GrassrootsHealth is a nonprofit public health organization dedicated to promoting optimal health worldwide through research, education, and advocacy, with a primary focus on the role of vitamin D. Through evidence-based education, resources, and our citizen-science approach to research, we empower individuals to make informed decisions about their health and healthcare providers to move research into practice.
With a panel of 48 senior vitamin D researchers from around the world contributing to its operations, GrassrootsHealth has been running the world’s largest public health intervention study since 2007 – the D*action field trial – to solve the vitamin D deficiency epidemic worldwide.
In 2007, GrassrootsHealth was founded by Carole Baggerly† with the mission of moving vitamin D research findings into the hands of the public and into practice. Over the past 15+ years, our global campaign has grown significantly, spreading important vitamin D research findings from the world’s top vitamin D scientists, reaching many more individuals, health care practitioners, and public health officials.
2018
NBJ Award for Excellence in Education
Recognized for outstanding leadership in public health education, making vitamin D research accessible to healthcare professionals and the public.
2018
Mercola Achievement Award
Honoring GrassrootsHealth’s dedication to evidence-based health education and scientific outreach.
2016
Humanitarian Award
Recipient of the American College of Nutrition Humanitarian Award for moving vitamin D research into public practice.
MS, LAc, CCN, has been working in the field of nutrition since 2004, with over 10 years of experience in the area of vitamin D research and education specifically. She joined GrassrootsHealth in 2012; her roles have included operations and project management, study design and coordination, communications, content writing, research reviews, and educational program development. Jen co-authored several papers and played a key role in the “Protect Our Children NOW!” project at the Medical University of South Carolina.
Founded GrassrootsHealth in 2007 after discovering vitamin D’s role in reducing breast cancer risk. Following her own experience with breast cancer, she met with vitamin D researchers around the world to formulate the Scientists’ Call to Vitamin D*action, a consensus statement on what was needed to solve the vitamin D deficiency epidemic, most importantly by achieving a 25(OH)D serum level of 40-60 ng/ml (100-150 nmol/L). She initiated the Vitamin D*action study as a way to provide public access to home vitamin D blood spot testing while gathering important research data and creating educational resources for all to use.
Correcting vitamin D to normal, optimized levels provides varied benefits—from being free of flu, colds, and respiratory infections, to a safer pregnancy, remission of autoimmune disorders, and improvements in conditions like hypertension, diabetes, depression, and anxiety.
Satya L. Nahu, MD
Participant
I’ve been part of the GrassrootsHealth D*action project since 2013, with my vitamin D levels consistently above 100 ng/ml. Since then, I’ve had very few colds, and when I contracted COVID in October, it was extremely mild, lasting only 5 days. I believe my high vitamin D levels played a key role in my quick and easy recovery.
BOB
Participant
My vitamin D has been tested regularly for 10 years. It cured my osteopenia, relieved arthritis, SAD, and pain, and restored my strength. I urge women to test their levels and keep them above 85 ng/ml, especially with a family history of cancer.
Z.J.
Participant
I’m impressed by the vital work you’re doing. Since discovering vitamin D in 2009, I’ve been taking 2000 IU daily, and my health has improved—my chronic gum disease even disappeared. Keep up the great work!
A.K. (2023)
Participant
I spent years on prescription drugs until learning about vitamins changed my life. Now, thanks to GrassrootsHealth, I have invaluable knowledge about vitamin D and omega-3s, which I share with others to help them achieve better health.
H.N. (2021)
Participant
At nearly 76, I strive to live the best life possible. As a substitute teacher and retired nurse, I know how important it is to maintain optimal health, especially vitamin D levels. Thanks to GrassrootsHealth, I feel empowered to stay healthy and active.
A.B. (2021)
Participant
Get your vitamin D level tested with our easy home blood spot test. Plus, explore additional nutrient testing for Omega-3s, Magnesium, and other important health measurements. Join the D*action Project to optimize your health and contribute to valuable research!
Enroll in D*action and Build Your Custom Test Kit – Choose from the Following Additional Tests
The Omega-3 Index can be an indication of risk for heart disease, loss of cognitive function, cellular aging, depression, dry eye disease, and death from all causes. The AA:EPA ratio and Omega-6:3 ratio are measures of pro/anti-inflammatory fatty acids; knowing these ratios can help you take more specific steps towards improving fatty acid status and achieving lower levels of inflammation through diet and supplements.
Check your magnesium level with or without levels of essential elements copper, selenium and zinc, and toxic elements lead, cadmium and mercury.
Measure the level of inflammation in your body with this test. An increase in CRP levels can indicate a hidden disease that has not yet been diagnosed; in fact, some research suggests that the level of CRP can predict heart disease even ten years before diagnosis. High CRP levels are often seen in acute inflammation and have been correlated with high cardiovascular disease risk, while smaller elevations are often indicative of chronic inflammation and chronic diseases, such as metabolic syndrome and diabetes.
