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Glycoalkaloids
**Glycoalkaloids** are naturally occurring nitrogen-containing compounds produced by potato plants as a chemical defense against pests and pathogens, concentrated in the skin, sprouts, and green tissue of the tuber.
Potato plants produce two primary glycoalkaloids: alpha-solanine and alpha-chaconine. Together they make up the total glycoalkaloid (TGA) content of a potato. They are bitter-tasting steroidal compounds, and their concentration rises with light exposure, mechanical damage, and sprouting — which is why greened or sprouted potatoes taste bitter and are best discarded.
Why glycoalkaloids matter
At sufficient doses, glycoalkaloids are toxic. The European Food Safety Authority estimates an acute toxic dose of 2–5 mg per kg of body weight, with symptoms — gastrointestinal and neurological disturbances — possible at 1 mg/kg (EFSA 2020 opinion on glycoalkaloids in food and feed). To keep dietary exposure well below that range, the maximum recommended TGA level in potatoes for human consumption is 200 mg/kg fresh weight (EFSA 2020 opinion on glycoalkaloids in food and feed), a threshold also applied by Health Canada and other regulatory bodies.
Ordinary potatoes sold for food fall under this limit. The concern for protein ingredients is different: glycoalkaloids can bind to potato proteins and concentrate during certain extraction methods. Animal evidence underlines the point — feeding salmon a potato protein product containing high levels of glycoalkaloids caused weight loss, an effect tied to the residual compounds rather than the protein itself.
How glycoalkaloids relate to potato protein isolate
The transition from whole potato to a purified isolate is, in large part, a story of removing glycoalkaloids and other anti-nutrients. Well-controlled isolation separates the protein fraction from the alkaloid-bearing compounds, leaving a product that no longer carries the bitter, potentially toxic load of a green tuber. For a fuller picture of how this fraction is separated, see what potato protein is and how it is made.
Removal is not always total. A 2024 analysis found that commercial potato protein isolates can still contain trace amounts of glycoalkaloids (Food Chemistry, 2025, PMID:40627963). Processing method matters: enzymatic hydrolysis approaches that target glycoalkaloids do not remove the aglycon — the sugar-free core molecule — which itself binds to potato proteins with negative effects. This is one reason third-party testing and a published certificate of analysis are useful for verifying what a finished isolate actually contains.
Glycoalkaloids and nightshade sensitivity
Potatoes are members of the nightshade family, and glycoalkaloids are among the compounds people on elimination protocols try to avoid. The initial stages of the Autoimmune Protocol (AIP), for instance, exclude all nightshade vegetables. Individuals following such protocols should treat potato-derived ingredients accordingly, regardless of how low the residual glycoalkaloid content is reported to be.
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