The amount of money that Americans spend in an effort to keep their faces youthful and their tummies taut - whether it's by a plastic surgeon's blade or by the cosmetologist's hypodermic of Botox - could rival any line item in President Obama's economic stimulus package.

But the age-fighting secret that most people don't know is that along with getting enough exercise, sleep and downtime, your greatest weapon is in your supermarket. Choosing the right foods can give your skin that dewy glow of youth. Can keep that spring in your step. And may even fight off diseases like Alzheimer's and cancer.

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Many in the medical community believe that one key to slowing the aging process lies in foods that help keep your immune system happy. According to Dr. Mark Liponis, corporate medical director of the prestigious health spa Canyon Ranch and author of "UltraLongevity," many diseases that we consider necessary evils of aging - arthritis, heart disease, dementia, even the stereotypical "look" of an aging body itself - have roots in excessive inflammation. This systemic inflammation is caused by an immune system out of kilter.