Elizabeth Hanus
NTR 402 Prof. FitzPatrick
10/24/14
Avocado Consumption in the Diet and Impact of Phytosterols
I.
INTRODUCTION:
The purpose of this paper is to examine the potential beneficial effects of avocado
consumption and phytosterols in the diet. Avocados can be a valuable addition to a wellbalanced diet because they contain healthy fats such as monounsaturated and
polyunsaturated fatty acids. In comparison, saturated or trans fatty acids could have
negative effects on blood cholesterol levels when consumed in excess. They also contain
compounds called phytosterols, which are cholesterol-like substances found naturally in
certain foods that have been shown to lower blood cholesterol levels by blocking
intestinal cholesterol absorption and reducing hepatic cholesterol synthesis (Duester,
2001). In addition, these compounds are suggested to have a beneficial effect on heart
health, weight loss, and risk of coronary heart disease (Dreher & Davenport, 2013).
Avocados are the fruit that contains the highest amount of phytosterols per serving at
57mg per 68g or one-half of an avocado. It was previously believed that oranges were the
fruit highest in phytosterols, but when compared with avocados ounce per ounce,
avocados ranked four times higher in phytosterol content, specifically beta-sitosterol
(Duester, 2001). Official serving size is one-fifth of an avocado (30g), but the National
Health and Nutrition Examination Survey (NHANES) reports that a more common
serving size typically consumed is one-half of an avocado (Dreher & Davenport, 2013).
II.
ACTIVE COMPONENTS
The active components in the avocado that make them beneficial to health, as previously
mentioned, are comprised of monounsaturated fatty acids, polyunsaturated fatty acids,
and phytosterols. The standard serving of avocado (one fifth or 30g) consists of 4.5g of
total fat, of which 3g are monounsaturated, 0.5g are polyunsaturated, and 0.5g are
saturated. The main three types of phytosterols in an avocado consist primarily of betasitosterol at 74.6mg per 100g of edible avocado, campesterol at 5.1g per 100g, and the
lowest stigmasterol at <3g per 100g (Duester, 2001). The structure of phytosterols is
similar to that of cholesterol in animals in that it stabilizes the cell membrane in plants,
providing structure to the phospholipid bilayers (Moreau, 2002). Phytosterols can also be
found included in commercial dietary supplements, but a similar amount of 132mg can be
found in the average California avocado weighing 173g (Duester, 2001).
III.
PROCESSING
It is worth noting that different varieties of avocados contain different nutrient profiles,
especially in relation to fat content. There are hundreds of varieties of avocados available
throughout the world, but the most popular varieties seen throughout grocery stores in the
United States are grown in California and Florida. The botanical name for avocados is
Persia Americana, and they are a member of the Lauraceae family, which includes the
plants that produce edible substances such as cinnamon, camphor, sassafras and bay leaf
(USDA, 2014). The avocado is distinguished by it’s oval shape, large inner pit and
surrounding light green, creamy flesh. Hass avocados, which are grown in the state of
California, are a variety known for their dark, purplish black, bumpy skin and light green
flesh. They are most often desired for their higher fat content and use in dips and spreads
such as guacamole. Other varieties grown in California include Bacon, Fuerte, Gwen,
Lamb Hass, Pinkerton, Reed, and Zutano (California Avocado Commission, 2014). The
other most common variety of avocado is grown in the state of Florida, sometimes
labeled as “lite” avocados due to their slightly lower fat and calorie content. This variety
has a smooth, green skin when ripe, and is desired in dishes where the slices of avocado
would need to hold their shape (Collins, 2013). There are over 50 varieties of Florida
avocados, but the most successful commercial varieties include Doni, Lula, Bernecker,
and Pollock (Specialty Produce, 2014).
IV.
