Native to Central and South America, avocados 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.
 
Avocado is derived from the Aztec word "ahuacatl."
 
Avocados are the fruit from the Persea Americana, a tall evergreen tree that can grow up to 65 feet in height. There are dozens of varieties of avocados, the most popular type of avocado in the United States is the Hass variety, which has rugged, pebbly brown-black skin. Another common type of avocado is the Fuerte, which is larger than the Hass and has smooth, dark green skin and a more defined pear shape.
 
Avocados vary in weight from 8 ounces to 3 pounds depending upon the variety. The edible portion of the avocado is its yellow-green flesh, which has a luscious, buttery consistency and a subtle nutty flavor. The skin and pit are inedible. 

Nutritional Profile
 
Although they are fruits, avocados have a high fat content of between 71 to 88% of their total calories - about 20 times the average for other fruits. A typical avocado contains 30 grams of fat, but 20 of these fat grams are health-promoting monounsaturated fats. Avocados contain oleic acid, a monounsaturated fat that may help to lower cholesterol. In one study of people with moderately high cholesterol levels, individuals who ate a diet high in avocados showed clear health improvements. After seven days on the diet that included avocados, they had significant decreases in total cholesterol and LDL cholesterol, along with an 11% increase in health promoting HDL cholesterol.
 
While avocados have a huge amount of fat, 25-35 grams on average, and an avocado is close to 300 calories, one-fifth of a medium avocado (30g) has 55 calories and is equal to 1 Weight Watcher point, and it's better for you nutritionally than many other popular one point snacks.
 
The monounsaturated fatty acids and oleic acid in avocados have shown to give significant protection for women against breast cancer.  Avocados also carry a concentrated source of carotenoid lutein, carotenoids and tocopherols which also fight against certain cancers. In a laboratory study published in the Journal of Nutritional Biochemistry, an extract of avocado containing these carotenoids and tocopherols inhibited the growth of both androgen-dependent and androgen-independent prostate cancer cells. Lutein has also been shown to be concentrated in the macula of the eye, and research suggests that it may help maintain healthy eyesight as we age. 
 
Japanese researchers have found avocados may also protect against liver damage. An Ohio State University study found that antioxidants in avocados can help fight oral cancer. Avocado compounds actually signal cancer cells to self destruct, a process called "apoptosis".

Avocados are also a great source of copper, and vitamins K, B6, C and E.   

 

One cup of avocado has 23% of the Daily Value for folate, a nutrient important for heart health. To determine the relationship between folate intake and heart disease, researchers followed over 80,000 women for 14 years using dietary questionnaires. They found that women who had higher intakes of dietary folate had a 55% lower risk of having heart attacks or fatal heart disease. Another study showed that individuals who consume folate-rich diets have a much lower risk of cardiovascular disease or stroke than those who do not consume as much of this vital nutrient.
 
Avocados contain more potassium than a medium banana-877 grams of potassium in one avocado vs 470 grams in a medium banana. And much less sugar!
 
Avocados are a good source of potassium, a mineral that helps regulate blood pressure. Adequate intake of potassium can help to guard against circulatory diseases, like high blood pressure, heart disease or stroke. In fact, the U.S. Food and Drug Association has authorized a health claim that states: "Diets containing foods that are good sources of potassium and low in sodium may reduce the risk of high blood pressure and stroke."
 
One cup of avocado a day can give great benefits to the heart because it gives a person 23% of their daily recommended allowance of folate. 
 
They are a great source for fiber and are known to have the highest fiber content compared to any other fruit; 75% insoluble and 25% soluble fiber.
 
Increase Your Absorption of Carotenoids from Vegetables
 
Enjoying a few slices of avocado in your tossed salad, or mixing some chopped avocado into your favorite salsa will not only add a rich, creamy flavor, but will greatly increase your body's ability to absorb the health-promoting carotenoids that vegetables provide.
 
A study published in the March 2005 issue of the Journal of Nutrition tested the hypothesis that since carotenoids are lipophilic (literally, fat-loving, which means they are soluble in fat, not water), consuming carotenoid-rich foods along with monounsaturated-fat-rich avocado might enhance their bioavailability.
 
Not only did adding avocado to a salad of carrot, lettuce and baby spinach or to salsa greatly increase study participants' absorption of carotenoids from these foods, but the improvement in carotenoid availability occurred even when a very small amount-as little as 2 ounces-of avocado was added.
 
Adding avocado to salad increased absorption of alpha-carotene, beta-carotene and lutein 7.2, 15.3, and 5.1 times higher, respectively, than the average amount of these carotenoids absorbed when avocado-free salad was eaten.  

 

Adding avocado to salsa increased lycopene and beta-carotene absorption 4.4 and 2.6 times higher, respectively, than the average amount of these nutrients absorbed from avocado-free salsa. Since avocados contain a large variety of nutrients including vitamins, minerals, as well as heart-healthy monounsaturated fat, eating a little avocado along with carotenoid-rich vegetables and fruits is an excellent way to improve your body's ability to absorb carotenoids while also receiving other nutritional-and taste-benefits.
 
How to Select and Store
 
Although the creamy rich Hass avocados 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.
 
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 Hass avocado weighs about 8 ounces on average and has a pebbled dark green or black skin, while the Fuerte avocado has smoother, brighter green skin. Avoid Fuertes with skin that is too light and bright. Florida avocados, which can be as large as 5 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.
 
Tips for preparing avocados
 
Use a stainless steel knife to cut the avocado in half lengthwise. Gently twist the two halves in opposite directions 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. Place the halves face down, then peel and slice. If the flesh is too soft to be sliced, just slide a spoon along the inside of the skin and scoop it out.
 
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.