Nov. 14. 2014
Nutrition Articles
McKel Hill, MS, RDN, LDN

McKel Hill, MS, RDN, LDN

Dietitian, Founder

Learn the basics of this essential macronutrient.

Ah carbohydrates. All three macronutrients (protein, fat, and carbohydrates) get singled out and taken to extremes when it comes to our health and especially when talking about weight loss/fat loss, but carbohydrates are the pinnacle of all the hype. Let me first start off by saying, we can’t hate on one macronutrient or give one special treatment over the other- they’re all incredibly important and vital to living whole and well.

With that said, far too often you hear extremes of both cases, no-carb diets to high-carb diets, both of which have no middle ground, little flexibility, and limited longevity. Today, I want to revisit the philosophy and mission of this blog in the first place: to strip down and get back to basics with living whole and well- and how carbohydrates play a role. There will be several parts to this topic on carbohydrates- because well, there’s so much to say! It’s also part of “The Basics” category, where you’ll find all things basic to living whole and well here on Nutrition Stripped- this is great to check out if you’re new here!

What are carbohydrates?

Biologically speaking, carbohydrates are large molecules or macromolecules (hence why we call carbohydrates 1 of the 3 macronutrients), containing hydrogen, oxygen, and carbon atoms- carbohydrates are typically stated as a saccharide, which means “sugar”. Saccharides (a.k.a. carbohydrates or sugars) are divided into 4 groups/types including monosaccharide, disaccharide, oligosaccharide, and polysaccharide. For those of you who know latin, this is easy to make out what each type is. Mono- meaning containing 1, dia- meaning 2, oligo- meaning 3-9, and poly- meaning more up to or more than 10; these are referring to how many monosaccharides (simple sugars) are in each saccharide. In a nutshell, monosaccharides and disaccharides (think of fruit or simple sugars) are digested very quickly and oligosaccharide and polysaccharide digest slowly (think of higher fiber carbs). Have I lost you yet? Good!

Monosaccharides, the building blocks of creating dia-, oligo-, and polysaccharides are 1) glucose, 2) fructose, and 3) galactose. Just some of many examples of dia-, oligo- and polysaccharides:

  • glucose + fructose = sucrose (table sugar, a disaccharide)
  • galactose + glucose = lactose (milk sugar, a disaccharide)
  • starch, glycogen, amylose, inulin = examples of polysaccharides, starches, and fibers
  • fructooligosaccharide (FOS) = a oligosaccharide found in veggies and fruits


How are carbohydrates used in the body?

Carbohydrates are our bodies preferred use of energy, we like carbohydrates for a reason! Our brains, muscle tissue, cells, etc., all utilize carbohydrates in different ways, amounts, and ratios. Remember, each gram of carbohydrate is roughly 4 calories, i.e. unites of energy.

Your body on carbohydrates:

  • Brain = uses about 120g glucose per day and the preferred energy source is solely carbohydrates, using about 60% carbs at resting rate (i.e. when you’re just sitting around!). But remember the body can create glucose even when there is little present from food.
  • Muscle = uses not only carbohydrates as fuel, but also ketone bodies and fatty acids. Also, muscle has the unique capability to store excess carbohydrates and carbohydrates in general, called glycogen, up to 1200kcal. Muscle is always “ready” for action with this much energy stored (think of when you’re working out), when at rest your muscle prefers to burn or use fatty acids. Also, don’t just think skeletal muscle here, your heart is a muscle too.
  • Fat cells = excess carbohydrates (triglycerides) are stored in our fat cells (adipose tissue) for later use of energy in multiple ways, through conversion processes. This is the delicate balance of trying not to over consume carbohydrates that may potentially be stored in fat cells (if your goal is fat maintaining or loss).
  • Kidneys = kidneys have a huge job at hand, they create urine through many processes to help our bodies get rid of what we don’t need and reabsorb what we can use again or are in need of (think minerals, sodium, glucose, etc.)
  • Liver = the grand-daddy of metabolic organs! The liver uses glucose for energy to process and metabolize everything we put into our bodies, from glucose, amino acids, and fatty acids.

