Which Carb Should I Eat? Understanding Macronutrients

You may have heard that overnight oats are a better breakfast choice than a cupcake. But why is that? While it’s true that both are primarily carbohydrates, when it comes to managing diabetes, not just any carb will do. By the end of this post, not only will you understand why, but you’ll also know how to choose the right carbs to control your diabetes.

What makes a carb a carb?

Of the macronutrients, carbohydrates are the most abundant in nature, and we typically consume nearly half of our calories by eating them. Almost all carbohydrates are made from plants. Whether you are eating spinach, rice, pasta, potatoes, yams, carrots, bananas, tomatoes, edamame (yes, 75% of edamame is carbohydrate), peanuts, plums, cauliflower, bread, corn, honey, cane juice, or table sugar, you are eating carbs in different forms. The easiest carbs to digest are quickly converted to glucose or fructose so our cells can use them to produce energy. Other carbs are very hard to digest or can never be fully digested. In terms of diabetes, the carb that our body cannot easily digest is almost always the one to choose!

What determines whether a carb is easy or hard to digest is the type of sugars it makes. Plants make simple sugars – glucose, galactose, and fructose – from sunlight, air, and water. Everything else that a plant makes, like its fruit, comes from these basic sugars. The simple sugar molecules are strung together in chains, just like beads on a necklace. These sugars in chains are called complex carbohydrates, and there are two types: starch and fiber.

How we digest carbs

All plants, like us, are made of cells, but plant cells have a hard cell wall that is mostly made of fiber. All the nutrients that we get from plants are packed inside their cells, surrounded and protected by the cell wall. When we eat fruits, vegetables, or nuts, our body takes several steps to extract the nutrients. In the first phase, as we chew we break down the bigger pieces into smaller pieces, which releases a little bit of simple sugar and gives us a sweet taste, most noticeable in the case of ripe fruit.

The chewed food then travels to our stomach, where, for the next several minutes to hours, the stomach breaks down the largest food particles into smaller pieces, pulling the cells apart from each other and breaking the cell walls open. Once the cell walls break open, the nutrients stored inside the cells, including the carbohydrates, are released for further breakdown and absorption. Simple sugars are quickly absorbed in the gut, while a good fraction of the complex carbohydrates, like starch, are further broken down into simple sugars for absorption. The broken cell walls that are mostly composed of fiber (a form of complex carb) are not fully digested, even though the trillions of microbes in the gut can break down some of the fiber for their own food. (Some of these gut microbes are also helpful in extracting other nutrients from our food.) Instead, the fibrous cell walls absorb a lot of water and become a gooey mass that travels down the intestine. This undigested fiber adds volume to our gut content and is essential for passing stool. So, when you eat foods high in fiber, like overnight oats, spinach, raw carrots, and almonds, you are feeding your gut’s good bacteria so that they can extract other nutrients you need from your food and also helping your gut stay healthy.

Factors that influence carbohydrate digestibility

Plants like legumes (peas, beans) and nuts can either be eaten raw or require cooking to break down chemicals that don’t taste good. Cooking breaks down plant cell walls, releases nutrients including carbohydrates, and makes starchy foods absorb water so that they can be readily digested in our stomach. Just the act of cooking also increases the amount of sugar that our body can easily obtain from plants. For example, your stomach gets more carbohydrates and at a faster rate from cooked carrots or spinach than raw carrots or spinach. Overcooking can break down and destroy some of the micronutrients in our food. Different carbs are broken down at different rates. For example, the starch in white rice is broken down faster than the starch in brown rice.

Many food items such as grains are pulverized to fine powder or flour. When wheat, rice, or corn are broken down to fine powder or flour, the process breaks down the cells to release the starch, which is often further broken down into smaller starch molecules. Subsequently, when we cook or bake the flour, it becomes even easier for our stomach to quickly extract the sugar it contains. In modern mills, the outside covering of the grains, which often contains more fiber, protein, and fat and other nutrients, is removed from the starchy inner part and the starch is often pulverized to flour. Such refined flour lacks many nutrients, has very little fiber, and, when cooked, becomes very easy for our stomach to digest to quickly release sugar. While having flour be easier to digest sounds helpful, the quick release of sugar is a problem in diabetes. So carbs that are digested slowly are almost always better than ones that are digested quickly, because they control blood glucose so that it does not rise too quickly or become too high. That’s why it is important to choose whole wheat flour instead of more-refined flour.

Putting it all together

When we eat raw, complex-carbohydrate-rich plants, like nuts, fruits, and vegetables, in addition to the carbs we also get a dose of vitamins, minerals, antioxidants, fiber, protein, and fat: all the nutrients our body needs. For example, nuts are good sources of proteins and fat; and beans, berries, leafy green vegetables, quinoa, and whole grains are all good sources of fiber. Even rice, wheat, oats and millet, which are mostly carbohydrate, also contain fiber, some protein, and vitamins and minerals. Cooked foods have more readily digested carbohydrates and some fiber. The carbohydrates in food made from fine flour are even more easy to digest and quickly release simple sugars into our body. That’s why foods that are made from fine flour, and cooked or baked and further mixed with added sugar and preservatives, are called “ultra-processed.” But despite their easy digestibility, ultra-processed foods such as doughnuts, cupcakes, white bread, etc., have some distinct disadvantages: they lack many nutrients, have very low fiber to feed our gut microbes (and even have preservatives that can kill our gut microbes), and are quick to raise blood sugar. Now you can see that, while quick oats and a muffin made with refined flour both may be more than 90% carbohydrate, the quick oats are much better than the muffin for better blood glucose and for gut health. Most ultra-processed foods are loaded with simple sugars that are quickly absorbed in our gut, which leads to a blood sugar rush.

So now you get the idea: Complex carbs – the carbs that are slower for us to digest – are almost always better for diabetes because they control blood glucose so that it does not rise too quickly or become too high. These foods include raw fruits and vegetables; nuts, seeds and legumes; and grains such as quinoa, barley flours, millet flours, amaranth flour, whole wheat flour, rolled oats, and red or black rice.

Fiber, in conjunction with complex carbohydrates, helps to slow down digestion, which in turn slows down the flood of glucose into the blood.