From Sunlight to Science: How Dr. Cedric Garland Helped Paved the Way for Health Independence with Vitamin D

Published on July 2, 2025

Helping to spread the life-saving findings of vitamin D scientists such as Dr. Garland and others…

Dr. Cedric F. Garland is a well-known epidemiologist and Professor Emeritus at the University of California, San Diego, recognized for his extensive research on vitamin D deficiency and its relationship to various health outcomes, particularly cancer prevention. He has published over 150 articles and books on the subject, often in collaboration with his late brother, Dr. Frank C. Garland, and other researchers like Dr. Edward D. Gorham.

Who is Dr. Cedric Garland according to Grok (and GrassrootsHealth)?  This fascinating and inspiring summary gives us just a glimpse of what Dr. Garland has accomplished, showcasing the amazing, kind, and incredibly intelligent person he is… 

Not only has Dr. Garland been a pioneer in UVB and vitamin D research, he has also played a central role in the foundation and operation of GrassrootsHealth and the Vitamin D*action study, serving as Principal Investigator since 2007. Below are some of his other outstanding achievements, many of which have touched the lives of countless individuals, doctors, and researchers over the last several decades, inspiring further investigation into the health-saving benefits of UVB and vitamin D.

Key Contributions and Studies from Dr. Cedric Garland

Vitamin D and Cancer Prevention:

Dr. Garland’s most influential work involving UVB and vitamin D began in 1974 when he and his brother noticed geographic patterns in cancer mortality rates, with higher rates of colon and breast cancer in northern U.S. counties compared to southern ones. This led to their seminal 1980 paper, “Do Sunlight and Vitamin D Reduce the Likelihood of Colon Cancer?” published in the International Journal of Epidemiology. They hypothesized that lower sunlight exposure in northern regions resulted in reduced vitamin D production, increasing cancer risk.

Their widely cited 2006 paper, “The Role of Vitamin D in Cancer Prevention” (American Journal of Public Health), reviewed 63 observational studies and concluded that sufficient vitamin D status (serum 25-hydroxyvitamin D [25(OH)D] levels of 40–60 ng/mL) is associated with lower risks of colon, breast, prostate, and ovarian cancers. It has been cited over 829 times.

A 2009 study in Annals of Epidemiology projected that raising serum 25(OH)D levels to 40–60 ng/mL could prevent approximately 58,000 new cases of breast cancer and 49,000 cases of colorectal cancer annually in the U.S. and Canada, reducing deaths from these diseases by three-quarters.

A 2018 pooled analysis (PLoS One) found that women with 25(OH)D levels ≥60 ng/mL had a significantly lower risk of breast cancer compared to those with levels <20 ng/mL. A 2023 study in JAMA Open Network (Kanno et al.) supported Garland’s findings, showing that 2000 IU/day of vitamin D3 improved survival by over 2.5-fold in patients with p53-immunoreactive digestive cancers, reinforcing vitamin D’s role in reducing cancer recurrence and mortality.

UVB-Vitamin D-Cancer Hypothesis:

The Garland brothers pioneered the UVB-vitamin D-cancer hypothesis, suggesting that ultraviolet B (UVB) exposure, which stimulates vitamin D synthesis in the skin, reduces cancer risk. Their ecological studies, using NASA satellite data and regression models, showed that higher UVB exposure (and thus higher vitamin D levels) correlated with lower cancer mortality rates.

They extended this hypothesis to breast, ovarian, and other cancers, noting that northern cities like Boston and Chicago had higher cancer mortality rates than sunnier cities like Miami due to limited vitamin D synthesis in winter months. Their work emphasized that moderate sun exposure and vitamin D supplementation could achieve optimal serum levels (55 ng/mL) for cancer prevention without significant health risks.

Other Health Outcomes:

Garland’s research also linked vitamin D deficiency to type 1 and type 2 diabetes, suggesting that higher 25(OH)D levels could reduce incidence.

His team was among the first to establish that secondhand smoke causes fatal coronary heart disease, influencing legislation banning smoking in public places in California.

Vitamin D Supplementation and Public Health:

Garland advocated for vitamin D supplementation (e.g., 2000 IU/day) and moderate sun exposure to achieve serum 25(OH)D levels of 40–60 ng/mL. A 2011 study he co-authored (Anticancer Research) analyzed vitamin D levels in 3,667 people and found that doses up to 10,000 IU/day were needed for some individuals to reach cancer-preventive levels, with genetics playing a significant role in response to supplementation.

