The California avocado: a new look
The avocado, a nutrient-dense fruit, can be an important component of a healthy diet because of its consumption pattern and nutrient profile. It is among the top 20 fruits sold in the United States. Consumption is increasing, but the amounts consumed per eating occasion were less in the late 1980s than in the late 1970s. It is used more now as an ingredient in a recipe or as a topping. Avocados increase the antioxidant, folate, potassium and fiber content of the diet. The fat content of avocados varies, depending on the season and stage of maturity. Early season fruit has about 2 g and the late season crop about 6 g of fat per 1-oz serving. Avocados contain primarily monounsaturated fatty acids, also provide the necessary essential fatty acids, are low in saturates and are free of cholesterol. These and other qualities help avocados meet the recommendations of the Surgeon General for healthy eating.
The avocado, 60% of which is consumed in California, is one of the top 20 fruits sold in the United States. With the spread of the popularity of Southwest cuisine, there is likely to be increased awareness and use of this little known fruit. Trends in avocado usage are shown in Figure 1. 2-4 In the 1977-78 Nationwide Food Consumption Survey (NFCS), the most frequently (27% of all eating occasions) consumed quantity was 4 oz per eating occasion (one half of an avocado). The second most frequent response, representing 18% of the eating occasions, was 2 oz or one quarter of an avocado. The next most frequently consumed amounts per eating occasion were 1 oz and 1/2 oz at 13 and 11%, respectively. A definite shift in consumption patterns occurred during the ensuing decade. Based upon the 1987-88 NFCS data, 1/2 oz per eating occasion was the most common pattern of consumption, accounting for 32% of the responses with consumption of 1.5, 1.0 and 3.5 oz per eating occasion representing 17, 16, and 15% of the responses, respectively.
The women and children’s responses in the 1985-86 and 1987-88 NFCS Continuing Survey of Food Intakes by Individuals II (CSFII) confirmed the trend toward smaller servings of avocado being consumed per eating occasion. These data show that this population favors a consumption per eating occasion of 1/2 ounce (1 tbsp) in both the 1985-86 and 1987-88 CSFII consumption, representing 30 and 28% of the responses from the two surveys, respectively. In both surveys, 3.5 oz represented one half of an avocado, reported by 10 and 18% of respondents, respectively.
Table 1 shows the nutrient composition of 1 oz (2 tbsp) of raw avocado. Avocados are a good source of dietary fiber, folate, vitamin [B.sub.6], vitamin E, vitamin C, phosphorus, potassium and magnesium. Information on the dietary fiber in avocados appears in Table 2. A comparison of nutrients in 1 oz of American cheese relative to 1 oz of avocado shows that amounts of vitamin E, folate, monounsaturated fatty acids, thiamin, niacin, vitamin [B.sub.6] and pantothenate are higher in avocado than in cheese, whereas the quantities of those nutrients for which current dietary guidelines suggest minimal consumption in the diet, e.g., sodium, total fat, saturated fat and cholesterol are lower in the avocado (Table 3). The addition of avocado to a low-fat diet contributes many important nutrients. Avocados have the highest dietary fiber content on a weight basis (1 g per oz and per 52 calories) of any fruit, which helps meet dietary guideline recommendations of consumption of 20 to 35 g of fiber per day. Total dietary fiber, mostly of the insoluble variety, makes up 3.2% of an avocado by weight. Of the fat in avocados, 60% is the monounsaturated fatty acid oleic acid (18:1), which has little or no effect in elevating serum cholesterol levels.
[TABULAR DATA OMITTED]
Dietary Fiber Content of
Type of Fiber (3.5 oz)
Total dietary fiber 3.2 g
Total soluble fibers 0.9 g
Hemicellulose 0.45 g
Pectins 0.45 g
Total insoluble fibers 2.3 g
Cellulose 1.22 g
Pectins 0.15 g
Lignin 0.21 g
Hemicellulose 0.72 g
Nutrient Comparison of Ameican Cheese and Avocado
American 1 oz
Fiber (g) 0 1
Total fat (g) 9 6
Monounsaturated fat (g) 2.5 3.5
Saturated fat (g) 5.5 0.8
Cholesterol (mg) 27 0
Vitamin E (mg) 0.2 0.6
Thiamin ([mu]g) 8 15
Niacin ([mu]g) <0.1 0.5
Vitamin [B.sub.6] ([mu]g) 0.02 0.08
Folate ([mu]g) 22 23.6
Pantothenic acid (mg) 46 158
Sodium 405 2
Calcium 3 175
Potassium 46 158
Calories 106 52
The avocado has many uses as documented in industry usage studies from 1986-90 (Table 4). The consistently most mentioned use was as an ingredient in green salad. For comparative purposes, the nutritive contents of three commonly eaten green salad recipes are given in Table 5. The first is without avocado, the next with avocado, and the third with cheese replacing the avocado. The salad with avocado and no cheese had less calories, saturated fat, cholesterol and sodium than did the salad with cheese. Percent Daily Values (DV), established by the FDA 2,000-calorie diet, are given where applicable.
