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In Your 60s and Beyond

The Food: Shellfish
Why: They're high in vitamin B12. This vitamin is found in lots of animal products, so unless you're vegan, it's rare to be deficient when you're younger. "But B12 needs stomach acid to be absorbed, and we start to lose stomach acid in our 50s and into our 60s," explains Kirkpatrick. Plus, there's a type stomach inflammation that occurs in up to 50 percent of elderly people that can make it hard to absorb B12, which means you'll need to eat more just to get your recommended intake. Finally, B12 is one of three B vitamins that can help lower your levels of an amino acid linked to dementia. (The other two B vitamins are folate and B6.)

Where else you can get B12: Rainbow trout and sockeye salmon, along with milk, yogurt and eggs.