March 2, 2017

Director's Letter 
Carole Baggerly 
Director, GrassrootsHealth 

It's March! I am excited that spring is on its way... even in sunny San Diego, it will be nice to have warmer days and more sunshine. 

This week we are bringing to light an issue that is known in the vitamin D community - the seasonal effects of vitamin D. We all know colds and flu are more prevalent in the winter, and here you will learn why. It isn't just that we are all cooped up together inside, you will see below the dramatic dips in vitamin D levels over the winter months.

How does this affect your health? First of all you need to find out how low your low is.... Now is the time to see what happened to your vitamin D level throughout the winter. Did you supplement enough? Use an indoor tanning lamp? Go to a tanning salon? Or travel to a location that still has vitamin D in the winter (below 32 degrees latitude)?

It is also very important for D*action research to have multiple readings for each participant, ideally every 6 months. D*action is crowdfunded, which means that your test not only pays for the actual blood spot card, but also for the research and publishing. We are happy to provide a discount the month of March thanks to two sponsors - Bio-Tech Pharmacal and Solar D Sunscreen. Both organizations are committed to vitamin D research and solving the world-wide vitamin D deficiency. 


Carole Baggerly 
Director, GrassrootsHealth 
A Public Health Promotion & Research Organization 
Moving Research into Practice NOW!
Paper of the Week:
Vitamin D Levels are Lowest in Feb/March

Sunlight and Vitamin D
A Global Perspective for Health
Matthias Wacker and Michael F. Holick
Vitamin D, Skin and Bone Research Laboratory
Boston University Medical Center
Published in Dermato Endocrinology
January 2013

This paper reviews how vitamin D is created in your body from the sun and how vitamin D affects your health. 

It starts with a prehistoric perspective and continues to explain the history of vitamin D in health - even the times when the sun was lauded as a healing agent and vitamin D was added to weiners and beer!

The paper thoroughly explains how vitamin D is made in the skin including a detailed explanation of three key factors to vitamin D production - the angle of the sun, your skin type, and your age.

Vitamin D and Season

This first chart reports vitamin D levels by month for a 1958 British Birth Cohort, 3725 men and 3712 women age 45 years. You can clearly see the lowest levels are in the winter months - January, February, and March.

Data from 1958 British Birth Cohort

This second chart illustrates the same seasonal differences with a multi-year study in Denmark of perimenopausal women. Again, you can see a dip in vitamin D levels in the winter moths of each year. 

Perimenopausal Women in Denmark

The paper continues, exploring benefits of sunshine other than vitamin D, and also reviews how vitamin D affects certain conditions including cancer, overall immunity, autoimmune diseases, cardiovascular health and mental health. 

This would be a great paper to bring to your next doctor visit, as you discuss your vitamin D level and how you want to maintain 40-60 ng/ml (100-150 nmol/L).

How Much Vitamin D Should I Take?

How much vitamin D should I take?

Using data from our D*action project, we have created 
D*calculator . With this calculator you can enter your current vitamin D serum level, your desired vitamin D serum level, and your weight. The calculator will tell you how much more vitamin D you need to achieve your desired serum level with both a 50% probability and a 90% probability.   Give it a try!

How does it work?

GrassrootsHealth has analyzed the data of all of our D*action participants. We have plotted the dose response curve - a line plot of the average serum levels associated with each supplement dose. You will see that every dose has a wide range of serum levels - which is why we can't recommend a specific dose without first testing.

50% probability? 90% probability?

Using the data plotted in the chart, we calculated the average serum level for each supplement dose, as defined by the blue line. We also did a probability-based analysis to determine the supplement dose necessary to move 50% of the population from one serum level to another, and another supplement dose that would get 90% of the population across that same range. Of course the 90% number is substantially higher. 

Think of vitamin D levels like cholesterol levels

It would be much easier if there were a magic number that worked for everyone, but there isn't. Instead, think of your vitamin D level like your cholesterol - this will help you expertly manage it. 

Like cholesterol...  not everyone has the same level. You can't predict by height, weight, diet, or supplementation what your level will be. You need to test.

