Evolutionary historian’s research links sodium toxicity to health concerns in Black communities

June 25, 2024
Photo of UNT professor Constance Hilliard in her office


Research by University of North Texas professor Constance B. Hilliard has uncovered a possible cause of key health issues among American individuals of African descent.

Hilliard, an African evolutionary historian in UNT’s Department of History, found that certain illnesses common in many Black American communities — like hypertension and kidney disease — may be explained by unique genetic variations. Hilliard’s research is detailed in her book Ancestral Genomics: African American Health in the Age of Precision Medicine, published by Harvard University Press.

Ancestral Genomics was inspired by an experience Hilliard had in 2008 while living in Japan. A visit to a Japanese doctor for hip pain resulted in an unexpected diagnosis of renal failure, based on comprehensive blood tests. But when Hilliard sought a second opinion from an American doctor, she was told she didn’t have kidney disease after all. She learned that although her bloodwork showed elevated creatinine levels by Japanese health standards, those same levels are considered by U.S. doctors to be normal in Black American populations.

Hilliard’s quest for an explanation involved years of interdisciplinary research. Her work led her to conclude that people of West African descent, whose ancestors would have had access to little or no salt, are likely to possess G1 and G2 variants of the APOL1 gene, which produces proteins that support the immune system. The G1 and G2 variants allow the body to absorb even trace amounts of sodium efficiently, increasing the likelihood of survival in salt-deficient regions.

“I devoted the early years of my career to translating manuscripts from Timbuktu and the medieval empires of Mali and Songhay. These chronicles described a lucrative trade in which elites inhabiting gold fields in the West African interior bartered gold for rock salt, pound for pound,” Hilliard says. “It was only later that I realized the vital need to use this historical precision as a tool for accurately identifying the function of African gene variants found in Blacks.”

Data from the National Institutes of Health shows that Black Americans in the U.S. are three to four times more likely to die from kidney failure than individuals of other racial backgrounds. The same data indicates 75% of Black Americans 55 and older live with high blood pressure. According to Hilliard’s research, those with the G1 and G2 variants require far less dietary sodium than those without. However, the average American consumes 3,400 milligrams of sodium each day.

By limiting their sodium intake, Hilliard says, carriers of the G1 and G2 variants may be able to avoid these common negative health outcomes.

“Few African American families are without members or friends who have not suffered from APOL1-triggered diseases such as salt-sensitive hypertension and kidney failure,” she says. “But the knowledge that these disorders may be preventable in some cases could be a Black health game changer.”