The Carbohydrate Controversy!Sep 22, 2023
Remember the macronutrients - protein, carbohydrates and fat?
The term carbohydrate (or saccharide, which means sugar) comes from the carbon, hydrogen, and oxygen molecules that are present in our foods: fruits and grains, and also vegetables and legumes.
Unlike essential amino acids and fatty acids, carbohydrates are not considered ‘essential’ because our body can change up the energy sources it depends on. This means we can obtain everything we need nutritionally from other food sources, so dietary carbohydrates are not necessary to maintain life.
This has brought about much debate over the inclusion and requirement of carbohydrates in our daily diets and where they should fit into it. Some experts claim we do not need them at all in our diets, while others suggest they should never be excluded. This once again, is a case that is largely dependent on the individual and their biochemistry, lifestyle, goals and activity levels. We cannot make any blanket statements in nutrition! As a result, we now have a number of different dietary protocols based on how they manipulate carbohydrates in the body. No wonder this can be so confusing!
Part 1: The Science
(Scroll down for Applications)
Dietary carbohydrates exist in three major classes: the monosaccharides, oligosaccharides and polysaccharides. Within these three groups, we can further break down the categories into specific carbohydrate types according to the variations in their molecular structure, from 1 to 10 or more molecules. This is why disaccharides are typically classified under oligosaccharides as they contain 2 molecules.
This is the simplest form of carbohydrate molecule, thus the term ‘mono’, meaning they only contain one sub-unit of sugar.
The three most important monosaccharides are glucose, fructose and galactose. These are known as ‘simple’ carbohydrates and are recognized by their sweet taste.
Glucose is the simplest form and final end product when we eat complex carbohydrates, and is one of the preferred fuel sources (the other is fat) for our brain, organs and working muscle. This is what is measured in blood at the doctor’s office.
Glucose is therefore easily used by the body and is has the three unique characteristics:
- Used for immediate energy,
- Stored within muscle or liver cells, as glycogen
- Converted to triglycerides to be stored as body fat when energy intake is higher than we need
Fructose is another monosaccharide that has to be metabolized within the liver in order for it to be converted to glucose. This is found in many natural and artificial foods and is considered the sweetest of the carbohydrates, hence the popularity in food manufacturing. Over the years, fructose has undergone a lot of debate, and many nutritionists will advise you to include some naturally occurring fructose from fruit, to get the many micronutrients that fruits contain – but not too much, and not from processed foods!
The last important monosaccharide is galactose. Just like fructose this carbohydrate molecule must be metabolized in the liver and will then be used in the same manner as glucose. Unlike the other two monosaccharides, galactose is not typically found alone in foods, but joined with other molecules to form disaccharides.
When monosaccharides join together they form disaccharides (2 molecule bonds) and oligosaccharides (2-10 molecule bonds). These form what are known as complex carbohydrates and are commonly found in 3 main carbohydrates types: sucrose, lactose and maltose.
Sucrose is also known as table sugar and is therefore the most well-known oligosaccharide. This carbohydrate occurs naturally in many of our foods (fruits, vegetables, beet sugar, cane sugar) and is essentially a combination of glucose and fructose.
Lactose is another common disaccharide, yet it only exists in animal milk from lactating animals, and is a combination of glucose and galactose. The body requires a special digesting enzyme called lactase to digest this type of carbohydrate.
The last important disaccharide is maltose, which is a combination of two glucose molecules. In nature this occurs during the sprouting of seeds, but it can also be artificially induced (known as malting) by the introduction of heat. This process is usually seen in the production of alcohol, as this carbohydrate provides that sweet taste in alcoholic products.
And if it sounds confusing to have so many similar names for these carbs, remember that they are all at their core sugars. The processed food industry often uses multiple kinds of these sugars in their products to mislead you as to the total amount of carbs in the product!
The last of the saccharide categories is polysaccharides, meaning a bonding of 10 or more molecules to form linear or complex chains.
A homopolysaccharide is one that is made of 10 or more monosaccharides of the same type e.g. all glucose.
A heteropolysaccharide is one that is made of 10 or more monosaccharides from two or more different monosaccharide types e.g. glucose and fructose.
When they are ‘branched’, this simply means they are bonded. Click HERE for an image that summarizes this information.
These types of saccharides are typically found in animal and plant sources, and the two main groups of polysaccharides are starch and fibre.
The starch molecule is the storage form of carbohydrates in plants e.g. grains, legumes, and potatoes. Within starch you have two forms: amylose and amylopectin.
Amylose is a linear chain containing hundreds of glucose units.
