DIET DETECTIVE: DO THEY HAVE NUTRITIONAL VALUE — ONIONS and CUCUMBERS
By Charles Stuart Platkin
Value: Aside from their health benefits, they add amazing flavor to almost all foods.
Nutrients: Onions belong to the lily family, the same family as garlic, scallions and leeks. A half cup is a good source of vitamin C (5.9mg, 10 percent of the recommended daily value). A half cup of onion is also a source of potassium, calcium, magnesium, phosphorus and dietary fiber.
Health Perks: Onions contain more quercetin than any other common fruit or vegetable. “This potent antioxidant has been linked to a reduction in the risk of heart disease, Alzheimer's, prostatitis and a variety of cancers (such as prostate and lung cancer). One Finnish study also found that men who ate the most foods high in quercetin had 60 percent less lung cancer, 25 percent less asthma and 20 percent less diabetes and heart disease deaths than the general population,” says Nicholas D. Gillitt, Ph.D., a nutrition researcher at Dole Nutrition Institute.
In addition to quercetin, onions contain the phytochemicals known as disulfides, trisulfides, cepaene and vinyl dithiins, all of which are known for their anti-cancer and anti-microbial properties. And, according to researchers at University of Wisconsin-Madison, onions also show anti-platelet activity (platelet accumulation is linked to heart disease), and they also may protect against gastric ulcers by preventing growth of Helicobacter pylori, a microorganism.
Finally, onions, like leeks, contain inulin, a probiotic fiber that can selectively improve the proportion of good bacteria in the colon. “These ‘good’ gut bugs, as well as providing a physical barrier to infection, have been linked to improved absorption of important minerals like calcium and magnesium,” says Gillitt.
Nutrition Stats: Serving size: 1/2 cup chopped (80g), 32 calories, 0.08g fat, 7.47g carbs, 1.4g dietary fiber, 0.88g protein.
How to Buy: According to chef and food expert Aliza Green, author of Field Guide to Produce (Quirk Books, 2004), you should “look for onions that are dry, firm and shiny, with thin skin. The necks should be tightly closed, with no sprouts emerging. Green sprouts are a sign of age and an indication that the onion sprouts will taste bitter. The outer skins should be papery and shiny, with a crackly feel, and can be loose or tightly fitting.” Additionally, according to Green, “Onions should smell mild, even if their flavor is not. Avoid those with green areas or dark patches.”
Examine the sprout end of Italian red onions: It is often sunken, and this is where the first signs of spoilage show. Avoid any onions with soft, deeply sunken tops and any black mold.
How to Store: Onions should be stored in a loosely woven bag — not plastic — in a cool, dark, dry and well-ventilated area, usually the refrigerator. For longer storage, wrap each onion separately in foil and refrigerate. Do not store onions under the sink or with potatoes, because potatoes give off moisture that can cause onions to spoil.
Value: One of the cucumber’s greatest values is what it does not have — calories. A half cup of sliced cucumber has less than 10 calories. And the expression “cool as a cucumber”? Apparently, because of its water content and strong flesh, a cucumber can be as much as 20 degrees cooler inside than on the outside – and the high water content also makes it a thirst quencher.
Nutrients: One 8¼-inch cucumber has 1.5 grams of fiber and is a good source of vitamin C (8.4 milligrams, or 14 percent of the recommended daily value). It’s also a source of thiamin, riboflavin, niacin and vitamin B6 — all very important B vitamins that are essential for cell metabolism, red blood cell production, a healthy immune system and other important health functions. It's also a source of vitamin A, which might help with eye health and reduce the risk of heart disease (the negative studies on vitamin A were related to supplements, not food). Cucumbers also have a decent amount of calcium (48mg, 5 percent of recommended daily values), iron (0.84mg, 4.68 percent of DV), magnesium (39mg, 10 percent of DV), phosphorus (72mg, 7 percent of DV), potassium (442mg, 13 percent of DV), zinc (0.6mg, 4 percent of DV) and copper (0.123mg, 6.17 percent of DV).
Health Perks: One cucumber has about one-third the recommended dose of vitamin K, about 50 micrograms. The majority of the population fails to get enough K, which is required to make at least three proteins that are essential for bone formation. “Studies have also linked diets adequate in vitamin K with a reduced risk of hip fracture in the elderly,” says Gillitt, who adds that there is encouraging research suggesting that vitamin K may inhibit the growth of tumors and cancer cells.
Nutrition Stats: Serving size: one cucumber (8¼ inches), 45 calories, 0.33g fat, 10.93g carbs, 1.5g fiber, 1.96g protein.
How to Buy: According to Green, you should choose cucumbers that are well-shaped, firm and deep green in color. “Cucumbers are quite perishable because of their high water content. Yellowing is a sign that the cucumbers are overgrown. Puffiness is a sign that they're starting to spoil. Shriveled or withered cucumbers will be dried out and tough. Choose hot-house cucumbers that are firm all the way to the tip with no soft spots, especially at the tips. Farm market and locally grown cucumbers are often not waxed, so they are entirely edible but won't keep as long as cucumbers that have been coated with wax for protection. Waxed cucumbers must be peeled. Hot-house cucumbers are wrapped in plastic for protection and are entirely edible.”
How to Store: Store cucumbers in the crisper drawer of the refrigerator for up to one week.
CHARLES STUART PLATKIN is a nutrition and public health advocate, founder and editor of DietDetective.com, the online source for nutrition, fitness, food, diet and wellness information. Copyright 2008 by Charles Stuart Platkin. All rights reserved. Sign up for the free Diet Detective newsletter and iTunes podcast at www.DietDetective.com.