An interesting new paper examines the risk of cardiovascular disease (CVD) related to avocado intake. It suggests that saturated fats of animal origin could be replaced at least in part by avocado with a beneficial effect on CVD risk.
The leading killer among Americans today is CVD, including both stroke and coronary heart disease (CHD). CVD is very much a disease following an unhealthy lifestyle, which has led to thousands of studies trying to delineate what could be considered a heart-healthy diet.
According to the American Heart Association (AHA), and the American College of Cardiology, only 5% to 6% of calories should come from saturated fats, the rest of the fat coming from monounsaturated fats (MUFA) and polyunsaturated fats, to prevent CHD. In such a scenario, avocados are a good source of nutrients, providing unsaturated fats and other bioactive compounds, phytochemicals, trace elements, and dietary fiber.
The Hass avocado is the most commonly used variety in the USA, with a single fruit (about four servings) weighing about 140 g providing 13 g of the unsaturated fatty acid oleic acid, similar to 42 g of almonds or two tablespoons of olive oil. It also provides 40% of the recommended daily allowance of fiber, a fifth of the potassium, a tenth of the magnesium, and 30% of the folate, with 15 g of MUFA and 3 g of PUFA.
A high intake of avocado is associated with higher high-density lipoprotein (HDL) levels, and a lower average body mass index (BMI), with a lower risk of metabolic syndrome.
What did the Study Show?
The current study, published in the Journal of the American Heart Association, looks at how avocado intake is related to the total CVD, CHD, and stroke risk, using data from two studies, namely, the NHS (Nurses’ Health Study) and the HPFS (Health Professionals Follow‐up Study).
Both are prospective cohort studies, the latter having begun in 1986, including male American healthcare professionals from 45 to 70 years of age, from all US states, and the former established in 1976, including female nursing professionals from 30-55 years from 11 states. Those included in the current study had no history of CVD, CHD, or stroke at baseline, and all were within the limits of recommended dietary intake.
The study thus included over 41,000 men and 62,000 women. The follow-up was, at median, about 13-14 years. During this period, over 14,00 cases of CVD were reported, approximately 6,700 and 7,600 among the male and female cohorts, respectively.
Avocado intake went up from about 0.2 servings per week among the HPFS cohort at the beginning to 0.4 servings per week in 2014. Among the female nurses, it went up from 0.1 servings per week in 1986 to 0.2 servings per week in 2010. Simultaneously, they reported a reduction in the use of other plant and animal fats.
Those who ate more avocado had a healthier diet overall, with more fruits and vegetables, grains, nuts, yogurt, and cheese. The highest average intake was 40 g per day.
Even after adjusting for race, age, smoking and alcohol status, physical activity, and other cardiovascular risk factors, including a family history of heart attacks, diabetes, and cancer, menopausal status, hypertension or high cholesterol levels, and current hormone pill intake, the risk of CVD was 16% lower among those who had two or more servings of avocado per week, even after compensating for the effect of a raised BMI. When other sources of dietary fat were adjusted for, the CVD risk was reduced by 11%. And finally, as avocado intake increased by a quarter-fruit (half a serving) per day, the risk decreased by 20%.
The highest vs. lowest intake categories showed a reduction in CHD risk by 21%. A reduction of 16% was observed by replacing a half-serving of avocado with margarine. Similar reductions were found for most animal fats, though the least was with mayonnaise.
The substitution of avocado for processed meats and yogurt also lowered CVD risk, but plant oil substitution by avocado appeared unnecessary. Overall, the risk of CVD went down by 20% to 30% if a half-serving of butter, cheese, yogurt, mayonnaise, margarine, or processed meats was replaced by avocado, yielding the same amount of calories from fats.
Surprisingly, half a serving of the plant oils (safflower, soybean, corn, and canola oils) with the equivalent amount of avocado was linked to an increase in stroke risk by almost 50%. The researchers say,
What are the Implications?
This study showed that those who ate more avocado vs. those who did not eat this fruit had a 16% lower risk of CVD and 21% risk of CHD. However, the stroke risk did not go down.
Compared with other commonly used dairy fats, margarine, or processed meats, avocados showed a decreased risk of both CVD and CHD, whereas this was not seen in comparison with other plant oils. Therefore, the study also indicates that any plant oil may be considered a healthy choice, like avocado.
Avocado provides not only the healthy fat oleic acid, a cardioprotective MUFA that regulates endothelial function, reduces hypertension, inflammation, and insulin resistance, but plant sterols that are the plant equivalents of cholesterol, in addition to dietary fiber.
This bears out earlier results showing that the substitution of avocado for 6% to 7% of MUFA in a moderate-fat diet reduces unhealthy serum lipids, including LDL, non-HDL, and LDL/HDL cholesterol ratios. Oxidized LDL is also decreased after this switch.
Again, the PREDIMED (Primary Prevention of Cardiovascular Disease with a Mediterranean Diet) trial showed that adding extra virgin olive oil to a Mediterranean diet reduced the cardiovascular event risk by over 30% in a high-risk population. Similar findings emerged from both US and Mediterranean population-based studies, and the NHS and HPFS cohorts in the current study also showed the same pattern. The highest consumption of olive oil was linked to a 14% reduction in CVD risk and 18% reduced risk of CHD, compared to the lowest.