelerate sprouting and potential greening.