HbA1c is a measure of how healthy average blood sugar levels have been in the recent few months, and is a better representation of blood sugar health than a single glucose measurement. Higher levels are associated with a higher risk of metabolic syndrome, diabetes, cardiovascular disease, cognitive diseases, and more.
Check your TSH level as an indicator of thyroid health.
The body needs at least 4000 IU/day in order to maintain a healthy concentration of 25(OH)D in the blood. Because most of us don’t get enough sun exposure, the little vitamin D we get that way, plus food and fortified food sources, totals no more than about 2000 IU/day. Thus in order to meet the body’s need for about 4000 IU/day, most adults should take supplements providing 1000-3000 IU daily. Check grassrootshealth.net to download a table showing the relationship between intake and resulting serum levels.
After you complete your questionnaire and pay for your test, your order is fulfilled within 2 business days. We ship first class mail from San Diego, CA.
It is currently taking from 10-15 days from the time you record doing the blood spot test (and mailing to GrassrootsHealth) until we post your results (US addresses.) You will receive an email (to the email address you provided as login to D*action) when we have the results.
The Omega-3 Index is a blood test that measures the amount of omega-3 fatty acids (EPA and DHA) in red blood cell (RBC) membranes. It is expressed as a percent of total RBC fatty acids. It is a long-term and stable marker of omega-3 status, and it reflects tissue levels of EPA+DHA. An Omega-3 Index over 8% is associated with the lowest risk of death from heart disease and below 4% with the highest.
The Omega-3 Index test can be added to any of the vitamin D testing kit combinations; the combined cost for just vitamin D and the Omega-3 Index is $119 plus shipping for a single kit, or you can choose to subscribe to receive a slightly discounted offer. With subscriptions we will automatically bill your credit card and ship you a test at the testing interval chosen. The cost includes the collection kit, the envelope to send in your blood spot, and a detailed report of your results, which will include your Omega-3 Index and your 25(OH) vitamin D serum level.
2007
2017
GrassrootsHealth found an inverse association between vitamin D serum levels and all non-skin cancer incidence. The analysis included pooled data from two study cohorts of women aged 55 years and older. Those with vitamin D serum levels ≥ 40 ng/ml, had a 67% lower risk of cancer when compared with those <20 ng/ml.
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, MPH et al. PLOS One, April 2016
This analysis found that women with vitamin D levels of 40-60 ng/ml have a 46% lower preterm birth rate than the general population (the findings were more robust in Hispanic and Black women). The analysis also showed a 59% lower risk for premature birth by pregnant women who had blood levels of vitamin D (25(OH)D) at or over 40 ng/ml by their third trimester than women who had levels below 20 ng/ml.
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 Wagner, et al. , Medical University of South Carolina, October 2015
Incidence rate of type 2 diabetes is >50% lower in GrassrootsHealth cohort with median serum 25-hydroxyvitamin D of 41 ng/ml than in NHANES cohort with median of 22 ng/ml
Sharon L. McDonnell, MPH et al., The Journal of Steroid Biochemistry and Molecular Biology,July 2015
The recommended intake of vitamin D specified by the IOM is 600 IU/day through age 70 years, and 800 IU/day for older ages. Calculations by GrassrootsHealth scientists and other researchers have shown that these doses are only about one-tenth those needed to cut incidence of diseases related to vitamin D deficiency. The authors propose a new RDA with a value of approximately 7,000 IU/day from all sources.
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, MD et al., Nutrients, March 2015
In a prospective study of 844 female participants aged 60+ years, GrassrootsHealth examined the relationship between serum 25(OH)D and the incidence of breast cancer. Those with concentrations ≥50 ng/ml had an 80% lower risk of breast cancer than those with concentrations <50 ng/ml, adjusting for age and BMI. These findings suggest that 25(OH)D concentrations above 50 ng/ml may provide additional benefit in the prevention of breast cancer.
25(OH)D Serum Levels May Provide Additional Reduction in Breast Cancer Risk
Sharon L. McDonnell, MPH et al. American Society for Nutrition, Scientific Sessions and Annual Meeting, April 2014
From 780 non-supplement taking, adult, D*action participants who completed a limited questionnaire on dietary intake along with a lifestyle questionnaire, some food sources were found to be associated with vitamin D serum levels: eggs, whole milk cottage cheese, red meat and total protein. 25(OH) D3 rose by about 1 ng/ml for each weekly serving of whole milk cottage cheese (3 oz) and each daily serving of one of the following: eggs (1 egg), red meat (3 oz) and total protein (3 oz).
