When it comes to fruit and vegetables, it’s not always what’s inside that matters most.Peels and rinds can pack much — sometimes most — of nature’s nutrition firepower.

A plant’s skin is its first line of defense against predators and environmental stress.When we consume those peels, the protective benefits of those phytochemicals get passed on to us.Below we explore a few of those possible benefits, with tips on how to give your peeler a rest.

Apples: A Red Delicious apple with skin has about twice as much fiber and 45% more phytochemicals than a naked one.Among these phytochemicals is quercetin, which is being studied for possible effects on Alzheimer’s, prostate pain,  bone health, and immunity.

TIP: Eating apples with peels on is a no-brainer — but you can also leave peels on in many apple dessert recipes, such as apple pie and our Cran-Apple Crisp.

Eggplant: In basic researchers, Japanese scientists found a compound in the skin of eggplants that may help halt cancer proliferation.Nasunin blocks the formation of blood vessels that feed malignant tumors, in lab research.

TIP: Slip a few unpeeled slices of eggplant into your lasagna — or toss with olive oil and roast ‘em on the grill.

Citrus: A recent British review of citrus oils suggests that compounds found in the peel of oranges, lemons, limes, and grapefruit could fight harmful foodborne pathogens. In other research, flavonoids found in orange and tangerine peels significantly lowered the LDL (bad) cholesterol levels of overfed hamsters.

TIP: Add a bit of citrus zest to marinades, dressings, and condiments or on top of grilled salmon.

Potatoes: Recently in lab studies, Indian researchers demonstrated that the polyphenolic extracts of potato peels can protect human red blood cells from the oxidative damage caused by free radicals.One of the polyphenolic compounds — chlorogenic acid — is concentrated in the peel along with extra fiber, potassium, and vitamin B6.

TIP: Eat the skin of your baked potato, or slice unpeeled potatoes, then toss with olive oil before oven roasting.

Watermelon: While the flesh is a top source of lycopene, another compound — the amino acid, citrulline — is highest in the rinds. Citrulline may function as a natural alternative to Viagra, increasing blood flow to the pelvic area by suppressing those enzymes that inhibit nitric oxide’s effects, as assessed in lab research.

TIP: Include more of the white rind next time you cut up a watermelon -– or get adventurous with Barbequed or Pickled Watermelon Rinds.

Published July 1, 2008