Heart Health: Support your Heart with the Mediterranean Diet

While it's no secret that cardiovascular disease is the number one cause of death regardless of age, ethnicity, or gender¹, choosing a heart healthy diet can be overwhelming. But what if one of the heart healthy diets available could enable your own gut bacteria to help fight heart disease?

The Mediterranean Diet has been long recognized as a cardioprotective diet and is defined as the traditional dietary pattern found in the early 1960s in Greece, Southern Italy, Spain, and other olive-growing countries of the Mediterranean basin. ² It is associated with a high intake of fruits, vegetables, legumes, nuts, and olive oil; a moderate consumption of dairy products and wine; and low intake of red and processed meat, butter, cream, sugar drinks, and sweet desserts. ^2,3

Characteristics also include:

• Whole grains such as cereal, rice, polenta, or bread as staple foods
• Vegetables and fruit (both fresh and dried) consumed raw or cooked
• Legumes (e.g. lentils, chickpeas, beans)
• Nuts (e.g. almonds, pistachios, hazelnuts, and walnuts)
• Herbs (e.g. thyme, rosemary, and basil)
• Spices (e.g. nutmeg, cinnamon, and saffron)
• Fish and other seafood are frequently consumed with meals with other meat (preferably lamb) typically reserved for fiestas
• Dairy products are consumed in moderation (especially yogurt and cheese, but not whole milk, butter, or cream)
• Olive oil consumed at nearly every meal with red wine consumed daily ^2,4

But what makes the Mediterranean Diet different than other popular diets advocating heart health? Relative to the American diet, the Mediterranean Diet results in a lower intake of omega-6 fatty acids (known for promoting inflammation) versus omega-3 fatty acids (known to be anti-inflammatory) as well as an overall lower intake of polyunsaturated fatty acids, lower intake of red meat, and much higher intake of plant-based foods and monounsaturated fats (e.g. olive oil). While the merits of these characteristics can be argued to promote heart health, the real answer to how the Mediterranean Diet stands out as a heart healthy leader may be in how this diet works with your own gut bacteria to prevent cardiovascular disease. Let's explain.

Several years ago, researchers from the Cleveland Clinic found the link between diets rich in animal fats including eggs, red meat, and high-fat dairy products and the development of heart disease. Here is what happens. When these foods are consumed, very high levels of the nutrients choline, lecithin, and carnitine are produced during their metabolism. Bacteria in the gut turn these nutrients into a substance known as trimethylamine, or TMA. As metabolism continues, TMA is converted by enzymes produced by our gut bacteria to trimethylamine N-oxide, or TMAO, a byproduct we would be better off without. Studies have found that increased blood levels of TMAO are associated with accelerated atherosclerosis in mice and with an increased risk of heart disease in humans. ⁵

This means that our gut bacteria are responsible for turning the nutrients found in a high animal-fat diet into a substance that sets in motion the process for developing heart disease. So how does the Mediterranean Diet fit in this picture?

A few years later, the same team of researchers from the Cleveland Clinic learned more about TMAO and specifically, how our gut bacteria could inhibit its formation rather than promote it. Specifically they have learned that substances found in the Mediterranean Diet (e.g. the polyphenols found in red wine, olive oil, etc.) produce a metabolite called DMB (3, 3, dimethyl, 1-butanol) that may block the enzymes that produce TMAO in the gut. ⁶

This discovery is exciting because it means that we may be able to target the way our gut bacteria converts the nutrients we consume into substances that protect our heart as opposed to ones that promote the development of heart disease. If more studies can be replicated to better understand this mechanism, this finding may even lead to one day treating heart disease by targeting the molecular pathways triggered by our gut microbiome with food vs. drugs. Until then, understanding how the nutrients found in the Mediterranean Diet could prevent TMAO formation may help explain one of the possible mechanisms by which the Mediterranean Diet could be cardioprotective.

As we wait for more details on how our gut bacteria could protect our heart, here are some tips for those who wish to adopt the Mediterranean Diet now.

• Focus on including an abundance of fruits and vegetables at every meal
• Include staples such as whole grains, cereal, rice and bread
• Limit red meat to no more than a few times per month
• Encourage grilled or baked freshwater fish 2-3 times weekly
• Replace butter with extra-virgin or virgin olive oil
• Add flavor to fruits, vegetables, and whole-grain pasta by using herbs and spices in conjunction with olive oil
• Consume nuts such as almonds, cashews, or pistachios as snacks
• Red wine in moderation, suggested as a small drink with evening meal

Written by Angie Cook, MS, RN, recent graduate of the Master of Science in Nutritional Sciences degree program from the University of Texas at Austin, Department of Nutritional Sciences.

References:

1. Widmer RJ, Flammer AJ, Lerman LO, Lerman A. The Mediterranean diet, its components, and cardiovascular disease. Am J Med. 2015;128(3):229-238. doi:10.1016/j.amjmed.2014.10.014
2. Martínez-González MA, Salas-Salvadó J, Estruch R, Corella D, Fitó M, Ros E. Benefits of the Mediterranean Diet: Insights From the PREDIMED Study. Prog Cardiovasc Dis. 2015;58(1):50-60. doi:10.1016/j.pcad.2015.04.003
3. Guasch-Ferré M, Merino J, Sun Q, Fitó M, Salas-Salvadó J. Dietary Polyphenols, Mediterranean Diet, Prediabetes, and Type 2 Diabetes: A Narrative Review of the Evidence. Oxid Med Cell Longev. 2017;2017. doi:10.1155/2017/6723931
4. Hoffman R, Gerber M. The Mediterranean Diet: Health and Science. Mediterr Diet Heal Sci. 2013;(2015):1-402. doi:10.1002/9781118785027
5. Wang Z, Klipfell E, Bennett BJ, et al. Gut flora metabolism of phosphatidylcholine promotes cardiovascular disease. Nature. 2011;472(7341):57-65. doi:10.1038/nature09922
6. Wang Z, Roberts AB, Buffa JA, et al. Non-lethal Inhibition of Gut Microbial Trimethylamine Production for the Treatment of Atherosclerosis. Cell. 2015;163(7):1585-1595. doi:10.1016/j.cell.2015.11.055