Low levels of vitamin D in the blood are linked to increased mortality. That is the conclusion of a large population-based Norwegian study. How did they discover that too little vitamin D might be deadly?
Mortality and Vitamin D:
Investigators followed more than 6,613 adults over nearly two decades. Participants completed numerous questionnaires about lifestyle, socio-economic status and chronic diseases. During clinical examinations they were weighed, measured and blood was drawn for later analysis.
The Follow-Up Told the Story on Too Little Vitamin D:
Over the 18 and a half year follow-up period, 1,539 people died. Those with the lowest levels of 25-hydroxyvitamin D in their blood were roughly 30 percent more likely to have died compared to those with the highest levels of this vitamin.
This correlation persisted regardless of whether participants had chronic diseases at baseline. (People already ill with chronic diseases might spend less time outside in the sun. The investigators checked to make sure that was not the explanation.)
The authors point out that the results of this study are similar to those from other investigations.
Sun et al, BMJ Open, Vol 7 (6), 2017
Other Studies on the Effects of Vitamin D:
Over the years, scientists have found that too little vitamin D boosts the risk of bladder cancer. In addition, people who live in areas with low sunshine appear to be more prone to multiple sclerosis. An early report has been confirmed by more recent research.
Vitamin D, Sunshine and MS:
Multiple sclerosis remains mysterious. The cause is uncertain and the course of the disease is unpredictable. In this disorder the immune system runs amok and attacks the myelin sheath that insulates nerves. Symptoms can include numbness, muscle weakness, difficulty with balance and coordination, fatigue and many others. Although there are new drugs to treat MS, there is no cure.
Two Factors in Multiple Sclerosis Risk?
An epidemiological study from England suggested that two factors may predispose susceptible patients to MS (Ramagopalan et al, Neurology, April 19, 2011). The investigators analyzed data over seven years and found the highest rates of MS occurred in areas that had less sunlight and higher rates of the infectious disease mononucleosis. The researchers speculated that if vitamin D levels are too low, the immune system may not be able to ward off late complications of the Epstein Barr virus that causes mono.
Previous studies have shown lower rates of MS where sun exposure is stronger, suggesting that there may be something about vitamin D levels that is protective. Numerous studies since then have confirmed that vitamin D levels help determine who develops this disease (Ontaneda, Hyland & Cohen, Annual Review of Medicine, 2012; Baarnhielm et al, European Journal of Neurology, July 2012; Sundstrom & Salzer, Acta Neurologica Scandinavica, 2015). The most recent review concludes that vitamin D appears to modulate the immune system, although it may also act through other mechanisms (Pierrot-Deseilligny & Souberbielle, Multiple Sclerosis and Related Disorders, May 2017).
Vitamin D and the Heart:
People with too little vitamin D seem more susceptible to heart attacks and stroke than those with higher amounts (Zhang et al, American Journal of Clinical Nutrition, April 2017). Unfortunately, taking supplements doesn’t always reduce the risk. Vitamin D deficiency reduces the flexibility and function of blood vessels (Al Mheid & Quyyumi, Journal of the American College of Cardiology, July 4, 2017). It is also linked to diabetes, high blood pressure and elevated blood lipids. Some of these effects might play a role in the excess mortality reported in the BMJ Open article.
Too Little Vitamin D and the Risk of Dementia:
Another previous study showed that inadequate vitamin D levels might be linked to a fate worse than death: dementia:
Low levels of vitamin D may put older people at substantial risk of developing dementia (Littlejohns et al, Neurology, Sep. 2, 2014). Over 1,600 volunteers over the age of 65 had their blood levels of vitamin D determined at the start of the study. None had dementia at that point.
After an average follow-up of six years, 171 of them had been diagnosed with dementia. Those who had the lowest levels of vitamin D in their blood at the beginning of the study were 50 percent more likely to have developed serious cognitive impairment. Those who were most severely deficient in this nutrient were 120 percent more likely to show clear signs of Alzheimer’s disease.
Will Supplements Help?
No one knows whether vitamin D supplements can stave off dementia in the elderly, but the evidence keeps mounting that low levels of this critical vitamin can increase the risk for serious health conditions. Unfortunately, the trouble lies in know whether supplements make a difference. The volunteers for most of the clinical trials had adequate vitamin D levels at the outset, so that the researchers were not able to see whether correcting low levels would change the outcome (Rejnmark et al, PLOS One, July 7, 2017).
Although doctors have long considered vitamin D2 and vitamin D3 equivalent as supplements, a recent study shows that vitamin D3 is more effective at increasing blood levels of 25-hydroxyvitamin D (Tripkovic et al, American Journal of Clinical Nutrition, July 5, 2017).
How much vitamin D should a person consider taking? A study of two doses to treat polycystic ovary syndrome (PCOS), a metabolic disorder that impairs women’s fertility, found that 4,000 IU daily was more effective than 1,000 IU per day (Foroozanfard et al, Hormone and Metabolic Research, July 5, 2017).
In The People’s Pharmacy perspective, your grandmother was right to send you out to play when you were little. She may even have dosed the family up with old-fashioned yucky-tasting cod liver oil. Although it was disgusting, cod liver oil contained vitamin D that helped people get through the winter with fewer infections.
Now it seems that grandma should be encouraged to go outside for a few minutes every day. That is one way to maintain healthy blood levels of vitamin D. Obviously, we are not suggesting that older people (or anyone else) should overexpose themselves to ultraviolet rays and the damage they can cause, so moderation is key. For more information on benefits, risks and sources of vitamin D, check our Guide to Vitamin D Deficiency.