Nina Teicholz: The Deal on DASH

By Dietdoctor @DietDoctor1

Recently, US News and World Report published its annual diet rankings, and as usual, DASH was at or near the top.

DASH is a diet that was designed to help reduce blood pressure for people with hypertension. It makes no sense to recommend this diet to a general population, for the main reason that DASH has pretty much only ever been tested on hypertensive ore pre-hypertensive subjects, who cannot be generalized to the population at large. Also, all trials have been short term, with outcomes indicating that DASH may actually cause heart disease-not prevent it.

Summarizing the trials

DASH has never been shown to be effective for preventing any nutrition-related chronic disease:

  1. DASH has never been shown to help people lose weight or prevent diabetes.
  2. DASH has, at best, mixed results for heart-disease risk factors. While it sometimes lowers LDL-C, (a possible, though unreliable sign of improving CVD risk) it invariably also lowers HDL-C and fails to lower (or raises) triglycerides (both reliable signs of increasing CVD risk).
  3. Only 1 DASH trial has lasted longer than 8 weeks (and that trial was only 4 months).

I've drawn evidence from a list of DASH studies in the 2015 US Dietary Guidelines advisory committee report, which cited DASH studies as evidence that its "Dietary Patterns" could prevent heart disease-but none of these trials did that.

The full table summarizing all the trials

The full table summarizing all the trials

In sum, a total of 2,162 people have been studied on DASH, in trials nearly all of which lasted 8 weeks or less. Only 60 of these 2,162 subjects were normal (not hypertensive/pre-hypertensive), and those 60 were adolescent girls.

The above is not a systematic review, obviously, so please feel free to let me know what is missing.

Note that when a small "high-fat DASH" study was conducted, it outperformed a regular DASH diet on improving cardiovascular risk factors. This is consistent with evidence that the vast majority of higher-fat diets outperform low-fat, high-carb diets on nearly all outcome markers.

If you use this evidence summary, please cite this post. Thank you!