Are Carbs Good or Bad for You?
Carbohydrates: Friend or Foe?
Author: Trish Shea, R.D.
In the last few years, carbohydrates have replaced fat as the villain in our diet culture.
When you hear the word carbohydrates what comes to mind? Do you envision a bakery brimming with confectionary treats, such as pastries, doughnuts, and cupcakes?
How about a large bowl of spaghetti with traditional tomato sauce and a large piece of buttered Italian bread? What about a plate of homemade stir-fry made with brown rice, lots of colorful vegetables, and edamame?
The point here is that many different types of food contain carbohydrates, but some are much healthier for us than others.
Yet, somehow healthy carbohydrates got lumped into the same category as the unhealthy ones and now all of a sudden, all carbohydrates are bad.
This line of thought is completely inaccurate, and here's why...
What Exactly are Carbohydrates Anyway?
Carbohydrates are one of the three macronutrients, along with protein and fat. When carbohydrates are digested, they are broken down into glucose. Unlike fats and protein, glucose is the primary source of energy for every cell in our body.
In fact, the brain would use glucose as its sole source of energy, however, it has to resort to other options, such as fat or protein, during times of prolonged starvation. Unfortunately for the brain and other organs, using fat and protein for fuel is not optimal.
Most people think of grains when referring to carbohydrates. It is important to know that a kernel of grain contains 3 edible parts:
- Bran: the outer layer of the grain that contains important antioxidants, B vitamins and ﬁber.
- Germ: part of the inner layer of the grain that contains many B vitamins, some protein, minerals, and healthy fats.
- Endosperm: makes up the bulk of the inner layer of the grain and contains mostly starchy carbohydrate, some protein, and a small amount of vitamins and minerals.
Whole grains contain all three parts of the grain kernel, whereas refined grains undergo a manufacturing process called milling, which completely removes the bran and germ, leaving behind the starchy endosperm.
This process also removes about 25% of the grain’s protein and at least 17 key nutrients, including important vitamins, minerals, and fiber. Nutrients may be added back into refined grain products, but they are still nutritionally inferior compared to whole grains.
Why does this matter?
We can break down whole grains and refined grains into two more distinct categories of carbohydrates:
- “Fast Carbs” (include Refined Grains)
- “Slow Carbs” (include Whole Grains)
Fast Carbs Vs Slow Carbs
Like I mentioned earlier, there are a huge variety of carbohydrates that await you on your next trip to the grocery store. It's important to understand how differently our bodies respond to each type of carbohydrate.
On one hand, we have fast carbohydrates, which are usually highly processed and provide energy in the form of calories, but contain little or no nutrients. Examples of fast carbs include things like:
- Starch (bagels anyone?)
- Refined grains
Refined grains include bagels, bread, baked goods, breakfast cereals, and many of our favorite snack foods, such as tortilla chips. Refined grains are basically anything made from processed flour.
Refined grains undergo manufacturing processes that dramatically alter them from their natural state. After being milled, refined grains may undergo extrusion cooking, which uses intense pressure and heat to process ingredients for cereal and many other types of food.
This process dramatically alters the physical properties of the original starch molecule, which basically predigests them for us.
How Fast Carbs Affect Our Blood Sugar
Since fast carbs are pretty much predigested, once they enter the upper GI tract, the body has little if any work to do in terms of digestion. This allows fast carbs to become rapidly absorbed into the bloodstream, which triggers a surge in blood glucose.
Elevated blood glucose then triggers a rise in insulin. Insulin is the “key” that unlocks cells so that glucose can travel from the bloodstream into the cell to be used for energy. Excess glucose is stored in the muscles, liver, and fat cells.
On the other hand, we have slow carbs. Slow carbs include minimally processed whole foods that are nutrient dense, meaning that these foods contain high amounts of vitamins, minerals, phytonutrients, and fiber.
Examples of slow carbs include:
- Whole grains
- Some nuts
Whole grains that are still considered to be slow carbs, include:
- Brown rice
How Slow Carbs Affect Our Blood Sugar:
Slow carbs contain fiber, which is unable to be digested by the GI tract. Instead, it travels to the large intestine, where it is digested by bacteria that reside in our microbiome.
Fiber allows for carbohydrates to be digested more slowly, which means that glucose is more slowly absorbed into the bloodstream. Because slow carbs are slowly absorbed, they do not spike our blood glucose or insulin levels like fast carbs do.
Why Slow Carbs Don’t Make Us Fat
1. Because they don’t cause spikes in blood glucose & insulin!
As mentioned before, slow carbs have a much different effect on our blood glucose than fast carbs do. Eating fast carbs spikes our blood glucose and insulin levels and because we may eat these carbs all day long, these spikes happen one after another.
This endless stream of quickly absorbable glucose and the subsequent elevations in blood glucose and insulin that go along with it, eventually wreaks havoc on our digestive and hormonal systems. This may lead to a whole host of issues, including weight gain and an increased risk for developing diabetes and cardiovascular disease.
2. We absorb less calories from them.
Did you know that the amount of calories that we get from our food depends on how processed the food is?
According to David Kessler’s book Fast Carbs, Slow Carbs: The Simple Truth about Food, Weight, and Disease, we absorb more calories per ounce of food from processed grains in foods, like chips or puffed cereal, than we do from whole grains, which contain fiber.
We do not absorb the calories in fiber because our bodies do not contain the enzymes necessary to break down fiber into glucose. Instead, fiber is used as an energy source to fuel the bacteria in our microbiome.
3. They release hormones that make us feel full.
Eating slow carbs causes the release of hormones that produce a sense of satiety and fullness, making it much harder to over eat these types of carbohydrates.
However, fast carbs are easy to over eat since they undergo ultraprocessing techniques that make them light, easy to chew, and easy to swallow. This is especially true because fast carbs don’t stimulate satiety hormones like slow carbs do. Instead, they are unable to trigger feelings of fullness and literally leave us “hungry” for more.
On your next trip to the grocery store, think about the type of carbohydrates that you are putting into your grocery cart.
- Eating ultraproccessed fast carbs, such as sugar and refined grains are associated with an increased risk of chronic disease and weight gain.
- Eating slow carbs, which are healthy, minimally processed carbohydrates, have many health benefits, including a reduced risk of chronic disease and weight maintenance.
The best choice for health, wellbeing, and longevity is to reduce your consumption of highly processed carbohydrates and instead, eat healthier carbohydrates that are high in fiber and nutrients!
- Edwards, Scott. “Sugar and the Brain”. Harvard Medical School Blavatnik Institute Neurobiology, President and Fellows of Harvard College, https://neuro.hms.harvard.edu/harvard-mahoney-neuroscience-institute/brain-newsletter/and-brain/sugar-and-brain.
- Kessler, David. Fast Carbs, Slow Carbs: The Simple Truth about Food, Weight, and Disease. HarperCollins, 2020.
- Ludwig, David S., et al. "Dietary carbohydrates: Role of quality and quantity in chronic disease." Bmj 361 (2018): k2340.
- “What is a Whole Grain?”. The Whole Grains Council, https://wholegrainscouncil.org/ what-whole-grain.