Vitamin D’s role in regulating calcium absorption and promoting bone growth was already determined. But now it appears that vitamin D has much wider effects.
Research at the Buck Institute shows that vitamin D works through genes known to influence longevity and impacts processes associated with many human age-related diseases. The study explains why vitamin D deficiency has been linked to breast, colon and prostate cancer, as well as obesity, heart disease and depression.
The study shines a light on protein homeostasis, the ability of proteins to maintain their shape and function over time. It’s a balancing act that goes haywire with normal aging — often resulting in the accumulation of toxic insoluble protein aggregates implicated in a number of conditions, including Alzheimer’s, Parkinson’s and Huntington’s diseases, as well as type 2 diabetes and some forms of heart disease.
Researchers found that vitamin-D3-induced lifespan extension requires the stress response pathway genes skn-1, ire-1, and xbp-1. Vitamin D3 (D3) induced expression of SKN-1 target genes but not canonical targets of XBP-1. D3 suppressed an important molecular pathology of aging, that of widespread protein insolubility, and prevented toxicity caused by human β-amyloid.
They also observed that D3 improves protein homeostasis and slows aging highlights the importance of maintaining appropriate vitamin D serum levels and may explain why such a wide variety of human age-related diseases are associated with vitamin D deficiency.
How much vitamin D do humans need and how do they best get it?
The issue is confusing with disagreement rampant among experts. The Institute of Medicine’s (IOM) latest recommendations (from 2011) pertain only to vitamin D’s role in bone health and fracture reduction.
Experts concluded that evidence for other proposed benefits of vitamin D was inconsistent, inconclusive, or insufficient to set recommended intakes. The IOM recommends a daily intake of 600 International Units (IU) for people between 1 and 70 years old, and 800 IU daily for those older.
The upper limit — the levels above which health risks are thought to increase — was set at 4,000 IU per day for adults. Excess vitamin D can raise blood levels of calcium which leads to vascular and tissue calcification, with subsequent damage to the heart, blood vessels and kidneys.
Many vitamin D researchers and some health organizations, including the Endocrine Society and the International Osteoporosis Foundation, disagreed with the IOM’s recommendations for daily intake, instead recommending supplementation of 800 to 2,000 IU per day, at least for people known or likely to have low blood levels.
The disagreement highlights another difficulty: measuring blood levels of vitamin D is problematic given a lack of standardization and reliability among labs. Blood levels of the precursor to the active vitamin D are measured in nanograms per milliliter (ng/mL) in the U.S.
Many researchers and expert groups have argued that a blood level of at least 30 ng/mL is optimal; some call for optimum levels to be set at 40 or 50 ng/mL. But the IOM report concluded that blood levels starting at 20 ng/mL would be adequate for bone health in the vast majority of people.