Diabetes and CAM: A Focus on
Dietary Supplements
Introduction
Diabetes is a chronic condition affecting millions of
Americans. Conventional medical treatments are
available to control diabetes and its
complications. However, some people also try complementary and
alternative medicine (CAM) therapies,
including dietary
supplements. This fact sheet provides basic
information on diabetes (with a focus on
type 2), summarizes scientific research on the
effectiveness and safety of selected supplements that people
with diabetes sometimes use, and suggests
sources for additional information.
Key Points
- In general, there is not enough scientific
evidence to prove that dietary supplements have substantial
benefits for type 2 diabetes or its
complications.
- It is very important not to replace conventional
medical therapy for diabetes with an unproven CAM
therapy.
- Tell your health care providers about any
complementary and alternative practices you use. Give them
a full picture of what you do to manage your health. This
will help ensure coordinated and safe care. Medicines for
diabetes and other health conditions may need to be
adjusted if a person is also using a dietary
supplement.
About Diabetes
Diabetes encompasses a group of diseases. Type 2
diabetes accounts for 90 to 95 percent of
all diagnosed cases and occurs more
frequently in older people. Type 1
diabetes, which accounts for 5 to 10 percent
of cases, usually strikes children and young
adults. A third form, gestational
diabetes, develops in some women during
pregnancy.
In all forms of diabetes, the body's ability to convert food
into energy is impaired. After a meal, the body breaks down
most food into glucose (a kind of sugar), the main source of
fuel for cells. In people with diabetes, the body does not make
enough insulin—a hormone that helps glucose enter cells—or the
cells do not respond to insulin properly. Often, both insulin
production and insulin action are impaired. Without treatment,
glucose builds up in the blood instead of moving into the
cells, where it can be converted into energy. Over time, the
high blood glucose levels caused by diabetes can damage many
parts of the body, including the heart and blood vessels, eyes,
kidneys, nerves, feet, and skin. Such complications can be
prevented or delayed by controlling blood glucose, blood
pressure, and cholesterol levels.
Type 2 diabetes, the focus of this fact sheet,
most often is associated with older
age (although it is increasingly being diagnosed
in children), obesity (about 80 percent
of people with type 2 diabetes are overweight), a
family history of diabetes, and physical
inactivity. Certain minority population groups are at
greater risk, as are women who have had gestational diabetes.
Type 2 diabetes usually begins as
insulin resistance, a disorder in which cells do not use
insulin properly. Symptoms develop gradually and may
include fatigue, frequent urination, excessive thirst and
hunger, weight loss, blurred vision, and slow-healing wounds or
sores. However, it is possible to have type 2 diabetes without
experiencing any symptoms.
People with diabetes should try to keep their blood glucose in
a healthy range. The basic tools for managing type 2 diabetes
are healthy eating, physical activity, and blood glucose
monitoring. Many people also need to take prescription pills,
insulin, or both.
To find out more about diabetes and related conditions, contact
the National Diabetes Information Clearinghouse (see
For More Information).
© iStock
2006
Dietary Supplements and Type
2 Diabetes
Some people with diabetes use CAM therapies for their health
condition. For example, they may try acupuncture or
biofeedback to
help with painful symptoms. Some use dietary
supplements in efforts to improve their
blood glucose control, manage symptoms, and lessen the risk
of developing serious complications such as heart
problems.
This section addresses what is known about a few of the many
supplements used for diabetes, with a focus on some that have
been studied in clinical trials, such as alpha-lipoic
acid, chromium, omega-3 fatty
acids, and polyphenols.
Alpha-lipoic acid (ALA, also known as
lipoic acid or thioctic acid) is an antioxidant—a substance
that protects against cell damage. ALA is found in certain
foods, such as liver, spinach, broccoli, and
potatoes. Some people with type 2 diabetes take ALA
supplements in the hope of lowering blood glucose levels by
improving the body's ability to use insulin; others use ALA to
prevent or treat diabetic neuropathy (a nerve disorder).
Supplements are marketed as tablets or capsules.
- ALA has been researched for its effect on insulin
sensitivity, glucose metabolism, and diabetic neuropathy.
Some studies have found benefits, but more research is
needed. (There are some studies, reported from outside the
United States, of ALA delivered intravenously; however,
this research is outside the scope of this fact
sheet.)
- Because ALA might lower blood sugar too much, people
with diabetes who take it must monitor their blood sugar
levels very carefully.
Chromium is an essential trace
mineral—that is, the body requires small amounts of it to
function properly. Some people with diabetes take chromium in
an effort to improve their blood glucose control. Chromium is
found in many foods, but usually only in small amounts;
relatively good sources include meat, whole grain products, and
some fruits, vegetables, and spices. In supplement form
(capsules and tablets), it is sold as chromium picolinate,
chromium chloride, and chromium nicotinate.
