Nutrition and Calories... and the link between them.
Nutrition and Calories are also about energy for the body.
Do you think eating 2,000,000 calories a day is difficult to do? Hardly. Many of us actually eat much more than that. To understand how this is possible, we need to know what the word 'calorie' really means...
This page is about nutrition and Calories. We want to know...
Do all nutrients contain energy? How is the energy in food measured anyhow? How do we know for instance, how much energy a slice of pizza, an apple, or any food provides us with?
We use the word 'Calorie' to represent the energy contained in the foods we eat but what does a Calorie really measure? Is it possible to really eat 2 million calories every day?
Nutrition and Calories - The link between the two...
From our previous topic on fitness nutrition, you'll recall that we discovered that all foods contain nutrients. Nutrients are used by the body for metabolic needs, for growth and development, and to supply us with energy.
Thus, nutrients contain energy which is released and converted to other forms of energy which our body then uses to do mechanical work.
Of the six basic nutrients that all foods are made from-- carbohydrates, fats, proteins, water, vitamins, and minerals, not all of them contain energy.
Water, as you can imagine, has zero energy. But so do all vitamins and minerals.
Hence, with the exception of alcohol, the only nutrients to contain energy are the three macronutrients carbohydrates, fats, and proteins. This simplifies our life a great deal.
Therefore, when it comes to nutrition and Calories, no matter what kind of food we eat, no matter how rare, exotic, or what country they may come from-- when we want to know how much energy we are consuming, we really only need to concern ourselves with carbohydrates, fats, and proteins.
But how do we know how much energy they contain?
To find this out, scientists use a device called a Bomb calorimeter. Some newer ones are not really that much larger than your microwave.
Typically, 1 gram of a macronutrient is placed in an explosive-proof steel container called a 'bomb' which itself, is submerged in water. The macronutrient is then ignited and burned in oxygen under pressure.
If you've ever sat around a camp fire with your friends and held marshmallows over the flames, you already know that food burns.
So in the bomb calorimeter, as the food burns, the water temperature rises due to the heat. Because it's fully insulated, the rise in water temperature reflects the heat liberated, or what is referred to as the heat of combustion.
The 'heat of combustion' of a food then, represents the food's total energy value. This energy value is expressed in 'Calories'.
Nutrition and Calories - The Calorie- A unit of energy measurement
Thus, the basic unit for measuring heat is the Calorie. So a Calorie is really nothing more than a measure of heat.
In nutrition, Calories and kilojoules are to energy what pounds and kilograms are to weight. Well, 'mass' actually. But we won't get into that…
America uses the English system of customary weights and measures, i.e., the Calorie. In many European countries the International System of Units is used, abbreviated as SI Units, based upon the decimal Metric system hence, the kilojoule.
Incidentally, it might interest you to know that the joule was named after the British scientist, Sir Prescott Joule (1818-1889). Sir Joule observed that when a paddle wheel was stirred vigorously, the water warmed. He concluded that the movement of the paddle wheel added energy to the water and that the degree to which the temperature of the water rose was directly proportional to the amount of work done.
Side Note:
One Calorie is equal to 4.186 kilojoules. To convert Calories to kilojoules, multiply the number of Calories by 4.186 (or round up to 4.2 for ease and simplicity.)
Conversely, One kilojoule is equal to 0.2389 Calories. To convert kilojoules to Calories, multiply the number of kilojoules by 0.2389 (or round up to 0.24 for ease and simplicity.)
Nutrition and Calories - Eating 2,000,000 calories a day?
Ever seen the word Calorie expressed as 'kcal'? Ever wondered what the "k" stands for?
You've no doubt noticed that I've used a capital 'C' when writing the word Calorie. This is because a 'calorie' and a 'Calorie' are not the same units.
One Calorie with a capital "C", refers to one 'kilogram calorie' or 'kilocalorie' for short-- often abbreviated further as 'kcal'.
In truth, the 'calorie' is such a small unit, it's fairly unmanageable to work with so we use the kilocalorie instead. In the same spirit that 1 kilojoule is equal to 1000 joules in the Metric system, 1 Calorie or kilocalorie is equal to 1000 calories in the English system.
Imagine if you will, a typical daily caloric intake of 2000 Calories. If we had to express this value in 'calories', we would have to say we ate 2,000,000 calories!
This is why we use the 'Calorie' instead of the 'calorie'.
However, for practical purposes when we talk about nutrition and Calories, the capital "C" is often dropped in common usage. But you should know that whenever you see the word 'calorie' anywhere, they really mean 'Calorie'.
So from here on in-- and throughout the entire website-- let's do the same and just use the word 'calorie' with a lower case 'c' even though we mean kilocalorie (i.e., 'Calorie').
But what is a calorie anyway?
Oddly enough, very few people can actually define the term calorie even though it is used by almost everyone.
To define calories then, we say 1 calorie (remember, we mean kilocalorie) is the amount of heat required to raise the temperature of 1 kilogram or 1 Litre of water by one degree Celsius.
What does this mean? Well, if an apple contains 80 calories, then releasing the potential energy contained within the apple will increase the temperature of 80 litres of water 1 degree Celsius.
Recall that inside the bomb calorimeter, the rise in water temperature reflects the heat liberated and the calorie is simply the basic unit for measuring heat.
So nutrition and calories are related to energy in the body. But is burning food in a bomb calorimeter the same as burning food in the body? You may be surprised to discover the answer. Find out more by following the link below...
To find this out, scientists use a device called a Bomb calorimeter. Some newer ones are not really that much larger than your microwave. 
