To the Editors:
As dietitians strive to learn more about dietary supplements and fabricated foods, it is important to stay abreast of new knowledge about whole foods. Recently, analysis of avocados has provided new information showing that this fruit is a significant source of dietary phytosterols. Avocados rank as the 14th most commonly consumed raw fruit in the United States (
(1)
).Phytosterols are the plant analogues of cholesterol. There are three predominant phytosterols: beta-sitosterol, campesterol, and stigmasterol (
(2)
), all of which function as anticholesterolemic agents ((3)
). The mechanism for the serum cholesterol-lowering effect of phytosterols involves inhibition of intestinal cholesterol absorption and decreased hepatic cholesterol synthesis ((3)
, (4)
).Hass avocados are the pebbly dark-skinned variety that is grown in California and accounts for over 75% of the nation’s domestic crop (
(5)
). For analysis, 36 just-ripe Hass avocados (those that yielded slightly to gentle pressure) were purchased from three San Diego supermarkets (12 avocados from each supermarket) on January 25, 1999, and again on May 5, 1999, to control for seasonal variation. The avocados were sent via overnight delivery to Covance Laboratories in Madison, Wisconsin, where each set of 12 avocados was hand-peeled, the stones were removed, and the fruit was combined to form one sample and then analyzed for sterol content.Among the phytosterols examined, the data clearly show that beta-sitosterol is most abundant, being present at 76.4mg per 100 grams of raw edible avocado fruit (Table 1). The next most abundant phytosterol is campesterol, which was present at 5.1mg per 100 grams. Stigmasterol was below the lower limit of detection (<3mg/100g).
Table 1Sterol composition of six samples of California Hass avocados.
| beta-sitosterol | campesterol | stigmasterol | |
|---|---|---|---|
| Sample (date) | mg/100g | mg/100g | mg/100g |
| 1 (01/25/99) | 64.4 | 4.5 | <3.0 |
| 2 (01/25/99) | 61.5 | 5.3 | <3.0 |
| 3 01/25/99) | 72.6 | 5.0 | <3.0 |
| 4 (05/05/99) | 98.4 | 5.8 | <3.0 |
| 5 (05/05/99) | 76.7 | 4.7 | <3.0 |
| 6 (05/05/99) | 84.8 | 5.4 | <3.0 |
| Mean | 76.4 | 5.1 | <3.0 |
| Standard Deviation | 12.5 | 0.4 | 0 |
The beta-sitosterol content of the 20 most frequently consumed fruits in the United States is shown in Table 2(
(1)
). Avocados clearly provide more beta-sitosterol than any of the other fruits with known values. On an ounce-per-ounce basis, avocados contain more than four times the beta-sitosterol of oranges, which had previously been reported as the richest known fruit source of beta-sitosterol ((2)
).Table 2Beta-sitosterol composition of the 20 most frequently consumed fruits in the United States.
| beta-sitosterol | |
|---|---|
| Fruit | mg/100g |
| Banana | 11 |
| Apple | 11 |
| Watermelon | 1 |
| Orange | 17 |
| Cantaloupe | 8 |
| Grapes | 3 |
| Grapefruit | 13 |
| Strawberries | 10 |
| Peach | 6 |
| Pear | 7 |
| Nectarine | NA |
| Honeydew | NA |
| Plum | 6 |
| Avocado | 76 |
| Lemon | 8 |
| Pineapple | 4 |
| Tangerine | NA |
| Sweet cherries | 12 |
| Kiwi fruit | NA |
| Lime | NA |
NA=Data Not Available
a Raw Edible Portion Weight
b Beta-sitosterol values for all fruits except avocado were previously reported
(3)
.Avocados meet the definition of a functional food as outlined by the ADA Position Statement in that they provide health benefits beyond basic nutrition (
(6)
). A typical California avocado weighing 173 grams would contain 132mg beta-sitosterol. This level is significant as a phytochemical, and is in the same range as that found in phytosterol dietary supplements.Dietitians can use the findings of this study to encourage the public to eat avocados as part of a phytochemical-rich diet.
References
Identification of the 20 most frequently consumed raw fruit, vegetables, and fish in the United States, 21CFR101.44 (Code of Federal Regulations, Title 21: Food and Drugs. Part 101: Food Labeling.)
- Sterol content of foods of plant origin.J Am Diet Assoc. 1978; 73: 39-47
- Effects of Dietary Phytosterols on Cholesterol Metabolism and Atherosclerosis.Am J Med. 1999; 107: 588-594
- Some aspects of mechanism of inhibition of cholesterol absorption by beta-sitosterol.Biochim Biophys Acta. 1983; 732: 651-658
- Non-Citrus Fruits and Nuts, 1998 summary united states department of agriculture national agricultural statistical services, released. July 1999
- J Am Diet Assoc. 1999; 99: 1278-1285
Article info
Identification
Copyright
© 2001 American Dietetic Association. Published by Elsevier Inc. All rights reserved.
