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Carbohydrates
What are Carbohydrates?
Carbohydrates come from a wide
array of foods - bread, beans, milk, popcorn, potatoes, cookies, spaghetti,
corn, and cherry pie. They also come in a variety of forms. The most common
and abundant are sugars, fibers, and starches. The basic building block of
a carbohydrate is a sugar molecule, a simple union of carbon, hydrogen, and
oxygen. Starches and fibers are essentially chains of sugar molecules. Some
contains hundreds of sugars. Some chains are straight, others branch wildly.
Carbohydrates were once grouped into two main categories. Simple carbohydrates
included sugars such as fruit sugar (fructose), corn or grape sugar (dextrose
or glucose), and table sugar (sucrose). Complex carbohydrates included everything
made of three or more linked sugars. Simple sugars were considered bad and
complex carbohydrates good. The picture is much more complicated than that.
The digestive system handles all carbohydrates in much the same way - it
breaks them down (or tries to break them down) into single sugar molecules,
since only these are small enough to cross into the bloodstream. It also converts
most digestible carbohydrates into glucose (also known as blood sugar), because
cells are designed to use this as a universal energy source.
Fiber is an exception. It is put together in such a way that it can't be
broken down into sugar molecules, and so passes through the body undigested.
You will
hear discussion of the glycemic index. The concept and application of it
is very complex and difficult. This is the simple version
Low Glycemic
Load
High-fiber fruits and vegetables (not including
potatoes) / Bran cereals / Many legumes, including chick peas, kidney beans,
black beans, lentils, pinto beans / Scotch oats, steel cut oats
These are the best Carbohydrate choices for
most people and especially diabetics. They are slower to be observed therefore
causing less insulin spiking.
Medium
Glycemic Load
Pearled barley / Brown rice / Oatmeal: 1 cup
cooked / Bulgur: 3/4 cup cooked / Rice cakes: 3 cakes
Whole grain (not whole wheat) breads: 1 slice / Whole grain pasta:
1 ¼ cup cooked / No-sugar added fruit juices: 8 oz
Baked potato / French fries
/ Refined cereal products / Sugar-sweetened beverages / Jelly beans / Candy
bars / Couscous / Cranberry juice cocktail / White basmati rice / White flour
/ sugar / White flour pasta / White bread
These are the foods to avoid as much as
possible for diabetics and people trying to loose weight, they are good for
quick energy for athletes.
Carbohydrates and the Glycemic Index
A new system for classifying carbohydrates calls into question many of the
old assumptions about how carbohydrates affect health. This new system, known
as the glycemic index, measures how fast and how far blood sugar rises after
you eat a food that contains carbohydrates. (1).
White bread, for example, is converted almost
immediately to blood sugar, causing it to spike rapidly. It's classified
as having a high glycemic index. Brown rice, in contrast, is digested more
slowly, causing a lower and more gentle change in blood sugar. It has a low
glycemic index.
Diets filled with high-glycemic-index foods,
which cause quick and strong increases in blood sugar levels, have been linked
to an increased risk for both diabetes (3, 4) and heart disease. (5, 6) On
the other hand, lower GI foods have been shown to help control type 2 diabetes.
(7)
One of the most important factors that determine
a food's glycemic index is how highly processed its carbohydrates are. Processing
carbohydrates removes the fiber outer bran and the vitamin and mineral
rich inner germ, leaving mostly the starchy endosperm. (See Fiber for more
information on whole grain foods.)
Going with the (Whole)
Grain
We've come a long way from the days when one of the knee-jerk answers
to the question "What should I eat?" was "Get a lot of carbohydrates." We
now know that the staple of most diets, carbohydrates, aren't all good or
all bad. Some kinds promote health while others, when eaten often and in
large quantities, actually increase the risk for diabetes and coronary heart
disease.
The resurgence of the Atkins diet and the rise of the South Beach
and other low carbohydrate diets have put the focus on the carbohydrates.
While it may be true that easily digested carbohydrates from white bread,
white rice, pastries, and other highly processed foods may contribute to
weight gain and interfere with weight loss, that doesn't mean all carbohydrates
are suspect. Regardless of what you've read or heard about the dangers of
carbohydrates, they are an important part of a healthy diet. Carbohydrates
provide the body with the fuel it needs for physical activity and for proper
organ function. The best sources of carbohydrates - fruits, vegetables, and
whole grains - deliver essential vitamins and minerals, fiber, and a host
of important phytonutrients. Carbohydrate foods are the largest group in
the USDA food pyramid. The higher a food is on the pyramid the less
you should eat of it. Complex carbohydrates are at the base of the pyramid. Other factors that influence how quickly
the carbohydrates in food raise blood sugar include:
Fiber.
