Avocado

Scientific Name(s): Persea americana Mill. Synonymous with P. gratissima Gaertn. Also referred to as Laurus persea L. Family: Lauraceae

Common Name(s): Avocado , alligator pear , ahuacate , avocato

Uses

The fruit commonly is eaten and the fruit oil is used for cosmetics. A limited number of studies indicate that avocado reduces cholesterol and improves lipid profile and may reduce symptoms of osteoarthritis. Seed derivatives reportedly have antitumor activity in rodents.

Dosing

Avocado oil/soy oil unsaponifiable fraction has been studied for osteoarthritis of the knee at 300 to 600 mg daily dosage. A Cochrane Database Systematic Review of osteoarthritis treatments cited use at 300 mg/day in 2 other studies where symptomatic relief was obtained.

Contraindications

Contraindications have not yet been identified.

Pregnancy/Lactation

Generally recognized as safe or used as food. Avoid dosages above those found in food because safety and efficacy are unproven.

Interactions

Avocado ingestion may decrease the anticoagulant effect of warfarin. Patients taking warfarin should consult their health care provider before eating avocado or taking herbal products.

Adverse Reactions

Allergy to latex, bananas, melons, and peaches may result in a cross-sensitivity to avocado; if allergic, use products that contain avocado with caution.

Toxicology

Large quantities of seeds or leaves appear to be toxic; however, only a small number of reports of toxicity caused by avocado have been published over the past 50 years.

Botany

The avocado grows as a large tree to heights of 15 to 18 meters. It bears a large fleshy fruit that is oval or spherical in shape; the skin of the fruit can be thick and woody. Although the plant is native to tropical America (Mexico and Central America), numerous varieties are now widely distributed throughout the world. 1

History

The avocado has been the subject of intense and varied use during the past, not only for food but also for medicinal purposes. The pulp has been used as a pomade to stimulate hair growth and to hasten the healing of wounds. The fruit also has been purported as an aphrodisiac and emmenagogue. American Indians have used the seeds to treat dysentery and diarrhea. Today, the fruit is eaten widely throughout the world, and the oil is a component of numerous cosmetic formulations.

Chemistry

The pulp of the avocado fruit is rich in a fatty oil, and this can account for up to 40% of its composition. In addition to sugars and carbohydrates, 2 bitter substances have been identified. 1

Avocado oil is derived from the fruit pulp and is composed primarily of glycerides of oleic acid and approximately 10% unsaponifiable compounds, such as sterols and volatile acids. Oleic acid is a beneficial monounsaturated fatty acid and its concentration ranges from 61% to 95% in an avocado. 2 The vitamin D content of the oil exceeds that of butter or eggs. 1

The large seed contains a wide variety of compounds, including fatty acids, alcohols, and a number of unsaturated compounds with exceedingly bitter tastes.

The leaves of the Mexican avocado have been reported to contain approximately 3% of an essential oil composed primarily of estragole and anethole.

Uses and Pharmacology

Lipid profile

Avocados frequently are included in healthy diets, and evidence suggests that they are highly effective in modifying lipid profiles.

Animal data

Research reveals no animal data regarding the use of avocado to modify lipid profiles.

Clinical data

In a randomized study, women chose a diet high in monounsaturated fatty acids enriched with avocado or a high-complex-carbohydrate diet. After 3 weeks, the avocado diet resulted in a reduction in total cholesterol level from baseline (8.2%); a nonsignificant decrease (4.9%) occurred with the comparison diet. Low density lipoprotein (LDL) cholesterol and apolipoprotein B levels decreased only in the avocado group. The authors concluded that an avocado-supplemented diet rich in monounsaturates can benefit serum lipid levels. 3 An avocado-enriched vegetarian diet was shown to reduce triglycerides and LDL cholesterol; however, a vegetarian diet cannot be recommended unconditionally in dyslipidemic patients. 4 A study in type 2 diabetes mellitus patients demonstrated improved lipid profiles and maintained glycemic control when the complex digestible carbohydrates in the diet were partially replaced with monounsaturated fatty acids, with avocado being one of the main sources. 5

Osteoarthritis
Animal data

Research reveals no animal data regarding the use of avocado for osteoarthritis.