[TABULAR DATA OMITTED]
From examination of the consumption data, it is evident that avocados were consumed quite differently in the late 1980s than in the preceding decade, suggesting that avocados are more commonly used as an ingredient in recipes (salad) or as condiments rather than as the main spread in a sandwich.
Clinical trials have shown that dietary fiber is helpful in the control of diabetes and improving glucose tolerance, in the reduction of serum cholesterol and possibly in reducing the risk of certain types of cancer.[8-10] The inadequacy of dietary fiber in the American diet has been a matter of concern. The average diet supplies about only 12 g of fiber per day, as opposed to the recommended 20 to 35 g per day. This has led to a nutrition education campaign for people to increase fiber intakes by eating more fruits, vegetables and grains. The avocado has the highest concentration of dietary fiber of any commonly eaten fruit. However, because the serving size for avocados is relatively small, on a per serving basis, several other fruits contribute more fiber.
Avocados contain all of the B vitamins, but are particularly high in folate providing 6% of the recommended daily intake per ounce. Folate is a necessary coenzyme involved in many metabolic pathways, including DNA synthesis. It is necessary for cell division and is especially important for pregnant women and children where cells are rapidly dividing. Folate deficiency has been implicated in the development of precancerous lesions, particularly in the cervix and colon. This may be a result of increased susceptibility of folate-deficient cells to carcinogens.[13,14]
Although folate is found in a variety of foods, as much as half may be destroyed in food preparation. Since avocados are usually eaten raw, destruction of the folate is minimal.
Antioxidants are important because of their possible effects on a number of diseases including cancer and heart disease.[16-19] Vitamins E and C are two antioxidants that work synergistically to protect cefls from oxidative damage resulting from normal metabolic processes and environmental sources.[20-22] Vitamin E is lipid soluble and acts to sequester free radicals in cell membranes, which are high in unsaturated lipids, making these particularly susceptible to oxidation. Vitamin C works inside the cell to sequester free radicals. Vitamins E and C in the diet increase plasma levels of these antioxidants and thus may affect an individual’s defense against oxidative damage. It has been reported that daily intakes of many people do not meet the recommended daily intakes for vitamin E. Dietary guidelines have emphasized increasing polyunsaturated fatty acids in the diet, which further increases the need for vitamin E. Including avocados as part of a diet provides a food source of both vitamin E and vitamin C.
Dietary recommendations suggest that monounsaturated, polyunsaturated and saturated fats be consumed in a 1:1:1 ratio in a healthy diet. However, food intake data from the National Health and Nutrition Examination Survey II show that the ratios of fatty acids in the American diet are too high for saturated and too low for monounsaturated and polyunsaturated fats. This imbalance in fatty acid intake can be partially corrected by substituting fat sources, such as avocado, with its higher monounsaturated fatty acid content for those foods with more saturated fatty acids such as cheese and butter spreads. It has been shown in clinical trials that substituting saturated fats with monounsaturated fats decreases risk for heart disease by decreasing serum cholesterol levels.[7,25-27] Since 60% of the fat in avocados is monounsaturated and only about 17% is saturated, its use in recipes helps establish a better fatty acid profile in line with current recommendations, whereas use of cheese and other common food toppings and spreads higher in saturated fatty acids is contrary to these recommendations. The fat content of avocados varies from season to season. Avocados harvested early in the season (November to March) have one-third the fat (2 g/oz) of avocados harvested later in the year (September and October) (6 g/oz) and one-third the fat of sour cream or cheese. Using avocados as toppings provides a low-fat substitute together with other nutritional benefits.
Avocados are a nutrient-dense food with the highest fiber content of any fruit. They serve as a source of food antioxidants, folate and potassium. Since avocados contain a high proportion of monounsaturated fatty acids and are naturally low in saturated fatty acids and free of cholesterol, their use can contribute to a healthier diet. When used in place of cheese, sour cream or other high saturated fat, cholesterol-rich toppings, avocados help meet current guidelines for healthy eating while also adding interesting flavors and esthetics to the diet.
