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Posted on Thu, Jan 31, 2008, 5:12 pm PST

When it comes to preventing the common cold, many people believe large supplemental doses of Vitamin C will do the trick – not the case.

While it’s true getting appropriate amounts of Vitamin C is vital for maintaining a healthy immune system (women require 75mg/day and men require 90mg/day), a recent comprehensive review showed that vitamin C in amounts greater than 200 milligrams – that’s more than double our recommended daily requirements - did not have an effect in boosting the immune system and/or preventing the common cold (except perhaps in serious athletes). 

With this information in mind, people should re-think popping large doses of supplemental vitamin C.  If you feel compelled to take an extra supplemental dose, stick with 200 milligrams - certainly no more than 500. Also, consider how quickly your Vitamin C adds up from food: 

• 1 red/yellow bell pepper = 280mg
• 1 cup cooked broccoli = 100 mg  
• 1 orange = 70 mg 
• 1 cup strawberries = 90 mg

On the other hand, exercise has a proven, powerful effect.  A study published last year in The American Journal of Medicine showed that when unfit, sedentary people started briskly walking 45 minutes a day - five days a week, they caught fewer colds over a one-year period. 

That's because each and every time you moderately exercise, the immune system starts functioning at a higher level - and remains elevated for about three hours - that's the body's first line of defense against bacteria, viruses and other invaders. 

However, because this is not long lasting, it's important for people to regularly exercise. Bottom line: the absolute best way to boost your immune system is to get plenty of regular exercise, and eat a diet rich in fruits and vegetables.

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This article was written by Joy Bauer, M.S., R.D., C.D.N. All Rights Reserved. Copyright 2008.