Clinical data

A combination of avocado/soybean unsaponifiables has been shown in 2 separate randomized trials to reduce nonsteroidal anti-inflammatory usage in patients with symptomatic osteoarthritis of the knee or hip. 6 , 7 , 8 Efficacy was greater in patients with hip osteoarthritis. 6 , 7 In vitro studies of this mixture and an in vivo model for studying cartilage destruction have shown that the mixture of avocado/soybean causes reduction of the spontaneous production of inflammatory mediators (eg, prostaglandin E 2 ) from chondrocytes. This specific combination of avocado/soybean (1 part avocado and 2 parts soybean), available as a capsule form in France, should be considered a delayed, symptom-modifying drug that has a persistent effect. 9 , 10 , 11

Other uses

Avocado oil has been used extensively for its purported ability to heal and soothe the skin. This use is based on the high hydrocarbon content of the pulp and oil, which is likely to be beneficial to dry skin.

A condensed flavonol isolated from the seed has been reported to have antitumor activity in mice and rats. 1 Several of the unsaturated oxygenated aliphatic compounds in the pulp and seed have been shown to possess strong in vitro activity against gram-positive bacteria, including Staphylococcus aureus .

In rats, avocado has been shown to have gastric mucosal protective effects and experimental suppression of hepatic injury. Exact mechanism(s) of these protective measures are under investigation, along with potential human application. 12 , 13

Dosage

Avocado oil/soy oil unsaponifiable fraction has been studied for osteoarthritis of the knee at 300 to 600 mg daily dosage. A Cochrane Database Systematic Review of osteoarthritis treatments cited use at 300 mg/day in 2 other studies where symptomatic relief was obtained. 6 , 14

Pregnancy/Lactation

Generally recognized as safe or used as food. Avoid dosages above those found in food because safety and efficacy are unproven.

Interactions

A decrease in the anticoagulant effect of warfarin was reported in 2 patients after avocado ingestion. 15 Based on their international normalized ratio (INR), both patients had been anticoagulated adequately. The patients experienced a fall in their INR during consumption of avocado (100 and 200 g daily). When avocado was eliminated from their diets, the INR increased and adequate anticoagulation was restored. One patient ate avocado again and experienced a decrease in INR, which increased when she stopped eating avocado.

Adverse Reactions

Manifestations of allergy to avocado may be limited to the mouth or throat (oral allergy syndrome: itchy mouth, throat, and swollen tongue) or oral symptoms with generalized symptoms (eg, wheezing, chest tightness, abdominal cramping, diarrhea). 16 Cross-sensitivity has been shown with melons (eg, cantaloupe), peaches, bananas, chestnuts, tomatoes, potatoes, and kiwi fruits. 16 , 17 , 18 Cross-sensitivity also has been seen in patients with natural rubber latex (eg, latex gloves) allergy and avocados. 17 , 18 , 19 This cross-sensitivity is called the “latex-fruit syndrome.” 19 An IgE-mediated inflammatory mechanism has been shown to be similar in producing an allergic reaction to latex, bananas, and avocados. 20 , 21

Toxicology

The poisoning of grazing animals that have ingested avocado has been reported, and this toxicity also has been observed in species as diverse as fish and birds. 1 Nevertheless, only a small number of reports of toxicity caused by avocado have been published over the past 50 years. A review of avocado toxicity reported that feeding dried avocado seed in a 1:1 ratio with normal food rations killed all mice tested. 22 The amount of avocado ingested ranged from 10 to 14 g. Signs of toxicity became apparent after 2 to 3 days and the animals generally died within the next 24 hours. Gross findings included hemorrhage into the brain, lungs, and liver. In cattle and goats, acute toxicity has been characterized by a cessation of milk flow and nonbacterial mastitis. Fish have been killed as a result of avocado leaves falling into a backyard pond. 22 Although the specific mechanism of toxicity is not clear, leaves fed to goats decreased milk production and increased AST and LDH enzyme levels.

