Scientists from Harvard Medical School and other institutions have found that the DASH diet may significantly reduce the risk of heart disease within just eight weeks.
Although modern risk calculators are widely used to guide decisions about preventive therapies, there has been limited evidence showing how lifestyle changes—particularly diet—can quickly lower long-term cardiovascular risk.
In the new study, researchers analyzed data from the original DASH (Dietary Approaches to Stop Hypertension) clinical trial to evaluate how the DASH diet affects estimated 10-year heart disease risk.
The DASH diet emphasizes eating plenty of fruits and vegetables, whole grains, lean proteins, low-fat dairy products, beans, nuts, and vegetable oils, while limiting sweets, sodium, and foods high in saturated fat.
Researchers compared three dietary patterns:
- A typical control diet reflecting common eating habits
- A fruits-and-vegetables diet
- The DASH diet
The analysis included data from 459 adults aged 22 to 75 who did not have heart disease and were not taking medication for diabetes or high blood pressure. Participants followed one of the three diets for eight weeks.
Compared with the control diet, both the DASH diet and the fruits-and-vegetables diet significantly reduced estimated 10-year heart disease risk:
- DASH diet: 10.3% reduction
- Fruits and vegetables diet: 9.9% reduction
The benefits were particularly strong among women and Black adults. Researchers found no significant difference in overall risk reduction between the DASH diet and the fruits-and-vegetables diet.
When examining blood pressure effects alone, the DASH diet showed a greater impact. Reductions in systolic blood pressure translated to:
- 14.6% lower risk with the DASH diet
- 7.9% lower risk with the fruits-and-vegetables diet
This suggests the DASH diet provided an additional 7.2% advantage in lowering blood pressure.
However, the study also noted a counterbalancing effect related to high-density lipoprotein (HDL) cholesterol. Changes in HDL levels associated with the DASH diet increased estimated risk by 8.8%, compared with a small reduction (−1.9%) seen with the fruits-and-vegetables diet.
Overall, the results indicate that switching from a typical American diet to either the DASH diet or a fruits-and-vegetables-rich diet can lower estimated 10-year heart disease risk by about 10% in as little as eight weeks.
The findings highlight the powerful role dietary changes can play in cardiovascular prevention and may help patients and healthcare providers set realistic expectations for how quickly lifestyle interventions can improve long-term heart health.
The study was published in The American Journal of Cardiology and conducted by Sun Young Jeong and colleagues.
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