|LE Magazine March 2000 |
Blueberries and bilberries slow brain aging and protect vision
by Ivy Greenwell
When it comes to antioxidant power, according to a measure called ORAC (oxygen radical absorbance capacity), blueberries are at the top of the USDA chart-ahead of blackberries, garlic, kale and strawberries, and far ahead of broccoli and spinach. Not only that, but they taste delicious. Here, nature has been gracious to us: a favorite food has been found to be a powerhouse of antioxidants. Talk about a miracle anti-aging food that is actually a treat!
Now, by all means keep eating spinach and kale-these vegetables contain the powerful carotenoids, lutein and zeaxanthin, as well as a sulfur-containing antioxidant, lipoic acid-nutrients that help protect us against macular degeneration and cataracts, and probably against cardiovascular disease and other aging-related disorders as well. Eating spinach, kale and other green leafy vegetables at least twice a week is highly recommended. But do consider consuming half a cup or more of blueberries every day in addition to all the vegetables and fruit you already consume. Yes, you've read that correctly: this article is urging you to eat blueberries every day. Why? Because adding blueberries to your daily diet could double your antioxidant intake from food. Frozen blueberries are fine when fresh ones are out of season. Wild blueberries may be more potent than the larger, sweeter cultivated blueberries, but even the cultivated blueberries apparently can pack a ferocious punch against free radicals.
Why this sudden urgency about eating blueberries? It started with the scientists at the USDA Nutrition Research Center on Aging at Tufts University in Boston. They have discovered that the blueberry comes close to being a miracle food, considering the important health and anti-aging benefits it offers. It is rumored that the Tufts researchers themselves have begun to eat blueberries by the pint during the berry season; off-season, their freezers are stacked with frozen blueberries. Dr. James Joseph, a senior scientist at Tufts, admits that he started adding blueberries to his morning protein shake after he saw the results of his own research. This comes as no surprise: scientists have known for a long time that restoring and maintaining youthful brain function is key in slowing aging.
European bilberries (Vaccinium myrtillus) and North American blueberries (Vaccinium corymbosum) are closely related; cranberries (Vaccinium macrocarpon) are also close cousins to blueberries. Scientists think that the antioxidant and general anti-aging benefits of the Vaccinium species berries come from the compounds that give them their deep pigmentation. These compounds are a class of flavonoids (phenolic compounds) called anthocyanins, which often occur together with proanthocyanidins. Proanthocyanidins are the precursors of anthocyanins, and also excellent antioxidants in their own right.
Sometimes these complex flavonoids are referred to by an older term that seems to be regaining popularity, namely "condensed tannins." It is these tannins that give flowers, vegetables and fruit hues that include deep red, purple, mauve, blue, all the way to the extremely dark blue of Northern European bilberries, which can appear practically black. Thus, the redness of strawberries and raspberries and the blueness of blueberries are due to the same class of compounds. Elderberry, persimmon, tart red cherries (tartness indicates the presence of condensed tannins), red and purple grapes, beets, purple cabbage, and the peel of the purple eggplant also contain anthocyanins and proanthocyanidins.
So do many flowers-the very names of certain anthocyanins such as petunidine, malvidine, delphynidine, and peonidine indicate in which flowers these anthocyanins were first discovered. The anthocyanins in hydrangea have the interesting property of imparting mauve-pink color when the plant grows in acid soil, and blue color in alkaline soil. The red-mauve hues of autumn leaves are also due to these complex polyphenols. Those stunning scarlets of New England in October are the gift of anthocyanins. The astringent taste of wine and unripe fruit is also due to various condensed tannins.
In addition, one of the most potent flavonoids-quercetin-widely researched due to its powerful anti-cancer, anti-inflammatory, and cardioprotective properties, is chemically closely related to anthocyanins. Quercetin is present in wine, ginkgo, onions, apples, black tea and grapefruit. But berries appear to have something possibly even more potent in some ways than quercetin: a simple phenolic compound called ellagic acid, which has emerged as a star in natural chemoprevention.
Please note that green tea contains mainly catechins, which are relatively simple phenolic compounds. "Simple" doesn't mean that they are less beneficial. Black tea and many fruits and vegetables contain mainly complex polyphenols, also called polymeric polyphenols, or condensed tannins. Both simple and complex polyphenols, often present side by side, have been found to have a wide range of health benefits. Ellagic acid, for instance, a powerful anti-carcinogen, is also present in many kinds of berries, including blueberries and raspberries, as well as in cherries and pomegranates. Catechins are found not only in green tea, but also in red wine and dark chocolate (cocoa powder and bittersweet chocolate are good sources; "white chocolate" does not contain polyphenols). Likewise, coffee contains not only caffeine (an alkaloid; by the way, caffeine is also a strong antioxidant), but also catechins, as well as simple phenolic acids, such as chlorogenic acid, caffeic acid, and tannic acid. Hence, for instance, the well-established effectiveness of coffee in decreasing iron levels, or helping fight certain bacterial and viral infections.
