This post is written by our guest blogger, Dr. Stephen Juraschek, an Instructor of Medicine at Beth Israel Deaconess Medical Center & Harvard Medical School.
The DASH-Sodium trial published in 2001 demonstrated that both the DASH diet and sodium reduction lowered blood pressure in adults who were not taking blood pressure medications. Both sodium reduction and the DASH diet lowered blood pressure.
When individuals combined reducing sodium with eating the DASH diet, blood pressure reduction was even greater. We asked the following question in our new study: does sodium reduction and the DASH diet impact blood pressure differently, depending on a person’s starting blood pressure? In this study, we put people into groups according to their starting blood pressure.
We then looked at the effects on blood pressure by:
- lowering sodium
- eating the DASH diet,
- lowering sodium and eating the DASH diet at the same time
All groups experienced a healthier blood pressure from sodium reduction or the DASH diet. We found that adults with a systolic blood pressure greater than 149 at the start of the study had greater effects from sodium reduction (7 to 10 points) than adults with a systolic blood pressure less than 130 at the start of the study (0 to 3 points). The DASH diet lowered systolic blood pressure 10 to 14 points among those with a systolic blood pressure greater than 149 at the start of the study versus on 2 to 4 points among those with a systolic blood pressure less than 130 at the start of the study.
When sodium reduction and DASH diet were combined, there was a clear trend in the effect of the interventions on systolic blood pressure: the higher your blood pressure, the more your blood pressure dropped. In the group with the highest blood pressure to start, we found that diet could lower systolic blood pressure more than 20 mm Hg. This finding was unexpected and quite impressive!
To place this in context, in order to approve a new anti-hypertensive agent, the FDA has said the drug should lower systolic blood pressure at least 3 to 4 mm Hg. Similarly, if you look at common classes of blood pressure medications like ACE inhibitors, beta blockers, or calcium channel blockers they all lower blood pressure 10 to 16 mm Hg. The effects we observed from diet are of a similar magnitude if not greater than some blood pressure drugs!
We also looked at the number of people with high blood pressure after they had been eating a better diet. After eating less sodium and the DASH diet during the study period, 75% of the study subjects in the group with the highest starting blood pressure had reached a healthy blood pressure! That is a big difference in effect.
This study also demonstrates the enduring value of the investment by the NIH/NHLBI to study the impact diet on health. We need more research on healthy diet! Eating is an essential aspect of human life – we all eat food! Further, the world population is growing at a rapid pace (estimated to be 9 billion by 2040). Understanding the impact of diet on human health has the potential to benefit the health of not only the current world population but the billions of people to come with subsequent generations.
The DASH-Sodium trial, a feeding trial, was an investment that continues to yield important and impactful information decades after the study about the ways food affects our bodies. The study authors are grateful to the NIH/NHLBI for investing in this important research and hope funding for these efforts will continue.
Dr. Stephen Juraschek is an Instructor of Medicine at Beth Israel Deaconess Medical Center & Harvard Medical School.