REFERENCES[1.] California Avocado Commission. Avocado usage survey 1986-1990. Santa Ana: California Avocado Commission, 1990. [2.] U.S. Department of Agriculture. Nationwide Food Consumption Survey/individual – spring quarter 1977-1978. Accession no. PB80-190218/HAE. Springfield, VA: National Technical Information Service, 1980. [3.] U.S. Department of Agriculture. Nationwide Food Consumption Survey/individual – winter quarter 1977-1978. Accession no. PB80-118853/HAE. Springfield, VA: National Technical Information Service, 1981. [4.] U.S. Department of Agriculture. Nationwide Food Consumption Survey/individual intake 1987-1988. Accession no. PB90-504044. Springfield, VA: National Technical Information Service, 1990. [5.] Schneeman BO. Soluble vs insoluble fiber-different physiological responses. Food Technol 1987;34:81-82. [6.] Position of the American Dietetic Association: health implications of dietary fiber-technical support. J Am Diet Assoc 1988;88:217-1. [7.] Grundy SM. Recent research on dietary fatty acids: implications for future dietary recommendations. Food Nutr News 1989;61:29-31. [8.] Pilch SM, Ed. Physiology effects and health consequences of dietary fiber. Springfield, VA: U.S. Department of Commerce, National Technical Information Service, 1987. [9.] Ink SL, Hurt HD. Nutritional implications of gums. Food Technol 1987;34:77-82. [10.] National Research Council. Recommended dietary allowances. 10th ed. Washington, DC: National Acadamy Press, 1989. [11.] Lanza E, Jones Y, Block G, Kessler L. Dietary fiber intake in the US population. Am J Clin Nutr 1987;46:790-7. [12.] Appling DR. Compartmentation of folate-mediated one-carbon metabolism in eukaryotes. FASEB 1991;5:2645-51. [13.] Butterworth CE, Hatch KD, Macaluso M, et al. Folate deficiency and cervical dysplasia. JAMA 1992;267:528-33. [14.] Mason JB. Folate, colitis, dysplasia, and cancer. Nutr Rev 1989;47:314-7. [15.] Murphy SP, Subar AF, Block G. Vitamin E intakes and sources in the United States. Am J Clin Nutr 1990;52:361-7. [16.] Buiatti E, Palli D, Decarli A, et al. A case-control study of gastric cancer and diet in Italy: II Association with nutrients. Int J Cancer 1990;45:896-901. [17.] Chen LH, Boissonneault GA, Glauert HP. Vitamin C, vitamin E and cancer (review). Anticancer Res 1988;8:739-48. [18.] Diplock AT. Antioxidant nutrients and disease prevention: an overview. Am J Clin Nutr 1991; 53:189S-93S. [19.] Esterbauer H, Dieber-Rotheneder M, Striegl G, Waeg G. Role of vitamin E in preventing the oxidation of low-density lipoprotein. Am J Clin Nutr 1991;53:314S-21S. [20.] Direct observation of a free radical interaction between vitamin E and vitamin C. Nature 1979;278:737-8. [21.] Freeman BA, Crapo JD. Biology of disease. Free radicals and tissue injury. Lab Invest 1982;47: 412-26. [22.] Slater GG, Shankman S, Shepherd JS, Alfin-Slater RB. Seasonal variation in the composition of California avocados. J Ag Food Chem 1975;23:468. [23.] Chow CK. Nutritional influence on cellular antioxidant defense systems. Am J Clin Nutr 1979;32:1066-81. [24.] Di Mascio P, Murphy ME, Sies H. Antioxidant defense systems: the role of carotenoids, tocopherols, and thiols. Am J Clin Nutr 1991;53: 194S-200S. [25.] Grundy SM, Florentin L, Nix D, Whelan MF. Comparison of monounsaturated fatty acids and carbohydrates for reducing raised levels of plasma cholesterol in man. Am J Clin Nutr 1988;47:965-9. [26.] Koumans AKJ, Wildschut AJ. Nutrition and arteriosclerosis: some neglected aspects. Clin Cardiol 1985;8:547-51. [27.] McDonald BE, Gerrard JM, Bruce VM, Corner EJ. Comparison of the effect of canola oil and sunflower oil on plasma lipids and lipoproteins and on in vivo thromboxane [A.sub.2] and prostacyclin production in healthy young men. Am J Clin Nutr 1989;50:1382-8.
Charlene Rainey is CEO of Nutrition Network, Inc., a company involved in providing industry with data on the nutritive profile of their products as consumed by the American public.
Mark Affleck is President of the California Avocado Commission.
Kari Bretschger is Managing Director of Bretschger and Associates, a marketing service firm.
Roslyn B. Alfin-Slater, Ph.D., is Professor Emerita of Nutrition in the School of Public Health, University of California, Los Angeles with special expertise in lipid nutrition.
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