Why you should know about OmniHeart


What is the best way to eat healthy? Currently this is an area that leaves more questions than answers, despite an increase in access to nutrition information. However, one study in particular – the Optimal Macronutrient Intake Trial to Prevent Heart Disease (OmniHeart) – has demonstrated some very impressive results in the realm of heart health. Nutrition experts around the world are excited about its potential.


In OmniHeart, researchers pitted three healthful diets against each other. Each of the three was high in vegetables and fruit, while low in salt, sugar and processed foods. The main difference being each diet provided 10% more calories from either protein, unsaturated fat or carbohydrates. Researchers wanted to explore the impact of these various diets on parameters including blood pressure, lipids  (e.g. cholesterol) and overall cardiovascular risk.


Wondering what your cardiovascular risk looks like? Heart disease and stroke are two of the top three killers in Canada with at least 90% of Canadians having at least one risk factor such as high blood pressure, high cholesterol, physical inactivity, smoking, alcohol, obesity and diabetes (PHAC, 2009; Heart & Stroke Foundation, 2011). The results of OmniHeart are relevant for all Canadians.


The OmniHeart Results


Blood Pressure

For individuals who had hypertension (high blood pressure), following any one of these diets provided a 13-16 point decrease in systolic blood pressure and a 7-8 point decrease for those with pre-hypertension (Appel et al., 2005).  To put this into context, the impact of the diet is equal or more than can be achieved by some blood pressure medications (Harvard Health Publications, 2013).


These results also have an important significance as they show that macronutrients (carbohydrates, protein and fat) have an impact on blood pressure when other factors such as micronutrients (e.g. potassium, magnesium, calcium) and weight are controlled.



LDL or low-density lipoproteins, also known as the “bad” type of cholesterol, are the type of fat that builds up in arteries causing them to narrow. Elevated amounts of LDL are associated with higher risk for  heart attack and stroke (AHA, 2012). Each of the OmniHeart diets lowered LDL cholesterol on average by about 0.3-0.4 points (Appel et al., 2005). For those that started the trial with high LDL levels, the benefit was greater with up to a 0.6 point reduction (Appel et al., 2005). If you were to compare this to the gold standard of cholesterol lowering medications, statins, they on average lower LDL by 1.8 points (Law & Rudnick, 2003). So while none of the OmniHeart trial diets provided a comparable decrease to the group of statin medications, it’s important to note any reduction in LDL levels is a step in the right direction.


Triglycerides are a type of fat that have been linked to heart disease and other metabolic issues (Miller et al., 2011). Production of this type of fat can be increased with high consumption of sugar and alcohol among other factors. In OmniHeart both the unsaturated fat diet and protein diet significantly decreased triglyceride levels by 0.11-0.19 points. The carbohydrate diet had little impact on lowering the triglyceride levels (Appel et al., 2005).


Cardiovascular Risk

Over the course of the OmniHeart study, the participant’s ten year risk assessment for cardiovascular disease decreased by a notable 20-30% (Appel et al., 2005)!


Which diet won?


While all diets successfully improved markers of health – there was a tie between two for first place. Both the high protein and high unsaturated fat diets received first class honors for heart health.  They were the best for reducing “bad” LDL cholesterol and triglycerides while providing an impressive reduction in the risk for heart disease.


What does the OmniHeart diet look like for adults?


While many of the food group categories and serving sizes may look familiar (i.e. Eating Well with Canada’s Food Guide), you’ll notice some changes including a big bump in the recommendations for vegetables and fruit and specific limits set on other items such as added sugar. The following adapted table is what 2100 calories a day would look like if you were to follow a hybrid of the protein and unsaturated fat OmniHeart diets (CSPI, 2013). Consider this an illustration of an ideal way to eat and a goal to work towards.


If you want to start implementing parts of the OmniHeart research into your diet now, the key take away messages are to:

  1. make vegetables and fruit the centre of your meals and snacks,

  2. aim for most protein choices to be from plant sources (this is where you get some of the blood pressure lowing benefits),

  3. don’t go overboard with grains and

  4. limit added sugar while opting instead for more natural sources of sugar from fruit and dairy.





Vegetables & Fruit

  • ½ cup fresh, frozen or canned

  • 1 cup raw leafy greens

  • 1 medium fruit





  • ½ cup cooked rice, bulgur, quinoa or cereal

  • 1 slice bread

  • ½ pita or tortilla





Low-fat Dairy        

  • 1 cup milk or yogurt

  • 40 g cheese





Legumes & Nuts

  • ½ cup cooked beans

  • ¼ cup nuts

  • 120g tofu





Fish, Poultry & Lean Meat

  • 120g cooked





Oils & Fats

  • 1 Tbsp





Desserts & Sweets

  • 1 tsp sugar

  • 1 small cookie





Your Choice: 1 extra serving of...

  • Fish, poultry, meat OR grains OR oils & fats OR desserts & sweets







American Heart Association. (2012). Good vs. bad cholesterol. Retrieved from http://www.heart.org/HEARTORG/Conditions/Cholesterol/AboutCholesterol/Good-vs-Bad-Cholesterol_UCM_305561_Article.jsp


Appel, L.J., Sacks, F.M., Carey, V.J., Obarzanek, E., Swain, J.F., Miller, E.R., Conlin, P.R., Erlinger, T.P., Rosner, B.A., Laranjo, N.M., Charleston, J. , McCarron, P., Bishop, L.M. (2005). Effects of protein, monounsaturated fat and carbohydrate intake on blood pressure and serum lipids: Results of the OmniHeart randomized trial. Journal of the American Medical Association, 295(19), 2455-2464.


Centre for Science in the Public Interest. (2013). Glimmers of Light? New clues to weight gain and loss, December 2013 [Table]. Retrieved from Nutrition Action Healthletter.


Harvard Health Publications. (2013). Blood pressure: What’s food got to do with it? Retrieved from http://www.health.harvard.edu/newsletters/Harvard_Mens_Health_Watch/2013/March/blood-pressure-whats-food-got-to-do-with-it?utm_source=mens&utm_medium=pressrelease&utm_campaign=mens0313


Heart and Stroke Foundation. (2011). Statistics. Retrieved from http://www.heartandstroke.com/site/c.ikIQLcMWJtE/b.3483991/k.34A8/Statistics.htm#riskfactors


Law, M.R., & Rudnick, W.A. (2003). Quantifying effect of statins on low density lipoprotein cholesterol, ischaemic heart disease, and stroke: systematic review and meta-analysis. British Medical Journal, 326.


Miller, M., Stone, N.J., Ballantyen, C., Bittner, V., Criqui, M.H., Ginsberg, H.N., ... Pennathur, S. (2011). Triglycerides and cardiovascular disease: A scientific statement from the American Heart Association. Circulation, 123, 2292-2333.


Public Health Agency of Canada. (2009). Tracking Heart Disease and Stroke in Canada, 2009. Retrieved from: http://www.phac-aspc.gc.ca/publicat/2009/cvd-avc/pdf/cvd-avs-2009-eng.pdf

Which diet is the best for heart health: a diet higher in protein, unsaturated fat or carbohydrate?

by Lindsay Buchanan, RD

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© 2018 by The Dietitians Network of Nova Scotia.