He is the principal investigator of the Vitamin D*Action study with GrassrootsHealth, promoting home blood spot testing to monitor and optimize vitamin D levels.

Notable Findings and Impact

Cancer Incidence and Mortality:  Garland’s studies consistently showed that higher serum 25(OH)D levels (≥40 ng/mL) were associated with a 50–75% reduction in cancer incidence and mortality for colorectal and breast cancers.

Global Perspective: His 2007 study estimated that 600,000 cases of breast and colorectal cancer could be prevented annually worldwide by achieving adequate vitamin D levels, particularly in northern regions.

Policy Influence: His work has influenced public health discussions, though he noted resistance from some authorities to adopting vitamin D supplementation widely, despite evidence like the VITAL study showing a 25% reduction in cancer mortality with 2000 IU/day.

Awards and Recognition

• Knighthood by Italy (2016) for his research on vitamin D and cancer prevention.
• Seelig Award (2017) from the American College of Nutrition.
• Arnold-Rikli Prize for contributions to photobiology.
• National Institutes of Health Research Career Award, among others.

Critical Perspective

While Garland’s work has been groundbreaking, some critics argue that ecological and observational studies, which form much of his evidence base, are prone to confounding factors. Randomized controlled trials (RCTs) like the VITAL study have shown mixed results, with smaller effect sizes (e.g., 17% reduction in cancer mortality) than Garland’s projections.  Meanwhile, experts in nutrient research argue that RCTs are not generally well-suited for nutrients and must be designed with specific criteria in mind.  Conclusions made about the research should therefore extend beyond RCTs to also consider the totality of evidence, including mechanistic studies, observational studies, and the like.

Conclusion

Dr. Cedric Garland’s research has significantly shaped the understanding of vitamin D’s role in cancer prevention and public health. His work with Frank Garland and others established a paradigm shift, linking sunlight, vitamin D, and reduced cancer risk, backed by decades of epidemiological data. While some skepticism remains, his findings have spurred clinical trials and public health initiatives by many over the last several decades, and his legacy continues through ongoing research and advocacy. For more details, you can explore his publications on PubMed or GrassrootsHealth’s website.

Support the Legacy of Dr. Garland and Vitamin D Advocacy

Dr. Garland’s groundbreaking work has laid the foundation for a broader movement toward health independence through vitamin D awareness and prevention-focused science. His legacy continues to inspire researchers, physicians, and public health leaders around the world.

To help continue this vital work and support other vitamin D freedom fighters advancing research, education, and public health efforts, make a contribution today. 🧡 Your support helps sustain important research, outreach, and advocacy grounded in the values promoted by Dr. Garland. Thank you for helping carry this mission forward.

Donate Today!

Measure Your Levels Today

Create your custom home blood spot kit to help determine if you are getting enough of the following nutrients shown to benefit overall health, along with other measures, including:

• Vitamin D
• Omega-3 Index plus Omega-3:Omega-6 and AA:EPA Ratios
• Magnesium (plus Zinc, Copper, Selenium, Lead, Cadmium & Mercury)
• hsCRP
• HbA1c
• Type 1 Diabetes Autoantibodies
• TSH

Enroll and test your levels today, learn what steps to take to improve your status of omega-3s, vitamin D and other nutrients and blood markers, and take action! By enrolling in the GrassrootsHealth projects, you are not only contributing valuable information to everyone, you are also gaining knowledge about how you could improve your own health through measuring and tracking your nutrient status, and educating yourself on how to improve it. Enroll in D*action and Test Your Levels Today!

How Can You Use this Information for YOUR Health?

Having and maintaining healthy vitamin D and other nutrient levels can help improve your health now and for your future. Measuring is the only way to make sure you are getting enough!

STEP 1 Order your at-home blood spot test kit to measure vitamin D and other nutrients of concern to you, such as omega-3s, magnesium, essential and toxic elements (zinc, copper, selenium, lead, cadmium, mercury); include hsCRP as a marker of inflammation or HbA1c for blood sugar health

STEP 2 Answer the online questionnaire as part of the GrassrootsHealth study

STEP 3 Using our educational materials and tools (such as our dose calculators), assess your results to determine if you are in your desired target range or if actions should be taken to get there

STEP 4 After 3-6 months of implementing your changes, re-test to see if you have achieved your target level(s)

Enroll in D*action and Build Your Custom Test Kit!

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