January 2020

2019: A Bad Year for Vitamin D

Several trials published in 2019 showed that vitamin D doesn’t benefit heart disease, various types of cancer, or diabetes. This differs from the promising findings from observational research, which suggested that vitamin D might benefit numerous conditions. So, what happened? Why don't the results from controlled trials support what we saw in observational studies?

Observational research doesn’t prove a cause and effect relationship; it can only suggest a link between two factors. Research found links between low vitamin D levels and increased risk for asthma – breast cancer – kidney disease – diabetes – and the list goes on. Unfortunately, the media reported these results as if the levels of vitamin D caused these effects. This cleared the way for research funding to find out if taking vitamin D could reduce the risk or improve symptoms of these conditions. Unfortunately, we now know it doesn’t.

Overall, taking vitamin D supplements doesn't really benefit any extra-skeletal conditions. But remind patients that taking vitamin D along with calcium is still appropriate for skeletal conditions such as osteoporosis. And people with confirmed vitamin D deficiency should still take a vitamin D supplement in addition to increasing dietary intake of vitamin D. If other patients want to increase their vitamin D levels, recommend they eat more fish, eggs, and fortified milk, and spend a brief period of time in the sunlight each day.

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