Amylopectin is a branched chain containing thousands of glucose units. Foods containing a high level of amylopectin tend to have a higher glycemic index (see below), as they increase blood sugar levels the most due to their larger surface area (speeds up digestion – enters blood faster).
Click HERE for an image that models the different starches.
Starches that are not digested in the stomach (remain intact) are known as resistant starches, and may then be broken down in the gut to benefit gastrointestinal health. (1)
Note – Humans and animals store glucose energy from starches in the form of the very large molecules, glycogen. This is typically stored in muscle and liver cells and provides quick energy due to its highly branched nature. This process is known as glycogenolysis.
The last kind of carbohydrate is dietary fibre, a complex carbohydrate made up of non-starch, polysaccharides, resistant starches and/or cellulose.
Dietary fibre used to be known as ‘roughage’, and refers to a group of substances in plant foods which humans do not possess the enzymes or digestive machinery to break down. Examples include pectin, gum and cellulose.
Previously it was considered that all fibre was completely indigestible and did not provide energy. Whilst this is technically true, we now know that some fibre types can be fermented in the large intestine by beneficial gut bacteria, which produce beneficial short-chain fatty acids (acetate, butyrate) and gases (methane, hydrogen and carbon dioxide).
It’s these short chain fatty acids that can be used as an energy source if they enter the bloodstream.
For more on types of fibre and how to get more, click HERE.
The Glycemic Index
The glycemic index or GI is a popular concept used to determine the effect of certain carbohydrates on blood sugar levels in the body. It therefore represents the metabolic response of the body to the carbohydrates we eat, and is classified into 3 groups:
- Low GI foods = <55 GI value
- Medium GI foods = 56 – 69 GI value
- High GI foods = 70 or greater
Foods that have a low GI do not raise blood glucose levels as much, nor as fast as foods that have a high GI. The GI for a particular carbohydrate is primarily dependent on the rate at which the food (and carbohydrate) is digested, thus resulting in how quickly glucose appears in the blood stream.
The GI index ranking is based on a standard food such as white bread or pure glucose which is given the arbitrary GI of 100. To work out the GI of a particular carbohydrate, the carbohydrates 2-hour glucose response curve is compared with 50g of carbohydrates from the control food i.e. white bread or glucose.
There are a number of important factors that will affect the digestion rate of a carbohydrate, namely: the type of carbohydrate, the amount, fibre content and proportion of other macronutrients present.
The initial decision to create the GI was based on the studies showing that unstable (rising and falling) blood sugar responses to food are linked with poorer health outcomes e.g. insulin-resistance, prediabetes and diabetes. Recent research however, shows no correlation between the GI of a food and cardiovascular diseases but it is a great tool to highlight how various carbohydrates will impact blood sugar levels and how the body may respond based on this. (2)
The main problem with using the standard GI is that it only accounts for the type of carbohydrate and not the amount. Therefore, the glycemic load or GL was introduced to represent the glycemic index adjusted for the amount of carbohydrates, thus representing the quality and quantity.
The ranking system works similar to the standard GI, as the higher the GL, the greater the expected increase in blood sugar levels.
The GL is calculated by multiplying the GI of a food by the grams of carbohydrates per serving size. Therefore, foods with a greater amount of protein, fat or acidity, will help blunt the glucose response, improving blood sugar levels.
Glycemic load = glycemic index x carbohydrate content in 100g portions. Glucose is used as the reference and has a glycemic index of 100.
The Glycemic Load of a food can be classified into 3 groups:
- Low GL = <10
- Medium GL = 11-19
- High GL = >20
Click HERE for a table that shows some of the common foods that their respective glycemic load.
The Role Of Carbohydrates
Carbohydrates have several important functions in the body:
- Primary and most efficient source of energy for the body and brain
- Protein sparing and prevents ketosis
- Source of B-vitamins for cholesterol metabolism
- Type of carbohydrates chosen determine:
- Fibre content of diet
- Glycemic load of diet
- Nutrient density & phytochemical content
The metabolism of carbohydrates is a highly complex topic. To simplify this: the cellular use of carbohydrates depends on their absorption from the gastrointestinal tract into the bloodstream, the activity and trained status of the individual.
In order to achieve this, all carbohydrates must be in the form of monosaccharides, so the body must break down polysaccharides and disaccharides through hydrolysis before absorption can occur.
Carbohydrates can be metabolized by 2 different pathways:
- Anaerobic pathway (glycolysis and glycogenolysis)
- Aerobic pathway (oxidative)
Part 2: Applications: What to Eat!
There’s no clear definition of exactly how many carbs should make up someone’s diet, as what might be right for one person may not be for the next. An individual’s optimal intake depends on age, gender, body composition, activity levels, personal preference, food culture and current metabolic health.
