October 15, 2014

Letter from the Director


Many of you are part of the largest cohort in the world of vitamin D replete individuals - the GrassrootsHealth D*action study. As participants, you test your serum vitamin D level from the privacy of your home, but each of you also contributes to the greater objective of moving science into practice. As we continue to gather information, we want to keep you informed about what we are finding. Before any information can come back to you, it must first go through a validation process so that we can make sure the information we are reporting on - the information you supplied - is as accurate as possible. GrassrootsHealth employs two full time analysts who validate and analyze the data collected through D*action tests and questionnaires. After validation, we work with scientists from our panel to target our analysis, write papers and publish results about a vitamin D replete community, the D*action community.


It has always been my goal to attack vitamin D deficiency from a different angle, not simply talking about it and raising awareness, but gathering data and using numbers to move beyond awareness and into action.


It has taken some time, but our grassroots effort has taken off and people in positions of power are starting to listen. My calendar is filling up with meetings with public health officials, insurance officers - people who can affect change for whole populations. Thank you all for helping to make this happen.


Today we are going to give you a peek at some of the D*action data as it relates to gender. Sometimes the data is surprising and other times, it is what you expect. Either way, you have to look at it to know.


Thank you,


Carole Baggerly

Director, GrassrootsHealth

A Public Health Promotion & Research Organization

Moving Research into Practice NOW!

Your Data Your Answers
Vitamin D and Gender

D*action is a study cohort with 7,809 members who have completed at least one questionnaire and blood test. Of these, 972 have completed 5 or more tests (over the span of up to 5 years). While the study is open to anyone, roughly 2/3 (64%) of the cohort is female, and it is mostly Caucasian (92%). The average age at sign-up is 51. The number 51 also represents the number of countries our participants call home, although 90% reside in the US or Canada.


Serum Levels are not Affected by Gender


While there is a big difference in the number of males and females enrolled, gender does not play a role in determining serum levels. The median serum level of males in our cohort is 45 ng/ml and for females is 43 ng/ml.  





Intake Methods are not Affected by Gender


As with serum levels, there is no difference by gender in how participants get their vitamin D. Of the D*action participants, 80% of both females and males take supplements. This matches what our scientists tell us - that most people will need a daily supplement, along with other sources (sensible sun exposure and food), to meet their daily requirement for vitamin D. It is recommended to use a combination of all three of these methods of vitamin D intake, to test periodically, and make adjustments as necessary to keep your serum level between 40-60 ng/ml.


How Much to Take?


Despite a difference in median weight, the median intake of supplements is the same for both genders, 4000 IU/day. This tells us what many of our scientists have shown in the past, that the RDA of 600 IU/day is simply not enough for most people to attain a serum level of 40-60 ng/ml. Many studies that have looked for the positive effects of vitamin D for preventive medicine have been negative simply because the dose was too low (200 IU/day up to 1000 IU/day). In fact, one of the groundbreaking studies led by Dr. Bruce Hollis from the Medical University of South Carolina in Charleston, found that a dose of 4000 IU/day in healthy pregnant women was safe and effective in raising circulating vitamin D to a level in the range of 40-60 ng/ml.


High Intake Levels and Kidney Stones


Some doctors remain wary of taking more than 2000 IU/day and they  quote what they learned in medical school, that too much vitamin D causes kidney stones. According to what we found with the D*action cohort, this simply isn't the case.


Our analysis, published in the American Journal of Public Health, found no statistically significant association between 25(OH)D serum levels and kidney stone risk. In fact, the researchers found a non-significant trend towards lower incidence of kidney stones for those with higher 25(OH)D serum levels. 

Editor's Note


It is great to have this data at our fingertips so that we can look at it in different ways and see if there are any differences between our participants and the normal world. What would be even better is to have more participants and more data!  


Do you have a friend you could tweet about this right now? Or have you taken one test and let more than 6 months or a year go by without following up with your 2nd or 3rd? The more data we have, the more we can get people in power to sit up and take action. Sometimes the small donation (of money and time) of doing your test every 6 months is the most important thing you could do to help GrassrootsHealth spread the word about vitamin D deficiency.


I know my family is due for their next blood spot test - how about you?



Susan Siljander      

Marketing Director, GrassrootsHealth

A Public Health Promotion &

Research Organization  

Moving Research into Practice NOW!



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Vitamin D and Pregnancy

4000 IU is safe

Summary article

View Here

Vitamin D and Kidney Stones

No correlation

Summary article

View Here


Vitamin D and Kidney Stones

Research Paper

Cedric Garland, Dr. P.H.

Robert P. Heaney, M.D.

October 2013




High Supplementation Safe for Pregnancy 

Research Paper
Bruce W. Hollis, Ph.D.
Carol L. Wagner, M.D.
September 2011


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You can prevent disease if just one more person finds out about the preventative properties of vitamin D and starts moving their blood serum levels to 40-60 ng/ml. 


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