Scientists review past medical records to study the relationship between physical activity and heart disease.

Doctors observe patients who choose to take a new medication and compare their outcomes to those who declined the medication.

A group of researchers surveys adults about their dietary habits and compares the results to their reported cholesterol levels.

Researchers randomly assign patients with high blood pressure to receive either a new drug or a placebo, then monitor their blood pressure over 6 months.

sterols

triglycerides

phospholipids

trans fatty acids