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15th July 2022
A daily avocado added to the diet of individuals with a body mass index (BMI) greater than 30 for a period of 6 months, did not lead to a reduction in visceral adipose tissue (VAT) volume compared to a habitual diet in which consumption was less than 2 avocados per month, according to the findings of a randomised trial by US researchers.
Visceral adiposity which is also referred to as visceral or central obesity, is strongly and positively associated with all-cause, cardiovascular disease and cancer mortality, independently of body mass index. One factor that can influence the extent of obesity is diet quality. For example, in one comparative study of a typical Western diet, e.g., based on a higher consumption of refined grains, red/processed meats and one based on non-hydrogenated fat, vegetables, eggs and seafood, i.e., with a better diet quality, found that those consuming the Westernised diet were more likely to be obese. One food associated with a better diet quality is avocado which contains monounsaturated fatty acids, dietary fibre, essential nutrients and various phytochemicals. In fact, one study concluded that avocado consumption was associated with improved overall diet quality and a reduced risk of metabolic syndrome. Moreover, in a randomised trial with overweight adults, half a daily avocado increased satisfaction by 26% and decreased the desire to eat by 40%. Nevertheless, in another comparative trial in which one group consumed a daily avocado, while there was significant weight loss, a decrease in BMI, total body fat and visceral adipose tissue, there were no differences between the two groups. Finally, in a 2021 study, again in which participants consumed a daily avocado, there was a change in abdominal adiposity distribution among females but not males.
In the present study, researchers set out to establish whether daily intake of an avocado for 6 months compared to a habitual diet, could alter visceral adiposity tissue (VAT) volume and various cardiometabolic markers such as the hepatic fat fraction, systemic inflammation and components of the metabolic syndrome in those with an elevated waist circumference. The study recruited adults aged 25 years and older, with a waist circumference of > 89 cm for women and > 101 cm for men. Participants were randomised to receive either a daily avocado or their usual diet and those in the control diet were instructed to limit avocado intake to less than 2/month. All participants underwent 2 abdominal MRI scans, one before the study and one after 6 months and the primary outcome was the change in VAT volume based on the MRI assessment.
Daily avocado intake and visceral adiposity
A total of 1008 individuals with a mean age of 50.3 years (72.4% women) were recruited and randomised to avocado (505) or a habitual diet. The overall mean waist circumference was 109 cm and the BMI ranged from 32.9 to 33.2, with a mean VAT of 3.2 litres and a hepatic fat fraction of 9.9%.
After 6 months, the reduction in VAT volume among those taking an avocado was 0.074 litres and 0.057 litres in the habitual diet group which represented a non-significant difference (p = 0.405). Similarly, there was no significant difference in the hepatic fat % (0.58 vs 0,21, p = 0.28) or changes in waist circumference (0.007 vs -0.108, p = 0.603) and the end of the trial.
The only significant changes were in total cholesterol levels (-4.908 vs-1.96, p = 0.026) and for LDL cholesterol (-4.94 vs -2.48, p = 0.038).
Based on these findings, the authors concluded that although diet quality was improved by the addition of a daily avocado, this did not translate into clinically important improvements in either visceral adiposity or other cardiometabolic factors.
Lichenstein AH et al. Effect of Incorporating 1 Avocado Per Day Versus Habitual Diet on Visceral Adiposity: A Randomized Trial J Am Heart Assoc. 2022
27th April 2022
A higher avocado intake reduces the risk of cardiovascular disease according to the findings from two large prospective studies reported by researchers from Harvard T.H. Chan School of Public Health, Boston, USA.
Cardiovascular disease (and which also includes coronary heart disease) represents the leading cause of death globally. Interestingly, studies suggest that there is a valid association between several dietary factors and patterns with coronary heart disease. One healthy food is avocado, which contains a large amount (71%) of monounsaturated fatty acids and helps to promote healthy blood lipid profiles, enhancing the bioavailability of fat soluble vitamins and phyto-chemicals from the avocado or other fruits and vegetables. In fact, there are data showing how avocado consumption is associated with a reduced risk of metabolic syndrome and other work has indicated that eating at least one avocado each day provides a beneficial effect on cardio-metabolic risk factors that extended beyond their heart-healthy fatty acid profile. Furthermore, a recent systematic review found that avocado intake increased serum HDL-cholesterol concentrations, prompting the authors to suggest that the association between avocado intake and cardiovascular risk should be confirmed by well-conducted prospective observational studies or long-term trials.
For the present study, the US team examined the association between a higher avocado intake and cardiovascular outcomes. They turned to data held in both the Nurse’s Health Study (NHS) and the Health Professionals Follow-up Study (HPFS), which are two prospective cohort studies which were initiated in the 1970’s and 1980’s respectively. In both of these cohort studies, participants were asked to complete validated questionnaires asking about lifestyle and diet every 2 years and from this information, the researchers were able to determine how much avocado was consumed. This was then categorised as never or less than once a month, 1 – 3 times per month, weekly and > twice a week. The primary outcome of interest was incident cases of total cardiovascular disease, which was a composite of several adverse cardiovascular outcomes e.g., fatal coronary heart disease. The main secondary outcome related to strokes.
Higher avocado intake and adverse cardiovascular outcomes
A total of 68,786 women from the NHS and 41,701 men from the HPFS who were free of cardiovascular disease and stroke at baseline were included and followed for 30 years (median for men was 13.3 years and 14.2 for women). During follow-up there were a total of 14,274 cases of cardiovascular disease (CVD) in both NHS and HPFS.
After adjustments were made for dietary and lifestyle factors, compared to those who did not eat avocados, individuals with a higher avocado intake (> twice/week) week had a 16% lower risk of CVD (hazard ratio, HR = 0.84, 95% CI 0.75 – 0.95) and a 21% lower risk of coronary heart disease (HR = 0.79, 95% CI 0.68 – 0.91). However, there was no significant reduction for stroke.
The authors calculated that for each half serving/day increase in avocado intake, the pooled hazard ratio for CVD was 0.80. In fact, the authors added that by replacing half a serving/day of margarine, butter, egg, yoghurt, cheese or processed meats with the equivalent amount of avocado would be associated with a 16 to 22% lower risk of CVD.
Pacheco LS et al. Avocado Consumption and Risk of Cardiovascular Disease in US Adults J Am Heart Assoc 2022