Americans spend hundreds of dollars annually on products to protect and improve their appearance. Around 30% of that is specifically for skincare.

Well, a new study in the Journal of Investigative Dermatology may help you save big bucks and improve your skin's health. It turns out that while all the popular vitamin C-loaded creams and treatments you buy may help your skin, eating a lot of vitamin C-rich foods is even more effective.

Study participants who raised their blood levels of vitamin C by eating two kiwifruit daily for eight weeks saw increased collagen production (which helps prevent wrinkles) and greater renewal of their epidermis, the outer skin layer.

That's beauty from the inside out.

Common fruits and vegetables with the most vitamin C include:

• Yellow peppers. One provides 380% of the daily value (DV), which is twice the amount that's in a green sweet pepper.

• Kale. Three ounces deliver 103% of the DV.

• Broccoli. Three ounces deliver almost 100% of the DV.

• Guava. One piece has 138% of the DV.

FYI: One medium kiwi only delivers 62% of the DV (hence subjects ate two a day in the study). And one medium-sized orange? Around 92% of the DV.

For great recipes with vitamin C-loaded ingredients, check out the tasty treats such as Vitality Smoothie in my "What to Eat When Cookbook." And for more help preventing skin aging (and premature aging of all your body's organs), read "The Great Age Reboot."