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Wed, May-26-04 14:11 |
The Avocado, Nutrition, and Your Metabolism
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Contrary to popular assumptions, the avocado can be a helpful part of a successful weight-management program. It brings several advantages.
1) Its monounsaturated fat speeds up the basal metabolic rate, as compared with saturated fat.
2) Its high fat content gives a quicker feeling of satiation ("fullness"), thus helping to reduce overeating.
3) Its high fat content makes an overall sound diet more palatable, reducing the temptation to binge on foods high in sugars or saturated fats.
4) Its rich supply of vitamins and minerals also makes the diet more wholesome and satisfying and thus more conducive to overall health and to moderation in consumption
... In the most pertinent experiment (Grant, 1960), a mean of just over one California avocado a day for a mean of 33 days increased average daily calories by a calculated 24% and fat by 54% but resulted in a weight loss averaging approximately 1 kg (2.2 lbs). This remarkable result (under exceptional and tightly controlled hospital conditions) should not be taken as a universal guarantee; individual results will vary depending upon complex individual metabolic histories and interactions. What can be said is that eating avocado has been shown to be fully compatible with good weight control...
"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)
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.
Stroke prevention. Heart disease, cancer and stroke are the three leading causes of death in the United States. Additionally, stroke can cause many years of partial or total incapacitation and tragic crippling. The Associated Press, 15 October, 1987, reported an interview with Dr. Louis Tobian of the University of Minnesota on protection from strokes by fruit and vegetable consumption, in particular, by high potassium intake. Dr. Tobian is quoted as suggesting that bachelors may die earlier than married men because they have less balanced diets, specifically insufficient in potassium. As the best sources of potassium, he included strawberry, banana, citrus juice, potatoes, and milk (avocado is not mentioned).
Smith et a/. (1983) measured potassium in 100 g portions of 10 tropical fruits (including avocado), seven common fruits, nine common vegetables, and eight tropical vegetables. The seven common fruits, including strawberry, banana and orange, ranged from 1/5 to less than half the potassium content of avocado. Similarly, the nine common vegetables ranged from less than 1/4 (summer squash) to less than 2/3 (carrots) the avocado level. The other, lesser used, tropical fruits ranged from 1/2 to just over half the potassium supplied by avocado. Tropical vegetables, which are rare in the United States, ranged upward from 1/5 to about the same potassium richness of avocado.
Prevention magazine for August, 1987, reported the results of a 1 2-year study of stroke entitled "Potassium was the key.", conducted jointly by the Schools of Medicine of the University of California San Diego and Cambridge University in England. A 40% reduction in stroke risk was associated with an average daily increase in potassium consumption of about 400 mg, the amount supplied by less than half an avocado! Moreover, blood pressure, a stroke factor, was linked in the same article to potassium-sodium imbalance, namely to a sodium excess. The avocado has about 52 times as much potassium as sodium. For the touted potassium-rich carrot, the potassium to sodium ratio is less than 7 to 1 according to the brochure by Dr. William Sears cited earlier. Moreover, vegetables high in potassium which include the common potato and winter squash, are commonly eaten cooked. Boiling can remove up to 30% of potassium originally present, according to a researcher cited in the above Prevention article, giving the avocado an additional advantage.
Finally, avocado and olive oils are the two chief foods that are very high in monounsaturated fats, while being comparatively low in both polyunsaturated and saturated fats. An Italian epidemiological survey of 4,903 people (reported in a press release in February, 1990, based on an article in the Journal of the American Medical Association), found that while both monounsaturated and polyunsaturated fat were associated with lower blood cholesterol as compared with saturated, only monunsaturated fat was also associated with lower blood pressure. The next part of this paper will look at factors contributing to a healthy heart and related to avocado consumption. There is evidence to indicate that eating avocado may reduce the incidence of all three of the major causes of death in the United States.
Protein. Cultivars vary somewhat but the dominant 'Hass' is about 2.4% protein on a fresh weight basis (Slater et al., 1975). This is unusually high for a fruit. Hall et al. (1980) compared the essential amino acid content of 15 fruits: the avocado was second only to the rare Tucuma from Brazil which had about three times as much as mango, orange, peach and persimmon, and about six times as much as the two other common fruits listed, apricot and apple. Polansky and Murphy (1966) compared the protein content of 26 more common fruits and vegetables (41 entries counting separate cultivars and years). The avocado was in first place with about two to ten times the protein content of the others. The avocado is a "complete food" in terms of protein, containing all 9 essential amino acids, although not in the ideal proportions
Diabetes. The 27 September, 1988, issue of the New England Journal of Medicine reported a 4-week comparison of individuals on the traditional type II diabetic's diet of low fat-high carbohydrate with those on a diet ...
lower in carbohydrates and higher in monounsaturated fat (the dominant kind in avocados). The monounsaturated diet offered better control of blood sugar levels, accompanied by lower triglycerides and higher HDL ("good" cholesterol). However, this needs confirmation, including more careful monitoring. Moreover, there is a report that avocado has an odd sugar type that depresses insulin production. Diabetics probably should consume avocados cautiously..
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). ..
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