Macronutrients (macro = large) are types of food that are required by the body in large quantities. The three different macronutrients are Carbohydrates, Fat, and Protein. A nutrition plan with tailored macronutrient content can help to decrease your risk of illness and injury, as well as maximise your training adaptations and improve your performance.
Carbohydrates (a.k.a. Carbs or Saccharides) are your body’s primary source of fuel during moderate to vigorous exercise. Carbohydrates are sometimes abbreviated as CHO, which represents their molecular structure of Carbon, Hydrogen, and Oxygen. Carbohydrates are not an essential macronutrient as they can be created through the breakdown of other non-carbohydrate sources, through a process called gluconeogenesis (gluco = sugar, genesis = creation). Carbohydrates provide 4 kcal/gram of energy and improve performance by increasing glycogen stores in the liver and muscles, increasing work capacity (i.e. how long you can exercise for). However, your body has limited stores for glycogen and excess dietary calories from carbohydrates will be stored as body fat. Carbohydrate intake can vary greatly with typical intakes ranging from very low (<50g/day) to high (>400g/day). Low-carb diets may aid in achieving weight loss goals or improve metabolic efficiency but conversely, very low-carb diets (a.k.a. Keto diets) may cause health complications for diabetic patients due to prolonged ketosis (the production of ketones as a substitute energy source for your brain). For the potential benefits and limitations of restricting or increasing carbohydrate intake, see the practical applications section. Carbohydrates come in four different forms: Monosaccharides, Disaccharides, Oligosaccharides, and Polysaccharides.
Monosaccharides (mono = 1, saccharide = sugar) include ribose and deoxyribose, which form an essential part of your DNA, as well as glucose, fructose, and galactose, which are “simple sugars” obtained from your diet.
Glucose is the end product of when larger carbohydrates are broken down during digestion and serve as the primary source of energy in the body. Glucose circulates in the bloodstream where it is transported to the muscles, brain, or internal organs. If not immediately needed, glucose can also be stored as Glycogen in the muscles and to a lesser extent the liver. Found naturally in a variety of food sources, glucose is sometimes referred to as Dextrose and simply blood sugar when in the bloodstream. How well regulated the sugar (i.e. glucose) is in your blood is a key factor in your risk of developing type 2 diabetes.
Fructose (a.k.a. Levulose or “Fruit Sugar”) is a monomer of glucose (i.e. they both have the same chemical formula C6H12O6). However, fructose cannot be used in its natural form and must be converted into glucose within the liver. Fructose is found naturally in small quantities in fruit and vegetables but is added to several processed foods in much higher quantities, often in the form of high-fructose corn syrup (HFCS). When eaten as part of whole fruit or small quantities of honey, fructose is not harmful to your health. However, when eaten in high volume as part of more heavily processed foods, which do not include the fibre and other key nutrients that affect how fructose behaves in your body, fructose can be detrimental to health and may increase your risk of non-alcoholic fatty liver disease and diabetes.
Galactose is another monomer of glucose and is combined with glucose to make the disaccharide lactose. Much like fructose, galactose cannot be used in its natural form and first needs to be converted into glucose within the liver.
Disaccharides (di = 2) including sucrose, lactose, and maltose, are composed of 2 simple sugars joined together.
Sucrose is a combination of glucose and fructose and its crystallised form is found in large quantities in sugar beets, sugar cane, and maple syrup. There are many common names for sucrose including table sugar, beet sugar, or cane sugar. Sucrose is also found in most fruit and vegetables in varying amounts. Sucrose is often purified and packaged as white, brown, and powdered sugars. However, despite these different purified varieties, excess calories
from sugar consumption, regardless of its type, can have a detrimental effect on your health. Sucrose is used in the production of some artificial sweeteners, which are potentially healthy alternatives to sugar as they contain low/no calories. Artificial sweeteners have previously raised concerns over potential increased cancer and diabetes risk. However, more recent reviews of the research have shown no significant correlation between artificial sweeteners and cancer or diabetes.
Lactose is a combination of galactose and glucose and is found only in the milk of mammals (e.g. breast milk, cows milk, goats milk, etc.). Lactose intolerance is a genetic inability to properly digest lactose that can result in uncomfortable digestive symptoms. Infants are well adapted to digest lactose, as newborns receive all of their required nutrients through their mother’s breast milk and have abundant amounts of the digestive enzyme lactase as we develop into adulthood this ability to digest lactose is sometimes lost due to declining levels of the lactase enzyme.
However, approximately 8,000-10,000 years ago in the region of modern-day Turkey the first adults able to digest lactose were recorded, due to a favourable mutation of the MCM6 gene. This mutation spread across Europe and beyond with up to 98% of Europeans possessing this favourable gene mutation and can digest lactose well. However, some areas of Asia have a 100% incidence of lactose intolerance due to a lack of the MCM6 gene. While lactose intolerance is primarily genetic, poor biodiversity of the Gut Microbiome or injury to the intestines may also cause lactose intolerance. Improving your diet diversity may eliminate food intolerances by improving your gut microbiome, discussed in detail in Chapter 6.
Maltose comprises of 2 glucose molecules bonded together and is formed when larger polysaccharides are broken down during digestion. Produced in nature, maltose occurs when seeds sprout and is important in initiating plant growth. This sprouting process is altered through heat in a process called malting.