- Chromium supplementation has been researched for its
effect on glucose control in people with diabetes. Study
results have been mixed. Some researchers have found
benefits, but many of the studies have not been well
designed. Additional, high-quality research is needed.
- At low doses, short-term use of chromium appears to be
safe for most adults. However, people with diabetes should
be aware that chromium might cause blood sugar levels to go
too low. High doses can cause serious side effects,
including kidney problems—an issue of special concern to
people with diabetes.
© iStock 2006
Omega-3 fatty acids are
polyunsaturated fatty acids that come from foods such as
fish, fish oil, vegetable oil (primarily
canola and soybean), walnuts, and wheat germ.
Omega-3
supplements are available as capsules or
oils (such as fish oil). Omega-3s are important in a number
of bodily functions, including the movement of calcium and
other substances in and out of cells, the relaxation and
contraction of muscles, blood clotting, digestion,
fertility, cell division, and growth. In addition, omega-3s
are thought to protect against heart disease, reduce
inflammation, and lower triglyceride levels.
- Omega-3 fatty acids have been researched for their
effect on controlling glucose and reducing heart disease
risk in people with type 2 diabetes. Studies show that
omega-3 fatty acids lower triglycerides, but do not affect
blood glucose control, total cholesterol, or HDL (good)
cholesterol in people with diabetes. In some studies,
omega-3 fatty acids also raised LDL (bad) cholesterol.
Additional research, particularly long-term studies that
look specifically at heart disease in people with diabetes,
is needed.
- Omega-3s appear to be safe for most adults at
low-to-moderate doses. Safety questions have been raised
about fish oil supplements, because some species of fish
can be contaminated by substances such as mercury,
pesticides, or PCBs. In high doses, fish oil can interact
with certain medications, including blood thinners and
drugs used for high blood pressure.
Polyphenols—antioxidants found in
tea and dark chocolate, among other dietary
sources—are being studied for possible effects on vascular
health (including blood pressure) and on the body's ability to
use insulin.
- Laboratory studies suggest that EGCG, a
polyphenol found in green
tea, may protect against cardiovascular
disease and have a beneficial effect on insulin activity
and glucose control. However, a few small clinical trials
studying EGCG and green tea in people with diabetes have
not shown such effects.
- No adverse effects of EGCG or green tea were discussed
in these studies. Green tea is safe for most adults when
used in moderate amounts. However, green tea contains
caffeine, which can cause, in some people, insomnia,
anxiety, or irritability, among other effects. Green tea
also has small amounts of vitamin K, which can make
anticoagulant drugs, such as warfarin, less effective.
Other supplements are also being
studied for diabetes-related effects. For example:
- Preliminary research has explored the use of
garlic for lowering blood glucose
levels, but findings have not been consistent.
- Studies of the effects of
magnesium supplementation on blood
glucose control have had mixed results, although
researchers have found that eating a diet high in magnesium
may lower the risk of diabetes.
- There is not enough evidence to evaluate the
effectiveness of coenzyme
Q10 supplementation as a CAM therapy for
diabetes; studies of its ability to affect glucose control
have had conflicting findings.
- Researchers are studying whether the herb
ginseng and the
trace mineral vanadium might help control glucose
levels.
- Some people with diabetes may also try botanicals such
as prickly pear cactus, gurmar, Coccinia indica,
aloe vera, fenugreek, and
bitter melon to control their glucose levels.
However, there is limited research on the effectiveness of
these botanicals for diabetes.
If You Have Diabetes and Are
Thinking About Using a Dietary Supplement
- Tell your health care providers about any complementary
and alternative practices you use. Give them a full picture
of what you do to manage your health. This will help ensure
coordinated and safe care. For tips about talking with your
health care providers about CAM, see NCCAM's Time to Talk
campaign at nccam.nih.gov/timetotalk/. Medicines for
diabetes and other health conditions may need to be
adjusted if a person is also using a dietary
supplement.
- Women who are pregnant or nursing, or people who are
thinking of using supplements to treat a child, should
consult their health care provider before using any dietary
supplement.
- Do not replace scientifically proven treatments for
diabetes with CAM treatments that are unproven. The
consequences of not following one's prescribed medical
regimen for diabetes can be very serious.
- Be aware that the label on a dietary supplement bottle
may not accurately reflect what is inside. For example,
some tests of dietary supplements have found that the
contents did not match the dose on the label, and some
herbal supplements have been found to be contaminated.
NCCAM-Funded
Research
NCCAM-supported research includes projects studying the effects
of:
- Chromium on glucose control and vascular function
- Yoga
in people at risk for diabetes
- Ginkgo
biloba extract on diabetes medicines
- EGCG on the body's response to insulin
- Reiki on diabetic
neuropathy and heart function.