Fiber shields the starchy carbohydrates in food from immediate and rapid
attack by digestive enzymes. This slows the release of sugar molecules into
the bloodstream.
Ripeness.
Ripe fruits and vegetables tend to have more sugar than unripe ones, and
so tend to have a higher glycemic index.
Type of starch.
Starch comes in many different configurations. Some are easier to break
into sugar molecules than others. The starch in potatoes, for example, is
digested and absorbed into the bloodstream relatively quickly.
Fat content and
acid content. The more fat or acid a food contains, the slower
its carbohydrates are converted to sugar and absorbed into the bloodstream.
Physical form.
Finely ground grain is more rapidly digested, and so has a higher glycemic
index, than more coarsely ground grain.
All these elements
lead to sometimes counterintuitive results. Some foods that contain complex
carbohydrates, such as potatoes, quickly raise blood sugar levels, while
some foods that contain simple carbohydrates, such as whole fruit, raise
blood sugar levels more slowly.
Although the fine points of the glycemic
index and glycemic load may seem complicated, the basic message is simple:
Whenever possible, replace highly processed grains, cereals, and sugars with
minimally processed whole grain products. And only eat potatoes - once on
the list of preferred complex carbohydrates - occasionally because of their
high glycemic index and glycemic load.
When Sugar Management Goes Awry
Digestible carbohydrates are broken down
in the intestine into their simplest form, sugar, which then enters the blood.
As blood sugar levels rise, special cells in the pancreas churn out more
and more insulin, a hormone that signals cells to absorb blood sugar for
energy or storage. As cells sponge up blood sugar, its levels in the bloodstream
fall back to a preset minimum. So do insulin levels.
In some people, this cycle doesn't work
properly. People with type 1 diabetes (once called insulin dependent or juvenile
diabetes) don't make enough insulin, so their cells can't absorb sugar. People
with type 2 diabetes (once called non insulin dependent or adult onset diabetes)
usually start out with a different problem - their cells don't respond well
to insulin's "open up for sugar" signal. This condition, known as insulin
resistance, causes both blood sugar and insulin levels to stay high long
after eating. Over time, the heavy demands made on the insulin making cells
wears them out, and insulin production slows, then stops.
Insulin resistance isn't just a blood sugar
problem. It has also been linked with a variety of other problems, including
high blood pressure, high levels of triglycerides, low HDL (good) cholesterol,
heart disease, and possibly some cancers. (10)
Genes, a sedentary lifestyle, being overweight,
and eating a diet filled with foods that cause big spikes in blood sugar
can all promote insulin resistance. Data from the Insulin Resistance Atherosclerosis
Study suggests that cutting back on refined grains and eating more whole
grains in their place can improve insulin sensitivity. (11)
No Carbohydrates?
Some popular diets, particularly the Atkins diet, treat carbohydrates as
if they are evil, the root of all body fat and excess weight. While there
is some evidence that a low carbohydrate diet may help people lose weight
more quickly than a low fat diet (12, 13), no one knows the long-term effects
of eating little or no carbohydrates. Equally worrisome is the inclusion
of unhealthy fats in some of these diets.
If you want to go the lower carb route,
try to include some fruits, vegetables, and whole grain carbohydrates every
day. They contain a host of vitamins, minerals, and other phytonutrients
that are essential for good health and that you can't get out of a supplement
bottle.
Adding Good Carbohydrates
Carbohydrates from fruits, vegetables, and grains should give you
the bulk of your calories. For optimal health, get your grains intact from
foods such as whole grain bread, brown rice, whole grain pasta, and other
possibly unfamiliar grains like quinoa, whole oats, and bulgur. Not only
will these foods help protect you against a range of chronic diseases, they
can also please your palate and your eyes.
Until recently, you could only get whole
grain products in organic or non-traditional stores. Today they are popping
up in more and more mainstream grocery stores. Here are some suggestions
for adding more whole grains to your diet:
Start the day with whole grains. If you're
partial to hot cereals, try old fashioned or steel-cut oats. If you're a
cold cereal person, look for one that lists whole wheat, oats, barley, or
other grain first on the ingredient list.
