In one study involving patients with high cholesterol levels, individuals with a diet high in avocados improved their cholesterolemia significantly: after seven days, total cholesterol and LDL cholesterol both decreased, and levels of "good" HDL cholesterol increased by 11%. This effect is probably due to avocados' high content in oleic acid, a monounsaturated fat.
A positive effect on blood pressure can also be observed, due to their high content in potassium: adequate levels of this mineral have been linked with an improvement in circulatory diseases, high blood pressure and strokes. The health claim has even been authorized by the US FDA, stating that Diets containing foods that are good sources of potassium and low in sodium may reduce the risk of high blood pressure and stroke.
Another important nutrient found in avocados is folate: its effects have been studied in a trial involving 80,000 healthy women, followed during a period of 14 years with dietary questionnaires. The study found that women with a higher intake of folate had a 55% lower risk of dying from heart disease, and a similarly lower risk of having heart attacks of any kind. A similar study showed a positive correlation with adequate folate intake and a reduction in the risk of developing cardiovascular disease. A cup of avocadoes contains 23% of the recommended Daily Value for folate!
Avocados are an important source of monounsaturated fatty acids, like oleic acid, which has been recently shown to protect significantly against breast cancer.
They also contain high levels of antioxidants, such as carotenoids: in particular lutein, zeaxanthin, alpha-carotene and beta-carotene, as well as significant quantities of liposoluble vitamins such as Vitamin E.
A lab study, published in the Journal of Nutritional Biochemistry, found that avocado extracts could inhibit the growth of prostate cancer cells (both androgen-dependent and androgen-independent), probably due to the extracts' high content in antioxidants.
The same researchers also attempted to expose prostate cancer cells to lutein alone, but it didn't provide similar effects: it seems that carotenoids, tocopherol (vitamin E) and oleic acid act in synergy to reduce proliferation of prostate cancer cells. Chemically, this can be explained by the fact that Vitamin E, as well as carotenoids, are fat-soluble, so fatty acids such as oleic acid are probably needed for these antioxidants to be absorbed.
A study, published in the March 2005 issue of the Journal of Nutrition, proved exactly that synergistic effect: since carotenoids are fat-soluble, consuming them with monounsaturated-fat-rich avocado might enhance their bioavailability, meaning they are more easily absorbed into the bloodstream.
Eating avocados is therefore particularly advised when eating carotenoid-rich foods, such as orange and red vegetables (like carrots and tomatoes): adding avocado to salads increased absorption of alpha-carotene, beta-carotene and lutein by an amount 7.2, 15.3, and 5.1 times higher relative to the same avocado-free salads.
Avocadoes provide the same effects even when added to sauces, increasing the absorption of lycopene and beta-carotene by 4.4 and 2.6 times, relative to the same amount of nutrients in an avocado-free sauce.
Oral cancer is quite rare, but when it's present, it's usually very deadly, with a mortality rate of about 50%, mostly due toe the difficulty in detecting it at early stages (numbers from Great Britain's Mouth Cancer Foundation).
Hass avocados (the most common variety), contain several different phytonutrients which have been proven to target multiple signal pathways, leading to an increase of free radicals inside cancerous and pre-cancerous cells in human: this means that only these cells are damaged, while normal human cells are not.
Other studies by UCLA scientists had already proven in the past that Hass avocados could inhibit the growth of prostate cancer cells, due to their high content in lutein, zeaxanthin, alpha-carotene and beta-carotene. Of these, about 70% is represented by lutein.