What You Need to Know About Carbohydrates
There are a wide range of different types of carbohydrates that exist on the carbohydrate spectrum, from white bread and pretzels to kiwi and spinach. All four of these foods fall under the carbohydrate umbrella which is why blanket statements that “carbohydrates are healthy” or “carbohydrates are unhealthy” is misleading. Some carbohydrates like non-starchy vegetables (ex: broccoli, purple cabbage, and onions) are the most nutritious foods available to man. On the other hand, diets rich in others like refined flours and sugars (ex: donuts, pastries, white bread) are a leading cause of poor metabolic health, insulin resistance, heart disease, inflammation and weight gain. In this article, we will dive into what carbohydrates are, different types of carbohydrates and takeaways for your overall health.
Shifting The Blame From Fat to Carbs
Of the three macronutrients–carbohydrates, protein and fat– carbohydrates seem to have the worst reputation today. During the days of the low-fat era about 40 years ago, fat was most demonized for being a more calorically dense food. Fat contains nine calories per gram, compared to protein and carbohydrates that only contain four calories per gram. But what researchers and consumers fortunately realized is that calorically dense healthy fats like extra virgin olive oil can lower blood sugar elevations and lead to higher levels of satiety than a diet filled with triscuit crackers. This was shown in a 2015 randomized control trial. Those who consumed a lower carbohydrate diet with healthy fats experienced greater improvements in their lipid profile, blood glucose stability, and reductions in diabetes medication requirement, compared to those on a low-fat diet. If you have recently switched from vilifying fat to vilifying carbohydrates, continue reading.
The Structure of Carbohydrates
Carbohydrates are made up of carbon, hydrogen and oxygen. They can be the primary energy source for the body and the brain (unless a person is in ketosis and fueling off of ketones) because the body converts carbohydrates into energy, which can then be store as glycogen. There are three primary reasons that carbohydrates are generally more problematic than ever are:
- The amount of carbohydrates that people eat, paired with their sedentary lifestyle and lack of physical movement is unequal. When you are more active, your sensitivity and ability to process carbohydrates increases.
- Most people are typically consuming too many refined carbohydrates, which are less nutritious and create a higher glycemic response.
- The carbohydrate density of foods has increased over the years.
Generally speaking there are two primary types: refined carbohydrates and whole food carbohydrates. Refined carbohydrates are primarily digestible carbohydrates such as glucose, fructose, and galactose. They are degraded by enzymes in the small intestine and rapidly released as glucose in the bloodstream. Conversely, whole food carbohydrates are largely made of indigestible carbohydrates, also known as dietary fiber, which is resistant to digestion in the small intestine and ultimately reaches the large intestine to feed the bacteria and short chain fatty acids in the gut microbiome.
Refined Carbohydrates
A few hundred years ago, companies learned how to refine grains like wheat and rice. This process can also be referred to as stripping the grain of much of it’s nutritional value and creating a simple chain of sugar molecules.
The refinement process involves stripping grains of it’s two most nutritious layers:
- The bran: contains resistant starch, protein, fibers, B vitamins, vitamin E, and polyphenols
- The germ: contains fiber, B vitamins, and healthy fats
The grain is stripped down to the third layer: the endosperm, which is starchy and highly shelf-stable. For a graphic demonstration, click here to review the research article that I co-authored in 2013. After removing these nutrients and layers from grains, companies synthetically add the nutrients back in the “enrichment” process. When reading labels, try to avoid any grains or flours that are enriched as this usually indicates the grain was initially stripped.
The body is highly efficient at breaking down the sugar molecules in the stripped grain, which leads to a faster rate of absorption and a faster rise in blood glucose levels. The impact that refined flour (like white bread) has on blood sugar spikes is comparable to that of refined sugar, due to the processing and removal of fiber.
