Newsletter #427 01/24/10


The Hass avocado (Persea americana Mill.) is a great American success story. A California mailman named Rudolph Hass discovered this cultivar, which turns purplish-black upon ripening, and patented the tree in 1935. Every Hass avocado tree in existence is derived from a single tree that Hass planted in La Habra Heights. (The tree was finally cut down in 2002.) While Hass avocados today constitute a billion dollar business, Hass himself made only $5,000 from his patent.


Hass avocados are often shunned by the health conscious because of their high fat content. But most of the fat in question is monosaturated, and thus is similar to olive oil. Other than its potential for adding poundage, avocados are a great source of nutrients, such as potassium and fiber. They have an abundance of vitamin C, vitamin E, vitamin K, folic acid, etc. Hass avocados contain the highest content of lutein among all commonly eaten fruits, as well as other carotenoids such as zeaxanthin, alpha-carotene, and beta-carotene.


In the past few years, there has been a steady stream of research on the anti-cancer potential of avocados. Scientists at Ohio State University (OSU) found that an extract of Hass avocado selectively induced apoptosis in cancer but not normal, human oral epithelial cell lines. Apoptosis is the most common form of programmed cell death (PCD) and is the way that most drugs actually kill cancer cells.


OSU scientists believe that consuming avocados may help prevent oral cancer (Ding 2009). “As far as we know, this is the first study of avocados and oral cancer,” said Dr. Steven M. Ambrosio of Ohio State. “We think these phytochemicals either stop the growth of precancerous cells in the body or they kill the precancerous cells without affecting normal cells. Our study focuses on oral cancer, but the findings might have implications for other types of cancer” (Science News 2007).


Another promising study from the University of California, Los Angeles (UCLA) showed that an extract of avocado inhibit the growth of both androgen-dependent and androgen-independent prostate cancer cell lines in the laboratory. This caught the attention of many patients, since there are few treatments that will work on prostate cancer that is no longer responding to hormone therapy. The mechanism of action was an arrest of the cell cycle accompanied by increased expression of the p27 protein. P27 helps regulate the normal cell cycle.


Many colorful fruits and vegetables also contain carotenoids. But UCLA scientists speculate that it is precisely because of the high monosaturated fat content that the carotenoids in avocado are absorbed into the bloodstream, “where in combination with other diet-derived phytochemicals they may contribute to the significant cancer risk reduction associated with a diet of fruits and vegetables” (Lu 2005).


So, yes, avocados can be fattening, but the monostatured oil in this case may be serving a very good purpose. Depending on your weight, adding avocados to the diet could be an excellent idea.


In addition, avocados are considered to be among the foods that have the least amount of pesticide residues. They therefore made the “Clean 15” list of the Environmental Working Group. Fewer than 10 percent of avocado samples had detectable pesticides, and fewer than one percent had more than one pesticide.


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