Also, researchers in the Diabetes
Unit of NCCAM's Division of Intramural
Research (DIR) are studying many aspects of
diabetes, including what happens when the body does not
properly react to insulin. DIR-sponsored clinical trials
include studies of the effects of vitamin C, glucosamine,
and dark chocolate on the body's response to insulin.
Selected Sources
About Diabetes
Dietary Supplements: Natural Medicines Comprehensive
Database
- Natural Medicines Comprehensive Database. Product
monographs. Accessed on January 21, 2008.
Dietary Supplements: Articles From Scientific Journals
Dietary Supplements: Articles From Scientific
Journals
Chromium
Coenzyme Q10
- Bonadkdar RA, Guarneri,
E.
Coenzyme
Q10. American Family
Physician.
2005;72(6): 1065–1069.
Garlic
- Agency for Healthcare Research and
Quality. Garlic: Effects on Cardiovascular
Risks and Disease, Protective Effects Against Cancer,
and Clinical Adverse
Effects.
Evidence Report/Technology Assessment no.
20. Rockville, MD: Agency for Healthcare Research
and Quality; 2000. AHRQ publication no.
01-E023.
- Banerjee SK, Maulik
SK.
Effect of
garlic on cardiovascular disorders: a
review. Nutrition
Journal.
2002;1(1):4.
Magnesium
Omega-3 Fatty Acids
- Agency for Healthcare Research and
Quality. Effects of Omega-3 Fatty Acids on
Lipids and Glycemic Control in Type II Diabetes and the
Metabolic Syndrome and on Inflammatory Bowel Disease,
Rheumatoid Arthritis, Renal Disease, Systemic Lupus
Erythematosus, and
Osteoporosis. Evidence Report/Technology
Assessment no. 89. Rockville, MD: Agency for Healthcare Research and
Quality; 2004. AHRQ publication no.
04-E012-2.
- Hartweg J, Farmer AJ, Perera R, et
al.
Meta-analysis
of the effects of n-3 polyunsaturated fatty acids on
lipoproteins and other emerging lipid cardiovascular risk
markers in patients with type 2
diabetes. Diabetologia
. 2007;50(8):1593-1602.
- Hartweg J, Perera R, Montori V, et
al. Omega-3 polyunsaturated fatty acids (PUFA) for type
2 diabetes mellitus:
review. The Cochrane Database of Systematic
Reviews.
2008; (1):CD003205. Accessed
on January
28, 2008.
- Letter regarding dietary supplement
health claim for omega-3 fatty acids and coronary heart
disease. U.S. Food and Drug Administration Web site.
Accessed at
www.fda.gov
on January 21, 2008.
- U.S. Food and Drug
Administration. What You Need to Know About Mercury
in Fish and Shellfish. U.S. Food and Drug Administration
Web site. Accessed at
www.fda.gov/Food/FoodSafety/Product-SpecificInformation/Seafood/FoodbornePathogensContaminants/Methylmercury/ucm115662.htm
on January 21, 2008.
Polyphenols
- Collins QF, Liu HY, Pi J, et
al.
Epigallocatechin-3-gallate (EGCG), a
green tea polyphenol, suppresses hepatic gluconeogenesis
through 5'-AMP activated protein
kinase. Journal of Biological
Chemistry.
2007;282(41):30143–30149.
- Fukino Y, Shimbo M, Aoki N, et
al.
Randomized
controlled trial for an effect of green tea consumption on
insulin resistance and inflammation
markers. Journal of Nutritional Science and
Vitaminology.
2005;51(5):335–342.
- Kim J, Formoso G, Li Y, et
al.
Epigallocatechin gallate, a green tea
polyphenol, mediates NO-dependent vasodilation using
signaling pathways in vascular endothelium requiring
reactive oxygen species and
Fyn. Journal of Biological
Chemistry 2007;282(18):13736–13745.
- Mackenzie T, Leary L, Brooks
WB.
The effect of
an extract of green and black tea on glucose control in
adults with type 2 diabetes mellitus: double-blind
randomized study. Metabolism
. 2007;56(10):1340–1344.
- Potenza MA, Marasciulo FL, Tarquinio M, et
al.
EGCG, a green
tea polyphenol, improves endothelial function and insulin
sensitivity, reduces blood pressure, and protects against
myocardial I/R injury in
SHR. American Journal of Physiology,
Endocrinology, and
Metabolism.
2007;292(5):E1378–E1387.
- Ryu OH, Lee J, Lee KW, et
al.
Effects of
green tea consumption on inflammation, insulin resistance
and pulse wave velocity in type 2 diabetes
patients. Diabetes Research and Clinical
Practice.
2006;71(3):356–358.
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