OmniHeart Feeding Study - OmniHeart Feeding Study
The goal of the trial was to evaluate use of the DASH diet, which is rich in carbohydrates and low in fat, with a modified DASH diet that replaces some of the carbohydrates with either protein or unsaturated fat on the effects on blood pressure and lipid parameters.
Patients Screened: 930
Patients Enrolled: 161
Mean Patient Age: Mean age 53.6 years
Age ≥30 years; systolic blood pressure 120-159 mmHg or diastolic blood pressure 80-99 mmHg
Diabetes, active or prior CVD, LDL >220 mg/dL, fasting triglycerides >750 mg/dL, weight >350 lb, use of medication that affects blood pressure or lipid levels, unwillingness to stop taking vitamin and mineral supplements, and alcoholic beverage intake of >14 drinks per week.
Systolic blood pressure and LDL cholesterol at the end of each diet period
Diastolic blood pressure, triglycerides, and HDL cholesterol at the end of each diet period
The trial was designed as a randomized, crossover study. Following a screening phase in which patients ate their own food and a run-in phase in which patients ate samples of the diet food, patients were randomized to either the DASH diet with the standard carbohydrates (58%), protein (15%), and fat (27%); the protein modified diet, with carbohydrates (48%), protein (25%), and fat (27%); or the unsaturated fat modified diet with carbohydrates (48%), protein (15%), and fat (37%), of which monounsaturated fat was 21%, polyunsaturated fat 10%, and saturated fat 6%. Patients were on the assigned diet for 6 weeks, where they ate prepared meals on-site during weekdays and ate prepared meals off-site during weekends. Following the 6 week diet period, participants ate their own food for 2-4 weeks, after which time participants crossed over to the next diet.
Mean baseline BMI was 30.2 kg/m2 and weight was 87.3 kg. As was intended, weight did not change with the different diets (86.3 kg with the carbohydrate diet, 86.0 kg with the protein diet, and 86.7 kg with the unsaturated fat diet). Systolic blood pressure was reduced with all three diets, but the reduction was greater in the protein diet (-9.5 mmHg; p=0.002) and the unsaturated fat diet (-9.3 mmHg, p=0.005) compared with the carbohydrate diet (-8.2 mmHg). Likewise, reductions in diastolic blood pressure were also greater with the protein diet (-5.2 mmHg; p<0.001) and the unsaturated fat diet (-4.8 mmHg, p=0.02) compared with the carbohydrate diet (-4.1 mmHg). LDL reductions were greater with the protein diet (-14.2 mg/dL; p=0.01) and non-significantly with the unsaturated fat diet (-13.1 mg/dL, p=0.20) compared with the carbohydrate diet (-11.6 mg/dL), as was total cholesterol (-19.9 mg/dL for the protein diet, -15.4 mg/dL for the unsaturated fat diet, and -12.4 mg/dL for the carbohydrate diet; p<0.05 for each vs carbohydrate diet) and triglycerides (-16.4 mg/dL for the protein diet, -9.3 mg/dL for the unsaturated fat diet, and +0.1 mg/dL for the carbohydrate diet; p<0.05 for each vs carbohydrate diet). Estimated 10 year coronary heart disease risk based on the Framingham risk score was lowered by 21% for the protein diet, 20% for the unsaturated fat diet, and 16% for the carbohydrate diet.
Among individuals with hypertension or prehypertension, use of a modified reduced carbohydrate DASH diet was associated with greater reductions in blood pressure and lipid parameters compared with use of the standard DASH diet.
The DASH diet, which is low in saturated and total fat, has been shown in previous randomized trials to be effective for reducing blood pressure and lipid parameters. However, a substantial portion of the DASH diet is made up of carbohydrates. The present study confirms the blood pressure and lipid reductions found in earlier trials with the standard DASH diet, but also showed additional reductions are possible by substituting more protein or unsaturated fats for some of the carbohydrates. It should be noted that the trial was conducted in a controlled manner in which all weekday meals were prepared and consumed on-site. Weight was maintained at a stable level in order to remove possible confounding of weight loss on the interpretation of the effect of the diet modification on the results.
Appel LJ, et al. Effects of Protein, Monounsaturated Fat, and Carbohydrate Intake on Blood Pressure and Serum Lipids. JAMA. 2005;294:2455-2464.
Presented by Dr. Lawrence J Appel at the American Heart Association Scientific Session, Dallas, Texas, November 2005.
Keywords: Cholesterol, Cross-Over Studies, Body Mass Index, Food Habits, Weight Loss, Coronary Disease, Prehypertension, Diet, Triglycerides, Hypertension, Fats, Unsaturated, Dietary Carbohydrates
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