Macronutrients: Part 2 – Carbohydrates
By Chris Zinn
Carbs have gotten kind of a bad rap over the years, haven’t they? People say all sorts of nasty things about them, claiming they're fattening, that they cause inflammation, and they’ve even been blamed for causing cancer!
The truth is, they aren't nearly as dangerous as they're made out to be, and I'm going to give you a full run-down on what carbs are REALLY all about.
What are carbohydrates?
Carbohydrates are macronutrients made up of long chains of smaller units called saccharides, or sugars (from the Latin /Saccharum/, or sugar).
Simple carbohydrate molecules (aka, simple sugars) have a basic ring structure of carbons and hydrogens.
One ring is called a monosaccharide (mono = one).
Two rings joined is a disaccharide (di = two).
A few rings joined are called oligosaccharides (oligo = few).
As carbohydrates link together in more intricate structures (hence the term, "complex carbohydrates"), they become structures knows as glycogen, starches, and various types of soluble and insoluble fibers.
We often call these complex forms of carbohydrates polysaccharides (poly = many).
Unlike proteins, carbohydrates don't contain nitrogen. This allows them to be metabolized more easily in processes that transfer energy within our bodies.
The chemical description of carbohydrates is Cn(H2O)n or, in English, one carbon for one water, giving carbohydrates their name (carbon + hydrate [water molecule] = carbohydrate!).
The ratio of water to carbon has to be 1:1 for a molecule to be a carbohydrate.
Because of carbohydrates' water-binding properties, we store about 3-4 grams of water per gram of stored carbohydrate in our bodies. Consequently, if we cut out carbohydrates from our diet, we'll quickly lose body water. This is why the start of a low carbohydrate diet sheds so much "weight" quickly; it's really just water weight.
Now, there are three major classes of carbohydrates. These classes progress from simple to complex.
Polysaccharides (broken down further into three sub-types)
Starch & dextrins
Like the amino acids that build proteins, it may be helpful to imagine monosaccharides as building blocks that can fit together in different ways to form other carbohydrates.
However, unlike amino acids, which must be used as specific building blocks for proteins (as dictated by DNA), monosaccharides can, in most cases, be used or processed interchangeably.
Polysaccharides are used for:
· energy storage (such as starch in plant cells or glycogen in animal cells),
· structure (such as cellulose in plants, or chitin that helps make up the exoskeletons of insects and crustaceans such as shrimp or lobster),
· mucus/joining fluid (mucopolysaccharides/ glycosaminoglycans), chondroitin, lubricin, hyaluronate (hyaluronic acid), heparin, dermatan, and keratin found in connective tissue, skin, synovial fluid, and eyes.
Plant cells have a wall that animal cells don't. This gives plants their structure and rigidity. The cell wall is mostly made of indigestible polysaccharides like cellulose (a structural plant fiber), pectin (more fiber), hemicellulose (yet more fiber), and a little protein. Cellulose is also made up of glucose units, but it has a long, straight structure with no coiling or branching.
Plants produce glucose via photosynthesis, using the sun’s energy, and store excess glucose as starch. The starch is contained within the plant's cells, organized into ball-like granules ranging from 1 to 110 μm across.
There are two forms of starch: amylose, and amylopectin. These two types of starch differ significantly in their three-dimensional structures:
Amylose is a single helical coil — think of it as a spring.
Amylopectin has helical coils that branch off from each other, with about 20 glucose molecules per branch. This increased branching for amylopectin means it's easier for enzymes to quickly get to it and break it down.
Different amylose and amylopectin arrangements can affect the shape of the starch granules within a cell. If you cut a granule in half crosswise, you'll see growth rings that are much like that of a tree trunk.
Starch digestion and absorption
Like protein, carbohydrates have a 3D structure, which also affects how we digest and absorb them. How much or how well we digest and absorb various carbohydrates depends on:
Chemical makeup: Which types of monosaccharides, how they're linked, the molecule size, etc.
Starch source: For instance, beans, grains, starchy vegetables, etc.
Food processing: Is the starchy food raw or cooked? Which cooking method? For instance, we can't digest the starch in many foods (such as potatoes) when raw. However, cooking (especially in moist heat) causes the plant cells to swell, explode, and become viscous, making the starch more digestible.
