Holy guacamole! Eating avocado may reduce cardiovascular risk

A 46-year-old maths teacher comes for review and to consider her risk of “heart disease”. She is interested as her maternal grandfather died from a heart attack at age 79. In addition, she tutors a group of 14-year-old students at the local college, and there had been a recent discussion among the group about the potential benefits of eating avocado as part of a packed lunch.

Your patient is a non-smoker, who only drinks about five units of wine a week. She walks with her girlfriends three mornings a week before school, and with her husband in the weekends. She eats a balanced diet, rarely eats takeaways and is of healthy weight.

She has no significant past medical history and does not take any regular medications. Her parents and two older brothers are well. Her other three grandparents lived into their 80s and 90s, and did not experience a cardiovascular (CVS) event. She is happily married, with three children aged 10 to 18.

Her examination is normal, her blood pressure is 125/75mmHg, and she has normal biochemistry and haematological blood test results, including a total cholesterol level of 4.0mmol/L with a low-density lipoprotein cholesterol level of 2.0mmol/L. You take the opportunity to obtain a baseline electrocardiogram.

1. What does the ECG show?
2. What advice might be suitable for your patient regarding her CVS risk?
3. What tests might potentially be of help?
4. Is eating avocado “good for the heart”?
5. How good is the evidence?
6. How does New Zealand stack up globally as an exporter of avocados?
7. How might you summarise the current knowledge on diet for her tutor group?

To have a definite ‘booking’ to consider cardiovascular risk throughout a patient’s life allows the question to be intermittently addressed

1. The ECG shows sinus rhythm, a normal axis and a rate of 61 beats per minute. As expected, it is normal.

2. All clinicians will realise she is at low personal CVS risk. Her lifestyle should be encouraged, and a further review of her CVS risk after five years would be reasonable. To have a definite “booking” to consider CVS risk throughout a patient’s life allows the question to be intermittently addressed. It should be remembered that low risk does not mean no risk.

3. The Progression of Early Subclinical Atherosclerosis (PESA) study from 2015 reported on 4182 participants in a fascinating analysis of the extent of subclinical atherosclerosis within an asymptomatic Mediterranean population (63 per cent male). The average age of these Madrid bank workers was 46 years. A positive CT calcium score test was seen in 5 per cent of women and 25 per cent of men. Carotid atherosclerotic plaque was seen by ultrasound in 24 per cent of women and 34 per cent of men.¹

You briefly discuss these more accurate “imaging” techniques to assess CVS risk, but decide to leave these tests for another five years, until your patient’s next CVS risk assessment. In her case, it just seems too soon to do this now, despite the PESA study!

4. You have become less enthusiastic about the regular continuing medical education Zoom meetings, which have resulted from the COVID-19 era, and you are now looking forward to face-to-face meetings (hopefully) in the near future. You and your friends have been distributing interesting papers via email, which you are often reading instead. With perfect timing, a colleague recently sent you a remarkable paper from the Journal of the American Heart Association.²

The paper reported on more than 110,000 men and women (combined from two separate studies) who were followed for more than 30 years. Results suggested that eating two or more servings of avocado a week reduces CVS events. After adjustment for lifestyle and other dietary factors, those with a higher avocado intake had a 16 per cent lower risk of CVS disease (95 per cent confidence interval 0.75–0.95) and a 21 per cent lower risk of coronary heart disease (95 per cent CI 0.68–0.91).²

5. You and your friend are both clear that this was an observational epidemiological study, unable to prove cause and effect. Nonetheless, the paper is of interest and consistent with many large trials now supporting a healthy dietary pattern as a key method of reducing CVS disease. A variety of contemporary studies support a diet that includes fresh salad, fruits, vegetables, grains, legumes, fish and, in reasonable amounts, meat, eggs and dairy. There might also be a role for intermittent fasting for 12 to 16 hours per day.³

6. The New Zealand Horticulture Export Authority website reports that as well as the local market, New Zealand currently produces 2 per cent of the global supply of avocados. We are the ninth largest international avocado exporter, being focused on the Asian market in particular.

There certainly seems to be room to expand this export of good, healthy food from our shores.

7. A succinct dietary message might be to limit processed foods, eat all fresh foods in moderation and, above all, to not put on excess weight. Oh, and enjoy your avocados!

Details have been changed to protect patient confidentiality

Chris Ellis is a consultant cardiologist at The Heart Group and Mercy Hospital, Auckland

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