Field Notes

Mediterranean Diet May Cut Women’s Cardiovascular Risk

Sticking closely to a Mediterranean diet cuts a woman’s risk of CVD and death by nearly 25%, finds a pooled data analysis of the available evidence—the first of its kind—published online in the journal Heart.

The findings prompt the researchers to call for more sex-specific research to guide clinical practice in heart health.

CVD accounts for more than one-third of all deaths in women around the world. While a healthful diet is a key plank of prevention, most relevant clinical trials have included relatively few women or haven’t reported the results by sex, the researchers say.

And current guidelines regarding how best to lower CVD risk don’t differentiate by sex.

To build on the evidence base to inform sex-specific guidance and clinical practice, the researchers trawled research databases for studies looking at the potential impact of eating a Mediterranean diet on women’s cardiovascular health and their risk of death.

The Mediterranean diet is rich in whole grains, vegetables, fruit, legumes, nuts, and extra virgin olive oil; moderate in fish/shellfish; low to moderate in wine; and low in red/processed meats, dairy products, animal fat, and processed foods.

From an initial haul of 190 relevant studies, the researchers included 16 published between 2003 and 2021 in their pooled data analysis.

The studies, which were mostly conducted in the United States and Europe, involved more than 700,000 women aged 18 and above whose cardiovascular health was monitored for an average of 12.5 years.

The results of the analysis showed that sticking closely to a Mediterranean diet was associated with a 24% lower risk of CVD, and a 23% lower risk of death from any cause in women. 

The risk of coronary heart disease was 25% lower, while that of stroke was also lower, although not statistically significant, in those who most closely followed this diet compared with those who did so the least.

Excluding each of the studies one at a time from the analysis didn’t materially affect the findings, “further supporting a strong inverse relationship for incident CVD and total mortality with higher Mediterranean diet adherence in women,” the researchers wrote.

They nevertheless acknowledge various limitations to their findings, including that all the studies analyzed were observational and relied on self-reported food frequency questionnaires. And adjustments for potentially influential factors varied across the included studies. 

But the Mediterranean diet’s antioxidant and gut microbiome effects on inflammation and cardiovascular risk factors are among the possible explanations for the observed associations, the researchers say. 

And the diet’s various components, such as polyphenols, nitrates, omega-3 fatty acids, increased fiber intake, and reduced glycemic load, may all separately contribute to a better cardiovascular risk profile, they suggest. 

“However, mechanisms explaining the sex-specific effect of the Mediterranean diet on CVD and death remain unclear,” they note, adding that the findings reinforce the need for more sex-specific research in cardiology.

“Female-specific cardiovascular risk factors, including premature menopause, preeclampsia and gestational diabetes, or female-predominant risk factors, such as systemic lupus, can all independently increase CVD risk,” they wrote.

“It’s possible that preventative measures, such as a Mediterranean diet that targets inflammation and CVD risk factors, impose differing effects in women compared with men,” they add.

— Source: The British Medical Journal

 

Low-Carb Diet Linked to Chronic Disease Risk

A new study of over 19,000 adults found a 15% higher likelihood of diabetes or history of stroke or heart disease among Americans restricting carbohydrates to less than 45% of energy compared with those eating a diet balanced in carbohydrates, fat, and protein. The risk was even higher (40%) among those eating a carbohydrate restricted diet that also was high in fat.

Public health is strongly affected by suboptimal diet patterns. They represent the leading risk factor for death from all causes and account for approximately one-half of all deaths from cardiometabolic disease, the authors say. Heart disease, diabetes, and stroke accounted for about 30% of the mortality burden in United States adults in 2019. Just to the north, heart disease remains the second leading cause of death in Canada.

When carbohydrates are restricted, energy from protein and fat increase as a percent of total calories ingested. When some or all of the carbohydrate calories are replaced with other macronutrients, this can lead to increased intake of fat. Therefore, researchers at William & Mary considered whether the amount and type of fat in the diet mattered. High dietary fat in a carbohydrate restricted diet was associated with higher prevalence of cardiometabolic disease. This occurred even for high polyunsaturated fat, which have been shown to support heart health.

So, what was the diet associated with the lowest prevalence of cardiometabolic health? “Our findings showed that recommended carbohydrate intake plus high monounsaturated fatty acid intake presented the strongest protective association with cardiometabolic outcomes of any dietary pattern we investigated in this study,” the authors say.

The first-of-its-kind, nationally representative study was led by William & Mary’s Zach Conrad and student Corina Kowalski and was supported by the Institute for the Advancement of Food and Nutrition Sciences. The researchers looked at cross-sectional health information from a nationally representative US National Health and Nutrition Examination Survey database on 19,078 people over a 20-year period.

The study, titled “Fat Intake Modifies the Association Between Restricted Carbohydrate Diets and Prevalent Cardiometabolic Diseases Among Adults in the United States: National Health and Nutrition Examination Survey, 1999–2018,” appears in the peer-reviewed journal Current Developments in Nutrition.

According to Conrad, “A restricted carbohydrate diet is associated with elevated prevalence of cardiometabolic disease in adult Americans, and even more so if dietary fat intake is high. Because the association is cross-sectional, causality cannot be determined; it’s possible that people with cardiometabolic disease start to restrict carbohydrate intake as a consequence of their health status. However, a diet pattern meeting recommended intakes for carbohydrates (45% to 65% of energy), fat (20% to 35% of energy), and protein (10% to 35% of energy) is supported by this research from a cardiometabolic perspective.”

The study can be found here.

— Source: Institute for the Advancement of Food and Nutrition Sciences