Quantifying the food sources of basal vitamin D input
Sharon L. McDonnell, MPH et al. Journal of Steroid Biochemistry and Molecular Biology, November 2013
Based on this analysis of data provided by D*action participants, non-food factors associated with vitamin D serum levels were indoor tanning use, sun exposure, body mass index (BMI), and percent of work performed outdoors.
Quantifyi on-food sources of basal vitamin D input
Sharon L. McDonnell, MPH et al. Journal of Steroid Biochemistry and Molecular Biology, November 2013
The research team used data collected from 2,012 participants enrolled in GRH’s D*action study. Thirteen individuals reported having kidney stones during the study time; occurrences were confirmed by medical records or interview. The study 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.
25-Hydroxyvitamin D in the Range of 20 to 100 ng/ml and Incidence of Kidney Stones
Stacie Nguyen, MPH et al. American Journal of Public Health, October 2013
In this re-analysis, the total basal input (food plus sun) was calculated to range from a low of 778 IU/d in patients with end-stage renal disease to a high of 2667 IU/d in healthy Caucasian adults. The authors conclude that:
1) all-source, basal vitamin D inputs are approximately an order of magnitude higher than can be explained by traditional food sources;
2) cutaneous input accounts for only 10–25% of un-supplemented input at the summer peak; and
3) the remainder must come from undocumented food sources, possibly in part as preformed 25(OH)D.
All-Source Basal Vitamin D Inputs are Greater Than Previously Thought and Cutaneous Inputs are Smaller
Robert P. Heaney, MD et al. The Journal of Nutrition, March 2013
In an analysis of vitamin D serum levels and daily supplemental vitamin D intake amounts for 7,324 D*action participants, we found that while average serum level rises with increased intake, there is a wide range of individual serum levels at any given intake amount. For example, with a supplemental intake of 4000 IU/day, serum levels were observed from 20 ng/ml (50 nmol/L) to 120 ng/ml (300 nmol/L).
Vitamin D Supplement Doses and Serum 25-Hydroxyvitamin D in the Range Associated with Cancer Prevention
Cedric F. Garland, Dr PH FACE, et al. Anticancer Research, 2011
In an analysis of vitamin D serum levels and daily supplemental vitamin D intake for 7,324 D*action participants, the study found that, while the average serum level generally increased with higher vitamin D intake, individual responses varied significantly. For instance, at a supplemental intake of 4000 IU/day, serum levels ranged widely, from as low as 20 ng/ml (50 nmol/L) to as high as 120 ng/ml (300 nmol/L).
The role of vitamin D in potentially reducing the risk and severity of COVID-19
Anticancer Research William Grant, Ph.D., et al., April 2020
This case report details the effects of high-dose vitamin D therapy in a multiple sclerosis (MS) patient, showing improvements in symptoms that suggest vitamin D’s potential immunomodulatory benefits for MS. The report underscores the importance of personalized dosing due to individual response variability and the need for monitoring to achieve safe and effective levels.
High-Dose Vitamin D Therapy in Multiple Sclerosis
Christine B. French et al., Journal of Medical Case Reports, 2019
Top Voted Vitamin D Resources
Explore the favorite vitamin D resources selected by the GrassrootsHealth community. These resources cover essential topics from dosage recommendations to the latest research findings.
Vitamin D Resource List Handout
Access our comprehensive list of vitamin D resources, including key information, research findings, and practical tips to help you optimize your vitamin D levels.
Does the Same Vitamin D Dose Work for Everyone?
Explore why vitamin D dosage may vary between individuals and how personal factors influence the optimal amount required for health.
GrassrootsHealth Participant Resources
Access comprehensive resources for GrassrootsHealth participants, including guides, tools, and educational materials on vitamin D and related nutrients.
Vitamin D Therapy and Autoimmune Disorders
Learn how vitamin D supplementation can play a role in managing autoimmune disorders, supported by current research and case studies.
GrassrootsHealth’s Breast Cancer Publication Achieves Top 10
Read about our impactful research on the relationship between vitamin D and breast cancer, recognized as one of the top 10 publications in the field.
Nutrients and Factors That Influence Vitamin D Levels and Dose-Response
Discover the additional nutrients and factors that can affect how the body processes vitamin D and the importance of a tailored approach to supplementation.
Seasonal Changes in Vitamin D Levels
Understand how the changing seasons can impact your vitamin D levels and why it’s essential to monitor and adjust your intake throughout the year.
We appreciate your interest in improving your health with vitamin D. Your commitment to understanding and managing your vitamin D level is a significant step towards better health.
Visit our blog for more information on vitamin D, other nutrients, and how they impact your health.
If you have any questions or need assistance, feel free to contact our support team at customerservice@grassrootshealth.net or visit our FAQ page.
