Miki Okae eats collagen-rich beef tendons.

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Mara says Japanese women believe their skin is the key to true beauty. Miki Okae, one of Japan's most famous beauty experts, says the ideal is fair, smooth skin. "Everyone demands that," she says.

While some Americans get collagen and Botox injections to erase wrinkles, Japanese women believe in a different approach—they consume collagen-infused foods. Miki says eating collagen-rich beef tendons is a regular part of her beauty routine. "I sneak out of the office when the supermarket opens to buy this," she says.

Many restaurants even feature collagen, which is derived from animals like cows and chickens, on their menus. "Collagen-infused food is everywhere in Japan," Mara says.

Watch Mara's report on Japanese beauty secrets. Watch

Every day for the past five years, Miyuki, a 30-year-old woman living in Tokyo, says she's been drinking a combination of collagen and water to look more youthful. Some days, she mixes the animal product with tea. "It makes my skin beautiful, I guess."

After speaking with women like Miyuki, Mara consults a dermatologist, who says there's no evidence that what you drink or eat will improve sagging skin or erase wrinkles...but that's not deterring millions of Japanese women. "People really swear by it. It makes them feel better," Mara says. "It makes them feel healthier and more beautiful."

One century-old Japanese beauty treatment also relies on an unusual ingredient...nightingale droppings. The bird droppings are made into a powder—known as Uguisu no Fun—mixed with soap and used as a face wash. Mara meets Kamiko and Miki, a mother-daughter pair who swear by this product. At ages 43 and 70, they say bird poop facials are their secret to looking young.