WHAT THEY’RE SAYING
Eating a Mediterranean Diet, high in either olive oil or nuts, may reduce the risk of having a stroke or heart attack or dying of cardiovascular causes.
WHAT WE KNOW
A Mediterranean Diet is characterized by high consumption of olive oil, fruits and vegetables, nuts, whole grains, moderate fish and poultry intake, and low intake of dairy, red meat, and added sugars. A number of epidemiological studies indicate that high adherence to a Mediterranean Diet is associated with reduced risk of cardiovascular disease (CVD).1,2 Further, smaller studies have determined the mechanisms by which a Mediterranean Diet may benefit the cardiovascular system, such as reducing inflammation, reducing blood pressure and blood glucose, and improving blood lipids.3,4 However, no randomized-controlled trials have examined whether or not a Mediterranean Diet can specifically prevent cardiovascular events like heart attack or stroke or CVD mortality.
In a randomized-controlled trial called the PREDIMED (Prevention with a Mediterranean Diet) study, 7,447 Spanish adults (55-80 years of age) at risk for CVD were randomized to either a Mediterranean Diet emphasizing extra-virgin olive oil, a Mediterranean Diet emphasizing nuts, or a low-fat diet.5 Those in the olive oil group were provided with ~4 tbsp of extra-virgin olive oil to consume each day, whereas those in the nut group were provided with one serving (~30 g) of almonds, walnuts, or hazelnuts to eat everyday. After approximately 5 years of follow-up, the study was stopped due to the cardiovascular benefit observed in those randomized to either of the Mediterranean Diet groups, making it unethical to continue the intervention for those in the low-fat group. Indeed, risk of heart attack, stroke, or dying from CVD was approximately 30% lower in either of the Mediterranean Diet groups compared with the low-fat group.
WHY THIS MATTERS
This study is particularly important and provides stronger evidence for the benefits of a Mediterranean Diet compared with previous studies because cardiovascular outcomes were evaluated instead of just risk factors for CVD like blood lipids, blood pressure, and inflammation. Additionally, the study is strengthened by its design wherein participants were assigned to a dietary intervention instead of simply trying to recall what they eat, a dietary evaluation technique that is subject to bias and error. The results from this study are also particularly striking when considering the dietary changes made in each group. The low-fat group only reduced fat intake by 2% (from 39% in the beginning to 37% at the end of the study) and all groups increased their intake of fruits and vegetables. The supplemental foods (olive oil or nuts) were responsible for the greatest differences in diet between the Mediterranean Diet and the low-fat groups, suggesting that the reduction in CVD risk may be attributable to nut and olive oil intake. The benefits of olive oil and/or nuts are likely due to their nutrient profiles. Both olive oil and nuts contain beneficial fats and polyphenols that act as antioxidants and anti-inflammatory agents, which protect the heart and blood vessels.
The results from this study indicate that following a Mediterranean Diet high in either nuts or olive oil significantly reduces the risk of developing CVD. We recommend incorporating nuts and olive oil into your daily diet. Check out our Top Ten Ways to Enjoy Nuts for some ideas! But remember that nuts and oils can spoil and go rancid over time, so be sure to store them properly. Buy nuts in small quantities and/or store them in the refrigerator or freezer. Most nuts will last for six months in the refrigerator or for up to a year in the freezer. To protect your olive oil from spoiling, store it in a tinted glass or plastic bottle in a cool, dark place for up to two months.
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