Published on March 8, 2018

International Women’s Day is a global day of celebration for the achievements of women. In light of that, we want to celebrate the research and work of some very special women in the world of vitamin D.


Joan Lappe, PhD, RN, FAAN

Associate Dean for Research
Beirne Endowed Chair in Nursing
College of Nursing
Creighton University

Dr. Lappe has led two multi-year randomized clinical trials at Crighton University to investigate the effect of calcium and vitamin D on cancer incidence in women aged 55 and older. Results of the first, published in 2007, showed that a dose of 1100 IU/day of vitamin D along with 1400-1500 mg/day of calcium helped raise the average serum vitamin D level to 38 ng/ml (from a baseline of 29 ng/ml) and prevent approximately 4 out of 5, or 80%, of all invasive cancers including breast cancer. The trial was repeated with a larger cohort of women and a treatment dose of 2000 IU/day vitamin D (rather than 1100 IU/day in the previous study) and 1500 mg/day of calcium, and results were published in 2017. Baseline vitamin D levels were higher in this second trial, with a mean of 33 ng/ml. At the end of 4 years, those in the treatment arm achieved a mean of 43 ng/ml. After excluding participants who withdrew from the study or developed cancer within the first 12 months from analysis, the study reports a 35% reduction in cancer in the vitamin D + calcium group compared to the placebo group.


In April 2016, Lappe joined with other leading vitamin D and cancer researchers and GrassrootsHealth to publish a paper focused on achieved vitamin D serum levels (rather than intake amount) and cancer incidence. In this study, data from the 2007 Lappe trial was joined with data from the GrassrootsHealth cohort to provide a larger sample size and a broader range of vitamin D levels than either group had alone. Results from this analysis showed that women with vitamin D serum levels greater than or equal to 40 ng/ml had a 71% lower risk of cancer than women with serum levels less than 20 ng/ml.


Carol L. Wagner, MD

Division of Neonatology
Department of Pediatrics
Medical University of South Carolina




Dr. Wagner has been a professor of pediatrics at the Medical University of South Carolina since 1992. Her research findings on the safety and effectiveness of vitamin D for promoting healthy pregnancies was instrumental in the development of Protect Our Children NOW! by GrassrootsHealth in 2012.

Over the last decade, her research has shown how important vitamin D is for a healthy pregnancy and how it has health implication for infants. When asked what she would want all pregnant women or women trying to become pregnant to know, she replied, “We think women in their child-bearing years should have a total circulating 25(OH)D level – the indicator of vitamin D status – of at least 40 ng/ml. That level is associated with better pregnancy outcomes, and that is what every pregnant woman and mother wants.” Further, she also stressed that it is important to realize “that vitamin D is a precursor to a hormone that affects every system in the body… While you can receive about 10% of your daily vitamin D requirements, at best, through a typical American diet, unless you take a supplement or have adequate sunlight exposure without sunscreen, you are at risk of being vitamin D deficient.”

Her message for the doctors of pregnant women is that “vitamin D given to pregnant women at 4400 IU/day is safe and effective in achieving vitamin D sufficiency (as defined by a total circulating 25(OH)D concentration of at least 40 ng/ml or 100 nmol/L) during pregnancy.”

Dr. Wagner’s research is not about trying to achieve “super levels” of vitamin D, but rather trying to find what it takes in today’s modern world, with less outdoor time and sunlight exposure, to reach the goal of vitamin D sufficiency and optimal health. In most cases, that involves taking a daily vitamin D supplement.

Currently, Dr. Wagner’s research is focused on exploring the effect of vitamin D on immune function in pregnant and lactating women and their babies. This research will help further the essential understanding of how vitamin D affects various systems in the body and our overall health.


JoEllen Welsh, PhD 

Empire Innovations Professor
Cancer Research Center
Department of Environmental Health Sciences
University at Albany
State University of New York



Dr. Welsh has been working on basic research into the mechanisms of how vitamin D works with regard to breast cancer for over 20 years, and how it is different in different types of breast cancer. From research in her lab we now know that vitamin D does have direct effects on breast cancer cells. From a 2015 interview, Dr. Welsh told us that for hormone-dependent breast cancers, “vitamin D is quite effective at stopping growth of those cells. In fact, it is as effective as Tamoxifen, which is a standard treatment.”


Dr. Welsh is now in the middle of a 5-year grant from the National Institutes of Health to study how vitamin D affects triple-negative breast cancer, for which there are not currently good treatments. She is looking at a specific pathway, linked to the survival of the breast cancer cell, that is inhibited by vitamin D.  This study is expected to provide a better understanding of how effective vitamin D is in the regulation of that pathway and whether vitamin D reduces growth and progression of triple-negative breast cancer.


In addition to her lab work, Dr. Welsh also serves as the Chief Financial Officer of the non-profit Vitamin D Workshop which hosts the annual international scientific meeting focused on the biology and health implications of vitamin D.  This year, the 21st Workshop on Vitamin D will be held in Barcelona, Spain, May 16-19.


Susan Whiting, PhD

Distinguished Professor of Nutrition
College of Pharmacy and Nutrition
University of Saskatchewan




Dr. Whiting has been a faculty member of the University of Saskatchewan since 1988. Her professional memberships include Dietitians of Canada, the Canadian Society for Nutritional Sciences, the American Society for Nutrition, and the American Public Health Association. Over the last three decades she has conducted research on how various aspects of diet and nutrition influence bone health; vitamin D has been part of that research since the early 2000s.


Dr. Whiting’s current research is an ongoing study of hip fracture in long-term care facilities (nursing homes) in Saskatchewan and investigating whether vitamin D supplements are helping to reduce the risk. Incidence rates of hip fracture have been documented and her team is now looking at vitamin D use over the past 5 years to see if voluntary use made a difference.


Another study in the works is to compare vitamin D intakes of Canadians reported in the 2015 Canadian Nutrition Survey with those reported in the previous 2004 survey. Has the increased information and interest in vitamin D, including the use of supplements, in the intervening years translated to changes in intake? Dr. Whiting suspects “that seniors improved intakes primarily through supplement use, but that children and young adults may be even lower as the few foods that provide vitamin D such as milk and oily fish are less popular with these age groups.”


We look forward to seeing what she finds in each of these projects!



Thank you!

A sincere thank you to each of these four women for the work they do to enhance our knowledge and understanding of vitamin D and how it affects our health. Thank you also to many more women working in the labs, analyzing data, managing and organizing projects, and all the other behind the scenes tasks that allow this research to be done.