Several studies have linked apples to a lower risk of heart disease. In addition, daily apple consumption was associated with a 27% lower risk of dying from a stroke and a 25% lower risk of dying from heart disease. Another review found that apple intake significantly decreased body mass index (BMI). One potential reason for this may be the concentration of flavonoids, including quercetin, in apples, which may help lower blood sugar and improve insulin sensitivity. People with an apple allergy should avoid apples and foods containing apples that could trigger symptoms.