ALLERGY, RESPIRATORY
Traffic, Dust Linked to Asthma in Kids
Air Quality Better in Northeast, Midwest
Using Music and Sports to Improve Kids' Asthma
ALTERNATIVE MEDICINE
Health Tip: Anticipating Acupuncture
Acupuncture May Not Help Hot Flashes
Acupuncture May Help Restore Lost Sense of Smell
ANIMAL CARE
Beware of Dog Bites
Safe Toys for Dogs
Separation Anxiety, Canine-Style
BONES & JOINTS
Occupational Therapy Plus Exercise Benefits Osteoarthritis
Alcohol Abuse Can Damage Bones
Rheumatoid Arthritis May Harm Gums
CANCER
Strenuous Daily Workout May Keep Cancer at Bay
Smoking Ups Risk of Second Breast Cancer
Healthy Behaviors Slow Functional Decline After Cancer
CAREGIVING
Hospital Practices Influence Which Moms Will Breast-Feed
Organ Donation Policies Vary Among Children's Hospitals
Acute Respiratory Distress Syndrome as Deadly as Ever
CIRCULATORY SYSTEM
Bye, Bye Back Fat?
Smog Tougher on the Obese
Varicose Veins May Mask Larger Problem
COSMETIC
Get Sugared!.... Its a sweet choice for hair removal
Wrinkle Fillers Need Better Label Warnings: FDA Panel
Gum Chewing May Cut Craving for Snacks
DENTAL, ORAL
An Oral Approach to Heart Disease
Gum Care Helps Control Type 2 Diabetes and Its Complications
Hormones May Be to Blame for Women's Cavity Rates
DIABETES
Strict Blood Sugar Lowering Won't Ease Diabetes Heart Risk
Exercise Protects Black Women From Type 2 Diabetes
Patients' Photos Help Boost Radiologists' Accuracy
DIET, NUTRITION
Western Diet Linked To Heart Disease, Metabolic Syndrome
Polyunsaturated Fats Really May Lower Heart Risk
More Educated Choose Healthier Foods, But Pay More
DISABILITIES
Could Your Cell Phone Help Shield You From Alzheimer's?
Review Finds Marijuana May Help MS Patients
ENVIRONMENTAL HEALTH
Years of Exposure to Traffic Pollution Raises Blood Pressure
Where You Live May Affect Your Cancer Diagnosis
Household Insecticides May Be Linked to Autoimmune Diseases
EYE CARE, VISION
Too Much Sun, Too Few Antioxidants Spell Eye Trouble
Music Can Help Restore Stroke Patients' Sight
Eye Test Could Spot Diabetes Vision Trouble Early
FITNESS
Yoga Can Ease Lower Back Pain
FDA Mandates New Warnings for Botox
Marathoners Go the Distance on Heart Health
GASTROINTESTINAL PROBLEMS
Bowel Prep Harder on Women Than Men
New Yogurt May Ease Stomach Ulcers
Japanese Herbals May Ease Gastro Woes
GENERAL HEALTH
When It Comes to Lifting, the Pros Have Your Back
Potassium-Rich Foods May Cut Stroke, Heart Disease Risk
Multivitamins Might Prolong Life
HEAD & NECK
Many Children Will Outgrow Headaches
Ski Helmets Encouraged for All
Zen May Thicken Brain, Thwart Pain
HEALTH & TECHNOLOGY
Airport Full Body Scanners Pose No Health Threat: Experts
Magnet Therapy May Ease Hard-to-Treat Depression
Using Light Therapy to Silence Harmful Brain Activity
HEARING
Noise Hurts Men's Hearing More, Study Shows
Summer Sounds Can Lead to Hearing Loss
HEART & CARDIOVASCULAR
Rheumatoid Arthritis a Threat to the Heart
Western Diet Linked To Heart Disease, Metabolic Syndrome
Kids With Vitamin D Deficiency Linked to Heart Trouble
INFECTIOUS DISEASE
Hand Washing 10 Times a Day May Help Keep Flu Away
Bacterial Infections May Succumb to Honey
Grapefruit Compound Inhibits Hepatitis C Virus
INFERTILITY
Obesity May Affect Fertility in Young Womene
KID'S HEALTH
Frequent Feedings May Be Making Babies Fat
Teen Internet Addicts More Likely to Self-Harm: Study
Health Tip: Back Pain in Children
MEN'S HEALTH
Noise Hurts Men's Hearing More, Study Shows
Could Chinese Herb Be a Natural Viagra?
The Dark Side of Vegetarianism
MENTAL HEALTH
Vitamin C Protects Some Elderly Men From Bone Loss
Musicians' Brains Tuned to Emotions in Sound
Teen Internet Addicts More Likely to Self-Harm: Study
PAIN
Are We Exercising Pain Away? Not So Much.
Alleviating Rheumatoid Arthritis
Acupuncture, Real or Fake, Eases Back Pain
PHYSICAL THERAPY
PREGNANCY
Mom's Extra Pregnancy Pounds May Raise Child's Heart Risks
Exercise As Well As Acupuncture, May Ease Polycystic Ovarian Syndrome
Woman in America Are Delaying Motherhood, Study Says
SENIORS
Common Antioxidant Might Slow Parkinson's
Life Expectancy in U.S. Hits New High
Exercise Helps Reduce Falls in Young and Old
SEXUAL HEALTH
SLEEP DISORDERS
Pay Attention to Signs That Say You're Too Fatigued to Drive
Sleeping Could Help Women Lose The Baby Fat
Exercising Throat Muscles May Relieve Sleep Apnea
WOMEN'S HEALTH
Women Who Run May Benefit From Extra Folic Acid
A Brisk Pace May Keep Stroke at Bay
Spice Compounds May Stem Tumor Growth
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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