Scientific Principles - All living organisms require a range of foods to supply their needs.

Scientific Principles

Assignment 1

All living organisms require a range of foods to supply their needs. Humans have special needs in terms of macro-components in their diet. The committee on medical aspects of food policy (COMA) produced a report in 1991 called Dietary reference values of food energy and nutrients for the UK, which updated dietary requirements

Dietary Requirements

Our energy and nutrient requirements vary according to our age, sex, body size and levels of activity. Since everyone is different, it is very difficult to be specific about individual energy and nutrient requirements. Scientists have estimated the requirements for groups of people with similar characteristics such as age, sex and levels of physical activity.

I recorded my diet over a period of three days on a diet collection sheet. (appendix 1) I found the foods I had consumed fitted into the following categories.

Proteins

Protein helps build muscles, protect our immune system and keep our body in top working order. It is important to eat some protein every day, preferably a little with every meal. The recommended protein intake for women is 44 grams a day and 56 grams for men. A good source of protein would contain about 21 grams per serving. Most foods contain small amounts of protein, but the best sources are meat, poultry, seafood, dairy products, soy products, legumes, nuts and seeds. Animal sources of protein can be high in saturated fat and cholesterol. For good health, it's important to choose lean sources of protein whenever possible. Other sources of protein such as legumes, nuts and seeds and some soy products are also good sources of fibre.

Carbohydrates

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Carbohydrates

Carbohydrates are the body's primary source of energy, and most people need about 50 percent of their calories to come from carbohydrates. That translates into 125 grams of carbohydrate per 1,000 calories. For example, if you eat 1,600 calories, you need 200 grams of carbohydrate. A good goal is to spread your carbohydrate intake evenly throughout the day, including a minimum of 12 grams of carbohydrate per 100 calories for each meal or snack. But it's important to remember that there are some health goals that can't be met by number alone. Carbohydrates in the form of added sugars found in candy, cookies, soda, sweetened beverages and sweet snack foods add unwanted calories. Carbohydrate naturally occurring in fruits, vegetables, dairy products and grains provides a variety of additional nutrients necessary to good health. But any form of carbohydrate can contribute to elevated blood sugar levels in people with diabetes.

Lipids

Fat is not a four letter word. In fact, as a supplier of concentrated energy and "essential fatty acids," it is a valuable and necessary part of a healthy diet. It is eating too much of the wrong kinds of fat that can cause health problems, and in this article I explain the differences between "good" and "bad" fats.

Why Some Fat is Good for You

Fat is where our body stores excess calories. When your body’s stores of carbohydrates have been depleted, which can occur after as little as 20 minutes of aerobic activity, it draws on necessary reserves of fat for energy.
Fat helps maintain healthy hair and skin.
Fat transports the important fat-soluble vitamins, A, D, E and K through the blood stream.
Linoleic acid, one of the most essential fatty acids, helps ensure proper growth and development for infants.

All Fats Are Not Created Equal

The fats we eat, as opposed to the ones that exist in our body and blood stream, are divided into three categories, according to the level of their hydrogen saturation. Most fats contain all three kinds but are named according to the one that predominates. They are:

saturated
monounsaturated
polyunsaturated

Saturated Fat

Saturated fats contain as many hydrogen atoms as possible, are found in animal fats such as in meat and cheese, and are solid at room temperature. Consuming saturated fats can lead to high levels of "bad" cholesterol. A note of explanation: "Good" cholesterol carries the artery-clogging cholesterol out of your body. "Bad" cholesterol carries the cholesterol around the body, depositing where it can cause serious problems. Saturated fats interfere with your body's natural "good" cholesterol to do its job of clearing cholesterol out of the blood and many studies have established a clear link between high blood cholesterol levels and heart disease.

Technically the difference between saturated versus unsaturated fats is in the type of chemical bonds they contain.

What are the differences between saturated and unsaturated fats? Unlike saturated fats, neither mono nor poly unsaturated fats increase cholesterol, these actually tend to decrease cholesterol. When most people try to tell you the difference between saturated and unsaturated fats, they usually use the example of butter and margarine.

So which is better for you? Butter is a saturated fat and margarine is an unsaturated fat. Unsaturated fats are less likely to clog up a person’s arteries in comparison to saturated fats. Mono-unsaturated fats are preferred more to poly-unsaturated fats. Nonetheless, in order to solidify margarine, some hydrogen’s are added, in a process called "partial hydrogenation". This creates trans fatty acids. There is increasing concern that trans fatty acids are unhealthy. Remember that all fats, regardless of type, contain the same number of calories. So in conclusion, margarine is better for you because it does not increase cholesterol like butter.

The observations from my dietary sheet show that I have consumed numerous carbohydrates and forms of lipids such as fats and oils.

Carbohydrates are one of the main forms of ‘quick’ energy. Examples of these would be glucose, sucrose and starch all of which are mainly sugars. Complex Carbohydrates are made up of two or more simple sugars linked together. Disaccharides are compounds that contain a bond between carbon (1) of one sugar and a hydroxyl group at any position on the other sugar.

The phospholipid bilayer where the cell membrane is an example of is composed of various cholesterol, phospholipids, glycolipids and proteins. Below is an example of a simple phospholipid bilayer.

The smaller molecules between the phospholids are cholesterol which help to give rigidity or stability to the membrane. The phospholipids are the hydrophilic circles with hydrophobic tails. And since most of the cell and area surrounding the cell is made up of water, these fatty acid tails always 'push' away from the water.