Tannins are very common in the plant world. Apart from the sources already mentioned, they are also found in the bark of various trees-the best-known bark extract, Pycnogenol, comes from the bark of the French Maritime Pine, Pinus maritima. The wide distribution of tannins in the plant kingdom is probably related both to their antioxidant and antimicrobial properties. The presence of tannins in wood, for instance, is likely to be a key reason for the durability of wood. The fact that chocolate doesn't spoil in spite of its high fat content is also due to these fascinating polyphenols. Also, in spite of containing sugar, chocolate, like tea and other flavonoid-rich foods, appears to help prevent cavities. There is emerging evidence that thanks to their antimicrobial action, flavonoids can help prevent dental decay and oral diseases.
Bioflavonoids in general are amazingly bioactive with a wide range of benefits. Like many other powerful antioxidants, they show a biphasic action, depending on the dose. Lower doses, available from diet and supplements (even if you take several capsules per day of various flavonoid extracts, it is still a fairly low dose) act as antioxidants and raise the levels of reduced glutathione (GSH) and vitamin C. Negative effects such as pro-oxidant action and glutathione depletion become an issue only if huge megadoses are taken over a longer period of time. Again: neither blueberry eaters nor supplement takers need worry, since it would be very difficult and extremely expensive to reach the kind of tissue concentrations at which damage from flavonoids might occur. As Dr. Shukitt-Hale says, "You can't overdose on blueberries."
At the same, we badly need more research to investigate some unanswered questions about the dose range that produces optimum results. And of course, as usual, there are questions about in-vivo effects and complex interactions. Taking a single very potent flavonoid such as quercetin in megadoses (several grams a day, for instance) for an extended period of time should not be done without the supervision of an experienced clinician. We must remember that flavonoid research is still in infancy, and our knowledge is partial at best.
A lot of the benefits of phenolic compounds stem from their antioxidant properties. Flavonoids are powerful scavengers of free radicals. They also enter the body's antioxidant network, boosting the levels of vitamin C and of our chief endogenous antioxidant, glutathione. Higher levels of ascorbate and glutathione mean better protection of DNA and cell proteins against free radical damage. Higher levels of glutathione also mean better recycling of other antioxidant compounds, including, very importantly, estrogens, to their reduced (antioxidant) form so that these substances do not produce damage. Estrogens are excellent at protecting neural membranes from peroxidation and preventing neural death-but only if there is sufficient glutathione to keep recycling these powerful hormones to their antioxidant form. Thus, the ability of phenolic compounds such as anthocyanins to raise glutathione levels is extremely important. This, together with the inhibition of the enzymes needed for cell proliferation, such as tyrosine kinase and ornithine decarboxylase, leads to a longer cell cycle and a lower cellular turnover, since fewer damaged cells need to be replaced. The implications for anti-aging and cancer prevention are profound.
You may wonder why flavonoids have such a wide range of physiological effects, resembling those of hormones. Apparently this stems from the fact that flavonoids have chemical and structural similarities to steroid hormones, thyroid hormones, prostaglandins, retinoids, and fatty acids. Thus it should not be altogether surprising that flavonoids can even affect gene expression-both the expression of our own genes, and the genes of the various bacteria and viruses that may invade us.
Flavonoids can also attach themselves to proteins, modulating the action of enzymes. They inhibit certain digestive enzymes and also the kinase enzymes necessary for cell proliferation. This partly explains how flavonoids can serve as a valuable adjunct cancer therapy for many kinds of cancer. When very high doses of flavonoids are used, the proliferation of normal cells is also inhibited, but that generally doesn't hurt these cells, which just "sit." In fully developed cancer, however, tumor cells cannot survive in the resting state.
On the other hand, very high levels of flavonoids are undesirable for women seeking to become pregnant, since these compounds are also known to decrease fertility, possibly by modulating hormone levels and even by interfering with the critical early stages of pregnancy. Soy and red clover phytoestrogens are a particular culprit here, acting as endocrine disruptors because of their high ability to bind to estrogen receptors. Less estrogenic flavonoids may have less impact on the menstrual cycle and other aspects of fertility. A lot remains to be explored.
We are barely beginning to research flavonoids and other phytochemicals in the kind of depth they deserve. For a long while it has been known that people who consume more vegetables and fruit showed significantly superior health compared to those eating the least, especially in regard to lower rates of cardiovascular disease and cancer. Now the reasons for this are emerging. While eating a wide variety of plant foods is highly recommended, due to the synergy of various phytochemicals, we are discovering that certain compounds are particularly valuable. The phytochemicals in blueberries and bilberries are now at the top of the list.
What is so special about blueberries and bilberries? They are the richest known source of anthocyanins. But it's possible that it is the synergy of the various compounds these berries contain that is responsible for the dramatic results recently obtained at Tufts University in Boston.
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