The avocado is colloquially known as the Alligator Pear, reflecting its shape and the leather-like appearance of its skin. Avocado is derived from the Aztec word "ahuacatl". Avocados are the fruit from Persea americana, a tall evergreen tree that can grow up to 65 feet in height. Avocados vary in weight from 8 ounces to 3 pounds depending upon the variety.

What's New and Beneficial about Avocados

• Consider adding avocado to salads, and not only on account of taste! Recent research has shown that absorption of two key carotenoid antioxidants—lycopene and beta-carotene—increases significantly when fresh avocado (or avocado oil) is added to an otherwise avocado-free salad. One cup of fresh avocado (150 grams) added to a salad of romaine lettuce, spinach, and carrots increased absorption of carotenoids from this salad between 200-400%. This research result makes perfect sense to us because carotenoids are fat-soluble and would be provided with the fat they need for absorption from the addition of avocado. Avocado oil added to a salad accomplished this same result. Interestingly, both avocado oil and fresh avocado added to salsa increased carotenoid absorption from the salsa as well. That's even more reason for you to try our 15-Minute Halibut with Avocado Salsaa great-tasting recipe that can help optimize your carotenoid health benefits.
• The method you use to peel an avocado can make a difference to your health. Research has shown that the greatest concentration of carotenoids in avocado occurs in the dark green flesh that lies just beneath the skin. You don't want to slice into that dark green portion any more than necessary when you are peeling an avocado. For this reason, the best method is what the California Avocado Commission has called the "nick and peel" method. In this method, you actually end up peeling the avocado with your hands in the same way that you would peel a banana. The first step in the nick-and-peel method is to cut into the avocado lengthwise, producing two long avocado halves that are still connected in the middle by the seed. Next you take hold of both halves and twist them in opposite directions until they naturally separate. At this point, remove the seed and cut each of the halves lengthwise to produce long quartered sections of the avocado. You can use your thumb and index finger to grip the edge of the skin on each quarter and peel it off, just as you would do with a banana skin. The final result is a peeled avocado that contains most of that dark green outermost flesh so rich in carotenoid antioxidants!
• We tend to think about carotenoids as most concentrated in bright orange or red vegetables like carrots or tomatoes. While these vegetables are fantastic sources of carotenoids, avocado—despite its dark green skin and largely greenish inner pulp—is now known to contain a spectacular array of carotenoids. Researchers believe that avocado's amazing carotenoid diversity is a key factor in the anti-inflammatory properties of this vegetable. The list of carotenoids found in avocado include well-known carotenoids like beta-carotene, alpha-carotene and lutein, but also many lesser known carotenoids including neochrome, neoxanthin, chrysanthemaxanthin, beta-cryptoxanthin, zeaxanthin, and violaxanthin.
• Avocado has sometimes received a "bad rap" as a vegetable too high in fat. While it is true that avocado is a high-fat food (about 85% of its calories come from fat), the fat contained in avocado is unusual and provides research-based health benefits. The unusual nature of avocado fat is threefold. First are the phytosterols that account for a major portion of avocado fats. These phytosterols include beta-sitosterol, campesterol, and stigmasterol and they are key supporters of our inflammatory system that help keep inflammation under control. The anti-inflammatory benefits of these avocado fats are particularly well-documented with problems involving arthritis. Second are avocado's polyhydroxylated fatty alcohols (PFAs). PFAs are widely present in ocean plants but fairly unique among land plants—making the avocado tree (and its fruit) unusual in this regard. Like the avocado's phytosterols, its PFAs also provide us with anti-inflammatory benefits. Third is the unusually high amount of a fatty acid called oleic acid in avocado. Over half of the total fat in avocado is provided in the form of oleic acid—a situation very similar to the fat composition of olives and olive oil. Oleic acid helps our digestive tract form transport molecules for fat that can increase our absorption of fat-soluble nutrients like carotenoids. As a monounsaturated fatty acid, it has also been shown to help lower our risk of heart disease. So don't be fooled by avocado's bad rap as a high-fat food. Like other high-fat plant foods (for example, walnuts and flaxseeds), avocado can provide us with unique health benefits precisely because of its unusual fat composition.

