A common genetic quirk that turns your skin yellow might actually protect your heart.

Nature · Published 3 October 2026 · Updated 25 October 2026 Swipe more like this →

In short: Gilbert's syndrome affects millions, often going unnoticed until a routine blood test reveals elevated bilirubin. While it can cause mild, temporary jaundice during stress or fasting, this harmless condition is increasingly viewed as a potential biological advantage, with evidence suggesting it may lower the risk of cardiovascular disease.

First described in 1901, Gilbert's syndrome is a hereditary condition characterized by a deficiency in the enzyme bilirubin UDP-glucuronosyltransferase (UGT). This enzyme is responsible for processing bilirubin, a yellowish pigment produced when red blood cells break down. In individuals with the syndrome, a genetic variation in the UGT1A1 gene—such as the (TA)7TAA promoter variant common in white populations or the Gly71Arg mutation in Asian populations—leads to a minimum 50% reduction in enzyme activity. This results in mild hyperbilirubinemia, where serum bilirubin levels fluctuate between 1 and 5 mg/dL.

The condition is often diagnosed around puberty, as hormonal changes and increased bilirubin production make the symptoms more apparent. While jaundice—a yellowing of the skin or eyes—can occur, it is typically triggered by external stressors like fasting, dehydration, strenuous exercise, or illness. Because the liver remains healthy and liver enzyme levels are normal, the syndrome is generally considered benign. It does not require treatment, and patients are typically advised only to manage triggers and consult a doctor before starting new medications, as the reduced enzyme activity can alter how the body clears certain drugs, such as irinotecan or specific HIV protease inhibitors.

Intriguingly, the mild elevation of unconjugated bilirubin may offer unexpected health benefits. Bilirubin acts as a potent antioxidant, and research suggests that individuals with Gilbert's syndrome may have a lower risk of coronary artery disease and other cardiovascular issues. Some studies have even linked the (TA)7/(TA)7 genotype to a significantly reduced risk of heart disease compared to those without the mutation. While debate persists regarding whether the condition should be classified as a disease at all, the current consensus emphasizes that for most, it is a harmless, and perhaps even protective, genetic variation.

General information, not professional advice. Spotted an error? Flag the card or see corrections and complaints.

Intellect Plus is a visual educational discovery platform for exploring fascinating facts and ideas. Brain Food, Not Brain Rot. What is Intellect Plus?

Related

• Yellow eyes in jaundice are not really the whites of the eyes
• Why your body’s waste product might actually be a powerful cellular protector
• Decoding Jaundice: The Three Pathways of Bilirubin Buildup
• A genetic glitch can mimic a severe vitamin deficiency
• A rare genetic glitch turns a vital nutrient into a silent, life-threatening toxin.
• Medieval English shoppers paid a whole sheep's worth for one pound of ginger
• An amateur in a dune buggy found a rival to Tyrannosaurus
• The ginkgo tree is a botanical survivor that has outlived millions of years of change.
• A microscopic parasite uses a clever shell to survive in water for months.
• The ginkgo has swimming sperm and survived the Hiroshima bomb
• A carnivore's gut runs on bamboo that is ninety-nine percent diet
• Ginseng sells billions of dollars a year despite no proven health benefit

More in Organisms · More in Nature · Latest · A–Z · All topics