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Good carb, bad carb

Confused about which carbohydrates you should be eating?

Welcome to the club.

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"It's the biggest lack-of-consensus issue in the U.S. diet today," said Dr. Dariush Mozaffarian, associate professor of epidemiology at Harvard School of Public Health. "We don't have a standard method for assessing their quality."

Carbohydrates, the most common of the three energy sources we get from food (the others are fat and protein), reside in the vast majority of our food, prominently in grains, vegetables, legumes and fruits. They are essential to good health — as long as you stick to the good sources and steer clear of the bad ones, which are linked to

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obesity
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and a host of chronic conditions, including

diabetes

and

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heart disease
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.

Most health experts agree that processed foods, sweetened beverages and refined grains such as white bread, pasta, flour and rice (which are stripped of their nutrients) are among the worst kinds of carbohydrate-rich foods you can eat.

Your digestive system breaks them down too easily, flooding the bloodstream with simple sugars (glucose), which in turn prompts a surge of the hormone

insulin

to carry the glucose into the body's cells, said Michael Roizen, chairman of the

Cleveland Clinic

Wellness Institute and co-founder of realage.com. Too much

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blood
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sugar and insulin for too long can be dangerous on several levels: more fat storage, less fat burning, malfunctioning proteins that eventually lead to organ damage, even

cancer

cell growth, Roizen said. Your brain also gets addicted to the high glucose levels, leaving you craving more.

What constitutes a good carb, however, can be trickier.

It's not as basic as "simple" versus "complex," as fruits contain simple sugars but are a highly desirable carb source.

Rather, four main factors determine the quality of a carb, Mozaffarian said:

dietary fiber

(the more the better); how fast it makes your blood sugar rise (aka glycemic index, the lower the better); whole-grain content (the more the better); and structure (if it's liquid, milled or pulverized, it's not as good).

So Cheerios, which are made of 100 percent whole grain oats, get a thumbs up for whole grain and fiber content, but the pulverized nature of the oats makes it inferior to intact whole grains, such as steel-cut oats, Mozaffarian said.

And pasta? It seems like the quintessential fattening carb, but in fact it has a lower glycemic index than rice or potatoes and is a "reasonable choice," he said.

Speaking of potatoes … the white ones have a high glycemic index, and studies have shown them to contribute to weight gain, so Mozaffarian banishes them to the "bad" list alongside Skittles. But other nutrition professionals, such as Stephanie Dunbar, director of nutrition and clinical affairs and the American Diabetes Association, gives potatoes the thumbs up because they have nutrients.

And then you have Jonathan Bailor, a health and fitness researcher who advises you source carbohydrates from citrus fruits, berries and a host of nonstarchy vegetables, such as spinach, and stay away from starches altogether — including whole grains. The best foods to eat, Bailor said, are those with greater water, fiber and protein content relative to their calories, so you get more bang for your buck.

"It's not that whole grains are evil; it's just absolutely not as good for us as nonstarchy fruits and vegetables," said Bailor, who recently published "The Smarter Science of Slim" (Aavia; $34.95), the result of a decade of reviewing more than 1,000 diet studies..

Reading the nutrition label can help guide people through the morass. Choose items with less sugar — Roizen says to aim for 4 grams or less — and more dietary fiber. And no, brown sugar and honey aren't metabolized any differently than the white stuff.But sugar doesn't tell the whole story, as refined starches with little sugar are still terrible for you.

As a general rule of thumb, Mozaffarian recommends that you look at the ratio of total carbohydrates in a serving to dietary fiber, as that captures both sugar and starch content. If the ratio is 10:1 or more, avoid it. If it's less than 5:1, it's very good.

If all the confusion makes you want to reach for a bowl of mac-and-cheese, rest assured that everyone can agree on this: Eating lots of nonstarchy vegetables does every body good.

Shopping list

Take this list shopping to help you weed out the bad carbs.

Bad carbs

Soft drinks

Sports drinks

Fruit drinks

Beer

French fries

White rice

White bread

Sugar-sweetened cereals

Bagels

Baguettes

Croissants

Potato chips

Pastries

Cookies

White crackers

Brownies

Cakes

Pies

Candy

Sugar

Brown sugar

Honey

Debatable

Corn

Popcorn

White potatoes

Pasta

100% fruit juice (limited quantities)

Good carbs

Spinach

Kale

Tomatoes

Mushrooms

Beets

Brussels sprouts

Broccoli

Onion

Squash

Artichoke

Berries

Oranges

Tangerines

Melons

Mangoes

Pears

Peaches

Low-fat Greek yogurt

Sweet potatoes

Peas

Black beans

Kidney beans

Lentils

Brown rice

Barley

Amaranth

Quinoa

Whole-grain bread

Whole-grain pasta

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