The Importance of Quality Carbohydrates in Human Nutrition

With the way people avoid them, you’d think carbs were the plague. How often do you hear someone brag about cutting out carbs or going keto like it gave them superpowers? If I had a penny for every time, I’d probably have enough to buy a cup of coffee.

So why the hate on sugars when they actually have a lot to offer? To clear things up, we first need to understand that not all carbs are created equal.

Science has long known that not all carbs are the same. So, how did they all get lumped together and turned into dietary villains? I think it stems from a decades-old misunderstanding that's been repeated by popular media.

As low-carb diets gained fame, the lines between good and bad carbs blurred. TV shows often claim that to lose 50 pounds, you must cut out carbs entirely and exercise like crazy. While exercise is fantastic for health, the idea that you need to become a gym rat and give up enjoyable foods to lose weight is simply not true.

Carbs, by themselves, have little impact on your weight. In reality, what matters most is this simple equation: calories in < calories out. This means you need to consume fewer calories than you burn to lose weight. But that doesn’t mean you can eat all the carbs you want without consequences.

The quality of the carbs you consume can either benefit or harm your health. In this article, we’ll focus on why the quality of the carb matters more than its quantity.

Carbs Unveiled

Let’s start by breaking down the differences among carbs. First, carbs can be categorized by their sugar chain lengths (polymerization) (Ludwig et al., 2018). Single sugar carbs (glucose, fructose, galactose) and two sugar carbs (lactose, sucrose, maltose) are known as monosaccharides and disaccharides, respectively; these are also called simple sugars (2018).

Complex carbs, as the name implies, are a bit more complicated. Oligosaccharides have chain lengths of 3-10, while the largest ones, polysaccharides, can contain anywhere from 11 sugars to over 1000 (Ludwig et al., 2018). The classification of carbs by their chain lengths is just the first step; the second is their source.

The main polysaccharides we’ll focus on are plant starch, resistant starch (RS), and dietary fiber. Plant starch is made from specialized plastids (amyloplasts) in leaves and crops (Lovegrove et al., 2015). Starch and resistant starch are mixtures of the glucose polymers amylose and amylopectin packed into tiny semi-crystallized granules (2015).

Dietary fiber, a non-starch, comes from the tissue of plants and seeds and can be either soluble or insoluble (Lovegrove et al., 2015). Soluble fiber and resistant starch are both indigestible and instead fermented in the large intestine (Ludwig et al., 2018).

This fermentation is important for blood sugar and metabolism regulation and may protect against colorectal cancer (Lovegrove et al., 2015; Reynolds et al., 2019). Insoluble fiber, while similar to soluble fiber and RS, isn’t fermented in the large intestine and acts more like a broom, sweeping through and cleaning your intestines on its way out.

Dietary fiber and resistant starch play crucial roles in gut health, specifically in the colonic microbiome. Great sources of these polysaccharides include whole grains, vegetables, fruits, and legumes (Lovegrove et al., 2015).

With differences in polymerization and origin come distinctions in the quality of carbs. This is determined by their digestion, glycemic response, and influence on health outcomes (Ludwig et al., 2018).

Digestion

Digestion begins in the mouth where food is partially broken down into smaller particles by salivary amylase and other enzymes (Lovegrove et al., 2015). These particles form a bolus and move down your esophagus into the stomach (2015). In the stomach, the food is softened and broken down into even smaller particles that your small intestine can absorb and send into your blood (2015).

Any carb that makes it past or can’t be absorbed by the small intestine ends up in the colon (large intestine) (Lovegrove et al., 2015; Reynolds et al., 2019). In the colon, the carbs are either fermented by gut microflora or excreted (Lovegrove et al., 2015; Reynolds et al., 2019; Hills et al., 2019).

This digestion process can vary greatly depending on the carb’s structure. In their raw form, polysaccharides are digested incompletely, reducing their energy provision (Hardy et al., 2015). To increase their digestibility and caloric capacity, they are gelatinized through mechanical (milling), thermal (baking), or hydrothermal means (boiling) (Lovegrove et al., 2015).

Glycemic Response

It was once thought that only the chain length affected a carb’s digestion rate; its structure is now believed to have just as large an influence (Ludwig et al., 2018). The longer a carb takes to digest, the less impact it will have on your body’s glycemic response system.

When we digest carbs, our body turns them into glucose (Ludwig et al., 2018). Your pancreas then releases insulin to either signal your organs to use the glucose for energy or store it as glycogen in the liver and muscles (2018). The amount of insulin released corresponds with the amount of glucose entering the bloodstream (2018).