HUMAN STUDIES
It has been proposed through various research studies that compounds in the avocado,
primarily different varieties of phytosterols, have had beneficial effects on blood lipid
levels and cardiovascular health when consumed along with a healthful diet. Due to this
research, the United States Cholesterol Education Adult Treatment Panel III has
recommended that 2g of phytosterols per day should be added to the diet to reduce lowdensity lipoprotein (LDL) cholesterol levels and reduce the risk of coronary heart disease
(Lin et al., 2009). Researchers such as Lin et al. have examined the effect of phytosterols
in their glycosylated form on cholesterol absorption in humans in a randomized crossover
study design. The study extracted phytosterol glycosides from soy lecithin, a bioactive
form of free phytosterols that have been shown to reduce cholesterol, as opposed to nonsoluble crystalline forms that have not been shown to have the same effect. Subjects
studied included 12 healthy individuals ranging from 18-80 years old with plasma LDL
cholesterol <190mg/dL and triglyceride levels <250mg/dL. Subjects were either given a
meal of phytosterol glycoside-enriched pudding, phytosterol ester-enriched pudding, or a
placebo pudding without phytosterols. Cholesterol absorption tests were administered and
plasma samples were taken before the start of the study and after the test meal was
consumed to evaluate the potential effect of phytosterols on cholesterol absorption. The
results concluded that phytosterol glycosides reduced cholesterol absorption by 37.6%
and phytosterol esters reduced cholesterol absorption by 30.6%, similar to results of other
studies pertaining to the subject matter. Thus, it is suggested that phytosterol glycosides
and esters appear to have a beneficial effect on reducing the absorption of cholesterol into
the human body.
Research suggests that a diet high in fruit and vegetables shows a correlation with a
decrease in body weight and lower body mass index (Fulgoni et al., 2013). While
avocados are higher in fat and energy density than other fruits and vegetables, they have
been shown to increase satiety and therefore it is likely the individual will eat less at
mealtimes (Bes-Rastrollo et al., 2008). Despite popular belief that foods high in fat will
lead to weight gain, several studies have shown that consuming healthy fats, such as
those found in avocados, can lead to a more significant weight loss when consumed in
moderation when compared to eating a low-fat diet (Bes-Rastrollo et al., 2008). This
effect has also been seen in foods such as olive oil and tree nuts (Bes-Rastrollo et al.,
2008), but a benefit of eating avocados instead of these particular foods for weight loss is
that they provide a similar nutrient profile with less than half of the calories per ounce
serving (USDA, 2011). Avocados can also be used in food preparation as an alternative
to other high-calorie foods such as mayonnaise or other dressings on sandwiches or
salads to reduce calorie content and increase nutritional value.
It has also been proposed through numerous clinical trials that consumption of
phytosterols can have a beneficial effect on cardiovascular health and reduced risk of
coronary heart disease (Dreher & Davenport, 2013). The reasoning for this claim is such
that by lowering LDL cholesterol and increasing HDL cholesterol to recommended
levels, heart health improves. In addition to phytosterols, avocados contain other nutrients
that are suggested to contribute to heart health, such as potassium, magnesium,
antioxidant vitamins such as vitamin E and vitamin C, vitamin K, carotenoids, and
phenolic compounds (Dreher & Davenport, 2013).
V.
CONCLUSION
The cost of avocados in the United States typically ranges from 1 to 2 dollars per avocado
(Hannaford Grocery, 2013), although the price may vary depending on abundance of the
crops each year and proximity to the states highest in avocado production, such as
California and Florida. When looking at the cost and value of phytosterol content, as
previously mentioned, the amount of phytosterols in one avocado is comparable to that of
a dietary phytosterol supplement (Duester, 2001). The cost of a dietary phytosterol
supplement, such as Benecol, can range from approximately 4 dollars for the enriched
margarine spread, which contains 0.5g of plant phytosterols per 1 tablespoon serving, or
up to 27 dollars for a chewable tablet containing 0.8g of phytosterols per tablet
(Hannaford Grocery, 2013). While the cost of buying a whole avocado can be slightly
higher than other products based on phytosterol content per serving, the avocado has
additional benefits not seen in other products such vitamin C and E, carotenoids, and the
healthy fat profile of monounsaturated and polyunsaturated fatty acids. However, it
would prove challenging to reach the 2g per day dose of phytosterols recommended to
lower LDL cholesterol and reduce risk of coronary heart disease with avocados alone.
In conclusion, based on the nutritionally dense profile of the avocado, including high
quantity of monounsaturated fatty acids, polyunsaturated fatty acids, and cholesterol
lowering properties of phytosterols and related impact on heart health and risk of
cardiovascular disease, it is suggested that avocados are a heart-healthy and beneficial
addition to a well balanced diet. In addition, avocados can have the potential to lower
LDL cholesterol when consumed daily in the diet and in addition to other plant sterolcontaining products.
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