This week’s post is from Roshini Raj, MD, a board certified gastroenterologist and internist, and one of Lose It!’s advisory board members!
What are carbs exactly?
Carbohydrates consist of starches, sugars, and fibers, and are found in grainy and starchy foods, like bread, pasta, potatoes, and fruit. Carbohydrates are either digestible (sugars, starches), or indigestible (fiber). Sugars and starches provide your body with energy in the form of calories and the fiber has four main roles; it:
- Keeps your digestive system healthy: a diet rich in insoluble-fiber can prevent constipation, keep the important bacteria in your gut happy, and reduce risk for colon cancer
- Improve Blood Sugar Control: fiber slows down the rate at which glucose (sugar) from food enters your blood stream. This means that your blood sugar doesn’t spike, your body doesn’t have to work as hard to manage a large dose of sugar, and you’re satiated for longer.
- Keep you full for longer — foods high in fiber fill us up without too many calories!
How are carbs digested?
Step 1: The Mouth
Unlike protein and fat, carbohydrate digestion actually begins right in the mouth! Your saliva includes a starch-digesting enzyme called “Amylase.” Have you ever noticed that when you chew starchy foods for a long time, they start to taste even sweeter? That’s because this amylase in your saliva is breaking the starches in the food down into simple sugars! From your mouth, the food & amylase go down your esophagus and on to the next step of digestion.
Step 2: The Stomach
Not too much happens to carbohydrates in the stomach. The amylase enzyme from your saliva is deactivated by the stomach acid, and the carbohydrates just sort of hang out there – no digestion occurs here.
Step 3: The Small Intestine
Now this is where things really get going! Remember the salivary amylase that started to break down starches and sugars in your mouth? Here in the stomach, pancreatic amylase (an enzyme send to your small intestine from your pancreas) picks up the starch-breaking-down job, along with the help of a few other enzymes. After all the sugars and starches are broken down into sugar molecules (remember, fiber isn’t digestible!), they absorbed through the walls of the small intestine, and make their way over to your blood stream, where they are first transported to the liver, where the different sugar molecules are all converted to glucose, and then released into the blood stream.
Step 4a: Blood Stream
Then, increased blood sugar levels trigger our pancreas to release insulin, which directs the blood sugar around your body, encouraging your cells to take in the glucose they need. This is how insulin lowers your blood sugar. If there is more glucose in your blood stream than your cells need, insulin will encourage your liver and muscles to store glucose as glycogen until your blood sugar is low again. If there’s still more glucose than your body can store, insulin will build fat molecules from the extra glucose and store it. Think of insulin as a traffic cop, directing glucose molecules around your body and helping them find a place to go.
While we’re on the topic, after insulin successfully lowers your blood glucose and you haven’t eaten in a while, your pancreas will produce glucagon, a hormone that tells your liver and muscles to give up that glucose it’s storing, thereby raising your blood sugar again!
Step 4b: The Large intestine
All right—back to the digestion. At this point all that’s really left of the food you ate is fiber, and things trapped within that fiber. Luckily, the bacteria that live in your large intestine really like fiber. They digest some of the soluble fiber here (which keeps them healthy and helps to reduce risk for colon cancer), and metabolize it into acids and gases (yes, this is why you fart!).
Step 5: The Rectum
Well we’ve made it to the end of the line now. That remaining fiber and other waste products escape from the digestive tract, and are excreted.
How many carbs should I be eating every day?
The USDA recommends that 45% to 65% of calories you eat come from carbohydrates, largely because the sugars and starches in carbohydrates provide fairly quick energy for you body in the form of calories. Different amounts of carbohydrates may be better for different people – this isn’t really a one-size-fits-all thing!
Something that IS a one size fits all thing, though, is the fiber recommendations. Women should aim for at least 25 grams of fiber a day, and men for 38 grams a day.
As you probably know, the recommendation for sugar is to keep intake low, but there isn’t a consistent recommendation. Some sources recommend that less than 6% of your daily calories come from sugar, and other recommend that less than 25% of calories come from sugar—two vastly different numbers!
The recommendations for carbs in general aren’t super specific, but if you focus on fiber you’ll be on track for very healthy carbohydrate digestion!
More about Dr. Raj:
Dr. Roshini Raj is a board certified gastroenterologist and internist. She is also a nationally known media personality; she is a Today Show contributor, the Good Day NY Medical Correspondent (Fox5) and the Medical Editor of Health magazine. She has also been quoted in The New York Times, The Wall Street Journal,Women’s Health and Fitness. Dr. Raj is the author of What the Yuck?! The Freaky & Fabulous Truth About Your Body. She also recently co-founded TULA (tulaforlife.com), a new probiotic skin care line.
Originally posted on Lose it!