Simple carbs are metabolized quickly which causes a rapid rise in blood glucose (hyperglycemia). A proportional spike in insulin (hyperinsulinemia) follows to counter this. Insulin spikes deposit fat more readily, increasing feelings of hunger and exhaustion (Ludwig et al., 2018).

If hyperinsulinemia becomes frequent, the response to glucose can weaken, leading to further problems. On the other hand, complex carbs like starch and dietary fiber take longer to digest, creating a slower, more controlled release of glucose, and an appropriate insulin response.

This not only maintains a healthy response system but also provides energy over a longer period, making you feel energized for more of the day.

Measuring Carb Quality

To measure a carb’s glycemic response and quality, we use glycemic load (GL). GL is better at predicting glycemic response than even the total amount of macronutrients consumed altogether (Ludwig et al., 2018).

It shows how much a particular carbohydrate serving raises blood sugar; the higher the GL, the more it spikes your blood glucose (Ludwig et al., 2018). To calculate GL, multiply the grams of carbs eaten by the food’s glycemic index (you can find this on Google) and divide by 100 (2018).

Simple carbs like sweets, potatoes, and refined grains tend to have higher GLs than complex carbs like starch and dietary fiber (Lovegrove et al., 2015).

Quality Carbs for Health’s Sake

The quality of carbs affects health outcomes. Eating low GL/high fiber foods like whole grains, legumes, and fruits is linked to significant reductions in body weight, LDL and total cholesterol, post-meal glucose levels, cardiovascular disease risk, type 2 diabetes risk, blood pressure, stroke incidence, and colorectal cancer risk (Ludwig et al., 2018; Reynolds et al., 2019; Schwingshackl et al., 2019).

However, fruit juice doesn’t offer the same benefits as whole fruit due to its lack of dietary fiber and added sugars (Ludwig et al., 2018). High GL foods have been linked to higher risks of type 2 diabetes, cardiovascular disease, stroke in women, and certain cancers (2018).

Refined grains like white rice and potatoes (similar to refined grains) are associated with greater weight gain and a higher risk of type 2 diabetes (Ludwig et al., 2018). Increased consumption of added sugars is associated with changes in energy intake and body weight (2018).

The World Health Organization (WHO) recommends keeping added sugars to less than 10% of your daily energy intake, with greater potential benefits at less than 5% (Ludwig et al., 2018).

Gut Health and Carbs

One of the best reasons to include good carbs in your diet is their role in gut health. The large intestine is home to many colonocytes and bacteria that help maintain metabolic stability (Hills et al., 2019). Since gut health is linked to BMI, waist-to-hip ratio, fasting blood glucose, and cholesterol status, it’s clear that a healthy gut is essential for overall well-being (2019).

When resistant starch and dietary fiber are fermented, they turn into short-chain fatty acids (SCFAs), the primary energy source for colonic cells (Lovegrove et al., 2015; Ludwig et al., 2018; Reynolds et al., 2019; Hills et al., 2019). SCFAs also play a role in metabolic signaling; butyrate, in particular, helps break down glucose and fat in the colon (Hills et al., 2019).

The interactions between the gut microbiome and the brain can also improve mental health and quality of life (Hills et al., 2019). Avoiding or restricting starch and dietary fiber can disrupt bacterial diversity and increase markers for frailty, co-morbidity, and inflammation (2019). Artificial food ingredients are also linked to decreased bacterial diversity (2019). These findings highlight the importance of including starch and dietary fiber in your diet.

Carbs and Cancer

Excessive consumption of non-fiber, high GL carbs is linked to colorectal cancer development through the Warburg Effect, where simple carbs provide energy for tumor cells via aerobic glycolysis (Maino Vieytes et al., 2019). Increased sugar intake can also exacerbate insulin resistance and cancer cell growth (2019).

In contrast, high-fiber polysaccharides reduce cancer risk by disrupting the insulin-IGF-1 axis, providing energy for regulatory hormones, and promoting gut bacterial diversity (Maino Vieytes et al., 2019; Reynolds et al., 2019). Although more research is needed to draw stronger conclusions, the findings so far support consuming more high-fiber carbs to combat cancer risk.

Cooking: Carbs’ Evolutionary Twist

If the health benefits alone aren't enough to convince you of the importance of carbohydrates, consider the pivotal role they have played in our evolution.

