Why are antioxidants marketed as anti-aging?
One of the most common explanations of why we age is "the free radical theory of aging," which proposes that aging is caused by damage that our bodies accumulate throughout our lives, which in turn is caused by free radicals. In general, signs of this type of damage are found more frequently in the elderly, and the elderly are also found to have lost some ability to prevent this damage. Because of these trends, the thinking goes, if we provide our body with more things that can prevent free radical damage, then we should slow down the aging process. Antioxidants are just such things! So, free radicals and their proposed function in aging are what the whole antioxidant industry is built to combat. Products from pomegranate juice to specialized skin creams all contain antioxidants, which are the molecules that protect your body's cells against the damage caused by free radicals.
Of course, nothing is that straightforward or we’d all be living to 200 already! The antioxidant industry is not a fountain of youth as it is sometimes advertised, but it is definitely based in real science and has real effects on health. So, to understand the free radical theory and this potential way to slow our common fate of aging, or at least helping us age more healthily, let’s take a step back and look at the whole system. We’ll start small, with free radicals themselves, where they come from, and what they do, and then we’ll move on to the mystery of aging and how antioxidants and free radicals fit in.
What exactly are free radicals and antioxidants?
Free radicals are molecules that are unstable because of the number of electrons they have. To try to become stable again, they react with surrounding molecules to get the necessary electrons. These reactions set off chains of damaging reactions. The result of these reaction chains is called “oxidative damage.”
Antioxidants, on the other hand, are molecules that allow free radicals to become stable again, stopping these destructive chain reactions.
Why are these reactions damaging? What happens when a molecule is attacked by a free radical?
All the molecules in our cells — our DNA, our proteins, our lipids, and so on — can only perform their roles correctly if they are in their correct and precise shape. When free radicals attack them, their conformation can change, and they may no longer perform their designated job in the cell.
More specifically, if DNA is the molecule that is attacked, chemical changes can happen to it such that it becomes impossible to replicate correctly. When DNA is copied with a mistake in it, this is when mutations arise. These mutations can happen anywhere, in any gene in your genome, causing the gene to code for a different, often non-functional protein. Such changes can lead to many things — from nothing, to terrible outcomes such as cell death or cancer.
Proteins themselves can also be damaged by free radicals. The precise shape and chemical make-up of a protein is what gives each one its specific function. For example, a protein that sits on the edges of your cells, waiting for signaling molecules to bind and tell the cell what to do, must be precisely shaped so that one end stays in the membrane of your cell, and the other end perfectly matches the shape of the signaling molecule it’s waiting for. If a free radical comes along and attacks it, the protein will change shape and will no longer be able to watch so perfectly. It can become a useless protein. If this happens once, not too much will likely happen, because your cells are constantly making new proteins to replace old ones. But if there is a regular onslaught of free radicals, protein damage can accumulate and the functioning of the cell can be compromised. Imagine a precisely ordered workplace, perhaps a factory, where staff are constantly falling asleep or putting the wrong parts into the assembly line. That can wreak a lot of havoc down the line!
Your cells are also made up of lipids, which can be damaged by free radicals as well. Lipids are fat molecules that make up the outer membrane of the cell and all the little functional compartments inside the cell. Lipids are also dependent on their shape and chemical properties, just like proteins are. If these are damaged, they can change shape, and in turn change the shape of the things around them. Lipid membranes are also the site of a lot of cell communication. Many proteins group together in the membrane, communicating complicated streams of information. If these membrane lipids get damaged, then the proteins sitting inside them may no longer be able to hold their own shape correctly anymore, and thus communication can be disrupted. What may be worse is that lipid damage caused by free radicals is largely responsible for atherosclerosis, or plaques in the arteries that cause strokes and heart attacks. Some research has even shown that it’s not so much fat itself that’s bad for you, but fat that has been attacked by free radicals.
Where do free radicals and antioxidants come from?
We largely make free radicals ourselves! In our cells are the energy producing organelles, the mitochondria. These organelles turn our food into energy that cells can use. In a way, these organelles are like tiny controlled furnaces, burning inside your cells and producing heat and energy. These reactions always produce a lot of free radicals on the side. There are things in our environment that cause us to be exposed to more free radicals, though, and we are beginning to see links between these things and diseases like cancer and Alzheimer’s. Many pesticides cause free radical damage, as do heavy metals like mercury and lead. Even eating too much sugar can cause damage by free radicals.
