During the waking and sleeping hours, our bodies are exposed to numerous free radicals. Free radicals are normal products of metabolism and are also derived from pesticides, industrial pollutants, smoking, alcohol, viruses, most infections, allergies, stress, even certain foods and excessive exercise. Free radicals create oxidation, the same process that turns iron to rust and the exposed surfaces of sliced apples brown. They are “free” in the sense of being unattached: molecular loose cannons that combine with oxygen in the air to initiate the process of spoilage. Internally, the same sort of deterioration occurs. Free radicals attack cell membranes, often in a matter of minutes. To counter the effects of free radicals, our bodies manufacture or rely on outside sources of antioxidants, whose purpose is to scavenge for free radicals, bind with them, and eliminate them before they contaminate healthy cells. Toxins, however, impede this process by creating too many free radicals, which quickly deplete the body’s reserve of antioxidant nutrients.
If free radicals are left to roam unimpeded throughout the body, the brain suffers many of the consequences. The brain, which consumes approximately 20% of the oxygen we breathe, is composed mostly of unsaturated fatty acids, complex molecules that are highly susceptible to free-radical damage because they have a “loose” hold on their electrons. Also, brain tissue is rich in iron, which can transform hydrogen peroxide, a byproduct of oxygen metabolism, into hydroxyl radicals, which are particularly dangerous forms of free radicals.Hydroxyl radicals can cause irreversible damage in the brain, because neurons (brain cells) cannot be regenerated. Neuronal damage can lead to memory impairment, loss of motor control, Alzheimer’s disease, Lou Gehrig’s disease, multiple sclerosis, and Parkinson’s disease.
Fortunately, the brain is protected by the blood-brain barrier, a layer of modified capillaries that makes access to the brain less permeable. This barrier keeps many toxins out of the brain, reducing (but not eliminating) the load of free radicals. However, it also prevents many antioxidants from entering the brain, allowing free radicals to accumulate.
Sleep can stem the influx of free radicals. When we sleep, the pineal gland in our brain produces a hormone called melatonin. Melatonin is best known for its hypnotic or sleep-inducing powers , but numerous scientific studies have shown that melatonin is a powerful antioxidant as well. And because melatonin is produced within the brain, it does not have to contend with the blood-brain barrier.
Studies prove that melatonin is a highly effective scavenger of hydroxyl radicals and peroxyl radicals, another type of toxic free radical. In fact, melatonin has been shown to be more effective in scavenging hydroxyl radicals than other well-known antioxidants such as glutathione. Melatonin appears to inactivate free radicals on a subcellular level, reaching the free radicals in DNA, proteins, and lipids. It also seems to stimulate important antioxidant enzymes, including superoxide dismutase, glutathione peroxidase, and glutathione reductase.
In experiments, melatonin has reduced the neuronal damage associated with Alzheimer’s disease and Parkinson’s disease. It has also been shown to prevent cataracts (caused by free-radical damage in the eye lens), as well as counteract the free-radical effects of toxins such as paraquat, carbon tetrachloride, and safole. Further studies have shown that prolonged periods of sleep deprivation—that is, prolonged periods without elevated production of melatonin—cause neuronal damage in animal subjects.
