ALLERGY, RESPIRATORY
Traffic, Dust Linked to Asthma in Kids
New Spray Could Benefit Cystic Fibrosis Patients
Keep Asthma, Allergies at Bay for the Holidays
ALTERNATIVE MEDICINE
Imaging Sheds Light on How Acupuncture Works
Green Tea May Help Brain Cope With Sleep Disorders
Uncover Why Turmeric Helps You Heal
ANIMAL CARE
'Comfort Dogs' Come to Emotional Rescue
Safe Toys for Dogs
Animals Respond to Acupuncture's Healing Touch
BONES & JOINTS
Study Shows Exercise Shields Against Osteoporosis
Fruits and Veggies May Strengthen Bones
Get in Step With Summer Foot Care
CANCER
Asthmatics Who Quit Smoking May Reverse Lung Damage
To Quit Smoking, Try Logging On
Low Vitamin D Levels May Initiate Cancer Development
CAREGIVING
Depression, PTSD Common Among Lung Transplant Patient Caregivers
Diabetes Epidemic Now Poses Challenges for Nursing Homes
Acute Respiratory Distress Syndrome as Deadly as Ever
CIRCULATORY SYSTEM
Walk 100 Steps a Minute for 'Moderate' Exercise
Mercury in Fish Linked to High Blood Pressure
Bye, Bye Back Fat?
COSMETIC
Study Evaluates Laser Therapies for Hair Removal
Science May Banish Bad Hair Days
Contact Lenses Boost Kids' Self-Image
DENTAL, ORAL
Sports Drinks May Be Tough on Teeth
Scientists Find Gene for Tooth Enamel
Hormones May Be to Blame for Women's Cavity Rates
DIABETES
Out-of-Control Blood Sugar May Affect Memory
'Standard' Glucose Test May Be Wrong One for Obese Children
Poor Blood Sugar Control After Heart Surgery Impacts Outcomes
DIET, NUTRITION
Coffee Drinkers Might Live Longer
Decline of Underweight Children in U.S. Continue to Fall
Pesticides on Produce Tied to ADHD in Children
DISABILITIES
Review Finds Marijuana May Help MS Patients
Could Your Cell Phone Help Shield You From Alzheimer's?
ENVIRONMENTAL HEALTH
What's Cookin'? It Could Be Air Pollution
Air Pollution May Cause Appendicitis: Study Reveals
Skin Woes Take Toll on U.S. Combat Troops
EYE CARE, VISION
Kids Think Glasses Make Others Look Smart, Honest
Kids' Eye Injuries From Golf Clubs Rare But Severe
Impotence Drugs Don't Harm Vision: Study
FITNESS
Avoiding a Holiday Season of Discontent
Mom and Baby Alike May Benefit From Exercise
Exercise Helps Reduce Falls in Young and Old
GASTROINTESTINAL PROBLEMS
Peppermint Oil, Fiber Can Fight Irritable Bowel
New Guidelines Issued for Management of IBS
Gum Chewing May Speed Colon Surgery Recovery
GENERAL HEALTH
Lower Vitamin D Levels in Blacks May Up Heart Risks
Internet Program Helps Problem Drinkers
Surgical Masks Could Prevent Flu, Maybe
HEAD & NECK
Ski Helmets Encouraged for All
Zen May Thicken Brain, Thwart Pain
Many Children Will Outgrow Headaches
HEALTH & TECHNOLOGY
Study Suggests Link Between Cell Phones and Brain Tumors
Imaging Sheds Light on How Acupuncture Works
E-Mailing Your Way to Healthier Habits
HEARING
Summer Sounds Can Lead to Hearing Loss
Noise Hurts Men's Hearing More, Study Shows
HEART & CARDIOVASCULAR
Exercise May Blunt Salt's Effect on Hypertension
Lack of Vitamin D Linked to High Blood Pressure
A Little Alcohol May Help the Heart: Studies
INFECTIOUS DISEASE
Dry Weather Boosts Odds of Flu Outbreaks
More Medicinal Uses for Pomegranate
The HPV Vaccine: Preventative Medicine or Human Sacrifice?
INFERTILITY
Obesity May Affect Fertility in Young Womene
KID'S HEALTH
Teen Internet Addicts More Likely to Self-Harm: Study
Coconut Oil May Help Fight Childhood Pneumonia
Childhood Dairy Intake Boosts Bone Health Later On
MEN'S HEALTH
Low Vitamin D Levels May Boost Men's Heart Attack Risk
Lots of Sex May Prevent Erectile Dysfunction
The Dark Side of Vegetarianism
MENTAL HEALTH
Heal Your Life® Tips for Living Well
Fear Response May Stem From Protein in Brain
Love Hormone May Ease Discussion of Painful Topics
PAIN
Are We Exercising Pain Away? Not So Much.
Acupuncture, Real or Fake, Eases Back Pain
Tai Chi May Help Ease Fibromyalgia
PHYSICAL THERAPY
PREGNANCY
Exercise As Well As Acupuncture, May Ease Polycystic Ovarian Syndrome
Placebo Acupuncture Tied to Higher IVF Pregnancies
Mom's Extra Pregnancy Pounds May Raise Child's Heart Risks
SENIORS
Nighttime Urination Linked to Higher Death Rate Among Elderly
Money May Matter, Health-Wise, in Old Age
Tai Chi May Help Ease Fibromyalgia
SEXUAL HEALTH
SLEEP DISORDERS
Moderate Aerobics May Ease Insomnia Symptoms
Pay Attention to Signs That Say You're Too Fatigued to Drive
Lose Weight, Sleep Apnea May Improve
WOMEN'S HEALTH
Most Women With Osteoporosis Unaware of Raised Fracture Risk
Spice Compounds May Stem Tumor Growth
Flame-Retardant Chemical Linked to Conception Problems
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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