Use whole grain breads for lunch or snacks.
Check the label to make sure that whole wheat or other whole grain is the
first ingredient listed.
Bag the potatoes. Instead, try brown
rice or even "newer" grains like bulgur, wheat berries, millet, or hulled
barley with your dinner.
Pick up some whole wheat pasta. If the
whole grain products are too chewy for you, look for those that are made
with half whole wheat flour and half white flour.
References
1. Jenkins DJ, Kendall CW, Augustin LS, et al. Glycemic index: overview of
implications in health and disease. Am J Clin Nutr 2002; 76:266S-73S.
2. Foster-Powell K, Holt SH, Brand-Miller JC. International table of glycemic
index and glycemic load values: 2002. Am J Clin Nutr 2002; 76:5-56.
3. Schulze MB, Liu S, Rimm EB, Manson JE, Willett WC, Hu FB. Glycemic index,
glycemic load, and dietary fiber intake and incidence of type 2 diabetes
in younger and middle-aged women. Am J Clin Nutr 2004; 80:348-56.
4. Willett W, Manson J, Liu S. Glycemic index, glycemic load, and risk of
type 2 diabetes. Am J Clin Nutr 2002; 76:274S-80S.
5. Liu S, Willett WC. Dietary glycemic load and atherothrombotic risk. Curr
Atheroscler Rep 2002; 4:454-61.
6. Pereira MA, Liu S. Types of carbohydrates and risk of cardiovascular disease.
J Womens Health (Larchmt) 2003; 12:115-22.
7. Brand-Miller J, Hayne S, Petocz P, Colagiuri S. Low-glycemic index diets
in the management of diabetes: a meta-analysis of randomized controlled trials.
Diabetes Care 2003; 26:2261-7.
8. Liu, S. Insulin resistance, hyperglycemia and risk of major chronic diseases--a
dietary perspective. Proc Nutrit Soc Austral 1998; 22:140.
9. Liu, S, Willett, WC, Stampfer, MJ, et al. A prospective study of dietary
glycemic load, carbohydrate intake, and risk of coronary heart disease in
U.S. women. Am J Clin Nutr 2000; 71:1455-61.
11. Liese AD, Roach AK, Sparks KC, Marquart L, D'Agostino RB, Jr., Mayer-Davis
EJ. Whole-grain intake and insulin sensitivity: the Insulin Resistance Atherosclerosis
Study. Am J Clin Nutr 2003; 78:965-71.
12. Foster GD, Wyatt HR, Hill JO, et al. A randomized trial of a low-carbohydrate
diet for obesity. N Engl J Med 2003; 348:2082-90.
13. Samaha FF, Iqbal N, Seshadri P, et al. A low-carbohydrate as compared
with a low-fat diet in severe obesity. N Engl J Med 2003; 348:2074-81.
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Disclaimer
The information found in this site is not intended to replace the knowledge and professional expertise of your doctor, registered dietician or other licensed medical professional. Consult your physician before doing any changes in your routine based on anything you read in these pages. The information on this site is the best information currently available to the site author and is believed to be reliable. All information is from the center for Disease Control, National Institute of Health, USDA, FDA, ADA, Harvard School of Public Medicine and a host of other unimpeachable sources. If any mistakes are found or if any information is disputed please email
Carbohydrates come from a wide
array of foods - bread, beans, milk, popcorn, potatoes, cookies, spaghetti,
corn, and cherry pie. They also come in a variety of forms. The most common
and abundant are sugars, fibers, and starches. The basic building block of
a carbohydrate is a sugar molecule, a simple union of carbon, hydrogen, and
oxygen. Starches and fibers are essentially chains of sugar molecules. Some
contains hundreds of sugars. Some chains are straight, others branch wildly.
We've come a long way from the days when one of the knee-jerk answers
to the question "What should I eat?" was "Get a lot of carbohydrates." We
now know that the staple of most diets, carbohydrates, aren't all good or
all bad. Some kinds promote health while others, when eaten often and in
large quantities, actually increase the risk for diabetes and coronary heart
disease.
Carbohydrates from fruits, vegetables, and grains should give you
the bulk of your calories. For optimal health, get your grains intact from
foods such as whole grain bread, brown rice, whole grain pasta, and other
possibly unfamiliar grains like quinoa, whole oats, and bulgur. Not only
will these foods help protect you against a range of chronic diseases, they
can also please your palate and your eyes.