Strengthening Heart Disease Argument with Green Tea

In a recent study, researchers found that people who drink green tea regularly tend to have lower rates of heart disease compared to those who do not drink green tea. The researchers concluded that drinking green tea directly contributes to reducing heart disease risk. However, the study did not control for factors such as diet, exercise, and genetic predisposition, which could also influence heart disease rates.

Based on the information provided, which of the following statements would most strengthen the argument that drinking green tea reduces the risk of heart disease?