Thursday, February 19, 2009

Great Combinations - Nutrients that are Better Together!

Some health-boosting nutrients work together with ease, while others are detrimental to one another. For example, did you know that if you add vitamin C-rich orange slices to a spinach salad, you'll absorb more iron than if you top the leafy greens with calcium-rich feta cheese? Don't worry: Learning which foods complement one another is not as difficult as it sounds. Remembering five basic pairings will go a long way toward maximizing your uptake of key nutrients from the foods you eat every day.

GOOD COMBO
Iron + vitamin C

Daily requirements: 10-20 mg iron; 1,000 mg vitamin C

No matter which foods you pair with meat, you absorb between 15 percent and 35 percent of the iron in meat (called heme iron). But if you're a vegetarian or eat primarily legumes and leafy greens, the bulk of your dietary iron is nonheme, which has an absorption rate of only 2 percent to 20 percent. Over time, inadequate absorption can lead to iron-deficiency anemia, a condition in which blood doesn't have enough healthy red blood cells to carry oxygen to tissues. Women are at particular risk for anemia; one in five women and half of all pregnant women are iron deficient.

To maximize your absorption of nonheme iron, add vitamin C-rich foods to your meal. Vitamin C (also called ascorbic acid) helps increase iron uptake by converting it into a more absorbable form or by preventing iron from binding to other elements during digestion, which renders nonheme iron unabsorbable.

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GOOD COMBO
Beta-carotene + fat

Daily requirement: 3-6 mg beta-carotene (equivalent to 833-1,667 IU vitamin A)

Certain healthy compounds — particularly heart-protective and cancer-fighting beta-carotene and other carotenoids like lycopene and lutein — in fruits and vegetables are fat soluble. That means a bit of healthy fat needs to be around in the digestive tract to help the body absorb the nutrients. “Adding fats to those foods allows for better absorption and bioavailability,” says Paula Mendelsohn, RD, CCN, a functional medicine nutritionist in Boca Raton, Florida. Recent research backs up this claim: Adding avocado to salsas and topping salads with full-fat dressing boosts carotenoid absorption compared with avocado-free salsa and fat-free or reduced-fat salad dressing.

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BAD COMBO
Calcium + iron

Daily requirements: 10-20 mg iron; 1,000 mg calcium

“When both calcium and iron are present at the same time or in similar concentrations, they compete to be picked up, transported, and absorbed,” says Mendelsohn. In an effort to maximize supply of these critical nutrients, people often load up on them and pair them together. Take what seem like natural fits: fortified cereal and milk, yogurt and granola, goat cheese and spinach salad, or a sandwich with deli meat and cheese. The iron-rich cereal, leafy greens, and meat battle the calcium-rich dairy for the body's attention. “But it becomes an issue only if the person is eating whole-grain cereal solely for its iron content and not for the fiber and other nutrients it contains,” Mendelsohn explains.

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BAD COMBO
Iron + tea polyphenols

Daily requirement: 10-20 mg iron

New research shows that polyphenols in green tea block iron absorption by binding with the mineral to form a dense complex that can't be transported across intestinal cell membranes into the blood. According to Okhee Han, PhD, assistant professor at Pennsylvania State University and key author of the 2008 study, black tea also thwarts iron absorption: The high levels of tannic acid form an insoluble bond with iron in the gut, making iron indigestible. White tea has not yet been studied for its effects on iron.

And coffee drinkers aren't off the hook either: “Coffee also contains similar compounds that can prevent iron absorption,” says Robert Rountree, MD, Delicious Living's medical editor and coauthor of The New Breastfeeding Diet Plan (McGraw-Hill, 2007). “Coffee and tea consumption are major causes of iron-deficiency anemia in cultures around the world, especially in pregnant women,” he says. It's worth noting that these drinks mainly affect nonheme iron synthesis; iron in meat may be able to overcome the problem. It may be possible to avoid the polyphenol-iron conflict if you drink tea at a different time of day than when you eat iron-rich foods, says Han.

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BAD COMBO
Zinc + phytates

Daily requirement: 8-15 mg zinc

Phytates, found mostly in whole grains, nuts, and beans and legumes, bind with zinc, forming an insoluble complex that decreases your body's ability to absorb the immunity-boosting and wound-healing mineral. Beyond its role in immune function and tissue repair, zinc helps maintain your sense of taste and smell and stimulates numerous biochemical processes in the body. “Phytates adversely affect the absorption and retention of many minerals in the body, including zinc, calcium, magnesium, and iron,” says Melissa Diane Smith, a nutritionist in Tucson, Arizona, and author of Going Against the Grain (McGraw-Hill, 2002).

To counteract this result, eat your whole grains and beans apart from your zinc-rich red meat, poultry, and oysters. The zinc in whole grains and beans competes with the phytates in those very same plant foods, but there's some evidence that cooking (think baking wheat bread) may destroy phytates and thus help improve zinc absorption.

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