Diets helping to maintain a healthy blood pressure

The DASH eating plan has been developed in the US as an approach to reduce elevated blood pressure through appropriate dietary choices (DASH = Dietary Approaches to Stop Hypertension). Randomized trials have shown which food categories help in establishing and maintaining a healthy blood pressure.

Diets helping to maintain a healthy blood pressure 4The original design was aiming to improve the typical US diet (control), with refined grains, dairy fat, meats and sugar and few fruits, nuts, legumes and vegetables, towards lower (saturated) fat and cholesterol intake, higher intakes of blood pressure relevant minerals (calcium, potassium and magnesium) as well as more fiber and protein. Also tested was the sole increase of fruits and vegetables resulting in similar levels of potassium, magnesium and fiber as in the DASH diet, but similar levels of fat, protein and calcium as in the control diet. In these trials sodium levels were similar between the 3 diets. Significant reductions in hypertensive, moderately hypertensive and pre-hypertensive people have been obtained in eight week trials, both for the systolic and the diastolic blood pressure.

The highest decreases were observed in participants with hypertension, and Afro-Americans responded with higher decreases versus Caucasians. Blood pressure was lowered in about 2 weeks and remained relatively stable for the remaining 6 weeks. At the end of the trials the fruit and vegetable diet reduced half as much in comparison to the DASH diet. The DASH diet consists of generous helpings of fruit and vegetables (8-10 portions per day), low fat dairy products (2-3 portions per day) and (whole) grain products (7-8 portions per day), eating nuts, seeds and legumes, emphasizing fish and chicken rather than red meat, and limiting fats and sweets.1,2

In the original DASH trial, lack of menu variety was a primary reason for lapses in dietary adherence. A recent review of 9 trials of the DASH diet with objective measures of compliance reported poorer adherence when dietary advice rather than foods was provided.3 Providing options within the dietary DASH advice approach that permit variation in the macronutrient substitution (exchange of sugars for fat) but still aiming at achieving the desired lower blood pressure and keeping lipid risk factors within acceptable ranges might improve longer term compliance.

A recent study4 explored this rationale by substituting full-fat dairy products for non-fat and low-fat dairy foods in conjunction with a reduction of 12% of energy in carbohydrate, primarily from sugars; the result of the exchanges was that saturated fat levels rose from 8% to 14% of energy. Dietary control was achieved by providing study participants with daily provision of foods up till 50% of total energy and the remaining part by detailed menus, shopping lists, and food preparation instructions. In total 36 participants completed all 3 experimental diets (control, normal DASH, higher fat DASH) in a cross-over design with 3 week interventions and 2 week wash-out periods. Both DASH diets decreased the systolic pressure with more than 3 mm Hg and the diastolic pressure with more than 2 mm Hg versus the control situation.

The higher fat DASH diet resulted in lower plasma triglycerides when compared to the normal DASH diet; both DASH diets reduced total and LDL cholesterol versus the control diet in a similar way. It was concluded that the fat modified DASH diet presents a less stringent dietary alternative for the normal DASH diet with more sugars ingested from sweets, sugary drinks and fruit juices.

References

  1. Appel LJ et al. A clinical trial of the effects of dietary patterns on blood pressure. N Engl J Med 1997; 336:1117-1124
  2. Craddick et al. The DASH Diet and Blood Pressure. Current Atherosclerosis Reports 5: 484-491 (2003)
  3. Kwan et al. Compliance with the Dietary Approaches to Stop Hypertension (DASH) Diet: A Systematic Review. Plos One October 2013 | Volume 8 | Issue 10 | e78412
  4. Chiu S. et al. Comparison of the DASH (Dietary Approaches to Stop Hypertension) diet and a higher-fat DASH diet on blood pressure and lipids and lipoproteins: a randomized controlled trial. Am J Clin Nutr doi: 10.3945/ajcn.115.123281