Consequence of Refining Grains
The faster that your blood sugar levels rise, the more insulin that you need to transport that sugar. Insulin is a fat-storing hormone that can also be inflammatory when produced by the body in excess. The goal for optimal health is to keep insulin levels low. In a healthy setting, it acts like a school bus that transports glucose from the blood, into the cell. When you eat foods that cause a lot of sugar to enter the blood at one time it can prompt a less healthy situation where the body overproduces insulin. If you produce too much insulin it will feel nearly impossible to slim your waist, despite your greatest efforts. For individuals that are insulin resistant, meaning the body doesn’t recognize the insulin being produced, the body will continue to overproduce insulin. This process can eventually lead to higher levels of inflammation, hormonal changes, and fat accumulation around the belly.
This can also be problematic for your arteries and overall heart health. Your blood vessels have a lining of cells that protect them and elevated sugars can create small holes in the arterial lining that can lead to increases in plaque buildup and inflammation. Additionally, having insulin resistance and diabetes can be damaging to the arteries because it deactivates a substance (a phosphokinase) that is responsible for the dilation and contraction of the arteries. This is why people that have diabetes are at a higher risk of heart disease.
A Diet High In Refined Carbohydrates & Sugar May Be Associated With:
-Decreased insulin sensitivity
-Increased weight gain
-Increased inflammation
-Increased triglycerides
-Increased LDL cholesterol
-Feeding pathogenic, opportunistic bacteria in the gut microbiome
-Feeding candida and yeast overgrowth
What About Gluten-Free Refined Carbs?
It may seem like gluten-free refined carbohydrates are a better alternative. For instance: if you purchase gluten-free white bread or pretzels then they are more nutritious. But unfortunately that is not true. While gluten-free diets can be necessary and beneficial for a variety of reasons, refined gluten-free pretzels, breads and cereals will spike blood sugar levels just as quickly as gluten-filled refined grains. Regardless of whether you eat gluten or not, you want to stick with whole food carbohydrates and opt for small amounts of 100% whole grains. The number or servings and tolerance to depends on your physical activity and unique metabolic needs.
Whole Food Carbohydrates
Whole Food Carbohydrates can also be referred to as intact carbohydrates. This is the nature-intended form of carbohydrates and should be the basis of carbohydrates that are consumed, in an attempt to decrease risk of chronic disease. The benefit of these carbohydrates, compared to refined carbohydrates is that they have fiber intact which can aid in slowing down blood sugar levels and therefore, lower production of insulin. Some may benefit further from consuming a low carbohydrate diet, as discussed below but that does not mean to cut out all carbohydratesall diets can be optimized when non-starchy vegetables are the foundation.
In addition to having a slower glycemic response, this group of carbohydrates are loaded with beneficial nutrients such as vitamins, minerals, fiber, phytonutrients and antioxidants. You need these types of carbohydrates to provide the fiber, prebiotics, micronutrients, and phytonutrients like carotenoids. Research shows that eating a variety of plant-based fiber and phytonutrients aids in lowering inflammation and stimulating a greater abundance of beneficial microbes such as Bifidobacterium and Lactobacillus.
This category includes:
Non-Starchy Vegetables: These are vegetables with little to no starch. Regardless of whether you eat low carb or vegan, it’s best for this group be the foundation of all diets. The exception is for those who experience GI symptoms after eating too many vegetables. For optimal nutrition, this group would take up most of your plate. In my BeingBrigid Balanced Plate Method, I recommend filling half of your plate with non-starchy vegetables like broccoli, kale, cauliflower, onions, cucumbers, etc. Get the full list here.
Fruits: Fruits are made up of simple, naturally occurring sugars but they also contain some fiber to help slow down absorption. Additionally, fruits are filled with vitamins, minerals and antioxidants. In order to get the most benefit from fruits without downsides of elevated blood sugar, it’s best to limit fruit to 2-3 servings per day (depending on physical activity and individual needs). Stick with lower sugar options like berries, apples, kiwi, lemons, limes, and coconut. And avoid fruit juices and dried fruit that raise blood sugars.