Health Benefits

Promote Heart Health

Before reviewing special health areas in which avocados truly shine in terms of their health benefits, it's worth remembering the big picture. That's exactly what Victor Fulgoni and his fellow researchers at Nutrition Impact, LLC did when they reviewed data from the federal government's National Health and Nutrition Examination Study (NHANES 2001-2006) and the dietary intake of 14,484 U.S. adults. Amazingly, only 273 adults participating in this study reported consumption of avocado within the last 24 hours. Amongst the 273 participants who reported recent consumption of avocado, however, nutrient intake was found to be significant higher than other participants for several vitamins (vitamin E and vitamin K), several minerals (potassium and magnesium), and at least one desirable macronutrient (total dietary fiber). Avocado consumers were also determined to be lower in weight and lower in body mass index than non-consumers. Total fat intake, total monounsaturated fat intake, and total polyunsaturated fat intake was higher in consumers of avocado, even though their overall calorie intake was not significantly different from non-consumers of avocado. This nationwide comparison of avocado consumers and non-consumers doesn't prove that avocado consumers get health advantages from avocado. Nor does it prove that avocado consumption makes us lower in weight. But it does point us in the general direction of viewing avocado as a health supportive food that may give us a "leg up" in terms of health and nourishment.

Wide-Ranging Anti-Inflammatory Benefits

The ability of avocado to help prevent unwanted inflammation is absolutely unquestionable in the world of health research. The term "anti-inflammatory" is a term that truly applies to this delicious food. Avocado's anti-inflammatory nutrients fall into five basic categories:

• phytosterols, including beta-sitosterol, stigmasterol, and campesterol
• carotenoid antioxidants, including lutein, neoxanthin, neochrome, chrysanthemaxanthin, beta-cryptoxanthin, zeaxanthin, violaxanthin , beta-carotene and alpha-carotene
• other (non-carotenoid) antioxidants, including the flavonoids epicatechin and epigallocatechin 3-0-gallate, vitamins C and E, and the minerals manganese, selenium, and zinc
• omega-3 fatty acids, in the form of alpha-linolenic acid (approximately 160 milligrams per cup of sliced avocado)
• polyhydroxylated fatty alcohols (PSA)s

Arthritis—including both osteoarthritis and rheumatoid arthritis—are health problems that have received special research attention with respect to dietary intake of avocado. All categories of anti-inflammatory nutrients listed above are likely to be involved in avocado's ability to help prevent osteoarthritis and rheumatoid arthritis. One especially interesting prevention mechanism, however, appear to involve avocado's phytosterols (stigmasterol, campesterol, and beta-sitosterol) and the prevention of too much pro-inflammatory PGE2 (prostaglandin E2) synthesis by the connective tissue.

Optimized Absorption of Carotenoids

No single category of nutrients in avocado is more impressive than carotenoids. Here's a list that summarizes key carotenoid antioxidants provided by avocado:

• alpha-carotene
• beta-carotene
• beta-cryptoxanthin
• chrysanthemaxanthin
• lutein
• neochrome
• neoxanthin
• violaxanthin
• zeaxanthin

Optimal absorption of these fat-soluble phytonutrients requires just the right amount and combination of dietary fats—and that is exactly the combination that is provided by avocado! Included within avocado are generous amounts of oleic acid, a monounsaturated fatty acid that makes it easier for the digestive tract to form transport molecules (chylomicrons) that can carry carotenoids up into the body. This great match between avocado's fat content and its carotenoids also extends to the relationship between avocado and other foods. Consider, for example, a simple salad composed of romaine lettuce, spinach, and carrots. This simple salad is rich in carotenoids, and when we eat it, we definitely get important carotenoid benefits. But recent research has shown that if one cup of avocado (150 grams) is added to this salad, absorption of carotenoids will be increased by 200-400%! This improvement in carotenoid absorption has also been shown in the case of salsa made with and without avocado. (That's even more reason, we think, to try our recipe for 15-Minute Halibut with Avocado Salsa!)

