Susan B. answered 10/29/14
Tutor
New to Wyzant
Using Natural Learning Styles to Discover the Joy of Learning
Hello Puro,
Your question shows critical thinking skills. There really is no way to know for sure what is being measured when a claim such as this is made. Unfortunately, much advertising has been reduced to short sound-bites such as this.
However, you can probably assume that those making this claim are measuring some sort of effectiveness in fighting disease or maintaining health. Often, a broad claim is bold and large to capture attention, while the supporting details are available in fine print or at an affiliated website.
Keep asking questions and digging deeper.
A good source for learning about vitamin C effectiveness in promoting health is:
http://health.howstuffworks.com/wellness/food-nutrition/vitamin-supplements/vitamin-c-benefits.htm
I hope this is helpful. Have a good day. :)