Bob Bergh Department of Botany and Plant Sciences, University of California
Purseglove (1968), In his authoritative textbook, labeled the avocado "...the most nutritious of all fruits." Noted food writer Gaylord Hauser once said of it: "In this single delectable fruit are combined the protein of meat, the fat of butter [but much more wholesome!], the vitamins and minerals of green vegetables, the flavor of nuts, a six course dinner ". America's greatest plant explorer, David Fairchild is attributed "...the avocado is a food without rival among the fruits, the veritable fruit of paradise." And in 1959, cereal pioneer John H. Kellogg maintained that "of all edible fruits, it stands pre-eminent as a source of concentrated nutriment adapted to human use. For purity, wholesomeness, ease of digestibility, and adaptation to human needs, it has few rivals and none that can fill its place." (Quotation courtesy of J. S. Shepherd).
Abstract. Avocado usage is reduced because of negative misconceptions. The avocado has various uses as a natural cosmetic, with advantages in rapid skin penetration, and as a superior natural sunscreen. Avocado oil has several culinary and health benefits. The greater use of whole fruit has important advantages: usefulness in human weight control, high nutritional density, source of major antioxidants, stroke prevention, fruit protein source, fiber source; as baby food, and other dietary benefits. Erroneous public perceptions of avocado calorie content and of cancer influences are noted.
Many people appreciate the delicious flavor of avocado, but are afraid of them for (mistaken) dietary reasons. They therefore avoid avocados or eat less than they could, because of incomplete or erroneous nutritional information. Most of us connected with the avocado industry have encountered such errors in understanding among friends or chance acquaintances. Indeed, on occasion, one even encounters them among "avocado" people.
These errors are diverse and recurrent. One sometimes feels a bit like Hercules of classical mythology battling the ugly Hydra: as soon as one evil head is cut off, two more grow in its place! Its seems worthwhile, therefore, to make a summary of the scientific findings concerning the avocado. We will begin with a brief look at cosmetics, then examine the more important food attributes, and close with an analysis of misconceptions in the press and among the public.
Avocado Cosmetics
Increasing recognition of unhealthful consequences from additives, preservatives, processing, and artificial products generally gives the avocado a major advantage as a food and also as a cosmetic. With increasing concern for the environment, an added plus for avocado cosmetics is that they are biodegradable. Consumers are beginning to favor basic, natural ingredients. Swisher (1988) discusses use of the avocado as a skin moisturizer, cleansing cream, makeup base, sunscreen, lipstick, bath oil, and hair conditioner. Toxicological tests of avocado oil products have provided an official health/safety assessment.
In skin care, the two major advantages of the avocado are its marked softening and soothing nature and its notable absorption. Compared with almond, corn, olive, and soybean oils, avocado oil had the highest skin penetration rate (Swisher, 1988).
In sunscreens, chemicals like PABA have superior effectiveness but cause skin irritation in some people. Because they are synthetic, there are lingering questions about long-term safety. Among eight plant oils, avocado oil proved the most effective sunscreen (Swisher, 1988).
Avocado Oil
Like olive oil, avocado oil is predominantly monounsaturated, a property which is thought to confer distinct health benefits. The avocado as a refined cooking oil has additional advantages (Swisher, 1988).
* It is unusually light, so it mixes well with other foods.
* It has a mild, delicate flavor, which enhances and brings out the flavor of other foods, instead of dominating them such as olive oil and other oils.
* Avocado oil withstands a high cooking temperature before breaking down, i.e. its "smoke point" is about 255C (490F), which is much higher than that of olive oil.
Fried foods presently have an undesirable health reputation, but use of olive and avocado oil could change that.
High nutritional density
The fourth reason given above for the avocado's role in weight control is its "rich supply of minerals and vitamins." More important than a food's calorie content is its total nutritional contribution to human needs. A good measure is nutrients per calorie. Different avocado analyses have given somewhat variable results. The most detailed publication is that of Slater et al. (1973). Their data indicate that one half of a 'Hass' avocado, about 80 g edible fruit, provides a substantial percentage of the daily nutritional needs of a child aged 7 to 10 (adult percentages are generally a little lower, especially iron for females) (Table 1).
The avocado contains little vitamin B 12 and calcium, limited zinc and modest phosphorus. Its half-a-fruit quota of riboflavin and thiamine for children is about 9.5 and 8%, respectively, hence about equal to its relative calorie contribution. But the striking thing is that no less than eight essential nutrients are apparently present in about a 2: 1 calorie ratio. Nor is that all; three additional nutrients, potassium, copper and pantothenic acid, (for which I could not find precise Recommended Dietary Allowances) are also estimated to be present in avocado at about twice the calorie content. Per calorie, the avocado is indeed remarkably nutritious.
There is not space here to discuss either the human body's uses or the status in typical diets of these various nutrients. Judgments vary; several surveys have concluded that one or another of them is deficient in a considerable portion of American diets. Next we will look briefly at one of the least discussed vitamins in the group of nutrients provided by the avocado.
Vitamin B6 (pyridoxine) is important for the nervous system, red blood cells, teeth and gums. The Harvard Health Letter for March, 1991, reported 1990 data indicating that most Americans consume too little of vitamin B6. Among good sources they list watermelon and banana (overlooking avocado). Polansky and Murphy (1966) compared the 86 content per unit weight of 26 vegetables and fruits. For total chromatographed 86' banana and avocado had the highest amounts, the remaining 24 vegetables had from 1/5 to 1/25 of the amount of the avocado, with watermelon 1/6. A more recent report by William Sears, M.D., privately printed Nature's Guide to First Foods"(1988) reports that avocado has three times as much B6 per g as banana.
Antioxidants and free radicals: cancer, cataracts and aging
The University of California at Berkeley Wellness Letter for October, 1991, discusses the basic role of oxygen for human cellular energy and for life, but notes that an inevitable by-product of this activity is the formation of highly reactive "free radicals." These unstable troublemakers can affect various cell constituents: perhaps artery walls or LDL cholesterol advancing coronary heart disease; eye lens tissue causing cataracts; a critical gene leading to cancer; perhaps arthritis; or DNA (the genetic material) causing gradual deterioration and aging.
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