ALLERGY, RESPIRATORY
Know Your Asthma Triggers
Molecule in Skin May Link Eczema and Asthma
Overweight Moms More Likely to Have Asthmatic Kids
ALTERNATIVE MEDICINE
Bitter Melon Extract May Slow, Stop Breast Cancer
Supplement Hampers Thyroid Cancer Treatment
Alternative Treatments May Boost IVF Success
ANIMAL CARE
Safe Toys for Dogs
Rest Easy. When It Comes to Swine Flu, Your Pet Is Safe
Beware of Dog Bites
BONES & JOINTS
Vitamin D Plus Calcium Guards Against Fractures
'Snowbirds' Beware the Climate Changes
Brazilian Mint Tea Naturally Good for Pain Relief
CANCER
Yoga May Bring Calm to Breast Cancer Treatment
Red Meat No No No But Oily Fish Yes Yes Yes
Strenuous Daily Workout May Keep Cancer at Bay
CAREGIVING
UV Lights, Fans May Curb TB Spread in Hospitals
Acute Respiratory Distress Syndrome as Deadly as Ever
Coordination Has Led to Quicker Heart Treatment
CIRCULATORY SYSTEM
Smog Tougher on the Obese
Support Network May Play Role in Benefits of Drinking
Firefighters Have Narrower-Than-Normal Arteries, Study Finds
COSMETIC
Mouse Study Finds Molecule That Tells Hair to Grow
Wrinkle Fillers Need Better Label Warnings: FDA Panel
Gum Chewing May Cut Craving for Snacks
DENTAL, ORAL
Gum Care Helps Control Type 2 Diabetes and Its Complications
Acid Drinks Blamed for Increase in Tooth Erosion
Scientists Find Gene for Tooth Enamel
DIABETES
Fish Twice a Week Cuts Diabetics' Kidney Risks
Strict Blood Sugar Lowering Won't Ease Diabetes Heart Risk
Arthritis Hits More Than Half of Diabetics
DIET, NUTRITION
Common Antioxidant Might Slow Parkinson's
School Meals Need to Get Healthier
Occaisonal Dieting May Cut Breast Cancer, Study Says
DISABILITIES
Review Finds Marijuana May Help MS Patients
Could Your Cell Phone Help Shield You From Alzheimer's?
ENVIRONMENTAL HEALTH
Global Warming Biggest Health Threat of 21st Century, Experts Say
Agent Orange Exposure Tied to Prostate Cancer Return
Plastics Chemical Tied to Aggression in Young Girls
EYE CARE, VISION
Statin Drugs Cause Eye Disorders
Eye Disease, Cognitive Decline Linked in Study
Blood Sugar Control Helps Diabetics Preserve Sight
FITNESS
MRSA Infections Can Bug Fitness Buffs
Simple Steps Get Walkers Moving
Seniors Who Exercise Help Their Health
GASTROINTESTINAL PROBLEMS
Intestinal Bacteria Trigger Immune Response
Gum Chewing May Speed Colon Surgery Recovery
HRT Use Raises Risk of Stomach Trouble
GENERAL HEALTH
'Soda Tax' Wins Health Experts' Support
Surgical Masks Could Prevent Flu, Maybe
Should the FDA Regulate Tobacco?
HEAD & NECK
Ski Helmets Encouraged for All
Zen May Thicken Brain, Thwart Pain
Many Children Will Outgrow Headaches
HEALTH & TECHNOLOGY
Airport Full Body Scanners Pose No Health Threat: Experts
Study Suggests Link Between Cell Phones and Brain Tumors
The Internet Is Becoming One-Stop Shopping for Health Help
HEARING
Summer Sounds Can Lead to Hearing Loss
Noise Hurts Men's Hearing More, Study Shows
HEART & CARDIOVASCULAR
Vitamin B3 May Help Repair Brain After a Stroke
An Apple a Day May Help Keep Heart Disease Away
Fewer Heart Attacks After England Goes Smoke-Free
INFECTIOUS DISEASE
Swine Flu Loves a Crowd
Dry Weather Boosts Odds of Flu Outbreaks
Swine Flu Now Reported in All 50 States
INFERTILITY
Obesity May Affect Fertility in Young Womene
KID'S HEALTH
Pregnant Women Exposed To Certain Pollutants Could Lower Childs IQ
Guard Kids' Eyes Against Long-Term Sun Damage
Scorpion Anti-Venom Speeds Children's Recovery
MEN'S HEALTH
Drinking Green Tea May Slow Prostate Cancer
Exercise May Prevent Prostate Cancer: Study Shows
Soy Linked to Low Sperm Count
MENTAL HEALTH
Drink Away Dementia?
The Acne Drug Accutane More Than Doubles Depression Risk
Musicians' Brains Tuned to Emotions in Sound
PAIN
Alleviating Rheumatoid Arthritis
'Cell Phone Elbow' -- A New Ill for the Wired Age
Tai Chi May Help Ease Fibromyalgia
PHYSICAL THERAPY
PREGNANCY
Exercise As Well As Acupuncture, May Ease Polycystic Ovarian Syndrome
Acupuncture May Relieve Acid Indigestation In Pregnancy
Acupuncture May Ease Depression During Pregnancy
SENIORS
For Older Walkers, Faster Is Better
Money May Matter, Health-Wise, in Old Age
Tai Chi May Help Ease Fibromyalgia
SEXUAL HEALTH
SLEEP DISORDERS
Sleeping Could Help Women Lose The Baby Fat
Pay Attention to Signs That Say You're Too Fatigued to Drive
Better Sleep, Grades Seem to Go Up
WOMEN'S HEALTH
Air Pollution Slows Women's Marathon Times
Natural Childbirth Moms More Attuned to Babies' Cry
Soy May Not Lead to Denser Breasts
Add your Article

