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Carbohydrates are one of the most prominent food groups in the diet. They are present as sugars, starches, and fiber in food. Glucose molecules are linked together to form starch and fiber. When carbohydrates enter the body, the fiber goes undigested, while the sugar and starch are broken down into glucose.  Glucose provides the energy required for bodily functions.  

Carbohydrates are commonly associated with weight gain. However, the right kind of carbs in the right amounts can earn a rightful place in your diet. 

Types Of Carbohydrates

Carbohydrates are subdivided into three categories depending on the number of sugars present and the nature of the chemical bonds between them.

Different types of carbohydrates

Although this is the conventional way of classifying carbohydrates, a more useful approach would be to classify them as refined and whole carbohydrates.

Whole carbohydrates include vegetables, legumes, whole fruits, and grains, which are unprocessed and thus have their nutrient content intact.

The stripping of nutrients in refined carbohydrates as a part of processing makes them 'empty calories.' This removal of the nutrients results in rapid absorption and metabolism of these carbohydrates. This results in spiked sugar levels and unstable energy levels.

The Story Behind Carbohydrates

Previous studies on the development of the brain and other human traits suggest that the shift from plant-based to meat-based diet played a critical role. Since then, a lot of evidence has come to light that indicates the involvement of plant-based carbohydrates in meeting the demands of the growing brain.

Further, the role of cooking in improving the digestion and breakdown of carbohydrates has also been factored in. 

According to Mark Thomas, an evolutionary geneticist from University College London, the brain's size started significantly increasing only around 800,000 years ago - which is speculated to be the time period where the usage of fire started. 

What does this mean?

Glucose is the main source of energy for the brain. When the cooked vegetables were consumed, the body had to put in much less work to convert the carbohydrates to glucose for feeding the brain.

For example, the starch in cooked potatoes digests 20 times faster than the uncooked ones. This suggests that cooked carbs, which became the major source of energy, contributed to brain growth.

To further investigate the hypothesis, the starch digesting enzyme amylase was studied. An analysis revealed that the genes that produce amylase started evolving to higher numbers around the same time cooking was started.

This was an advantage since more amylase was required to digest the increasing amounts of starch consumed. So, with every mouthful, the brain derived more energy from the starch.

There are still uncertainties about the antiquity of cooking and the reason for the increase in the amylase enzyme gene. However, the above-mentioned correlation cannot be just dismissed as a coincidence!

Genetics Of Weight Gain On Carbohydrate Intake

AMY1 gene

The AMY1 gene encodes the enzyme amylase, which is responsible for the digestion of starch. Salivary amylase is the enzyme found in your saliva, which begins the process of digesting starch in food. It breaks the insoluble starch into smaller soluble forms. High-AMY1-gene copy number (number of copies of a gene) indicates increased secretion of amylase. This results in a faster breakdown of starch. The difference in the copy number of the AMY1 gene is reported to be the genome's largest influence on obesity. According to a recent study, each copy of AMY1 decreases the risk of obesity 1.2-fold.

rs4244372

rs4244372 is a Single Nucleotide Polymorphism (SNP) in the AMY1 gene. The A allele in this SNP is associated with a lower copy number of AMY1 gene, and hence poor starch metabolism. People who have the AA type may tend to put on more weight on carbohydrates when compared to the people who have the TT or the AT type.

Do All Carbohydrates Cause Weight Gain?

Refined carbohydrates cause sudden spikes in sugar levels. As the sugar levels rise, the body produces insulin to regulate them. Insulin converts excess sugar into fat. A higher spike in sugar levels results in increased insulin secretion, which leaves you with excess stubborn body fat. Various studies show that refined carbohydrates are associated with type 2 diabetes and heart diseases.

Whole carbohydrates, also known as complex carbohydrates, have natural fiber components in them. This fibrous part is easy to digest and thus helps us stay full for a longer time. A balanced diet that is rich in natural fiber helps maintain the blood sugar levels in our body. These foods have a low glycemic load. Glycemic load estimates how much a person's sugar level will rise upon consuming food. A low glycemic load indicates longer digestion time and a smaller spike in blood sugar levels.

An ideal whole carb diet contains seeds (chia seeds and pumpkin seeds), grains (quinoa and oats) with fresh vegetables and fruits. Many nutritionists also advise a switch from white rice to brown rice. This is because brown rice is packed with nutrients that help us prevent heart diseases and type 2 diabetes. 

