Have you ever treated yourself to a delicious cup of tea fortified with antioxidants? How about dark chocolate with antioxidants? Antioxidant water? Antioxidant facial wipes? While there is no problem with treating yourself, there is one if you've been told that antioxidants work.
Advertisements will try to tell you that your cells consist of free radicals--highly reactive chemicals that destroy everything in their path and cause you to age. But take a step back and ask yourself: Where are these free radicals coming from? That's actually an age-old question. Approximately 2.7 billion years to be precise.
Microbes first appeared on Earth 3.8 billion years ago. They made their living using carbon dioxide and hydrogen that was ejected into the atmosphere by volcanic eruptions; a metabolic process that still occurs in the soil, in cows, and in your gut. These ancient bacteria also had plenty of iron floating around in the Earth's seas, which they brought in and used for a range of cellular processes. Consequently, the cells had pools of iron associated with their DNA and protein. Most importantly, there was no oxygen.
A billion years later, a group of bacteria figured out how to use sunlight, carbon dioxide, and water to make sugar--a process we call photosynthesis. Unfortunately, the byproduct was oxygen, a reactive chemical that was capable of oxidizing iron. Initially, there was plenty of environmental iron and other minerals that consumed oxygen, keeping its atmospheric levels low for another billion years. Eventually, the abundance of photosynthetic bacteria released more oxygen compared to the amounts that were being lost due to reactions with iron. As a result, present-day levels of oxygen accumulated in the atmosphere.
Oxygen presented an exciting new opportunity to microbes: they could now use it to respire. The problem was that oxygen also reacted with cellular components and generated reactive oxygen species. One of these species includes hydrogen peroxide, which can be purchased from drug stores to daub on cuts and kill bacteria. Our body's defense system also uses it to spray invading bacteria. Hydrogen peroxide is dangerous because it reacts with the iron inside cells to generate hydroxyl radicals. That's right. Your cells have inherited an ancient dependency on iron, which is why when oxygen enters your cells it generates free radicals, which are extremely reactive and can damage any molecule they encounter, including DNA.
Despite the damage these radicals can inflict, our cells are still alive because we have inherited both the vulnerability to oxygen and defense mechanisms against it from ancient microbes. Our cells deal with oxidative stress by getting rid of the stress and repairing the damage it causes. We have dedicated enzymes that can reduce the concentrations of hydrogen peroxide and other reactive oxygen species to innocuous levels. In other words, our cells are bathed in enzymes, such as catalase, and chemicals, such as glutathione, ascorbate, and vitamin E, that act as antioxidants. Additionally, because hydroxyl radicals are so reactive, their lifetime inside cells is very short.
So why does the antioxidant industry claim that their products work? No, it's not corporate greed. Or that's not the only reason. Even though green tea and dark chocolate contain antioxidants, it's unclear whether those molecules can find their way from the digestive system into our cells. And even if they do, it's impossible that they can provide further protection in addition to what our cells already do. Catalases react with hydrogen peroxide at a rate that is 1 billion times higher than glutathione or ascorbate. Additionally, detecting oxidative stress inside cells is tricky. The dyes that are typically used in labs to detect oxidative stress can react with other cellular components, muddying the interpretation of experiments that try to understand whether a particular antioxidant can work. Studies that suggest external antioxidants are helpful depend on these dyes. There is no convincing, direct evidence that external antioxidants have any benefits. In fact, in 2012 the USDA removed the antioxidant content of various foods from their websites because of the lack of evidence. They recognized that these incorrect measurements are routinely misused by food and dietary supplement manufacturing companies to promote their products and misguide their consumers.
Your body doesn't need your help to deal with free radicals. They have learnt how to do so from their billion-year-old ancestors. So if you're at the grocery store agonizing about whether you need regular food or those rich in antioxidants, pick the one that tastes better. At the very least, your taste buds will thank you.
