James Fleet

Educational Background

  • B.S., Animal Science at Cornell University in 1981
  • M.S., Animal Nutrition at University of Delaware in 1984
  • Ph.D., Nutritional Biochemistry at Cornell University in 1988

Awards & Honors

  • Director, Interdepartmental graduate Nutrition Program (INP), 2003-present
  • Editorial Board, Endocrinology, 2015-present
  • Executive Committee for the International Workshops on Vitamin D, 2016-present
  • Member, Expert Panel on Vitamin D and Multiple Sclerosis for the MS Society of Canada, 2016-present
  • Member, Chemo and Dietary Prevention Study Section (NIH), 2012-2016
  • Cancer Research Award from Lafayette Lions Club, 2012
  • University Faculty Scholar from Purdue University, 2004 - 2009
  • Member, Integrative Nutrition and Metabolic Processes Study Section (NIH), 2004 - 2009
  • Mead-Johnson, Young Investigators Award from American Society for Nutrition Science, 2001

Activities & Memberships

  • Member, American Association for Cancer Research, 2009 - Present
  • Member, American Gastroenterological Association, 2002 - Present
  • Member, American Association for the Advancement of Science, 1999
  • Member, American Society for Nutrition, 1992 - Present
  • Member, American Society for Bone and Mineral Research, 1991 - Present


Funding Sources: NIH (awards from NIDDK, NCI), American Institute of Cancer Research, Showalter Trust

Our laboratory is focused on two major themes: (1) the molecular regulation and genetics of bone and mineral metabolism, (2) mechanisms of carcinogenesis and cancer prevention. Many, but not all, of our projects revolve around the role of vitamin D in health.

Vitamin D is an essential dietary nutrient that can also be produced by skin after exposure to sunlight. Thus, low dietary vitamin D intake (a common problem in the US) and low sunlight exposure (as in the winter months) leads to low blood levels of vitamin D (low status). Population based studies show that low vitamin D status is associated with higher rates of several major chronic diseases including osteoporosis and epithelial cell cancers of the prostate and colon. The work that my laboratory conducts is pertinent to these problems. We use cell and animal models to directly test the validity of these associations and we examine mechanisms by which vitamin D regulates processes relevant to these conditions using the tools of physiology, genetics, and molecular biology.

VITAMIN D AND CALCIUM METABOLISM: Vitamin D acts in the body only after it has been metabolized to 1,25 (OH)2 vitamin D, or calcitriol. Calcitriol, in turn, stimulates intestinal calcium absorption to compensate for habitual low dietary calcium intake. Low efficiency of calcium absorption is a risk factor for hip fracture in elderly women. In addition, the intestine of older humans and animals is resistant to the stimulatory effects of calcitriol. We examine the regulation of intestinal calcium absorption by calcitriol as well as test mechanisms by which calcium crosses the intestinal barrier. More recently we have shown that vitamin D metabolism, intestinal calcium absorption, and bone mass are all subject to significant interactions between genetics and diet.   Thus, our work has relevance to the personalization of dietary calcium and vitamin D requirements to optimize bone health.

VITAMIN D AND CANCER: Epithelial cell cancers result from the accumulation of gene mutations or chromosomal aberrations in cells. These changes lead to the unrestrained cellular proliferation that is the basis for tumor formation. Evidence from populations, animals, and cells suggest that high vitamin D status reduces the risk for certain cancers and that calcitriol can suppress cellular proliferation and promote the development of mature epithelial cells. The molecular mechanism for the anti-cancer effects of calcitriol in cancer is not clear but may include direct protective effects on epithelial/normal tissue stem cells or indirect effects mediated through anti-inflammatory actions of vitamin D on the immune system. Our lab conducts mechanistic and translational studies on the mechanism of calcitriol-mediated cancer prevention and we focus on cancers of the prostate and colon.

Many studies, including our own, use transgenic and knockout mice to evaluate the role that specific proteins play in biological processes (i.e. a reverse genetics approach). As alternate way to learn how a physiologic system is controlled is to use a forward genetics approach whereby the genes controlling the variability in a phenotype (e.g. intestinal calcium absorption) is used to identify the genetic controls over the trait. This approach uses models with known natural genetic variation and couples the mapping of traits to genes using statistical approaches like quantitative trait loci (QTL) mapping. Our goal is to find the genes controlling the metabolism of mineral elements, especially calcium and phosphorus. We are also interested in learning how genetics controls the response of mice to dietary mineral inadequacy.

Discovery Publications

A complete list of Dr. Fleet's publications is available here.


Vitamin D Videos: A series of 6 short videos to help consumers better understand the role of vitamin D in health.

What is vitamin D? 
Are you getting enough vitamin D?
How much vitamin D do you need?
What factors affect the amount of vitamin D you need?
Where can I get vitamin D?
Are vitamin D supplements safe?

Engagement Publications

  • Fleet, J.C. Vitamin D Fact Sheet 2010. Purdue Extension publication.

Books, Chapters & Monograph Publications

A complete list of Dr. Fleet's publications is available here.


  • Summer Workshop on Big Data Training for Translational Omics Research: Organize and co-teach with 3 other faculty.  This is a 2 week intensive, hands-on workshop on the analysis of high density omic data.  Target audience is biomedical researchers who are novices in big data science.
  • NUTR 60500: Teach first year graduate students basic concepts in cell and molecular biology using intestine as a model system, teach physiologic and molecular importance of specific vitamins and minerals in disease risk (e.g. vitamin D and calcium in osteoporosis and cancer, folate in neural tube defects, iron in anemia) (4 cr, annually in Fall).
  • NUTR 69400: Teach graduate students how to organize research data for presentation at national meetings in the form of a 12 minute oral presentation or a poster presentation (1 cr, annually in Spring).
  • NUTR 62700 (Scientific Writing) Teach graduate students how to research and write a critical review on a scientific topic.   A 20 page review is completed during the semester (1 cr, annually in Fall)
  • NUTR 62600 (Advanced Presentation Skills): Teach graduate students how to organize information from multiple scientific reports and present a 40 minute research-based seminar for a professional audience. (1 cr, annually in Spring)

James Fleet

Faculty Associate:  
  Center on Aging and the Life Course

Office: STON G1B
Phone: 765.494.0302
Fax: 765.494.0906
E-Mail: fleet@purdue.edu

Department of Nutrition Science, 700 W. State Street, West Lafayette, IN 47907-2059(765) 494-8228, Fax: (765) 494-0674

© 2016 Purdue University | An equal access/equal opportunity university | Copyright Complaints | Maintained by: Nutrition Science

If you have trouble accessing this page because of a disability, please contact Purdue Marketing and Media at marketing@purdue.edu.