Published on December 21, 2017


William Grant, PhD, presents a 50 minute talk on vitamin D and health. A summary is below.

Bill Grant giving SVI talkVitamin D Physiology

Grant starts with a definition of terms and general functions associated with vitamin D, including D3 vs. D2, 25(OH)D, 1,25(OH)D,  as well as an explanation of vitamin D receptors (VDRs).

Grant details skin pigmentation and its relationship to vitamin D, the sun, and skin cancer.

Vitamin D Recommendations

Current recommendations of adequate intake and blood levels of vitamin D (25(OH)D) from the Institute of Medicine (IOM), 20 ng/ml, are reviewed along with those of the Endocrine Society, 30 ng/ml, and Vitamin D advocacy groups such as GrassrootsHealth, 40-60 ng/ml. Grant explains why each group came up with their recommendations and leaves it to the listener to decide what is best for them.

Sources of vitamin D, with the sun being the primary source, are reviewed in the next segment, and he spends a good amount of time explaining how to get vitamin D from the sun, as well as other positive effects of sun exposure. Other sources of vitamin D are supplements and diet, although it is hard to get very much from diet, especially for vegans and vegetarians. In addition to vitamin D, other benefits of sun exposure are also mentioned.

Those most likely to have low levels of vitamin D include people who are indoors most of the time, especially at mid-day; dark skinned; obese; or older than 60.

Grant recommends testing 25(OH)D level because of the prevalence of deficiency and also the variable response to supplementation. (Explanation from GrassrootsHealth data here.)

Major Health Outcomes Related to Vitamin D

Benefits of higher levels of vitamin D include a reduced risk of several diseases and health conditions. He presents data starting with the Garland-brothers map of colon cancer mortality rates across the US (similar to the map on this blog). UVB and its association with other cancer types are also presented. Grant also discusses vitamin D and its associations with flu, pregnancy, athletic performance, autism, ADHD, dental caries, sleep, verbal fluency, cognitive decline, dementia, erectile dysfunction, testosterone, surgery recovery and overall mortality.

He presents his research which found if the world doubled their vitamin D level (from 22 ng/ml to 44 ng/ml) this could increase life expectancy by 2 years.

Where is Vitamin D Policy Headed?

Grant notes that 4-5 major vitamin D trials will complete data collection in 2017 or 2018 and will likely be the basis for upcoming recommendations.

How to Conduct Vitamin D Clinical Trials

Grant explains that research trials should be based on vitamin D levels, not by dosage groups. It is important to take baseline vitamin D measurements, have a group of people that start deficient, and make sure dosages raise vitamin D levels adequately.

Where to Go For More Information

Some resources for additional information include GrassrootsHealth, Vitamin D Wiki, and the Vitamin D Council.


Silicon Valley Health Institute Meeting
Vitamin D Update
William Grant, PhD
October 2017
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Sunlight, Nutrition and Health Research Center