Vitamin D deficiency is one of the most common nutritional deficiencies worldwide, yet it does not affect everyone equally. While seasonal changes, especially the winter months, play a major role in lowering vitamin D levels, there are several well-established factors that can significantly increase an individual’s risk of deficiency year-round.

Last week, we focused on the influence of the seasons on vitamin D levels, and how this time of year is when a majority of the population is at their highest risk of deficiency. Understanding the additional following risk factors for vitamin D deficiency is essential for both individuals and practitioners, as it helps identify who may need higher intake, closer monitoring, or more frequent testing year-round.

New Dr. John Campbell video reviewing the 2014 research paper reporting a statistical error in the estimation of the Recommended Dietary Allowance for Vitamin D. The corrected amount should have been 8,895 IU/day not 600 IU/day. Learn more:

Winter in Canada means cold temperatures, snowy weather and reduced daylight hours. The season also often brings an increase in common illnesses like the cold, flu and other respiratory issues that can affect our overall health. 

Maintaining a balanced diet and an active lifestyle can help boost your immune system and mood throughout winter, but even those with the best diets can be afflicted by vitamin deficiencies. As Canadians, we’re especially susceptible to lower levels of vitamin D, which is only produced when skin is exposed to sunlight.

Miranda Popen, a nutritionist who specializes in hormone health, describes Canadians as “basically running on airplane mode for half the year” due to the lower levels of sunlight we receive. 

In 1982, PubMed, a research database, indexed 740 papers with “vitamin D” in the title. In 2020, there were 5,566. Clearly, interest has increased. Today, vitamin D is studied as a system-wide regulator and an essential component of skeletal, immune, metabolic, cardiovascular, neurological, and inflammatory processes.

Even a century ago, nutritionists feared the dangers of vitamin D deficiency. Warnings were dismissed as “alternative thinking.”

Vitamin D was discovered in the early 20th century, when researchers noticed that children deprived of sunlight developed rickets, a bone-softening disease that left them bow-legged and deformed. In 1903, Niels Ryberg Finsen, a Danish physician with Icelandic roots, received a Nobel prize for pioneering the therapeutic use of concentrated light. Sanatoriums, which emphasized sunlight exposure and cod liver oil rich in D, were common treatments for tuberculosis and other infections, but Finsen’s work explained it.

New study shows that if you reduce sun exposure enough to save 1 death from skin cancer, that would cause an extra 75-135 deaths from other causes.

Severe vitamin D deficiency is associated with a higher rate of hospitalisation for respiratory tract infections such as bronchitis and pneumonia, according to a new study led by the University of Surrey. Scientists found that those with a severe deficiency (below 15 nnmol/L) were 33 per cent more likely to be admitted to hospital for treatment than those with sufficient levels of vitamin D (at least 75 nmol/L). 

In the largest study of its kind, analysing NHS data from the UK Biobank, researchers from Surrey, in collaboration with the University of Reading and University of Oxford, investigated the association between vitamin D status and the rate of hospitalisation due to respiratory tract infections. Middle and older-aged adults are at a high risk of developing respiratory tract infections, with lower respiratory tract infections (pneumonia and bronchitis) ranking amongst the top 20 leading causes of mortality globally for individuals aged 50-74 years and in the top 10 for those aged 75 years and older.