Chef Tim Says...

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Dr. Tim Says....

The DASH Diet and the Mediterranean Diet

The DASH Diet (Dietary Approaches to Stop Hypertension) is so successful because its foundations are drawn from research on the Mediterranean diet. Many of the researchers who took part in the initial DASH study were the same who detailed the benefits of the Mediterranean diet. If you look at them side by side it’s easy to see how similar they are:

DASH Diet Mediterranean Diet
whole grain products Grains,
whole grain products
Vegetables Vegetables
Fruit Fruit and Nuts
Low-fat or fat-free dairy Low-fat or fat-free dairy
Meats, poultry and fish Less meat and lean meat
  More fish
Nuts, seeds, and dry beans Legumes (note nuts above with fruit)
Fats and oils More unsaturated and less saturated fat
  Alcohol in moderation

The results of the initial DASH study found that those following the diet had both lower systolic and diastolic blood pressures in those without high blood pressure. The effect in those with hypertension was even greater, with blood pressure reductions of around 11 points.1 This was profound information at the time, but as researchers are prone to do, they thought that they might be able to do better.

At the time there were questions about whether lowering the sodium content in the DASH diet might be even more effective. The three diets in the DASH diet study contained approximately 3,000 mg sodium per day. A follow up trial, the DASH - Sodium study was devised with two diets similar to the control diet and the DASH diet in the previous study.

Each diet plan was devised with three levels of sodium - the original 3,000 mg per day as well as 2,400 mg and 1,500 mg levels. The study was designed as a crossover trial where each of the 6 groups followed the diet for a month and changed diets at the beginning of the following month. This intervention strategy insures that the results of each plan are valid in all the participants.

Control Diet DASH - Sodium Diet
3,000 mg 3,000 mg
2,400 mg 2,400 mg
1,500 mg 1,500 mg

The original DASH diet with 3,000 mg sodium lowered blood pressure in all of the participants to the levels seen in previous studies. Lowering sodium intake to 2,400 mg/day effectively reduced blood pressure for all participants. (2)

Sodium intakes at 1,500 mg per day, however, lowered blood pressure by twice as much with a reduction of 8.9 points (systolic) and 4.5 points (diastolic). Once again, the effect was greater in those who were already hypertensive with a drop in blood pressure of 11.5 points (systolic) and 5.7 points (diastolic).

The challenge for the DASH diets was that both of the studies were designed by giving the participants pre-prepared food. That level of control makes it easier for researchers to prove that a diet works and they wondered whether simply teaching people how to eat would offer the same benefit.

Researchers in the PRIMIER trial divided study participants into three groups:

Advice-only (control): Participant received a single education session with printed handouts.

Established recommendations: This group received behavioral counseling of 18 sessions with trained interventionists (typically registered dietitians) over 6 months using recommendations for non-pharmacologic management of hypertension including:

  • reduced sodium intake
  • increased physical activity
  • limited alcohol intake,
  • weight loss

Established-plus-DASH: The final group also had 18 sessions based on the established recommendations plus the DASH diet.

The results were similar to the controlled studies with those following the DASH diet showing a 25% reduction in the number having high blood pressure. Even better, 35% of those who with hypertension at the beginning of the study were more likely to have optimal control of their pressures.

Outcome Baseline Advice Only Established Recommendations Established
+ DASH Diet
% with Hypertension 37 26 17 12
% with Optimal control 0 19 30 35

These studies were amongst the first large scale controlled trials to prove the impact of diet on high blood pressure. The best part is that the research has been repeated with Mediterranean diet giving you great options in getting healthier and staying healthy.

1. Appel LJ, Moore TJ, Obarzanek E, et al. A clinical trial of the effects of dietary patterns on blood pressure. DASH Collaborative Research Group. N Engl J Med 1997; 336:1117-1124.

2. Sacks FM, Svetkey LP, Vollmer WM, et al. Effects on blood pressure of reduced dietary sodium and the Dietary Approaches to Stop Hypertension (DASH) diet. DASH-Sodium Collaborative Research Group. N Engl J Med 2001; 344:3-10.

First posted: May 14, 2012