How do carbohydrates impact your health? - Richard J. Wood

 Which of these has 

the least carbohydrates? This roll of bread? This bowl of rice? Or this can of soda? 

It's a trick question. Although they may differ in fats,

vitamins, and other nutritional content, when it comes to carbs,

they're pretty much the same. So what exactly does that mean

for your diet? 

First of all, carbohydrate is 

the nutritional category for sugars and molecules that your body breaks down

to make sugars. Carbohydrates can be simple or complex

depending on their structure. This is a simple sugar,

or monosaccharide. 

Glucose, fructose, 

and galactose are all simple sugars. Link two of them together,

and you've got a disaccharide, lactose, maltose, or sucrose. Complex carbohydrates,

on the other hand, 

have three or more simple sugars

strung together. Complex carbohydrates with three

to ten linked sugars are oligosaccharides. Those with more than ten

are polysaccharides. During digestion, your body breaks down those

complex carbohydrates 

into their monosaccharide building blocks, which your cells can use for energy. So when you eat 

any carbohydrate-rich food, the sugar level in your blood,

normally about a teaspoon, goes up. 

But your digestive tract doesn't respond

to all carbohydrates the same. Consider starch and fiber, both polysaccharides, both derived from plants, both composed of hundreds to thousands

of monosaccharides joined together, but they're joined together differently, 

and that changes the effect 

they have on your body. In starches, which plants mostly store

for energy in roots and seeds, glucose molecules are joined together

by alpha linkages, most of which can be easily cleaved

by enzymes in your digestive tract. But in fiber, the bonds between

monosaccharide molecules are beta bonds, which your body can't break down. Fiber can also trap some starches,

preventing them from being cleaved, resulting in something called

resistant starch. So foods high in starch,

like crackers and white bread, are digested easily, quickly releasing a whole bunch of glucose

into your blood, exactly what would happen if you drank

something high in glucose, like soda. 

These foods have a high glycemic index, the amount that a particular food

raises the sugar level in your blood. Soda and white bread have a similar

glycemic index because they have a similar effect

on your blood sugar. 

But when you eat foods high in fiber,

like vegetables, fruits, and whole grains, those indigestible beta bonds slow 

the release of glucose into the blood. Those foods have a lower glycemic index, 

and foods like eggs, cheese, and meats

have the lowest glycemic index. When sugar moves from the digestive tract

to the blood stream, your body kicks into action to transfer it

into your tissues where it can be processed 

and used for energy. Insulin, a hormone 

synthesized in the pancreas, is one of the body's main tools

for sugar management. When you eat and your blood sugar rises, insulin is secreted into the blood. It prompts your muscle and fat cells

to let glucose in and jump starts the conversion

of sugar to energy. The degree to which a unit

of insulin lowers the blood sugar helps us understand something called

insulin sensitivity. The more a given unit of insulin

lowers blood sugar, the more sensitive you are to insulin. 

If insulin sensitivity goes down,

that's known as insulin resistance. The pancreas still sends out insulin, but cells, especially muscle cells,

are less and less responsive to it, so blood sugar fails to decrease, and blood insulin continues to rise. Chronically consuming 

a lot of carbohydrates may lead to insulin resistance, and many scientists believe

that insulin resistance leads to a serious condition

called metabolic syndrome. 

That involves a constellation of symptoms, including high blood sugar, increased waist circumference, and high blood pressure. It increases the risk 

of developing conditions, like cardiovascular disease and type II diabetes. 

And its prevalence is rapidly increasing

all over the world. As much as 32% of the population

in the U.S. has metabolic syndrome. So let's get back to your diet. Whether your food tastes sweet or not,

sugar is sugar, and too many carbs can be a problem. So maybe you'll want to take a pass on that pasta sushi roll pita burrito

donut burger sandwich. 

The things we eat and drink on a daily basis can impact our health in big ways. Too many carbohydrates, for instance, can lead to insulin resistance, which is a major contributor to cardiovascular disease and Type 2 Diabetes. But what are carbs, exactly? And what do they do to our bodies? Richard J. Wood explains.
Lesson by Richard J. Wood, animation by Qa'ed Mai.