Diet can help lower hypertension and improve heart function in patients suffering from a common type of heart failure, according to a new research.

After 21 days of following a low-sodium Dietary Approaches to Stop Hypertension (DASH) eating plan, patients saw a drop in blood pressure similar to taking anti-hypertension medicine.

Scott Hummel, M.D., cardiologist at the University of Michigan Frankel Cardiovascular Center, said that their work suggests diet could play an important role in the progression of heart failure, although patients should always talk to their doctor before making major dietary changes.

Heart failure with preserved ejection fraction, or "diastolic" heart failure, happens when the heart becomes stiff and does not pump out enough blood.

The patients, most of them in their 60s and 70s, agreed to keep food diaries and eat only the meals prepared for them in the metabolic kitchen at the University of Michigan Clinical Research Unit.

The meals, which could be picked up and heated at home, matched the DASH diet eating plan, which is high in potassium, magnesium, calcium and antioxidants and is recommended for hypertension treatment by the National Institutes of Health and the American Heart Association.

The study diet also contained a daily sodium intake of no more than 1,150 milligrams. That's much lower than what adults in the United States usually eat - about 4,200 mg a day for men, and 3,300 mg a day for women.

The U-M study, although small, showed the DASH diet can improve left ventricular relaxation and reduce diastolic chamber stiffness, meaning a more efficient transfer of blood between the heart and arteries, Hummel says.