In the U.S. health care system not all patients are treated equally. As a result, these patients — minorities — often have worse health outcomes and higher mortality rates than whites. However, a recent study shows in more equal health systems void of racial biases, blacks have inexplicably better health outcomes than their white counterparts.

The American health care system is far from flawless, and even when you take out the many socioeconomic factors that limit black Americans’ access to adequate health care, studies have shown that racial biases often can affect the way doctors treat black patients, often leading them to prescribe lower doses of medication than they would to white patients with the same condition. In a recent study currently published in the online journal Circulation, a team of researchers explored what would happen if these racial injustices were removed from the health system.

The team chose to use the U.S. Department of Veterans Affairs as a model for a racially equal health care system, since racial biases are far less likely to occur in this system. The team recorded the mortality rate of 2,525,525 whites and 547,441 blacks who had received care from the VA for nine years, and they were surprised at what they found. More than 638,000 men died by the end of the study, but the mortality rate of blacks was 24 percent higher than for whites. The annual mortality rate for white men was 31.9 per 1,000, compared to only 22.5 per 1,000 for black men. Blacks were also found to be 37 percent less likely than white men to develop heart disease, the leading cause of death in the U.S, although the incidence of stroke remained constant among the different races. This discrepancy remained even when the team took other factors such as age, gender, income, education, blood pressure, medications, and body mass index into account.

“We thought we were going to show they do the same if the same care is offered to both groups,” said senior author Dr. Kamyar Kalantar-Zadeh, a nephrologist and epidemiologist at UC Irvine, as reported by The Chicago Tribune. “But we found blacks do even better.”

The reason for this unexpected result is still unknown. According to the researchers, it may have occurred because the blacks who received VA health care treatment were on average in better health than the general population of black Americans. Other factors such as diet and exercise, which were not taken into account for the study, may also explain the racial gap. However, the results could also suggest that controversial idea that blacks may have genetic or other biological advantages that make them more resilient to disease than whites.

Blacks are not the only ethnic minority found to have inexplicably better health than white Americans. In what is known as the Hispanic Paradox, doctors have noted that although Hispanics living in the U.S. are poorer, have more physically demanding jobs, and less access to education and health services, their health is generally better than non-Hispanic whites, The BBC reported. Although researchers have yet to explain this paradox, researchers believe that low smoking rates, younger populations, and closer family ties and a sense of community, which foster good mental health, all contribute to Hispanics living in generally good health.

However, despite these findings, other research has shown minorities do face more health risks than white Americans, with black Americans and Hispanics being more likely than whites to develop and die from a number of diseases, such as diabetes. The Centers for Disease Control and Prevention cites economic factors like education and income, access to healthy food retail, unemployment, and health care access as the main determinants of health inequalities.

According to the Department of Health & Human Services, disease prevention health care, which involves focusing on preventing disease before it happens, is the key to closing this racial disparity. Preventive practices could help to dramatically curb the mortality rates caused by obesity, diabetes, and heart disease in all populations.

Source: Kovesdy CP, Norris KC, Boulware LE, et al. Association of Race with Mortality and Cardiovascular Events in a Large Cohort of US Veterans. Circulation. 2015.