Meal factors: What other nutrients are in the meal, such as protein, fat, other carbohydrates, etc.
Gastrointestinal handling: How much and how quickly our bodies digest and absorb the starch, with the small intestine handling glycemic (glucose- yielding) carbohydrates and the large intestine handling non-glycemic carbohydrates such as fiber.
If you or someone you know have a lactose intolerance, it’s because they don’t have the enzyme that is responsible for breaking down the sugar. This causes bloating in the gut as it draws in water.
The glycemic index (GI)
You may be familiar with the glycemic index (GI), which is a measure of how quickly and significantly a given food can raise our blood sugar.
The GI tells us how much blood sugar goes up when we consume 50 g of usable carbohydrate from a particular food. It's a relative measure, determined against a specific reference food — 50 g of carbohydrate from pure glucose, given a GI value of 100. Each food's GI score is then calculated relative to this value of 100.
The less processed and higher-fiber a food is, the more complex its carbohydrate molecules usually are. Because of this, those foods will usually take longer to digest and have a lower GI.
If you love to wake up and have a big bowl of Reese's Puffs, you're consuming a very high GI food. Lower glycemic foods include legumes, whole grains, and vegetables.
When blood glucose goes up quickly, insulin usually responds quickly. The amount of insulin released usually matches the amount of glucose present.
This leads to a common myth: all of your carbohydrates should come from low GI index foods.
While it is an impressive measure of the physiological response to carbohydrates in the diet, the GI doesn't tell the whole story.
This is primarily because you don't usually eat one food by itself. How often do you sit down at the dinner table and think, "Mmmmm, time to eat some grain!".
Probably not too often would be my guess.
Glycemic load (GL)
Researchers often use the glycemic load (GL) as another, more realistic measure. The glycemic load of a food is based on the glycemic index multiplied by the food's serving size.
While this gives a better picture of how fast or significantly blood sugar may go up after a meal, GL still has some of the same problems as GI. It also doesn't take into account the other elements the food may have to offer (fiber, water, phytochemicals, macronutrients, etc.).
Insulin index (II)
While GI and glycemic load are somewhat useful in determining overall glucose
load, they aren't the best predictors of the insulin response to a meal, which is the
measure most closely correlated with health.
Another index, the insulin index (II), measures the amount of insulin the body produces in response to a particular food.
Interestingly, the II does not always match the GI. You may be surprised to know, in fact, that high-protein and high-fat foods can stimulate more significant insulin responses than you'd expect. In contrast, some high-GI foods produce surprisingly low insulin responses.
When people with underlying insulin resistance eat moderate and high-GI foods, their bodies produce more insulin than a healthy person's.
Why are carbohydrates important?
The main job of carbohydrates is to provide energy. They also do other things throughout the body, such as create various structures and substances.
Physiological requirements for carbohydrate
The brain is the most energy-demanding organ in our body, consuming about 20% of our total resting energy expenditure. The daily Recommended Dietary Allowance (RDA) for carbohydrates to meet the brain's energy needs is about 125-130 grams (500-520 calories) per day for adults and children.
The difference between carbohydrates and protein and fats is that you don't need to consume them to survive. There are no essential carbohydrates. However, that does not mean you don't need them at all. If we don't consume carbohydrates in our diet, our body will make them for you from other macronutrients.
If you manufactured 125-130 grams of glucose in the absence of dietary carbohydrate, about 40% of that glucose would come from fat, and about 60% would come from amino acids that can be turned into carbohydrates.
In some situations, such as particular medical conditions, people may choose low-carbohydrate and ketogenic diets. In these cases, clinicians suggest that those on a very low-carbohydrate diet eat 100 to 150 grams of protein daily to meet glucose production needs and maintain a positive nitrogen balance.
However, as with protein, adequate is not necessarily the same as optimal.
Some people, especially most athletes, will feel, perform, and recover better with relatively more carbohydrates in their diet.
In certain stress conditions, like trauma and sepsis, which require more energy for recovery and rebuilding, carbohydrates can dramatically improve outcomes.
Carbohydrate-containing foods, especially minimally processed whole foods, also contain a vast array of other nutrients (such as vitamins, minerals, and phytonutrients) along with water and fiber.