Starchy Vegetables: These vegetables tend to be higher in starch and include potatoes, cassava, rutabaga, plantains, parsnips, butternut squash, and acorn squash. They provide a great source of vitamins, minerals, fiber and phytonutrients but they come with a medium carbohydrate load (about 15g per one serving). I recommend counting this group as the starch in your meal, not as your unlimited vegetable group.
Beans/Lentils: Different types of legumes (red lentils, black lentils, chickpeas, and dried beans) are slower absorbing carbohydrates because they are high in dietary fiber, phytonutrients and plant-based protein. A randomized control trial found that incorporating beans and lentils was associated with better glycemic control and lower risk of Coronary Heart Disease in those with Type 2 Diabetes. This amazing plant-based source of protein and fiber can be beneficial but to maintain a low glycemic diet, stick to no more than 1-2 servings per day.
Whole Grains: Gluten-free grains that are 100% whole grain include quinoa, brown rice, black rice, certified GF steel cut oats, amaranth, buckwheat, sorghum, millet, and teff. If you eat gluten, 100% whole wheat, rye and barley would also be included. These can all be good options in smaller servings. They provide a slower blood sugar response compared to refined grains but will impact blood sugar levels. Due to this, I recommend a few servings per day, at most. Many people do also benefit from a grain-free diet, for reasons discussed below. Because of this, whole grains are not essential in the diet, if you are making up for the nutrients in other foods.
Dairy: Foods like milk and yogurt also provide a source of carbohydrates and some protein. If you replace cow’s milk with almond milk that naturally decreases the carbohydrate content. If you consume dairy and tolerate it well, be sure to purchase organic as often as possible. This category is also not essential in the diet, if you are making up for the nutrients in other foods.
Low Carbohydrate Diets
I often recommend a low carbohydrate diet for clients who have insulin resistance or high blood sugar levels. Even for those who eat low carbohydrate or a ketogenic diet, you still want to eat as many carbohydrates in the form of non-starchy vegetables as possible. Eating enough non-starchy vegetables (about 5g of carbs per 1 cup) can be a challenge for people on a ketogenic diet if you are limited to 30g of total carbohydrates per day. Be sure to prioritize non-starchy vegetables over protein bars with functional/synthetic fibers added.
Net Carbohydrates
Net carbohydrates can be a great way to measure the impact that the food is likely to have on your blood sugar. Net carbohydrates can be calculated with this simple equation:
Total Carbs – Dietary Fiber = Net Carbs
Since fiber is not digested, net carbs are the amount of carbohydrates left after fiber is accounted for. The benefit of tracking net carbohydrate intake is that fiber does not count towards your carbohydrate intake. Inadequate fiber intake is all too common amongst most adults and ketogenic adopters alike so I absolutely encourage you to count net carbohydrates and to prioritize a diet rich in fiber.
This chart below provides a helpful overview of net carbohydrates found in various plant-based carbohydrates.
| Food Example | Total Carbs (g) | Fiber (g) | Net Carbs (g) |
| Avocado | 9 | 7 | 2 |
| 1/2 bell pepper | 5 | 2 | 3 |
| 1 cup brussels sprouts | 4 | 2 | 2 |
| 1 oz cashews | 9 | 1 | 8 |
| 2 tbsp almond butter | 6.0 | 3 | 3 |
| 1/4 cup red lentils (uncooked) | 30 | 15 | 15 |
| 1/4 cup quinoa (uncooked) | 28 | 3 | 25 |
Glycemic Index
One way that researchers have tried to distinguish between slow and fast carbohydrates is it to look at the glycemic index of a food. There is not one best practice for measuring this universally because the research is mixed but there are some helpful takeaways in reviewing the glycemic index scale. The glycemic index was developed by researchers as a way to measure how slowly or how quickly certain foods caused increases in blood glucose levels.
Research demonstrates that diets high in the glycemic index are associated with a 23% respective risk of Cardiovascular Disease. A 2014 study published in the American Journal of Clinical Nutrition found that a low glycemic index/moderate carbohydrate diet is a more effective strategy for weight loss and improved insulin sensitivity than a traditional low fat/high glycemic index diet.