While our own cells are a major source of free radicals, we also make a lot of antioxidants ourselves, to keep the balance. Many enzymes are made in our cells whose whole job is to make free radicals stable again so they don’t attack our cells. One such enzyme is called super oxide dismutase. In addition to our own enzymes, we also get antioxidants from food, in the form of vitamins C, E, and A, for example.
Okay, so let’s get back to aging! How is it linked with free radicals, and can we really prevent aging with antioxidants?
There are many links between aging and oxidative stress and damage. All those types of damage described above — damage to DNA, proteins, and lipids — are found more frequently in the elderly. The elderly have also been found to have a reduced capacity to make antioxidants, and the pathways used to repair oxidative damage have been found to be weakened. Mitochondria themselves, the source of many free radicals, also get damaged and wear out with age, starting a cycle of overproducing free radicals that in turn cause even more damage. These correlations between oxidative stress and the elderly go on and on in many tissue types. They also come into play for age-related diseases like Alzheimer’s and Parkinson’s, diseases in which mitochondrial damage and over production of free radicals is thought to be at least partially causative.
Some of the clearest oxidative stress correlations in humans are in relation to high blood pressure, general cardiovascular risk, and cancer — all problems that are more common the older you get. Markers of oxidative damage correlate very well with those three causes of death in long term studies, meaning, for example, that the people with the most oxidative stress in their lipids were most likely to die of cardiovascular disease.
That’s all pretty good evidence, but things start getting trickier to follow when you go beyond correlation to really find causation. For instance, it is difficult to do aging studies in humans, because we live so long. Imagine taking a group of 20-year-olds, telling them to eat a cup of blueberries a day for the rest of their lives, and watching them age for 60 more years. It’s not very easy. Besides the fact that your participants probably wouldn’t do as they were told for 60 years, you as the researcher might even die before the study was completed! Another more realistic option is to use model organisms for aging studies — organisms that have shorter lives, such as flies or mice. You could also do short-term studies in humans in which you look at markers of oxidative damage and any death or decline seen in those years, while modifying something relatively easy to change in the diet. This is all pretty complicated to do, however.
Intrepid scientists are doing it, though! One example of an elegant combination of these experiments has been done with tea. Flies and mice that were given tea, or chemicals isolated from tea, both showed extended lifespans, sometimes of up to 15%! That’s the equivalent of a human extending their lifespan from 80 years to 92 years. If those twelve years are healthy, that’s a big deal. In humans, we have also seen that drinking tea increases the antioxidants circulating in the blood, and even reduces oxidative DNA damage in blood cells. Like anything though, having too much tea, and the antioxidants associated with it, has been shown to have negative effects as well, particularly on reproduction; flies that were given excessive amounts of green tea had far fewer offspring.
Other studies have produced some very hopeful results as well. Researchers have looked at blueberries and their antioxidant effect on aging and age-related decline. In fact, some of these studies even went beyond general oxidative damage to report that blueberry juice or compounds found in blueberries even appear to slow neuronal decline and memory loss in rats.
So, what’s the point?
There is a good amount of evidence linking aging to free radicals and oxidative damage, and another good bunch of evidence showing that consuming antioxidant rich foods can have beneficial effects against this damage, allowing animals to age a bit more slowly and perhaps without losing as many abilities.
But, you know, we’re not fruit flies or rats living in a lab. Our lives are more complicated than that (and there’s a lot more research out there complicating this topic!). But if you want to eat blueberries and drink green tea every day for breakfast, while there is no guarantee that you’ll live to be a spritely 110 years old, you’ll probably end up healthier than if you eat Lucky Charms every morning.
Another notable thing in these studies is that for the most part, the best antioxidants are found in plants, particularly in brightly colored fruits and vegetables. And the negative effects of antioxidant treatment, such as in those fruit flies whose reproduction was reduced, come from extremely excessive consumption. Taken together, these results seem to point to a pretty simple solution that people have been recommending for generations: Eat a varied diet full of fruits and vegetables, and don’t go crazy over any one thing.