When building muscle, carbohydrates help enhance anabolic signaling (i.e., cellular communication that encourages nutrient storage, growth, and repair). For many people looking to add muscle and mass, carbohydrates may be necessary.
Are all refined grains bad?
To suggest that all refined grains are “bad” is going to leave a lot of people who consume them out in the cold for no good reason.
Refined grains may be beneficial for several reasons.
They’re easier to digest
This may be especially useful for athletes who need quick fuel. Refined grains can digest much more quickly since they have been partially processed already.
Whole grains would not be a good choice for an athlete that requires some quick energy as they will take much longer to digest and may make the athlete feel full or “heavy”.
Quicker to prepare when short on time
For someone who may not have a lot of time, a refined carbohydrate option, which is typically quick to prepare, may be the difference between quick oats in the morning or a fried fast-food sandwich for lunch when they can’t take the hunger anymore.
They may be part of the culture
Try telling an Italian to stop eating pasta. It’s not going to happen. And while pasta may not be the healthiest option, it is part of the culture for that person and it’s a big part of their life.
How miserable would family dinners be in an Italian household where one of the family members is on a diet and has to only eat cracked wheat while the others chow down on some Spaghetti aglio. I can hear heckling just thinking about it.
Debunking carbohydrate myths
So, what do you say to the people spouting these lies about carbohydrates and their evilness?
I'll give you a few examples of what some myths might be and explanations for them.
Carbs cause you to gain weight
Simply put, no, they don't.
However, there are a few reasons why people may think this.
Carbohydrates are the first macronutrient to be digested in the stomach after consumption. Meaning, eating the same volume of carbs compared to protein will not fill you up as much or keep you as full for as long.
It's also easier to overeat carbohydrates, which contributes to your overall caloric intake.
Without getting too deep into it, what causes you to gain weight is consuming more calories than you burn.
Low carb diets will help you lose weight
This kind of lines up with the previous myth.
Yes, the keto diet is trendy, and it may even work well for some people. The low carbohydrate diet itself isn't doing the magic; instead, it's the subsequent decrease in total calorie intake.
The keto diet is also notoriously hard to stick to in the long run. The most crucial factor in nutrition success is consistency, so this option usually isn't the right choice.
What is often a better alternative is to choose a positive eating strategy that you can stay consistent with.
Carbs cause inflammation
You may have heard people say that carbs are bad because they cause inflammation. Really what they meant to say was - excess sugar (which is technically a carb) may cause inflammation.
We know excess sugar intake is not good for you but let's not lump other carbohydrates into that group.
Conversely, some whole-grain carbohydrates are recommended for people with cardiovascular disease (CVD) because they may, in fact, actually decrease inflammation.
What carbohydrates should you eat?
Well as always, it depends.
If blood sugar is a concern, choose whole grains that are rich in protein and fiber and consume your refined grains with protein or fat.
If you have GI issues such as IBS, opt for mostly whole grains, but use lower fiber refined grains to soothe flair ups.
If you have celiac disease, chose naturally gluten-free options such as quinoa and buckwheat.
If you are trying to lose fat, consume whole grains most of the time to help you feel fuller longer
If you’re trying to gain muscle, allow some room for refined grains, they’ll help you add calories to your intake.
So, to wrap it up this week – no, carbs are not public enemy number 1!
However, you do need to be aware of the types of carbohydrates that are available, why you would or would not want to eat certain types of carbohydrates, and then make an informed choice.
Constantly reaching for low-nutrient, high glycemic, simple, sugary carbohydrates is not a good plan for anyone!
But demonizing all carbs is also doing a disservice to the people out there who will live a much happier, healthier life by eating carbohydrates. If it is going to help them feel better and stick to a healthier diet over the long-run, then eating carbs is worth it!
As with man other things in life, it pays to understand an issue from different perspectives and points of view before jumping to conclusions. You also must dig deep enough to have all the facts about what carbohydrates do and don’t do before deciding whether or not you’ll eat them, and especially before telling someone else whether or not they should eat them!
So, that’s enough about carbs…
What about fat?
In next week’s blog we’ll discuss everything about fat; why people confuse dietary fat with body fat, if fat deserves the hate it gets, and what it really does in the body.