Carbohydrates
What are Carbohydrates?
Carbohydrates are found in a wide
array of both healthy and unhealthy foods-bread, beans, milk, popcorn,
potatoes, cookies, spaghetti, soft drinks, corn, and cherry pie. They also come
in a variety of forms. The most common and abundant forms are sugars, fibers,
and starches.
They are called carbohydrates because,
at the chemical level, they contain carbon, hydrogen and oxygen. Foods high in
carbohydrates are an important part of a healthy diet. Carbohydrates provide
the body with glucose, which is converted to energy used to support bodily
functions and physical activity. But carbohydrate quality is important; some
types of carbohydrate-rich foods are better than others:
- The healthiest sources of carbohydrates-unprocessed or minimally processed whole grains, vegetables, fruits and beans-promote good health by delivering vitamins, minerals, fiber, and a host of important phytonutrients.
- Unhealthier sources of carbohydrates include white bread, pastries, sodas, and other highly processed or refined foods. These items contain easily digested carbohydrates that may contribute to weight gain, interfere with weight loss, and promote diabetes and heart disease.
Function of carbohydrates
Carbohydrates provide fuel for the
central nervous system and energy for working muscles. They also prevent
protein from being used as an energy source and enable fat metabolism.
All carbohydrates we consume are
digested into monosaccharides or simple sugars before they’re absorbed by the
body, regardless of whether the food source is a simple sugar cube or a
high-fiber, low glycemic index bowl of oatmeal. It’s just that the “healthier carbohydrates”
are digested and absorbed much slower while the “non-healthy” carbohydrates are
digested very quickly.
Once broken down and absorbed, these
monosaccharides/sugars go to the liver to fill energy stores. After that, they
enter the bloodstream and venture out to the other cells of the body. This is
when insulin is released to handle this “sugar load” on the body. Carbohydrates
are primarily a source of immediate energy for all of your body’s cells.
Carbohydrates also cause a release of
insulin. A larger insulin response can be beneficial at certain times (like
after an intense workout) and not so beneficial at certain times (like before
bed).
Simple vs. complex carbohydrates
Carbohydrates are classified as simple
or complex. The difference between the two forms is the chemical structure and
how quickly the sugar is absorbed and digested. Simple carbohydrates are
digested and absorbed more quickly and easily than complex carbohydrates.
Simple carbohydrates contain just one
or two sugars, such as fructose (found in fruits) and galactose (found in milk
products). These single sugars are called monosaccharides. Carbohydrates with
two sugars - such as sucrose (table sugar), lactose (from dairy) and maltose
(found in beer and some vegetables) are called disaccharides.
Simple carbohydrates are also in
candy, soda and syrups. However, these foods are made with processed and
refined sugars and do not have vitamins, minerals or fiber. They are called
"empty calories" and can lead to weight gain.
Complex carbohydrates
(polysaccharides) have three or more sugars. They are often referred to as
starchy foods and include beans, peas, lentils, peanuts, potatoes, corn,
parsnips, whole-grain breads and cereals.
Simple carbohydrates cause bursts of
energy much more quickly than complex carbohydrates because of the quicker rate
at which they are digested and absorbed. Simple carbohydrates can lead to
spikes in blood sugar levels, while complex carbohydrates provide more
sustained energy.
Studies have shown that replacing
saturated fats with simple carbohydrates, such as those in many processed
foods, is associated with an increased risk of heart disease and type 2
diabetes.
Sugars, starches and fibers
Sugars
Carbohydrates break down into smaller
units of sugar, such as glucose and fructose. The small intestine absorbs these
smaller units, which then enter the bloodstream and travel to the liver. The
liver converts all of these sugars into glucose, which is carried through the
bloodstream - accompanied by insulin and converted into energy for basic body
functioning and physical activity.
If the glucose is not immediately
needed for energy, the body can store up to 2,000 calories of it in the liver
and skeletal muscles in the form of glycogen. Once glycogen stores are full, carbohydrates
are stored as fat. If you have insufficient carbohydrate intake or stores, the
body will consume protein for fuel. This is problematic because the body needs
protein to make muscles. Using protein instead of carbohydrates for fuel also
puts stress on the kidneys, leading to the passage of painful byproducts in the
urine.
Fiber
Fibers promote healthy bowel movements
and decrease the risk of chronic diseases such as coronary heart disease and
diabetes. However, unlike sugars and starches, fibers are not absorbed in the
small intestine and are not converted to glucose. Instead, they pass into the
large intestine relatively intact, where they are converted to hydrogen and
carbon dioxide and fatty acids. Its recommended to consume 14 grams of fiber
for every 1,000 calories. Sources of fiber include fruits, grains and
vegetables, especially legumes.
Starches
Carbohydrates are also found naturally
in some forms of dairy and both starchy and nonstarchy vegetables. For example,
nonstarchy vegetables like lettuces, kale, green beans, celery, carrots and
broccoli all contain carbohydrates. Starchy vegetables like potatoes and corn
also contain carbohydrates, but in larger amounts. Nonstarchy vegetables
generally contain only about 5 grams of carbohydrates per cup of raw
vegetables, and most of those carbohydrates come from fiber.
Good carbohydrates vs. bad carbohydrates
Carbohydrates are found in foods you
know are good for you (vegetables) and ones you know are not (candy). This has
led to the idea that some carbohydrates are "good" and some are
"bad." Carbohydrates commonly considered bad include sodas, highly
processed foods, white rice, white bread and other white-flour foods. These are
foods with simple carbohydrates.
Carbohydrates usually considered good
are complex carbohydrates, such as whole grains, fruits, vegetables, beans and
legumes. These are not only processed more slowly, but they also contain a planty
of other nutrients.
Good carbohydrates are:
- Low or moderate in calories
- High in nutrients
- Devoid of refined sugars and refined grains
- High in naturally occurring fiber
- Low in sodium
- Low in saturated fat
- Very low in cholesterol and trans fats
- High in calories
- Full of refined sugars
- High in refined grains
- Low in many nutrients
- Low in fiber
- High in sodium
- High in saturated fat
- High in cholesterol and trans fats
Glycemic index
The glycemic index is one of the most
important aspects to consider when deciding what carbohydrates to incorporate
into your diet. Every food is given a rating. This rating is related to its
effect on spiking your blood sugar.
This is important because when your
blood sugar spikes, your pancreas secretes the hormone insulin to shuttle this
glucose from your blood into your body cells. The glycemic index is based on a
base value of glucose. Glucose, which can be almost immediately absorbed into
your blood, is given a value of 100. Values of other foods are based on their
comparison to glucose.
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