Malting is the first step used in the production of some alcoholic beverages, most notably beer. Very few food and drinks contain maltose other than alcoholic beverages; however, sweet potatoes are a healthy source of maltose.
Simple sugars are not inherently bad and do serve a purpose in performance and health. The primary concern around simple sugars should be their overall quantity in your diet and origin. Wherever possible aim for natural, minimally processed, and unrefined sources of simple sugars to maximise their health and performance benefits and limit potential risks. You should also try to ensure the majority of your carbohydrates are from complex carbohydrates, which we’ll cover next.
Oligosaccharides (oligo = a few) are composed of 3-9 combined simple sugars and include raffinose and inulin. Along with Polysaccharides, these types of carbohydrates are known as “complex carbohydrates”.
Raffinose is the family name of oligosaccharide compounds found primarily in beans, broccoli, wholegrains, cabbage, and asparagus. The most common of these compounds are raffinose (a trisaccharide) and stachyose (a tetrasaccharide), which both contain different combinations of the simple sugars glucose, galactose, and fructose. Raffinose compounds have typically lower nutritional value due to poor digestibility. However, they serve as a beneficial source of prebiotics for the gut microbiota.
Inulin (not to be confused with Insulin) is a form of stored energy, produced in plants and similar to that of glycogen in humans. Inulin is a type of fibre, which aids in digestion and like raffinose serves as a prebiotic for the gut microbiota. Quality sources of inulin include chicory root, artichokes, asparagus, bananas, wholewheat grains, garlic, and leeks. While inulin supplements are available, it is still much more effective when derived from a healthy diet.
Polysaccharides (poly = many) contain between 10 and thousands of glucose units and come from both plant and animal sources. The most important types of polysaccharides are starch, fibre, and glycogen.
Glycogen is the storage form of glucose and is stored in small quantities within the liver and skeletal muscles. In total, there is approximately 15 g of glycogen stored within the body per kg of bodyweight. As a result of these relatively small stores, glycogen is only used as a temporary source of energy. Once depleted, your body will switch back to using fat stores as its primary source of energy. As the body’s capacity to store glycogen is limited, excess glucose is converted into fat and stored around the body either viscerally (i.e. around the organs) or subcutaneously (i.e. under the skin). Glycogen metabolism plays a key role in the regulation of blood sugar levels working in partnership with the hormone insulin. Insulin promotes the storage of glucose as glycogen, as well as promoting glucose uptake by the cells and glycolysis. Maximising your glycogen stores is important to optimising your performance, regardless of whether you engage in high-intensity, short-duration sports or longer lower-intensity endurance sports. For every 1 g of glycogen stored in the liver and muscles, an additional 3 g of water are stored. Therefore, 500 g of stored glycogen would equal a weight gain of 2 kg (500 g of glycogen + 1.5 kg of water). As discussed in Chapter 1, glycogen is utilised during longer bouts of exercise and in some energy pathways lead to the production of lactate. However, lactate can be converted into pyruvate and then back into glycogen once exercise intensity decreases or stops altogether.
Starch is the storage form of carbohydrates in plants and is found in 2 forms: Amylose and Amylopectin. Amylose makes up roughly 30% of the starch in all plants whereas amylopectin makes up the remaining 70%. The ratio between amylose and amylopectin within food sources helps determine its digestibility. For example, foods with a relatively high proportion of amylopectin are digested well and increase the speed of absorption of other nutrients in the diet, whereas foods with relatively higher amylose are digested poorly which slows the absorption of other nutrients from the diet. This helpful regulation of the rate of absorption is important to ensure the nutrients in your diet have the right amount of time to be properly absorbed and utilised. Starch does not complete this job alone, in fact, it is more of a supporting player to dietary fibre.
Fibre is classified as a structural non-starch polysaccharide. Fibre is found in the cell walls of leaves, stems, roots, and seeds, and contains different types of fibre that act differently in your body, depending on whether or not they are soluble in water. As a result, fibre is often divided into 2 types: Soluble Fibre and Insoluble Fibre. Soluble fibres include Psyllium, Pectin, Beta-Glucan, and Guar Gum whereas insoluble fibres include: Cellulose, Hemicellulose, Lignin, and Chitin. Dietary fibre aids in digestion by providing bulk to the food residues that pass through the intensities. It achieves this by holding onto large amounts of water. This is why good hydration is important for maintaining healthy digestion. Individually, the soluble fibre shortens the time food residues take to travel through the intensities (a.k.a. transit time), whereas the insoluble fibre helps the food residues to “scrape” along the lining of the intensities to aid in nutrient absorption. Fibre causes similar satiating effects as protein and is therefore helpful during weight loss efforts. Good sources of soluble fibre include oats, whole grain rice, vegetables and fruits. Good sources of insoluble fibre include wholewheat bread and flour, vegetables, and wholegrains.
If you would like to learn about the other two macronutrients and how to practically apply this info to help you reach your goals, please check out our book Eat Move Perform: Volume 1 - Nutrition & Supplements which will be available on Amazon and all good booksellers from August 2020. Volume 1 covers Energy Balance and Metabolism, Macronutrients, Micronutrients, Meal Frequency & Timing, Bioavailability, The Gut Microbiome, Diets, and Supplements.