Digestion of carbohydrates

Carbohydrate digestion starts in the mouth as all digestion does, but especially with the digestive enzyme amylase helping to specifically breakdown carbohydrates, then goes into the stomach where stomach acids meets with the chyme (mixed food) and further breaks down before entering into the small intestine where again digestive enzymes are released and breaks down into monosaccharides to be absorbed in the small intestine. Ultimately, glucose goes into the liver where the liver distributes the energy- whether storing it into fat cells or utilizing it for immediate energy in other cells of the body. All other carbohydrates not absorbed in the small intestine reach the large intestine and colon, these are fibrous carbohydrates and are partially digested by bacteria. Fiber can’t be digested or absorbed like other carbohydrates, but contributes to the bulk of our stools- an important part of our digestive health! Also, follow along with this cool image.

How do we use carbohydrates and what’s with all those g-terms?

Insulin, glycogen, gluconeogenesis- what does it all mean?! I’m touching on just the bare basics here, there is so much more science behind this!

  • Insulin: an anabolic (building) hormone produced in the pancreas (from beta-cells), which regulates the metabolism of glucose (a.k.a. sugar/carbohydrates) and fats and promotes absorption of glucose from our blood into muscle and fat tissues and promotes fat to be stored versus used for energy. In a nutshell, insulin works to decrease blood sugar when it’s high or in response to food/carbohydrates so that energy can be used or stored for later.
  • Glucagon: Opposite of insulin, it’s a catabolic (breaking down) hormone produced in the pancreas (from alpha-cells), to raise/increase the concentration of glucose in the blood. It does this by signaling the liver to release glycogen (stored carbohydrates) into glucose. In a nutshell, glucagon works to increase blood sugar when it’s low, examples of when this happens: hypoglycemia, low carb dieting, starvation, or adrenaline. 
  • Glycogen: the storage form of carbohydrates, most of which are stored in the liver and muscle.
  • Gluconeogenesis: making glucose from alternative sources like from amino acids and fatty acids (i.e. proteins and fats).
  • Glycogenolysis: breakdown of glycogen in muscle and liver tissue and regulated by insulin and glucagon.
  • Glycogenesis: synthesis (i.e. making) of glycogen, also activated by insulin with high glucose in the blood (i.e. high carbohydrate meals)

How many carbohydrates do we need?

Technically, none. The human body can survive off of other energy sources like fatty acids and amino acids, BUT it does prefer carbohydrates- and I’d recommend that too! How much you need depends on your genetics, age, gender, lifestyle, activity level, injuries, disease states, etc. ALL play a role in how many carbohydrates your body needs to fuel. In part II I’ll talk more on this with carbohydrate centered diets, in the meantime set up a one on one with me to figure out your intake with your body goals. A silly analogy but true, there’s a cozy middle ground for carbohydrate intake, just like Goldilocks you don’t too much or too little- just right!

More resources for your reading pleasure on all things carbohydrates: Krause Nutrition textbooks, Basic Medical Biochemistry, Nutrition Therapy and Pathophysiology (newest edition will contain some of my photography- cool beans!), and Advanced Nutrition and Human Metabolism. Phew, that was a long one! Well I hope after reading this you have a better understanding of what carbohydrates are and what they do for us. Stay tuned for part 2 where I talk about my favorite sources of carbohydrates, how to use them in meals, portions, and timing carbohydrates to work for your goals! What else would YOU like to learn about carbohydrates? Let me know so I can get to writing!

xx McKel

p.s. I have the launch of the Nutrition Stripped Supper Clubs “Fall Supper” this Saturday that I’m beyond excited for! Can’t wait to show you all pictures over the weekend next week- meanwhile be sure to keep up with me on instagram!