Vitamin D is a fat-soluble vitamin that acts as a steroid hormone and controls the expression of many genes. Our primary source of vitamin D occurs through UVB radiation by the sun onto our skin. To note, mushrooms that have been in the sun also have the capacity to make vitamin D with sun exposure.
Several factors predispose us to vitamin D deficiency and these include: skin pigmentation, aging, obesity and sunscreen use (1). In fact, using sunblock with SPF 15 or higher blocks 100% of vitamin D production in the skin. And if you have more skin pigmentation, then you require 3-5 times longer exposure to make the same amount of vitamin D as a person with white skin tone because melanin is a natural sunscreen. A 70 year old produces 4 times less than a 20 year old. And lastly, it is possible that deficiency in this vitamin is more prevalent among obese individuals because the vitamin gets diluted throughout the body (2). Other sources include oil-rich fish such as salmon, mackerel, and herring and mushrooms that have been in the sun.
Having adequate levels of vitamin D is very important because it regulates calcium, phosphorous, and bone metabolism. vitamin D deficiency is associated with Alzheimer’s disease, Parkinson’s, cognitive impairment, and cancer. Actually, there is an increase in all-cause mortality associated with D deficiency (1). There is a lot of research emerging in this field supporting the optimization of D levels. For example, high-dose vitamin D supplementation improves visual memory (3), vitamin D deficiency during pregnancy has been linked to autism (4), and vitamin D supplementation (along with Calcium) is shown to prevent colon cancer, to name a few (5).
When it comes to longevity, vitamin D plays a critical role. In one study, vitamin D extended the median lifespan of a nematode by 33% by engaging in known longevity genes (6). In another study looking at stress, mood, and longevity, vitamin D (along with other compounds) may act on certain genes and promote longevity (7). Telomeres are a way to measure our cellular age. They exist at the ends of chromosomes and function to protect DNA. Each year we age, our telomeres shorten until the cell dies (8). Individuals in the highest quartile between 40-60 nmol/L had longer lifespans (9). Further, mice that had both too little and too much vitamin D experienced premature aging (10).
Everyone should have his or her vitamin D levels checked at least once per year. Don’t just supplement blindly because too much vitamin D can be just as bad as not enough! Aim for levels between 30 and 80 ng/ml and keep in mind that vitamin D deficiency is VERY COMMON, especially to us living in the good ol’ Pacific Northwest where the sun don’t like to shine.