When looking at the different metabolic processes and their ability to supply energy for athletic performance, it is very clear that carbohydrates are an essential component of an athlete’s diet.
Therefore, people who are physically active and have more muscle mass, can tolerate and in fact, need a lot more carbohydrates than those who are sedentary. In an active person’s diet, the amount of carbs can have a significant impact on the glycogen stores and therefore athletic performance.
Metabolic health is also a very important factor, as for those with metabolic syndrome, obesity or type II diabetes, the rules change significantly. Those who fall into this category do not require nearly as much carbohydrates as healthier and more active individuals.
For those seeking fat loss and improved health (the majority improving their nutrition) a lower carbohydrate approach (meaning compared to the typical Western/processed food diet) appears to work well. (3) (4)
Studies show that lower-carbohydrate diets reduce appetite, which usually results in a lower energy (kCal) intake. (5) This phenomenon is in part, due to the appetite-suppressing effects of higher protein and fat intake (as they are used to replace carbohydrates). And, because energy balance is key for fat loss, a lower-carbohydrate diet may help to increase fat loss too! (6) (7)
A lower carbohydrate diet can also improve health markers such as lowering blood sugar, blood pressure and triglycerides. (8) (9) (10).
A low-carbohydrate diet can suppress appetite, increase the thermic effect of food (protein needs more energy to digest) and normalize blood sugar (consistent energy). A lower-carbohydrate diet DOES NOT have magical effects that will help you lose weight when energy balance (calories) is not in check.
Note: Just because a food is labelled “keto” doesn’t mean it is healthy – there are no standards regulating this kind of label. The same is true for labels like paleo, vegan, gluten-free, etc – all of these labels can be used on highly processed, unhealthy food products. The key is to read the ingredients and choose ones that are minimally processed and Real Food.
A lower-carbohydrate diet is a fantastic approach for some individuals, while for others, it is the last thing they want to do. When experimenting with a low-carb diet, it is important to monitor how you react to this approach and to make changes if you are not enjoying it.
General Recommendations of Average Intake
HIGH-CARB DIET – 200G+ PER DAY (>5 g/kg/day)
Some people do very well on a higher-carbohydrate diet, and may still lose body fat. Most are not so lucky, and those who can, usually fall into the same category – young, lean, active individuals with high energy outputs.
If you do not tick those boxes the chances are that you will require less carbohydrates especially if weight loss is a goal.
MODERATE CARB DIET – 100-200G PER DAY (>3 g/kg/day)
This is a very common daily carb range for the majority of active and healthy people looking to cut the body fat. This still allows for some starch in the diet, yet limits the amount quite significantly.
You still get all the benefits of having carbs in the diet (so we feel good and perform well), yet lower the intake and overall amount to therefore optimize fat burning (to look good).
An example of a Moderate Carb diet would be a Mediterranean-style diet that includes only minimally-processed Real Food.
LOWER-CARB DIET – <100g per day (< 3g/kg/day)
This can be described as a ketogenic diet (although it usually requires <50g/day) – one in which no starchy carbs (or very little) are consumed daily. This is when the body is forced to use fat for energy.
To do this, the person will go through a fat adaption phase, when the body releases ketones for muscle and brain fuel. This can be the most difficult part of such a diet as energy levels can significantly drop until this process is complete.
This energy slump is also common for those transitioning from, for example, a high carb diet containing high sugar and processed foods to a moderate carb diet plan (but is still not a reason to stay with an unhealthy diet!).
Most people lose weight quickly on a lower carb plan, and it also suits those who are inactive, diabetic or seeking that last bit of fat loss. A low carb diet also works better with females, as they carry much less body weight than men, meaning they require less energy as a result.
THE MAGIC 100
How to start? Try starting at 100g of carbohydrates (not including fibre) daily. This is a moderate amount of carbs for the majority of people and allows for ample amounts of starch too. It is in between a low and a high carb diet, and a good starting point for most to adjust as they need, based on results.
Adjustments should be gradual and calculated, unless you have greatly over/under-estimated their needs. Reduce or increase by 20-30g at a time.
As you can see, there is a lot of controversy, and there are many opinions and much confusion, concerning dietary carbs.
There is no such thing as "one size fits all" -- and this means that you don't need to follow anyone else's eating plan, no matter how insistent they are!
Rather, eat what you like (as long as it is healthy real food), pay attention to how your body responds both short- and long-term, and make any adjustments needed.
Eating should be an enjoyable activity, not one with too many rules and restrictions!
For more info on this and other natural health topics:
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