Antioxidant hoopla is long on marketing and short on science
It’s important to eat fruits and veggies but we should be aware of the hype, too
I stopped counting at about 20, but could have gone on and on. I was scanning product labels for the term “antioxidant” as I recently meandered through a Whole Foods supermarket in New York.
There were juices from exotic berries, fruit concentrates, smoothies, an array of teas, dried plums, fresh blueberries and powdered extracts of vegetables, grape seeds and pine bark. And of course, innumerable capsules and pills loaded with vitamins, polyphenols and minerals, all touting their potential to ward off disease and even boost life expectancy thanks to their powerful antioxidant properties.
What we have here is a modicum of science laced with a huge dose of marketing. We can’t live without oxygen. It is critical to respiration, the process by which cells use food components, mostly glucose, to produce energy.
To simplify: Electrons are removed from glucose, causing it to break down, eventually forming carbon dioxide that is exhaled. These electrons are transferred to oxygen via a complex series of reactions allowing it to combine with hydrogen to form water. The overall process leads to the release of energy and is basically analogous to burning a fuel, be it wood, coal or gasoline. Fuel combines with oxygen to produce carbon dioxide and water with the simultaneous release of energy.
Our cells are actually little furnaces, and much like real furnaces, they produce byproducts, the notorious free radicals. Electrons extracted from food can go astray and add to oxygen molecules to produce super-oxide, a free radical that can trigger a cascade of reactions forming other free radicals referred to as “reactive oxygen species (ROS).” These then can damage biomolecules such as proteins or DNA by ripping electrons from them.
Such damage has been linked to cancer, heart disease, diabetes, arthritis and cataracts, as well as the aging process. To complicate matters, free radicals are also produced on exposure to ultraviolet light, X-rays, ozone or tobacco smoke. No surprise that by the 1980s, free radicals had been cast as molecular villains that had to be expunged. The question was how?
A clue surfaced from the numerous epidemiological studies documenting that a diet rich in fruits and vegetables reduces the incidence of the various diseases associated with freeradical damage.
Fruits and vegetables are composed of hundreds of compounds, many of which are capable of donating electrons to ROS, which neutralizes them.
These are the “antioxidants,” commonly portrayed as the heroes in the war waged against free radicals. Plants produce these compounds to protect themselves from oxidative damage caused by the oxygen they generate during photosynthesis.
A seductive hypothesis now evolved. Squeezing more of these plant antioxidants into our body would allow them to act as sponges, mopping up those nasty free radicals.
Companies soon flooded the shelves with supplements containing vitamin E, vitamin C, beta-carotene and a host of plant polyphenols.
Cash registers jingled and people filled toilets with expensive urine, since a good proportion of the antioxidants end up being excreted. That wasn’t the major problem, though.
The real problem was that properly controlled studies did not demonstrate a benefit from taking antioxidant supplements, and in some cases even showed harm.
Smokers actually increased their risk of lung cancer by taking beta-carotene!
Maybe, then, isolated antioxidants in pills aren’t that useful, but what about those smoothies and other beverages that are touted as being especially high in antioxidants?
In a British trial, 10 healthy volunteers were asked to avoid foods and beverages containing antioxidants for 48 hours before consuming a smoothie advertised as being rich in antioxidants. Blood samples were then periodically tested for antioxidant status during the next 24 hours. After an hour, there was an increase in antioxidant concentration, but then levels quickly dropped below baseline, only getting back to normal after a day.
So, even if antioxidants do neutralize free radicals, taking in more does not seem to be more effective, since after an hour the blood has actually a reduced antioxidant potential. This may be due to the body’s tendency to deal with a sudden rise in blood components through homeostasis, the self-regulating process by which biological systems tend to maintain stability while adjusting to conditions.
Current scientific opinion is that the benefits of fruits and vegetables may be due to factors other than their antioxidant content and that free radicals may not be as villainous as previously believed.
For example, subjects engaged in exercise training do not derive the benefit of increased insulin sensitivity when taking antioxidant supplements, possibly because the antioxidants neutralize free radicals that signal the body to respond to exercise.
While high doses of free radicals are indeed dangerous, it seems that at low levels they induce a protective response to disease and aging.
By all means, eat those fruits and vegetables, but cast a wary eye on the antioxidant hype.