DASH Diet and Blood Pressure

The concept that diet and blood pressure are linked has been discussed since at least the 1920s.  In 1926, Donaldson noted that “vegetarians, we believe, run a consistently lower blood pressure than those who use flesh foods.” [1]

Dr Frank Sacks [2] is a medical doctor and Professor of Cardiovascular Disease Prevention, Department of Nutrition at the Harvard School of Public Health.

He was:

  • Chair of the Design Committee of the DASH study which lead to the DASH diet.
  • Co-Chair of the OmniHeart Trial that showed that variations of the DASH diet that are higher in protein or unsaturated fat improved blood pressure and lipid risk factors when compared to the DASH diet.
  • Principal Investigator of the Pounds Lost trial which compared 4 diets varying in protein, carbohydrate and fat content. 811 overweight people were studied for 2 years.  All diets showed the same beneficial effects on weight loss and risk factors for heart disease.[3]
In 1975, he was the lead author in a paper studying lipids and lipoproteins in vegetarians. [4]  The study compared a group that was predominately vegetarian with some participants consuming eggs and fish with a control group “consuming the usual American diet”.   The mean values of the two groups are summarised below.
MeasureUnitsVegetarianControl
Cholesterolmmol/L (mg/dL)3.3 (126)4.8 (184)
LDL cholesterolmmol/L (mg/dL)1.9 (73)3.1 (118)
VLDL cholesterolmmol/L (mg/dL)0.31 (11.8)0.44 (17.2)
HDL cholesterolmmol/L (mg/dL)1.1 (42)1.3 (49)
Triglyceridesmmol/L (mg/dL)0.7 (59)1.0 (86)
Weightkg5873
Subscapular skinfoldmm617
According to the authors, the study “showed that consumption of dairy foods and eggs, but not body weight, was associated with the lipoprotein and cholesterol findings”.

In a paper [5] Dr Sacks co-authored in 1974 noted that “the declared consumption of food of animal origin was highly significantly associated with systolic and diastolic BP after the age and weight effects were removed.”

Another paper [6] from 1981 states “the study suggests an adverse effect of consumption of beef on plasma lipid and BP levels”.  The study actually showed that there was a significant increase in systolic blood pressure and plasma cholesterol after a 4 week period of adding 250 g of beef per day to a strict vegetarian diet.

Dr Sacks is well aware that vegetarian diets are associated with lower blood pressure.


The Dietary Approaches to Stop Hypertension (DASH) trial tested 3 types of diet with 459 people to study the effects on blood pressure.  The results were published in 1997. [7] [8]

The study papers noted that “vegetarians tend to have lower blood pressures than nonvegetarians” [9] and “a predominantly vegetarian dietary pattern is often present in these cultures that have generally low BPs.” [10]

In the DASH trial, the participants were randomly assigned one of the 3 diets for an 8 week period.

The Control Diet was “typical of the diets of a substantial number of Americans”.  The Fruits-And-Vegetables Diet provided “more fruits and vegetables and fewer snacks and sweets than the control diet but was otherwise similar to it”.  The Combination Diet was “rich in fruits, vegetables, and low-fat dairy foods and had reduced amounts of saturated fat, total fat, and cholesterol.”

Compared with the control diet, the combination diet reduced systolic blood pressure by an average of 5.5 mmHg and the fruits-and-vegetables diet reduced systolic blood pressure by 2.8 mmHg – not a substantial improvement for 8 weeks.

The fruits-and-vegetables diet is a misleading label.  The fruits-and-vegetables diet had a higher intake of red meat than the other 2 diets and a greater intake of total meat than the combination diet.  The combination diet had more vegetables than the fruits-and-vegetables diet. [11]

Below is a comparison of the control diet, with the fruits-and-vegetables diet and the “ideal combinationdiet. [12]

Food groupsControl
g/day
Fruit & veg
g/day
Combo diet
g/day
Red meat (beef, pork, lamb and veal)9510824
Meat (red meat, fish, poultry)192172139
Vegetables147272345
Dairy products8959485
Fats and oils544326
Sweets and sugar containing snacks1522822
Given that “ideal combinationdiet had more vegetables and less meat and less red meat than the fruits-and-vegetables diet then it is expected that the blood pressure would be lower.

The “Ideal Combination Diet” had a very large increase in the amount of dairy consumed, despite the fact that Sacks published a paper[13] that “showed that consumption of dairy foods and eggs, but not body weight, was associated with the [adverse] lipoprotein and cholesterol findings”.

The OmniHeart Trial compared the standard DASH diet with 2 variants.  The first variant replaced some carbohydrate with protein and the second variant replaced some carbohydrate with unsaturated fat.  The “OnmiHeart Diets provide more options for heart health”. [14]

  1. Diet 1: (Carbohydrate)A carbohydrate-rich diet of 58% carbohydrate, 15% protein, and 27% fat.

  2. Diet 2: (Protein)A higher protein diet that had 10% more protein and 10% less carbohydrate (48% carbohydrate, 25% protein, and 27% fat).  The 10% protein increase in the higher protein diet emphasized plant protein.  It was noted that the meat and dairy food sources were also increased “somewhat”.

  3. Diet 3: (Unsaturated fat)A higher unsaturated fat diet that had 10% more unsaturated fat and 10% less carbohydrate (48% carbohydrate, 15% protein, and 37% fat). Olive oil, canola oil, and olive oil spread were used as the unsaturated fat source.

