Avocados – way to go

"Eat to Live, Not Live to Eat"
John H Weisburger, 2000

Fruits mainly store energy as carbohydrates but avocados, like olives, predominantly use lipids. Lipids are the norm for seeds and nuts, but again there are exceptions such as carbohydrate storage in chestnuts. The edible portion of avos consists of 73% water, 15% lipids, 8.5% carbohydrates and 6.7% fibre, and while having a slightly higher calorie content (160kcal/100g) than typical fruits, they are a nutrient-rich food containing significant amounts of minerals and other important phytochemicals. The 15% total lipids (fats) is made up of approximately 2.1% saturated (SFA), 9.8% monounsaturated (MUFA) and 1.8% polyunsaturated (PUFA) fats, so fat content is largely of the healthy non-saturated types. Furthermore, the ratio of omega-6 to omega-3 polyunsaturates is favourably less than one. On a population level they're not as frequently eaten as more common fruits such as apples or oranges for a variety of reasons, some of which are - increased cost, availability, buttery texture, lack of sweetness and concern that higher calories would lead to unwanted weight gain. The following US study (Nutrition Journal 2013, 12:1) demonstrates that this last concern is unwarranted, and in fact avo consumers had lower body mass index and better levels of various markers of well-being compared to non-consumers.

Avocados contain monounsaturated fatty acids, dietary fibre, essential nutrients and phytochemicals. However, no epidemiologic data exist on their effects on diet quality, weight management and other metabolic disease risk factors. The objective of this research was to investigate the relationships between avocado consumption and overall diet quality, energy and nutrient intakes, physiological indicators of health, and risk of metabolic syndrome. Avocado consumption and nutrition data were based on 24-hour dietary recalls collected by trained National Health and Nutrition Examination Survey (NHANES) interviewers. Physiological data were collected from physical examinations conducted in NHANES Mobile Examination Centres. Diet quality was calculated using the USDA's Healthy Eating Index-2005. Subjects included 17,567 US adults 19 years of age or more (49% female), including 347 avocado consumers (50% female), examined in NHANES 2001–2008. Least square means and standard errors were determined using appropriate sample weights, with adjustments for age, gender, ethnicity, and other covariates depending on the dependent variable of interest. Avocado consumers had significantly higher intakes of vegetables, fruit, diet quality, total fat, monounsaturated and polyunsaturated fats, dietary fibre, vitamins E, K, magnesium, potassium and vitamin K, and lower intakes of added sugars. No significant differences were seen in calorie or sodium intakes. Body weight, body mass index and waist circumference were significantly lower and HDL-cholesterol (the good one) was higher in avocado consumers. The odds ratio for metabolic syndrome was 50% lower in avocado consumers vs. non-consumers. We conclude that avocado consumption is associated with improved overall diet quality, nutrient intake, and reduced risk of metabolic syndrome. Dietitians should be aware of the beneficial associations between avocado intake, diet and health when making dietary recommendations.

Metabolic syndrome is a significant risk factor for cardiovascular disease and diabetes. It increases markedly with age and is present in more than 42% of adults over the age of 60 in the US. Consequently a 50% reduction in this incidence through consumption of avos is very important for individuals and for societies in terms of lost productivity, quality of life and overwhelming medical costs. Like any epidemiologic study there can be many confounding variables that might have contributed to the reported results. But the 50% reduction was found after allowing for contributions due to age differences, gender, ethnicity, poverty-income ratio, physical activity, smoking and alcohol intake. Only 347 out of 17,567 people (ie 2%) stated they regularly consumed avos (70g or about half a fruit/d). This proportion seems absurdly low but it is in a society where no more than 3% of US men and 6% of women meet recommended daily fruit and vegetable intake. This is such a long way from being ideal, is it any wonder that metabolic syndrome is at epidemic proportions there?

Other studies addressing the unfounded concern about possible weight gain or negative effects with avos have been reported. A US 2013 clinical trial found that addition of half an avo to a standard lunch was associated with improved meal satisfaction and decreased desire to eat over the next 5 hrs, and substitution for an equivalent number of calories in the lunch led to a significant reduction in blood insulin level over the next 3 hrs. An Australian crossover trial in men studied the effects of two iso-caloric diets – one high SFA (milk, butter, cream, cheese and fatty meat)/low MUFA and the other high MUFA (avos, nuts and olive oil)/low SFA for 4 wks on each diet. Even though calories were the same in each diet, fats provided by MUFAs led to lower bodyweight and fat mass. And another Sth African study found that consumption of 200g/d avos within an energy-restricted diet in overweight and obese adults did not compromise weight loss when substituted for an equivalent number of calories in the daily diet. One underlying mechanism that helps understand these bodyweight outcomes is that MUFAs, the principal component of avo lipids, are more likely to be oxidised in the body (increased thermogenesis) whereas SFAs are more prone to fat storage. At a broader level than all the above, an increasing number of clinical and pre-clinical studies in the last 20yrs have now reported positive effects on cardiovascular health, DNA damage protection, osteoarthritis, eye and skin health and various cancers.

Some other features of avos worth considering are:

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