Carbohydrates have traditionally formed a large part of our meals and secured their place in our hearts and stomachs. Especially our stomachs. Once we understand our energy needs we can start to match our consumption appropriately.
Carbohydrates serve as our primary source of energy. Their consumption forms a large proportion of our diet. This seems logical, more carbohydrate, more energy. As simple as we like to make things, this isn’t the case. There are consequences to exceeding energy demand.
How We Use Carbohydrate As Energy
Carbohydrates enables proper function of the Central nervous system, brain, heart, liver, kidneys and muscles. The body’s cells use glucose as the most efficient source of energy. After you eat carbohydrate, glucose from the blood is extracted by cells that require energy.
The remaining portion of glucose gets stored in the form of glycogen in the muscles and liver. When blood glucose is low and you require energy, glycogen from the liver and muscles breaks down to liberate glucose. This allows cells to use glucose as energy. This keeps blood glucose levels stable until the next meal.
When a meal rich in carbohydrate is eaten, blood glucose levels will rise. Insulin signals cells to take the energy they need until satisfied. Insulin also signals the liver and muscles to store glycogen. If these stores are full and there is still a high amount of glucose in the blood, insulin stores it as fat. The action of insulin is like a traffic cop, it will direct the traffic to where it needs to go at the right time.
- Insulin signals for cells to take glucose from the blood and gets used as energy.
- Insulin signals the storage of remaining glucose to the muscles and liver as glycogen.
- If glucose is still present in the blood, insulin signals for glucose storage in fat cells as triglycerides.
When glucose is low the body has a secondary and tertiary means of using energy.
When reserve glycogen stores fall, glucose can be made in the liver from amino acids. These come from the breakdown of protein from muscle tissue. This isn’t ideal as it means that we slowly lose our muscle mass. Fortunately the human body has developed a very clever way of using fat as energy before we dip into our muscles. When blood glucose is low, cells cannot use glucose as energy.
Therefore fat is liberated and used as an auxiliary source. Fat is liberated in the form of Ketones, also used by cells for energy. The body begins to accept these as fuel and fat stores become depleted. This fuel energy pathway we call ketosis. This defence mechanism is what low carbohydrate diets rely upon for the you to lose weight. Diets higher in carbohydrate produce more blood sugar responses, using less fat as energy.
There are two types of carbohydrate both of which differ significantly in the way they provide us nourishment.
Long chains of polysaccharides (many bonded sugars) constitute complex carbs. Long chain sugars are also known as starch. Due to longer chained sugars, breakdown takes time and doesn’t induce a rapid rise in blood glucose. Instead, they produce a steady insulin release, supplying sustained energy meaning you are fuller for longer.
High amounts of fibre account for the many benefits including solid digestion and nutrient uptake. This positively alters the activity of digestive enzymes (1). A high level of fibre accompanies an abundance of micronutrients which prevent against development of heart disease and diabetes (2). Additionally, fibre improves weight loss and maintenance (3) through a greater feeling of fullness (4). It also improves gastrointestinal function (5). The greatest protective effects from fibre are not experienced simply due to the amount of fibre, but more so the variety of fibre (6). Variety is the spice of life so mix it up with:
- Rice, quinoa, pasta, breads and cereals.
- Legumes, beans, peas, pulses
- Green vegetables
- Starchy vegetables – potatoes, carrots, pumpkin, parsnip.
Refined varieties of starchy carbohydrates made from white flour require consumption in moderation. These include white pasta, white rice, white bread, cereals. These are stripped of fibre and associated micronutrients. As much as 60-90% of B vitamins, Vitamin E, Folate and other nutrients are lost in the milling process (7) .
So when the nutrients are gone that just leaves the calories. When we eat calories we want as many nutrients present as possible. Go for unrefined whole grains – Rice, Buckwheat, Quinoa and whole grain pasta, breads and cereals. Be warned some whole wheat foods are partly comprised of nutritionally sparse white flour. Deceivingly, many products will say whole grain on the packaging when they are not.
Simple carbohydrates are single branched molecules known as monosaccharides (simple sugars). These are quickly utilised as energy causing a surge in blood glucose. Because they are short chained, they do not require nearly so much time for breakdown, which causes a spike in insulin. Insulin clears to the now abundance of energy (glucose) in the blood.
The rapid rise and fall in blood glucose will upset normal appetite regulation and cause onset of hunger shortly after eating. Simple sugars get added to foods to enhance the flavour, and as preservatives contain very little to no fibre and micronutrients. The calories consumed are empty. Consuming large amounts of sugar causes rapid fluctuations in blood sugar and may eventually lead to insulin resistance. Cells require more insulin to uptake glucose, resulting in high blood pressure, weight gain and cardiovascular disease (8).
Sugar from fruit (fructose) although a simple sugar, comes with vitamins, minerals and fibre. The matrix of nutrients is more complex.
Simple sugars hide in unsuspecting places:
- Honey, Agave nectar, Molasses, Maple syrup
- White, brown sugar (sucrose) – cakes, candies, sodas, fruit juice, breads
- Corn syrup – sodas, biscuits, cereals, breads
- Fruit sugar (fructose) – fruit
- G Isaksson, I Lundquist, and I Ihse. 1982. Effect of dietary fibre on pancreatic enzyme activity in vitro. The importance of viscosity, PH, ionic strength, absorption and time of incubation. Gastroenterology. 82: 918-924.
- Erkillä A. T, Lichtenstein A.H. 2006. Fiber and cardiovascular disease; how strong is the evidence? Journal of Cardiovascular Nursing. 21(1):3-8.
- Joanne L. Slavin Ph.D., R.D. 2005. Dietary Fibre and body weight. Nutrition. Vol 21.(3):411-418.
- A Raben, N Christensen, J Madsen, J Hoist, and A Astrup. 1994. Decreased postprandial thermogenesis and fat oxidation but increased fullness after a high-fiber meal compared with a low-fiber meal. American journal of clinical nutrition. 59: 386-94.
- Barbara O. Schneeman Ph.D. 1998. Dietary Fiber and gastrointestinal function. Vol 18.(4): 625-632.
- Bengmark. S. 2000. Colonic food: pre- and probiotics. American journal of gastroenterology. 95 (1 supp.): S5-7.
- H. A. Schroeder. 1971. losses of vitamins and trace minerals resulting from processing and preservation of foods. American journal of clinical nutrition. 24, 562
- Vasanti S. Malik, Barry M. Popkin, George A. Bray, Jean-Pierre Després, Frank B. Hu. 2010. Sugar-Sweetened Beverages, Obesity, Type 2 Diabetes Mellitus, and Cardiovascular Disease Risk. Circulation.121:1356-1364.