Food provides your body with all of the essential elements and building blocks it needs to function. In other words, food provides your body with fuel. Your body's three main sources of food fuel are carbohydrates, fats, and proteins. All have very specific functions and are used continuously to keep the body running.
As any Ferrigno will tell you, "Eat to live. Don't live to eat." When viewing food as fuel for life, rather than an end in and of itself, you'll gain control of your eating habits as well as learn to appreciate food for what it can do for you - depending on your lifestyle needs.
Carbohydrates, used by all body tissues, are the body's primary source of energy. They provide the fuel needed for cells in the body to function. Carbohydrates are found in starchy foods, sugars, fiber, fruit, dairy products, legumes, and some vegetables. They are also found in most processed foods. When digested, carbohydrates are broken down into blood sugar (glucose) or converted into glycogen (a storage form) and stored in the liver for later use.
The brain relies almost entirely on this glucose for fuel and, considering the brain is the body's engine room, a continuous supply is necessary. This is why during taxing mental tasks such as studying we tend to crave sugary or starchy foods. Glucose is also important for nerve, intestine, kidney, and muscle function(remember, the heart is a muscle). Moreover, glucose is the primary source of energy used during physical activity.
Found in oils, nuts, and avocados (unsaturated), and animal and dairy products (saturated), dietary fats are a major source of energy for the body. They take longer than carbohydrates to break down (and use energy from carbohydrates to do so), but once they have, they yield far more fuel than their sugary co-workers. On average, the body starts using stored fats for energy after half an hour of continuous physical activity (so if losing fat is the goal, cardiovascular exercise needs to continue for longer than half an hour).
Fat has other crucial roles. One role is to protect and cushion your delicate, vital internal organs (think bubble wrap). Another role is the maintenance of your body's cell walls. This is particularly important for the nervous system as, without perfectly intact cell walls, messages are unable to be transmitted along the nerve pathways. The presence of fat is also vital for the absorption of certain vitamins (A, D, E, K) that are important for body functioning.
Protein is what we're made of. It provides the building blocks for every cell in the body. Protein is found in meats, poultry, seafood, eggs, dairy, nuts, and legumes. If no carbohydrates are available, the body turns to protein for energy. However, this is not the body's choice. It prefers to use protein for growth, for the repair and maintenance of all body tissues, to make hormones (essential for body functioning) and enzymes (essential for breaking down our ingested nutrients), and to keep up our immunity. Additionally, without protein, we would be unable to build or maintain muscle mass.
Substances Critical to Fuel Absorption
Although not direct sources of fuel, fiber, organic acids, polyols, and ethanol are critical to the proper absorption and function of fuel sources - either positively or negatively.
One member of the carbohydrate group deserves a special mention and has received much scrutiny from researchers in recent years for its health implications. Dietary fiber is only found in plants - fruits, vegetables, legumes, nuts and grains - and is the part of the plant that cannot be digested. Fiber adds bulk to food residues in the gut, "sweeping" out the large intestine as it passes through, and ensuring the gut walls stay clean and food residues exit the body in a timely fashion. Additionally, the presence of fiber in the gut increases the absorption of nutrients passing through it, nutrients required for energy and functioning.
Organic acids in the body include lactic, acetic, formic, citric, oxalis, and uric acid. While some may be ingested with food, organic acids are primarily a by-product of our body's metabolism. Some of these organic acids are excreted from the body, however, others, like lactic and citric acid, are re-broken down and re-used for energy as needed. Some studies indicate that lactic acid may be just as important to brain function as glucose.
Another member of the carbohydrate family, polyols are also called sugar-alcohols. They are found in stone fruits and some vegetables. They are commonly used as sugar substitutes in sugar-free foods such as gum and toothpaste. Polyols have fewer calories than other carbohydrates, meaning they provide less energy, but they do have other health benefits. The body does not absorb polyols but rather uses them more like digestive fibre.
You may be more familiar with another term for ethanol: alcohol. Ethanol is absorbed quickly into the bloodstream and is toxic to the body. It is picked up by the liver and processed for disposal immediately upon consumption. Unfortunately, the liver can only work so fast and, in the meantime, the ethanol remains in the blood and is circulated to the brain, to which it acts as a depressant. Meanwhile, any real nutrients like carbs or proteins are just sitting idly by, likely to be stored as fat if too many alcohol calories have been consumed.
The Bottom Line
You are what you eat is not just an ad slogan. You truly get out of your food what you choose to put in. A balanced diet full of a healthy variety and mix of foods is exactly what we need to fuel the body and ensure balanced, healthy functioning of the mind, body, and spirit.
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