Should You Avoid Carbohydrates Completely?

Other than being an important source of energy to the body, carbohydrates also perform the following functions:

Carbohydrates Help Maintain A Healthy Gut

Research tells us that a fibrous diet can help maintain a healthy gut. Complex carbohydrates contain a sugar component and a fiber component. Fiber is present in two categories, soluble and insoluble. Soluble fiber helps maintain bowel movements, as well as the consistency of the stool. Insoluble fiber relieves constipation and prevents various digestive tract diseases. Studies also show that a diet rich in fiber helps maintain our blood sugar levels and also benefits our heart.

Carbohydrates Influence Heart Health

While refined carbs are not really your heart's best friend, dietary fiber can help maintain blood sugar levels and is heart-healthy. When fiber passes through the intestines, it prevents reabsorption and hence, the buildup of bad cholesterol. This reduces the risk of heart diseases. 

Dr. Tamar Polonsky, MD, from the University of Chicago Medicine, said that foods that contain complex carbs "decrease inflammation and help us decrease the risk of plaque buildup in our arteries." Plaque is the deposition of certain substances in the blood vessels that block the blood flow. This buildup is caused by fat, cholesterol, and calcium that is present in the blood. This can potentially lead to a heart attack or stroke. Polonsky advises us to stick to healthier carbohydrates with less fat and cholesterol to prevent these.

Carbohydrates Help Maintain Muscle Strength

Our body stores the extra glucose in the form of glycogen (another sugar), which is very important to us. When there's no available glucose from carbohydrates, the body breaks down the muscles to generate glucose for energy. To prevent muscle mass loss due to starvation, the consumption of adequate amounts of carbs is essential.

Carbohydrates Can Improve Mental Health

Apart from all the impacts on physical health, research suggests that carbohydrates can improve mental health as well. A study from the Archives of Internal Medicine showed that people who were on a low-carbohydrate diet for a year experienced symptoms of depression and anxiety. 

Food Sources That Have Low Carb Content

The idea behind a low-carbohydrate diet (for weight loss) is that if the body does not receive the extra carbohydrate, no excess fat will be stored. Instead, the fat already present will be burnt for energy. 

Plant Sources Of Low-Carbohydrates Foods

Animal Sources Of Low-Carbohydrates Foods

High-carbohydrate need not necessarily be our enemy. In fact, high carbohydrate foods with adequate fiber are extremely healthy. 

Food Sources Of Complex Carbohydrates

All these foods are rich in fiber and help us from feeling hungry frequently. They also help us maintain good gut and heart health. 

Summary

Carbohydrates are one of the major food groups. There are two types of carbohydrates - whole or complex and refined. Whole/Complex carbohydrates present in food like oats and bananas are healthy, while the refined carbohydrates are "empty calories" that spike your blood sugar levels. The starch in the carbohydrates is digested by the salivary enzyme, amylase, encoded by the AMY1 gene. A higher copy number of the AMY1 gene is considered beneficial, as it results in a faster breakdown of starch. rs4244372 is an SNP in the AMY1 gene associated with the difference in the copy number of the gene. People who have the AA type tend to have a low copy number and hence may be poor digestors of starch. These people are at an increased risk for weight gain on carbohydrate consumption and may benefit from a low-carbohydrate diet. Some low carbohydrate foods include leafy greens, nuts, and olive oil. Animal foods like lean meat and fish are low in carbohydrates. Another option can be switching to a fiber-rich carbohydrate (complex carbohydrates) diet. Fiber is digested slowly and thus keeps you full for longer. Quinoa, buckwheat, berries, and sweet potatoes are good sources of complex carbohydrates.

References:

  1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6485469/
  2. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4712930/
  3. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3836142/
  4. https://pubmed.ncbi.nlm.nih.gov/24008907/
  5. https://en.wikipedia.org/wiki/Glycemic_load
  6. https://www.hsph.harvard.edu/news/features/gnet-brown-rice-diabetes/
  7. https://pubmed.ncbi.nlm.nih.gov/21332763/
  8. https://pubmed.ncbi.nlm.nih.gov/23422921/
  9. https://www.uchicagomedicine.org/forefront/heart-and-vascular-articles/the-benefits-carbohydrates-can-have-on-heart-health
  10. https://pubmed.ncbi.nlm.nih.gov/19901139/
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