Oatmeal was the first whole food which the FDA has allowed to have a health claim on the label. I do not believe everything the FDA does is for the good of the public, but this is a good move and article [link below] from the FDA Consumer magazine should help you.
Basically it's the beta-glucan soluble fibre in whole oats which is responsible for the lowering of total and LDL blood cholesterol levels, as seen in various studies.
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