We can survive minutes without oxygen, days without water and weeks without food; food is not that important relative to the other two. Food serves two purposes, the provision of energy and secondly the provision of vitamins and minerals and essential molecules required by human cells for healthy living. Human cells are not the only items in our bodies that need feeding. We also have to feed the 600 to 800 trillion healthy bacteria that reside in our gut. If they are not healthy neither are we!
The food components that provide energy are carbohydrates, fatty acids (fat), proteins and alcohol. In general our body’s preference is to use the sugars in carbohydrates first, then fats, and then protein. Alcohol cannot be directly used for energy and is toxic. It is cleared from the blood by the liver, and converted to fat by it, which then can be stood or used by our cells for fuel. Only the sugar glucose (the fuel in mosts carbs) and fat can be used directly by our cells for fuel. Protein must first be converted into a type of “sugar” before it can be used for fuel.
Our body has two fuel storage systems. One is a compact form of the sugar glucose called glycogen, it is stored in the liver and the muscles. About 120gm can be stored in the liver and distributed as needed to the rest of the body whereas the amount stored in the muscles can only be used by the muscles. The amount of the sugar glucose that can be stored is limited. On the other hand the amount of fat that can stored is unlimited, our body can keep adding it until it eventually kills us. There is no specific storage system for protein or alcohol, they must be converted to glucose (if there is enough storage space) of fat to be stored, and this is the case. Our bodies cannot dispose of excess energy, it just stores it. When we eat food we either use it or store it, we have no overflow valve to get rid of extra energy.
We have two states of operation, a resting state (like when we are asleep). The amount of energy consumed in the resting state is called our Basal Metabolic Rate (BMR). This is the energy required to keep us breathing, our heart pumping, maintain the constant body temperature and keep our organs alive. For most of us this is between 60% and 75% of our daily energy usage, the rest is taken up by exercise. It is important to note that the liver’s glucose storage capacity is not enough to get us through a day if we don’t eat any carbs (sugar). When this happens then fat is released from storage to make up the energy shortfall. This is especially important point for those of us attempting to lose weight.
In Australia the energy in food is measured in, and recorded on nutrition labels, as Kilojoules. In other parts of the world, and in some medical journals and books Kilocalories are used on the foods to measure the energy in food.
From highest to lowest fats have 37kJ per gram of weight, alcohol 29kJ, proteins and carbohydrates have about 17kJ per gram. But food can also include other components that have little or no energy because they are not easily digestible, an example is fibre. Most natural foods also contain large quantities of water, and water provides no energy at all.
Counting "Calories" to manage diet and eating habits is a waste of effort and time. Our bodies manage foods in different ways and these are not dependent on the foods "theoretical" energy content. For example fats have the highest energy content, but they are also "satiating" which means they reduce the feeling of hunger and increase the feeling of fullness. Our bodies lose protein every day and it has to be replaced. Protein consumption that replaces that part of protein lost provides no energy at all. Carbohydrates contain sugar and fiber. Fiber is indigestible and provides no direct energy for human cells, yet it is still counted as providing "carbohydrate" energy on food labels. Calorie counting is just one of the reasons most weight loss diets eventually fail.
These are necessary elements like trace elements, vitamins, minerals and phytochemicals incorporated in natural foods that are either essential because our bodies chemical systems need them to operate properly and can't manufacture them or even though they may not be essential they may be good for our long term health. In a modern western society all of the substances we need are provided in the natural foods available to us. Information on micronutrients will be published in a separate section on "food additives and supplements".
How much we eat, what we eat, and when we eat are the primary lifestyle factors influencing our rate of biological ageing. Our rate of biological ageing is directly linked to our "Health Span". Our Health Span is the number of years we live before being diagnosed with an age related disease like Alzheimer's, Type II diabetes, heart disease, some cancers and numerous other debilitating diseases.
We may be born with lucky genes or bad genes. Whichever the case may be, eating properly increases our chances for a longer, vital, and enjoyable life.
We are what we have eaten, and will become what we eat!!!!!!!