The glycemic index (GI) is reported on a scale of 0-100. Foods that score above 70 are considered high glycemic and foods below 40 are low. Foods like white bread and whole wheat bread have a glycemic index of about 75, boiled carrots have a 39, and a raw apple has a 36. There are several limitations to this measurement, including that it only measures glucose and the serving size for testing is 50g, which is not a realistic serving for a person. More on the glycemic index + load in future articles.
Acellular Carbohydrates vs Cellular Carbohydrates
One last comparison of different types of carbohydrates is the difference between acellular and cellular carbohydrates which impacts a food’s carbohydrate density. There is not a lot of strong scientific backing to this concept but it is a philosophy that I subscribe to.
In this 2012 review, the author points out that “ancestral foods” have much lower carbohydrate densities than flour and sugar-containing foods. This property appears to be independent of the food’s glycemic index. Having a low carbohydrate density does not necessarily mean that a food is low in the glycemic index. Foods such as sweet potatoes (low carbohydrate density) usually have a similar glycemic index as brown rice (high carbohydrate density) but the difference is found in their carbohydrate density.
Foods with a high carbohydrate density are acellular carbohydrates which are found in flour, sugar and grains (even whole grains). They lack intact cells which likely has a negative effect on the health of the gut microbiome and metabolic disease. Foods that are cellular are lower in carbohydrate density because they store their carbohydrates in organelles as part of fiber-walled living cells. Cellular carbohydrates include root tubers, fruits, leafy vegetables or functional plant parts such as leaves and stems.
The carbohydrate density of foods has increased dramatically overtime with our modern world and is much higher than our ancestral world. But the argument is that the glycemic index of foods did not necessarily change.
The article suggests that Mediterranean dietary patterns could be expected to offer slight improvements over an unrestrained Western diet. This is likely due to the natural emphasis of more cellular plant foods, like vegetables and fruits and fewer refined carbohydrates that happen to be acellular. This may explain why some people are successful following a Mediterranean Diet while others experience greater benefit with a more paleo approach to eating.
Carbohydrate Needs for Exercise
Carbohydrates 101 tells us that carbs are used as an immediate source of energy. This is why athletes and those who exercise at high levels require adequate sources of carbohydrates that are broken down to glucose and stored for later use in the liver and muscles, in the form of glycogen. The only exception to that is athletes who eat a ketogenic diet and become what’s called “fat adapted”, meaning they teach their bodies to fuel on ketones from fat rather than carbohydrates. But most active adults, need to rely on carbohydrate-rich foods to meet the body’s increased glucose demands. In the case of athletes, carbohydrate-rich foods are best when consuming both pre and post-workouts. This does not mean fueling on sticky buns. It means consuming whole food carbohydrates that are discussed in this article.
If your level of physical activity is not as high, then you have less of a need to consume carbohydrate-rich foods and will generally want to stick with lower glycemic carbohydrates that still provide fiber.
Takeaway Points
- All carbohydrates are not “bad”. Fruits and vegetables provide an abundance of antioxidants and fiber that help lower inflammation.
- Eat fewer refined carbohydrates if they are a staple in your diet. Try not to buy them at home–out of sight often means out of mind.
- Eat more whole food carbohydrates to get more fiber and gut-friendly nutrients, especially from non-starchy vegetables. If you experience GI symptoms from eating vegetables, consider working with a functional dietitian to identify the root cause.
- Your carbohydrate needs vary for every individual based on physical activity, age, gender, health goals, insulin sensitivity, thyroid and adrenal health and gut microbiome.
- Consider testing your blood sugar levels at home to identify your blood sugar response to various carbohydrate containing foods. I use the KetoMojo with my clients.
- Low carb diets can also be a beneficial intervention for weight loss, lower levels of insulin resistance, and improved gut microbiome health. But that still does not mean that all carbs are “bad”.