Like cholesterol...  if the test did not come back with your desired result you need to make a change.  For cholesterol that might be diet and exercise. For vitamin D it is likely to be more sun, supplements, or vitamin D rich foods.

Like cholesterol... you have to make the change consistently for a period of time, we recommend six months, and test again. See if your changes were effective. Do you need more? Less?

Calculate Now

Make a Difference Today - Join D*action Research!

When we first started D*action many people could not get cost-effective vitamin D tests. Now, people use D*action because they...
  • want an independent test of vitamin D
  • want a test in the comfort of their home
  • don't have insurance
  • want to support GrassrootsHealth
We have a large number of participants (blue balls), but relatively few of our participants are regulars who test 1-2 times per year (the smiley face ball). While data from each and every participant is helpful and appreciated, our research becomes more robust with each return test and questionnaire. Additional tests over time also allow us to better analyze conditions that change over time (i.e. pain, cold, flus, falling, broken bones) and see how those conditions relate to changes in serum level.

We are offering a special through the end of March, with the help of sponsors Bio-Tech Pharmacal and Solar D - a one-time participation for $49! 
This special offer is available to current participants, subscribers, and even new participants. 

Your data has been presented to large audiences, published in journals, read by doctors world-wide. Here are some examples of how your vitamin D data has contributed to research and made a difference:
Order a test today, coupon code EndOfWinter.

10% off 
in March with coupon code GRHMar10

Bio-Tech Pharmacal has been providing quality nutraceuticals (dietary supplements) for over 32 years! 

D3-50,000 IU, D3Plus, D3/K2, and more!

cGMP/FDA registered facility

25% off 
in March with coupon code

Prevents burning

Allows UVB 
No harmful ingredients

Paper of the Week

Sunlight and Vitamin D
A Global Perspective for Health
Matthias Wacker and Michael F. Holick
Vitamin D, Skin and Bone Research Laboratory
Boston University Medical Center
Published in Dermato Endocrinology
January 2013
Research Top 10

Serum 25-Hydroxyvitamin D Concentrations ≥40 ng/ml are Associated with >65% Lower Cancer Risk: Pooled Analysis of Randomized Trial and Prospective Cohort Study
Sharon L. McDonnell, et al.
April 2016

Post-hoc analysis of vitamin D status and reduced risk of preterm birth in two vitamin D pregnancy cohorts compared with South Carolina March of Dimes 2009-2011 rates
Carol L. Wagner, et al.
The Journal of Steroid Biochemistry and Molecular Biology
October 2015

Incidence rate of type 2 diabetes is >50% lower in GrassrootsHealth cohort with median serum 25-hydroxy-vitamin D of 41 ng/ml than in NHANES cohort with median of 22 ng/ml
Sharon L. McDonnell, et al.
The Journal of Steroid Biochemistry and Molecular Biology
July, 2015

Letter to Veugelers, P.J. and Ekwaru, J.P., A Statistical Error in the Estimation of the Recommended Dietary Allowance for Vitamin D.
Robert Heaney, et al.
March 2015

Quantifying the food (and non-food) sources of basal vitamin D input
Sharon L. McDonnell, et al.
Journal of Steroid Biochemistry and Molecular Biology
November 2013

25-Hydroxyvitamin D in the Range of 20 to 100 ng/ml and Incidence of Kidney Stones
Stacie Nguyen, et al.
American Journal of Public Health
October 2013

A Novel Approach Localizes the Association of Vitamin D Status With Insulin Resistance to One Region of the 25-Hydroxyvitamin D Continuum
Robert P. Heaney, et al.
Advances in Nutrition
May 2013

All-Source Basal Vitamin D Inputs are Greater Than Previously Thought and Cutaneous Inputs are Smaller
Robert P. Heaney, et al.
The Journal of Nutrition
March 2013

Vitamin D Supplement Doses and Serum 25-Hydroxyvitamin D in the Range Associated with Cancer Prevention
Cedric F. Garland, et al.
Anticancer Research

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