Ask the Experts: Nutrients in Carrot Peels; Lemon-Lime Soda; Canned Beans
Q. Is it true that most of a carrot’s nutrients are in or just below the skin, so it shouldn’t be peeled?
A. Emily S. Mohn, PhD, and Elizabeth J. Johnson, PhD, both scientists in Tufts’ HNRCA Antioxidants Research Laboratory, respond: “Carrots consist of three major layers: 1) the peel/skin (outermost layer), 2) the phloem (intermediate layer) and 3) the xylem (inner core). Generally, all of the peel and a very small portion of the phloem are removed when a carrot is peeled.
“Vitamin C and niacin are most concentrated in the peel but can be found in appreciable amounts in the phloem. As for beta-carotene (an orange pigment and plant form of vitamin A), the peel and phloem have approximately equal amounts. That is why both peeled and unpeeled carrots have the same orange color. The xylem contains the lowest amount (about 10% of the total) of beta-carotene. But, the xylem contains the majority of the calcium, potassium, magnesium and phosphorus present in carrots. And, both peeled and unpeeled carrots are good sources of fiber.
“As for carrots’ phytonutrients (compounds with potential, but uncertain health benefits), a little more than half are found in the peel. However, about 40% of the phytonutrients are found in the phloem and about 10% in the xylem.
“Overall, while removing the peel reduces some phytonutrients and small amounts of the vitamins and minerals in carrots, there is plenty of nutritional value left behind. Remember, the peel is only a small portion of the total vegetable. If you prefer the taste, texture or look of peeled carrots (or the convenience of baby carrots), you can certainly incorporate them into a healthy dietary pattern. But, this root vegetable is perfectly safe to eat unpeeled, as long as it is adequately washed.”
Q. Does lemon-lime soda count as one of the sugar-sweetened beverages we’re advised to limit? Lemon-lime makes it sound a little healthier.
A. Paul Jacques, DSc, director of Tufts’ HNRCA Nutritional Epidemiology Program, answers: “Yes, lemon-lime soda sweetened with any caloric, refined sweetener (like high fructose corn syrup or cane sugar) is a sugar-sweetened beverage and should be limited or avoided. There’s a lot of observational research showing sugar-sweetened beverages are associated with metabolic diseases like heart disease, abdominal obesity and fatty liver.
“To help put the added sugars in soda into perspective, consider that 4 grams of sugar is about 1 teaspoon. So, the 38 grams of sugar in a 12-ounce can of lemon-lime soda equals 9½ teaspoons sugar. The 2015–2020 Dietary Guidelines for Americans advise limiting added sugars to less than 10% of daily calories. So, for example, a female needing 1,600 calories a day should limit added sugars to less than 40 grams (10 teaspoons) a day.
“Lastly, despite the splash of lemon-lime flavor in the product description, the drink has no nutritional value but about 150 calories per can.”
Q. Are nutrients lost by rinsing canned beans?
A. Diane McKay, PhD, an assistant professor in Tufts’ Friedman School, says: “Many recipes advise rinsing and draining canned beans, which reduces sodium (by 41%, on average, in one study). However, some of the minerals beyond sodium and certain vitamins (such as folate and other B vitamins) that are soluble in water also leach into the liquid part of canned beans. So, portions of these nutrients are lost by draining and rinsing (example, below). But there are still plenty of nutrients left in canned beans after rinsing and draining, including a good amount of fiber. You can make up for small losses of nutrients like potassium and folate by tossing beans on a leafy green salad or adding an extra vegetable to your dish.
“If you don’t plan to rinse canned beans, such as if you’re including the canning fluid in chili, stew or soup, it’s especially wise to buy reduced-sodium beans. Canned beans labeled ‘reduced sodium’ have at least 25% less sodium per serving than the regular version.”
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