The 10% reduction in carbohydrate in the higher protein diet and the higher unsaturated fat diet was achieved by replacing some fruits with vegetables, reducing sweets, and using smaller portions of grain products

Nutrient (% of calories)Carbohydrate
Diet
Protein DietUnsaturated Fat
Diet
Carbohydrates584848
Total fat272737
Monounsaturated fat131321
Protein152515
According to the study, “all three diets reduced blood pressure, total and low-density lipoprotein cholesterol levels, and estimated coronary heart disease risk” and the “partial substitution of carbohydrate with protein and unsaturated fat likely led to further improvement in CVD risk factors.” [15]

The conclusion from this paper states that “the OmniHeart diet patterns offer substantial flexibility in macronutrient intake that should make it easier to eat a heart-healthy diet and reduce cardiovascular disease risk.”

Despite the claims that the “DASH diet is a carbohydrate-rich, reduced-fat diet” [16], a diet consisting of 58% carbohydrate and 27% total fat is not a high-carbohydrate diet nor a low-fat diet.

In 2018, the DASH diet was ranked Best Diet Overall for eighth year in a row by U.S. News and World Report.[17]


Seven Day Adventist studies have shown that as the diet becomes increasingly vegan then the prevalence of hypertension (high blood pressure) decreases. [18]

A similar conclusion was found in meta-analysis study from 2014 [19] and the earlier studies from Harvard School of Public Health that were highlighted earlier.

It is hard to escape the conclusion that the DASH diet and its variants are not the most effective way of solving high blood pressure.

Footnotes

  1. Donaldson, A. N. (1926) The relation of protein foods to hypertension. California and Western Medicine. 24 (3), p330
  2. Harvard School of Public Health (n.d.) Frank Sacks | Harvard T.H. Chan School of Public Health [online]. Available from: www.hsph.harvard.edu/frank-sacks/ (Accessed 18 October 2016).
  3. de Souza, R. J. et al. (2012) Effects of 4 weight-loss diets differing in fat, protein, and carbohydrate on fat mass, lean mass, visceral adipose tissue, and hepatic fat: results from the POUNDS LOST trial. The American Journal of Clinical Nutrition. 95 (3), 614–625.
  4. Sacks, F. M. et al. (1975) Plasma Lipids and Lipoproteins in Vegetarians and Controls. New England Journal of Medicine. 292 1148–1151.
  5. Sacks, F. M. et al. (1974) Blood Pressure in Vegetarians. American Journal of Epidemiology. 100 (5), 390–398.
  6. Sacks, F. M. et al. (1981) Effect of Ingestion of Meat on Plasma Cholesterol of Vegetarians. Journal of American Medical Association. 246 (6), 640–646.
  7. Appel, L. J. et al. (1997) A clinical trial of the effects of dietary patterns on blood pressure. New England Journal of Medicine. 336 (16), 1117–1124.
  8. National Heart Blood and Lung Institute (2014) What Is the DASH Eating Plan? [online]. Available from: www.nhlbi.nih.gov/health-topics/dash-eating-plan (Accessed 17 September 2015).
  9. Vogt, T. M. et al. (1999) Dietary Approaches to Stop Hypertension: Rationale, Design, and Methods. Journal of the American Dietetic Association. 99 (8S), pS12
  10. Sacks, F. & Kass, H. (1988) Low blood pressure in vegetarians: effects of specific foods and nutrients. American Journal of Clinical Nutrition. 48 p795
  11. Karanja, N. et al. (1999) Descriptive Characteristics of the Dietary Patterns Used in the Dietary Approaches to Stop Hypertension Trial. Journal of the American Dietetic Association. 99 (8), pS21
  12. Karanja, N. et al. (1999) Descriptive Characteristics of the Dietary Patterns Used in the Dietary Approaches to Stop Hypertension Trial. Journal of the American Dietetic Association. 99 (8), S19–S27.
  13. Sacks, F. M. et al. (1975) Plasma Lipids and Lipoproteins in Vegetarians and Controls. New England Journal of Medicine. 292 1148–1151.
  14. Harvard Health Publications (n.d.) OmniHeart Diets Provide More Options for Heart Health. [online]. Available from: www.health.harvard.edu/PDFs/OmniDiets.pdf
  15. Swain, J. F. et al. (2008) Characteristics of the Diet Patterns Tested in the Optimal Macronutrient Intake Trial to Prevent Heart Disease (OmniHeart): Options for a Heart-Healthy Diet. Journal of the Academy of Nutrition and Dietetics. 108 (2), 257–265.
  16. Carey, V. J. et al. (2005) Rationale and design of the Optimal Macro-Nutrient Intake Heart Trial to Prevent Heart Disease (OMNI-Heart). Clinical Trials. 2 (6), 529–537.
  17. National Institutes of Health (2018) DASH ranked Best Diet Overall for eighth year in a row by U.S. News and World Report.
  18. Pettersen, B. J. et al. (2012) Vegetarian diets and blood pressure among white subjects: results from the Adventist Health Study-2 (AHS-2). Public Health Nutrition. 15 (10), 1909–1916.
  19. Yokoyama, Y. et al. (2014) Vegetarian diets and blood pressure: a meta-analysis. JAMA Internal Medicine.  174 (4), 577–587.

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