Optimal Macronutrient Intake Trial to Prevent Heart Disease (OMNI Heart)

Objectives

The objective of this study was to compare the effects of 3 healthy diets, each with reduced saturated fat intake, on blood pressure and serum lipids.

Background

While reduced intake of saturated fat is widely recommended for the prevention of cardiovascular disease (CVD), the type of macronutrient (carbohydrate, protein, or unsaturated fat) that should replace saturated fat was unresolved.

Subjects

The trial included 164 total subjects recruited from 2 clinical centers: Johns Hopkins Medical Institutions (Baltimore, MD) and Brigham and Women’s Hospital (Boston, MA). Subjects were generally healthy adults, age ≥30 years with a systolic blood pressure (SBP) 120-159 mm Hg or diastolic blood pressure (DBP) 80-99 mm Hg. This range includes individuals with prehypertension (systolic, 120-139 mm Hg or diastolic, 80-89 mm Hg) and stage 1 hypertension (systolic, 140-159 mm Hg or diastolic, 90-99 mm Hg). Exclusion criteria included diabetes, prior or active CVD, LDL-cholesterol >220 mg/dL, fasting triglycerides >750 mg/dL, weight more than 350lb, taking medication for reduction of blood pressure lipid levels, unwillingness to stop taking vitamin and mineral supplements, and alcoholic intake of more than 14 drinks per week. The mean age of the participants was 53.6 years, 45% were women, and 55% were African American.

Design

Three healthy diets were tested: a carbohydrate-rich diet similar to the DASH diet, a protein rich diet−about half from plants, and a diet rich in unsaturated fat, mostly monosaturated fat. Subjects spent 3 periods of 6 weeks on each diet. There was 2-4 week washout periods in between the diets−subjects ate their own food during these periods. At the beginning of the study there was a run-in period of 6 days, afterwards the subjects were randomized to 1 of the 6 sequences of the 3 diets. All the food during the study was provided by the researchers. The participants came to the study site weekdays for lunch and food for the other two daily meals, snacks, and weekend meals were provided for the participants to take home. Calories were adjusted in order to maintain weight and to avoid confounding effects of weight loss in the study. Potassium and sodium were also maintained during the study.

Conclusions

A healthy diet with partial substitution of carbohydrate with either protein or monosaturated fat can further lower blood pressure, improve lipid levels, and reduce estimated cardiovascular risk.

Publications

Appel LJ, Sacks FM, Carey VJ, Obarzanek E, Swain JF, Miller ER 3rd, Conlin PR, Erlinger TP, Rosner BA, Laranjo NM, Charleston J, McCarron P, Bishop LM; OmniHeart Collaborative Research Group. Effects of protein, monounsaturated fat, and carbohydrate intake on blood pressure and serum lipids: results of the OmniHeart randomized trial. JAMA. 2005 Nov 16;294(19):2455-64.

Furtado JD, Campos H, Sumner AE, Appel LJ, Carey VJ, Sacks FM. Dietary interventions that lower lipoproteins containing apolipoprotein C-III are more effective in whites than in blacks: results of the OmniHeart trial. Am J Clin Nutr. 2010 Oct;92(4):714-22. Epub 2010 Sep 8.

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