Around 2 million years ago, Homo Erectus emerged, bringing with him notable physical changes: increased height, reduced tooth and gut sizes, and the ability for sustained running (Hardy et al., 2015). While it was long believed these changes were due solely to a shift from plant-based diets to meat consumption, recent research suggests that carbohydrates were just as crucial.

Our brains are energy-intensive, consuming a significant portion of our resting metabolic rate, primarily fueled by carbohydrates (Ludwig et al., 2018). The availability of more energy could have facilitated brain growth. Evidence points to changes in tooth formation and digestive tract size in Homo Erectus, likely due to the adoption of cooking (Hardy et al., 2015).

Raw starches, encased in crystalline granules, are difficult to digest and provide a low energy yield (Hardy et al., 2015). Early humans would have needed to consume large amounts of fibrous plants to meet their energy needs (2015). Cooking, however, gelatinized starches, making them easier to digest and more energy-rich (2015).

This dietary shift might explain the increased number of genes for salivary and pancreatic amylase, enzymes that break down starch (Ludwig et al., 2018; Hardy et al., 2015). A diet with more easily digestible carbs could have reduced the energy demands of our digestive systems, allowing more glucose to be allocated to brain development (Hardy et al., 2015). These findings highlight the importance of carbohydrates not only for our health but also in our evolutionary progress.

Carbs: Boosting Health and Athletic Performance

For practicality and overall health, prioritizing fiber intake can be more beneficial than focusing on the glycemic index or load of foods. A daily fiber intake of 25-29 grams significantly reduces the risk of various diseases (Reynolds et al., 2019). While low glycemic index foods also show health benefits, the evidence isn't as strong as it is for dietary fiber.

Diets rich in complex carbs and fiber, such as the DASH and Mediterranean diets, are particularly effective at reducing blood pressure (Schwingshackl et al., 2019). Low-carb diets also show benefits, primarily due to the reduction in simple carbohydrates as a whole (2019). Overall, diets featuring low glycemic load and high fiber content are highly advantageous for health.

For athletes, carbohydrates are essential. In endurance events lasting more than an hour, consuming 60-80 grams of carbs per hour can enhance performance (Jeukendrup, 2014). Carbs help delay fatigue, increase time to exhaustion, and improve skills, particularly in sports with intermittent exertion, like soccer (2014).

Drinking carbohydrate-rich beverages during long exercises can reduce perceived exertion and increase power output (Jeukendrup, 2014). However, for strength training, increased carbohydrate intake does not seem to provide additional benefits if you are already well-fed (Henselmans et al., 2022). Normal glycogen stores should suffice for most training sessions, provided you do not exceed 10 sets per muscle group and take adequate rest between sets (2022).

For competitive athletes or those engaging in high-intensity exercise, it is recommended to consume 0.3 grams of carbs per kilogram of body weight per hour within three hours before an event or 1.2 grams per kilogram per hour before a second same-day workout to maximize glycogen resynthesis (Henselmans et al., 2022).

In Conclusion: Carbs Reimagined

In the complex narrative of nutrition, where carbohydrates have been cast as both heroes and villains, it is essential to understand their true role with a discerning eye. Carbohydrates, often unfairly vilified, deserve a balanced reevaluation. The focus should not only be on the quantity of carbs consumed but on their quality.

Science invites us to recognize that not all carbs are created equal. From the simple sugars of monosaccharides and disaccharides to the complex carbohydrates found in plant starch, resistant starch, and dietary fiber, the variety of carbohydrates offers numerous benefits. Our digestive system, a well-orchestrated process, handles these carbs differently based on their structure. Cooked crystalline polysaccharides, for instance, become more digestible, helping to maintain steady blood sugar levels and providing a sustained energy supply.

When it comes to health, fiber-rich foods stand out as the true champions, surpassing the glycemic index in importance. Diets that prioritize dietary fiber can significantly reduce health risks and enhance overall well-being.

For athletes, carbohydrates reveal their energy-boosting prowess, especially in endurance sports. Consuming carbs during prolonged physical activity helps delay fatigue and improve performance. In strength training, while a well-fed state suffices, carbs play a critical role in maximizing glycogen stores for competitive athletes before intense workouts.

The story of carbohydrates spans our evolutionary journey, from fueling our brain's energy needs to enhancing our culinary practices through cooking. This tale of adaptation and transformation underscores the importance of carbohydrates as indispensable allies in our quest for better health and well-being.

As we move beyond the simplistic view of carbohydrates, let us appreciate the value of quality carbs. By making informed dietary choices that emphasize the quality of our carbohydrate intake, we can align our nutrition with the harmony of our health and heritage.

Citations

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