Antioxidants Blunt Exercise Benefit, Study Shows

By Steven Reinberg
HealthDay Reporter

MONDAY, May 11 (HealthDay News) -- Exercise helps increase insulin sensitivity and ward off diabetes, but taking supplemental antioxidants such as vitamins C and E actually blunts that benefit, researchers report.

Exercise helps increase the body's sensitivity to insulin by making reactive oxygen species, or "free radicals," which antioxidants work against. These free radicals are thought to damage cells and speed the aging process, but they are also used by the body to prevent cell damage after exercising, the researchers say.

"When you exercise you do improve your insulin sensitivity, and if you are at risk for diabetes improving insulin sensitivity is good," said researcher Dr. C. Ronald Kahn, the Mary K. Iacocca Professor at the Joslin Diabetes Center and Harvard Medical School.

Part of the reason that exercise improves insulin sensitivity is that it causes oxidative stress on the muscles. The muscles respond to this stress by creating free radicals, Kahn said.

"If you take antioxidants like vitamins C and E, you block the oxidative stress response, but you also block the beneficial effects of exercise on insulin sensitivity," he said.

The report is published in this week's online edition of the Proceedings of the National Academy of Sciences.

For the study, Kahn's team looked at the benefit of exercise in increasing insulin resistance in 39 young men, roughly half of whom were taking supplemental vitamins C and E.

Kahn's group found that men taking vitamin supplements had no change in their insulin resistance, but men not taking vitamins had an increase in free radicals, which increases insulin resistance. A month after stopping the vitamin supplements insulin sensitivity was restored, the researchers noted.

"If you are exercising, in part, to reduce diabetes risk, you shouldn't take vitamin C and E, because you are going to block some of the beneficial effect of the exercise to prevent the diabetes," Kahn said.

Dr. David L. Katz, director of the Prevention Research Center at Yale University School of Medicine, thinks this study raises doubts about the benefits of taking antioxidant supplements, but not about the value of these vitamins in the foods people eat.

"We have long held out hope that antioxidant supplements, among them vitamin C, vitamin E, beta carotene, and more recently lycopene and others, would help prevent diseases from the common cold to cancer, heart disease to diabetes," Katz said. "But to date, virtually all of the best research evidence is contrary to this hope."

This study has a counter-intuitive conclusion, namely that antioxidant supplements may actually interfere with the beneficial effects of exercise on insulin sensitivity, Katz said.

"This is a small and short-term study, and thus cannot tell us definitively that antioxidant supplements are harmful in diabetes or the insulin-resistant state that often precedes it. But that is precisely what the study suggests may be true," Katz said.

For now, there is substantial uncertainty about any health benefits and the potential harms of antioxidants as supplements, Katz said. "But we have no such confusion about the powerful health-promoting effects of wholesome, mostly plant-based diets and regular physical activity."

More information

For more information on antioxidants, visit the U.S. National Library of Medicine.



SOURCES: C. Ronald Kahn, M.D., Mary K. Iacocca Professor, Joslin Diabetes Center and Harvard Medical School, Boston; David L. Katz, M.D., M.P.H., director, Prevention Research Center, Yale University School of Medicine, New Haven, Conn.; May 11-15, 2009, Proceedings of the National Academy of Sciences, online

Last Updated: May 11, 2009

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