Factors That Determine Aging: Telomere Length, Vitamin D, and Calories
George tells me he's 21 years old. But he looks 70 to me.
George has gray thinning hair, he stoops forward rather than standing erect, the flesh on his upper arms hang loosely, he's got wrinkles on his hands and face, brown spots on the back of his hands and arms.
"I don't believe you. I think you're 70 years old."
"Prove it," he says.
Minus any formal identification like a driver's license, how do I prove that George is fibbing and is really 70-something, not 20-something? If George were a tree, I could cut him down and count his rings. Is there such an age-counter in humans?
This is actually a fascinating area of research, looking for reliable biomarkers of aging.
One such marker of aging is telomere length. Telomeres were once dismissed as nonsense sequences in human DNA. However, geneticists have proposed that, because telomeres shorten with aging, they provide the body's cells a timeline of aging. This way, George's cells act like they are 70 (if he is, indeed, pulling my leg), not 13, and don't start producing adolescent levels of growth hormone and testosterone in preparation for puberty.
What factors can slow or stall the shortening of telomere length? There are two I'm aware of:
1) Calorie deprivation--i.e., eating fewer calories. Dr. Roy Walford tried (though failed) to prove this in humans during his Biosphere2 experience, based on his work in mice that showed that calorie deprivation nearly doubled lifespan.
2) Vitamin D-Researchers from St Thomas' Hospital and the London School of Medicine found that, in cells from humans, the higher the vitamin D, the longer the telomere length. The highest vitamin D levels conferred a 5-year effective difference in telomere length.
Might vitamin D provide a means of turning back the clock of aging?
Aging and vitamin D:
As with nearly all other hormones (yes, vitamin D is a hormone, not a vitamin), as we age, we lose the capacity to activate vitamin D in the skin.
Between ages 20 and 70, we lose 75% of the ability to activate vitamin D with exposure to sunlight. So our friend, George, maintains about 25% of his original youthful capacity to activate vitamin D with sunlight.
This would explain why 70-year olds like George come to my office, just back from the Caribbean and sporting dark brown tans, are still deficient, often severely, in blood levels of vitamin D (25(OH) vitamin D).
A practical way of looking at it is that anyone 40 years old or older has lost most of the ability to activate vitamin D.
This often makes me wonder if the loss of vitamin D activating potential is nature's way of getting rid of us. After all, after 40 years of age, we've pretty much had our opportunity to recreate and make our contribution to the species.
Is the programmed decline of vitamin D skin activation a way to ensure that we develop diseases of senescence (aging)? The list of potential consequences of vitamin D deficiency¾osteoporosis, poor balance and coordination, falls and fractures; cancer of the breast, bladder, colon, prostate, and blood; reductions in HDL, increases in triglycerides; increased inflammation (C-reactive protein, CRP); declining memory; coronary heart disease¾Isn't that also pretty much a list that describes aging?
Clinical studies supporting vitamin D's effects on preventing or treating cancer, osteoporosis, lipid abnormalities, inflammation, cardiovascular disease, etc., is developing rapidly.
Now the big question: If declining vitamin D is nature's way of ensuring our decline and death, does maintaining higher vitamin D also maintain youthfulness, even extend life? Compelling data suggest that it just might.
So, if I could look inside George's cells and count his telomeres, I could judge with confidence that he was really 70 years old. Or, he could take vitamin D sufficient to increase blood levels to a healthy range and be more like 65. Let's take it a step further: What would happen to someone like George who began maintaining healthy levels of vitamin D earlier in life at, say, 30 years old? Would George maintain disease-free youthfulness longer? Will he live a vigorous life until 90 years of age, 100, maybe 110?
As appreciation for the profound health effects of vitamin D and this nationwide "experiment" in vitamin D restoration progresses, we will likely find out.