jamesbond 2007-9-18 16:18
The Nutritional Biochemistry of Chromium(III)
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[Name] The Nutritional Biochemistry of Chromium(III)
[Author] John B. Vincent
[Publisher] Elsevier B.V.
[Key Words] Biochemistry, Chromium
[Briefing]
The manufacture and sale of chromium nutritional supplements has become a
multimillion-dollar industry; these supplements are available in a variety of forms for
human consumption including pills, sports drinks, smoothies, and chewing gums and
have been recommended for use under certain conditions as supplements in cattle and
swine diets. In 1999, sales of products containing chromium reached almost half-abillion
dollars, making the supplements second in sales only to calcium among mineral
supplements. Popular interest in chromium(III) is large, as evidenced by numerous
recent articles in women’s magazines and fitness and health magazines as one might
expect for a supplement which has been touted to reduce fat and build muscle without
exercise.
Since the 1960s, chromium has been generally believed to be essential for proper
carbohydrate and lipid metabolism. Chromium deficiency has been suggested to lead
to symptoms associated with adult-onset diabetes and cardiovascular disease, and these
supplements have recently found potential as therapeutic agents in the treatment of adultonset
diabetes. However, since the mid-1990s, the long-standing belief that chromium
as chromium(III) is essential for humans and other mammals has been seriously questioned,
especially since how chromium might function in the body has not been firmly
established. The recent lowering of the suggested adequate daily intake of chromium
by the National Academies of Science has been questioned by the supplement industry.
While the original proposals for a biological role for chromium(III) at molecular levels
have been discredited, recent proposals have appeared including a role enhancing insulin
receptor’s action in the insulin-signaling pathway and that chromium(III) gets converted
to the carcinogen chromate (of Erin Brokovich fame), which is the biologically active
agent. However, the recent research is not without its own questions.
While the benefits of chromium(III) supplementation of healthy humans
(e.g., weight loss and increased muscle mass) have all but been discredited since 2001,
the use of pharmacological, rather than nutritional, doses of chromium may have beneficial
effects on type II diabetes, cardiovascular diseases, and related conditions. The use
of these large doses of chromium requires that the toxicological properties of chromium
supplements be established. Starting with reports in 1995 that chromium picolinate
could have deleterious effects, numerous studies have appeared on potential effects from
chromium picolinate and other chromium supplements. Deciphering this literature can
be difficult for the non-expert, especially given attacks by the supplement industry on
the academic researchers whose results question the safety of the supplements. This has
lead to assessments of the safety of chromium picolinate by the National Academies of
Science, Food and Nutrition Board (UK) and the Food and Drug Administration. Similarly,
the compound is currently being tested for toxic effects by the National Institutes
of Health, which at the same time has recently had a funding initiative to look at using
chromium supplements as an adjuvant therapy for diabetes.
The aim of this book is to examine the four most controversial areas of chromium
nutrition and chemistry: (1) Is chromium an essential element? (2) What biochemical
role if any does chromium(III) have in the body? (3) Can large doses of chromium(III)
be used to treat type II diabetes, cardiovascular disease, and related medical conditions?
and (4) Is the use of chromium(III) supplements of health concern? This is to be
accomplished by having chapters in the four areas written by multiple experts in these
areas; however, the experts generally voice opinions on both sides of the issue.
In Chapter 1, I and my graduate student Dontarie Stallings (Department of
Chemistry and Coalition for Biomolecular Products, the University of Alabama) outline
the research on chromium from the time it was first proposed to be an essential
element until 1995, a decade before this book project was initiated. Four chapters
address the first aim of the book – whether chromium is an essential element. In
Chapter 2, Barbara Stoecker (Regents Professor, Department of Nutritional Sciences,
Oklahoma State University and a member of the National Academy of Science panel
that established the adequate intake (AI) value for chromium) reviews the data used to
determine the AI for chromium. In Chapter 3, Dr Diane Stearns (Department of Chemistry
and Biochemistry, Northern Arizona University) argues that chromium should not
be classified as an essential element. In Chapter 4, Dr Henry C. Lukaski (Assistant
Director of the Grand Forks Human Nutrition Center of the USDA) reviews evidence
for effects from chromium supplementation on changes in body mass and body composition,
while in turn, Dr Merlin Lindemann (Department of Animal and Food Sciences,
University of Kentucky) in Chapter 5 describes the effects of chromium supplementation
of animal feed.
Two chapters address the second aim – whether chromium has a biochemical role
in the body. In Chapter 6, Dr Weiyue Feng (Institute of High Energy Physics, Chinese
Academy of Sciences) reviews how chromium is transported in the body and what this
might imply about potential functions for chromium; and in Chapter 7, I and my graduate
student Randall Bennett review the recent proposals for how chromium might affect carbohydrate
and lipid metabolism. The third aim is addressed in Chapter 8 by Dr William
Cefalu (Pennington Biomedical Research Center, Louisiana State University), who
reviews the potential use of chromium as a therapeutic agent and Debasis Bagchi
(Department of Pharmacy Sciences, Creighton University Medical Center) and colleagues
in Chapter 9.
Chapters 10–12 comprise the fourth aim and are, thus, focused on whether
chromium supplementation could result in any toxic effects, perhaps the hottest and most
highly debated area of current chromium research. In Chapter 10, Diane Stearns analyzes
the results of in vitro and cell culture studies on the toxicity of chromium(III) compounds,
while Peter Lay and colleagues (Centre for Heavy Metals Research, and Centre
for Structural Biology and Structural Chemistry, University of Sydney) in Chapter 11
discuss the implications of recent studies that indicate that chromium(III) complexes may
be redox active in vivo. Max Costa and graduate student Qingdong Ke (Nelson Institute
of Environmental Medicine, New York University School of Medicine) in Chapter 12
survey toxicological studies on chromium(III) compounds.
Finally, Dr Forrest Nielsen, a distinguished nutritionist at the Grand Forks
Human Nutrition Center of the USDA but who has not worked directly in the field
of chromium nutritional biochemistry, has provided a summary of the arguments
in each of the four areas and presented his own conclusions and interpretations in
Chapter 13.