Bibliography

1. Leung AY, Foster S. Encyclopedia of Common Natural Ingredients Used in Food, Drugs, and Cosmetics . New York, NY: John Wiley and Sons; 1980.
2. Alvizouri-Muñoz M, Carranza-Madrigal J, Herrera-Abarca JE, Chavez-Carbajal F, Amezcua-Gastelum JL. Effects of avocado as a source of monounsaturated fatty acids on plasma lipid levels. Arch Med Res . 1992;23:163-167.
3. Colquhoun DM, Moores D, Somerset SM, Humphries JA. Comparison of the effects on lipoproteins and apolipoproteins of a diet high in monounsaturated fatty acids, enriched with avocado, and a high-carbohydrate diet. Am J Clin Nutr . 1992;56:671-677.
4. Carranza-Madrigal J, Herrera-Abarca JE, Alvizouri-Muñoz M, Alvarado-Jimenez MDR, Chavez-Carbajal F. Effects of a vegetarian diet vs. a vegetarian diet enriched with avocado in hypercholesterolemic patients. Arch Med Res . 1997;28:537-541.
5. Lerman-Garber I, Ichazo-Cerro S, Zamora-Gonzàlez J, Cardoso-Saldaña G, Posadas-Romero C. Effect of a high-monounsaturated fat diet enriched with avocado in NIDDM patients. Diabetes Care . 1994;17:311-317.
6. Little CV, Parsons T, Logan S. Herbal therapy for treating osteoarthritis (Cochrane Review). In: The Cochrane Library . Chichester, UK: John Wiley & Sons, Ltd; 2004.
7. Blotman F, Maheu E, Wulwik A, Caspard H, Lopez A. Efficacy and safety of avocado/soybean unsaponifiables in the treatment of symptomatic osteoarthritis of the knee and hip. A prospective, multicenter, three-month, randomized, double-blind, placebo-controlled trial. Revue Du Rhumatisme . English Edition. 1997;64:825-834.
8. Maheu E, Mazières B, Valat JP, et al. Symptomatic efficacy of avocado/soybean unsaponifiables in the treatment of osteoarthritis of the knee and hip: a prospective, randomized, double-blind, placebo-controlled, multicenter clinical trial with a six-month treatment period and a two-month follow-up demonstrating a persistent effect. Arthritis Rheum . 1998;41:81-91.
9. Khayyal MT, El-Ghazaly MA. The possible chondroprotective effect of the unsaponifiable constituents of avocado and soya in vivo. Drugs Explt Clin Res . 1998;24:41-50.
10. Henrotin YE, Labasse AH, Jaspar JM, et al. Effects of three avocado/soybean unsaponifiable mixtures on metalloproteinases, cytokines and prostaglandin E 2 production by human articular chondrocytes. Clin Rheumatol . 1998;17:31-39.
11. Boumediene K, Felisaz N, Bogdanowicz P, et al. Avocado/soya unsaponifiables enhance the expression of transforming growth factor beta 1 and beta 2 in cultured articular chondrocytes. Arthritis Rheum . 1999;42:148-156.
12. Dunjic BS, Axelson J, Hashmonai M, Bengmark S. Gastric mucosal protective capacity of avocado: phospholipids as an active principe? (A-3). Dig Dis Sci . 1996;41:431. Abstract.
13. Kawagishi H, Fukumoto Y, Hatakeyama M, et al. Liver injury suppressing compounds from avocado (Persea americana). J Agric Food Chem . 2001;49:2215-2221.
14. Appelboom T, Schuermans J, Verbruggen G, Henrotin Y, Reginster JY. Symptoms modifying effect of avocado/soybean unsaponifiables (ASU) in knee osteoarthritis. A double blind, prospective, placebo-controlled study. Scand J Rheumatol . 2001;30:242-247.
15. Blickstein D, Shaklai M, Inbal A. Warfarin antagonism by avocado. Lancet . 1991;337:914-915.
16. Telez-Diaz G, Ellis MH, Morales-Russo F, Heiner DC. Prevalence of avocado allergy among atopic patients. Allergy Proc . 1995;16:241-243.
17. Crisi G, Belsito DV. Contact urticaria from latex in a patient with immediate hypersensitivity to banana, avocado and peach. Contact Dermatitis . 1993;28:247-248.
18. Beezhold DH, Sussman GL, Liss GM, Chang N-S. Latex allergy can induce clinical reactions to specific foods. Clin Exp Allergy . 1996;26:416-422.
19. Brehler R, Theissen U, Mohr C, Luger T. Latex-fruit syndrome: frequency of cross-reacting IgE antibodies. Allergy . 1997;52:404-410.
20. Ahlroth M, Alenius H, Turjanmaa K, et al. Cross-reacting allergens in natural rubber latex and avocado. J Allergy Clin Immunol . 1995;96:167-173.
21. Lavaud F, Prevost A, Cossart C, et al. Allergy to latex, avocado pear, and banana: evidence for a 30KD antigen in immunoblotting. J Allergy Clin Immunol . 1995;95:557-564.
22. Craigmill AL, et al. Toxicity of avocado (Persea americana [Guatamalan var]) leaves: review and preliminary report. Vet Hum Toxicol . 1984;26:381.

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