Supports Cardiovascular Health

Avocado's support for heart and blood vessels might be surprising to some people who think about avocado as too high in fat for heart health. From a research standpoint, however, many metabolic aspects of heart health - including levels of inflammatory risk factors, levels of oxidative risk factors, and blood fat levels (including level of total cholesterol) - are improved by avocado. In addition, we know that heart health is improved by intake of oleic acid (the primary fatty acid in avocado) and by intake of omega-3 fatty acids (provided by avocado in the form of alpha-linolenic acid and in the amount of 160 milligrams per cup). Since elevated levels of homocysteine form a key risk factor for heart disease, and since B vitamins are very important for healthy regulation of homocysteine levels, avocado's significant amounts of vitamin B-6 and folic acid provide another channel of heart support.

Research on avocado and heart disease remains in the preliminary stage, with studies mostly limited to lab studies on cells or animals fed avocado extracts. But we fully expect to see large-scale human studies confirming the heart health benefits of this unique food.

Promotes Blood Sugar Regulation

One of the most fascinating areas of avocado research—and one that may turn out to be the most unique for health support—involves carbohydrates and blood sugar regulation. Avocado is relatively low-carb food, with about 19% of its calories coming from carbs. It's also a low-sugar food, containing less than 2 grams of total sugar per cup, and falls very low on the glycemic index. At the same time, one cup of avocado provides about 7-8 grams of dietary fiber, making it an important dietary source of this blood sugar-regulating nutrient. Given this overall carb profile, we would not expect avocado to be a problematic food for blood sugar unless it was eaten in excessive amounts (many cups per serving).

Within its relatively small carb content, however, avocado boasts some of the most unusual carb components in any food. When it is still on the tree, avocado contains about 60% of its carbs in the form of 7-carbon sugars. In sizable amounts, 7-carbon sugars (like mannoheptulose, the primary carb in unripened avocado) are rarely seen in foods. Because of their rare status, food scientists have been especially interested in the 7-carbon sugars (mannoheptulose, sedoheptulose, and related sugar alcohols like perseitol) found in avocado. The 7-carbon sugars like mannoheptulase may help regulate the way that blood sugar (glucose) is metabolized by blocking activity of an enzyme called hexokinase and changing the level of activity through a metabolic pathway called glycolysis. Research in this area is still a long way from determining potential health benefits for humans from dietary intake of these 7-carbon sugars. But it's an exciting area of potential health benefit for avocado, especially since this food is already recognized as low glycemic index.

One final interesting observation comes from this research on avocado and its carbs: after five days of ripening (post-harvest, beginning with removal of the avocado from the tree), the carb profile of avocado changes significantly. The 7-carbon sugars change from being the predominant form of carbs in avocado (60%) to being an important but minority component (between 40-50% of total carbs). With ripening, the 5-carbon sugars—especially sucrose—become the predominant carbs. While it's too early in the research process to draw health-oriented conclusions from this information, these findings may be encouraging us to consider degree of avocado ripeness as an important factor in its health benefits. We already know to stay away from an extremely overripe avocado that has become overly soft and has developed dark sunken spots on its skin. Perhaps off in the future, we'll be able to zero in on exact amounts of avocado ripeness that offers different types of unique health benefits, including carb-related benefits.

Anti-Cancer Benefits

The ability of avocado to help prevent the occurrence of cancers in the mouth, skin, and prostate gland has been studied in a preliminary way by health researchers, mostly through the use of lab studies on cancer cells or lab studies involving animals and their consumption of avocado extracts. But even though this anti-cancer research has been limited with respect to humans and diet, we believe that the preliminary results are impressive. The anti-cancer properties of avocado are definitely related to its unusual mix of anti-inflammatory and antioxidant nutrients. That relationship is to be expected since cancer risk factors almost always include excessive inflammation (related to lack of anti-inflammatory nutrients) and oxidative stress (related to lack of antioxidants). But here is where the avocado story gets especially interesting. In healthy cells, avocado works to improve inflammatory and oxidative stress levels. But in cancer cells, avocado works to increase oxidative stress and shift the cancer cells over into a programmed cell death cycle (apoptosis), lessening the cancer cell numbers. In other words, avocado appears to selectively push cancer cells "over the brink" in terms of oxidative stress and increase their likelihood of dying, while at the same time actively supporting the health of non-cancerous cells by increasing their supply antioxidant and anti-inflammatory nutrients. We look forward to large-scale studies in this area involving humans and dietary consumption of avocado.


Description

There are dozens of varieties of avocadoes. The rich and creamy Hass variety is the most popular type of avocado in the United States, and 95% of all avocados grown in the United States are produced in California, original home of the Hass variety. They are generally available throughout the year, they are the most abundant and at their best during the spring and summer in California and in October in Florida. During the fall and winter months you can find Fuerto, Zutano and Bacon varieties. While avocados are technically fruits, we have categorized them here as vegetables since this is how they are usually considered from a culinary perspective.

History

Avocados are native to Central and South America and have been cultivated in these regions since 8,000 B.C. In the mid-17th century, they were introduced to Jamaica and spread through the Asian tropical regions in the mid-1800s. Cultivation in United States, specifically in Florida and California, began in the early 20th century. While avocados are now grown in most tropical and subtropical countries, the major commercial producers include the United States (Florida and California), Mexico, the Dominican Republic, Brazil and Colombia.

How to Select and Store

A ripe, ready-to-eat avocado is slightly soft but should have no dark sunken spots or cracks. If the avocado has a slight neck, rather than being rounded on top, it was probably tree ripened and will have better flavor. A firmer, less mature fruit can be ripened at home and will be less likely to have bruises. The average California Hass avocado weighs between 165-170 grams (about 6 ounces) and has a pebbled dark green or black skin, while the Fuerte avocado has smoother, brighter green skin. Florida avocados, which can be as large as 3 pounds, have less fat and calories, but their taste is not as rich as California varieties.

A firm avocado will ripen in a paper bag or in a fruit basket at room temperature within a few days. As the fruit ripens, the skin will turn darker. Avocados should not be refrigerated until they are ripe. Once ripe, they can be kept refrigerated for up to a week. If you are refrigerating a whole avocado, it is best to keep it whole and not slice it in order to avoid browning that occurs when the flesh is exposed to air.

If you have used a portion of a ripe avocado, it is best to store the remainder in the refrigerator. Store in a plastic bag, wrap with plastic wrap, or place on a plate and cover with plastic wrap. Sprinkling the exposed surface(s) with lemon juice will help to prevent the browning that can occur when the flesh comes in contact with oxygen in the air.

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Tips for Preparing and Cooking

Tips for Preparing Avocados

Use a stainless steel knife to cut the avocado in half lengthwise. Gently twist the two halves in opposite direction if you find the flesh clinging to the pit. Remove the pit, either with a spoon or by spearing with the tip of a knife. Next, take each of the avocado halves and slice lengthwise to produce four avocado quarters. The use the California Avocado Commission's "nick and peel" method to peel the avocado. Just take your thumb and index finger to grip an edge of the avocado skin and peel it away from the flesh, in exactly the same way that you would peel a banana. The final result will be a peeled avocado that contains most of that dark green outermost flesh that is richest in carotenoid antioxidants.

You can prevent the natural darkening of the avocado flesh that occurs with exposure to air by sprinkling with a little lemon juice or vinegar.

The Healthiest Way of Cooking Avocados

Many avocado recipes that you'll find in cookbooks and on the Internet include avocado as an ingredient in its raw, unheated form. In the World's Healthiest Foods recipes, we also favor this approach. We simply cannot think of a better way to preserve the health benefits made possible by avocado's unique and delicate fats. If you do plan to use avocado in a recipe that calls for heat, we recommend that you use the lowest possible temperature and least amount of cooking time that will still work with your particular recipe. Our purpose in making this recommendation is to help you minimize damage to avocado's unique fats. We've seen one research study showing that approximately 40 seconds of microwave heating on medium heat is a heating method that doesn't significantly change the fatty acid profile of avocados. Sometimes we like to add avocado to a dish that has been cooked. This is a similar approach to some traditional Mexican recipes. For example, in Mexico they add sliced avocado to chicken soup after it is cooked. The avocado warms and mingles well with the soup but retains its nutritional concentration since it is not cooked.

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