ABC OF NUTRITION:
Despite the craze to greatly reduce or eliminate whole food groups from our diet, our bodies require a variety of foods to get all the nutrients we need to function our best.
There are six basic nutrients that we can’t live without: carbohydrates, protein, fat, water, vitamins and minerals. Understanding why we need certain nutrients is the first step in improving your nutritional status. In addition, these basics give a solid foundation on which to intelligently evaluate the health claim headlines we are exposed to daily.
Carbohydrates are the body’s first choice and major source of energy. All carbohydrates are broken down into glucose (except fiber which will be mentioned in a moment), the compound that fuels every cell in your body. In fact, glucose is the only fuel used by the brain.
Made up of chains of sugar molecules, carbohydrates are divided into two groups:
Simple carbohydrates (one to two sugar units) are found in fruit, table sugar and products made with sugar.
Complex carbohydrates (more than two sugar units) are found in potatoes, rice, cereals, beans, grains and many vegetables. Animal products contain no carbohydrates at all.
A healthy diet should consist of approximately 60% carbohydrates, with an emphasis on complex carbohydrates. Your body has to work harder to break down complex carbohydrates into glucose, thereby providing a steady stream of energy. In addition, complex carbohydrates generally contain more vitamins and minerals than their simple sugar counterparts.
Complex carbohydrates are also a wonderful source of dietary fiber. Because human digestive enzymes cannot break down the bonds that hold fiber together, fiber provides no nutritional value or calories to your diet. However, far from unimportant, fiber absorbs large amounts of water, moving solid materials through the digestive tract, preventing constipation and possibly some types of colon cancer.
Based on the Recommended Daily Allowances (RDA) published by the U.S. Departments of Agriculture and Health and Human Services, in 1995, the average adult should consume daily:
6-11 servings a day of grains (bread, cereals, pasta, rice)
2-4 servings of fruit
3-5 servings of vegetables
Another essential nutrient, protein makes up virtually every part of your body: the keratin in your nails and hair, the proteins in red blood cells that carry oxygen, and the proteins that make up your muscles, just to name a few.
The protein that we consume is broken down into amino acids. There are 22 amino acids, that when strung together in different combinations, make up all the proteins needed by the human body.
Nine of the amino acids are considered essential, meaning that they must be obtained from dietary protein sources. The other 13 are considered nonessential – not because we don’t need them – but because our bodies can synthesize them from fats, carbohydrates, and other amino acids.
Protein sources are also classified on the basis of how many of the essential amino acids they provide. Animal sources of protein such as meat, fish, poultry, eggs, and dairy products are considered high-quality or complete protein sources because they contain sufficient amounts of all the essential amino acids.
On the other hand, proteins from plants including grains, fruits, vegetables, beans, nuts and seeds are often considered low-quality proteins or incomplete proteins in that they are not as easily absorbed by our bodies or used as efficiently and are missing one or more of the essential amino acids.
The exception is the soybean. Soybeans and soybean products contain sufficient amounts of all nine essential amino acids and are a great source of protein for vegetarians and vegans.
In nature, complete protein sources such as animal products are also high in fat and consumption should be limited. However, you can combine two incomplete proteins (often lower in fat) to make a complete protein source. For example, combining bread and peanut butter. By themselves, both bread and peanut butter lack one or more of the essential amino acids, but when combined, provide a complete, high quality source of protein. Other common combinations include rice and beans, cereal and milk, and macaroni and cheese.
How Much Protein Do You Need?
Nutritionists recommend that healthy adults consume 0.8 grams of high-quality protein for every 2.2 pounds of body weight or according to the USDA Food Guide Pyramid you should consume daily:
2-3 servings of meat, poultry, dry beans, eggs, and nuts
2-3 servings of milk, yogurt, and cheeses
Although we are bombarded with messages to cut the fat in our diet, the bottom line is — we need fat. Fat is the most concentrated source of stored energy in our bodies and is necessary for making hormones such as testosterone and estrogen, the absorption of fat-soluble vitamins, body temperature regulation, and a host of other important functions.
Glucose is still the body’s first choice energy source, but if you run out of glucose, your body will begin to break down stored fat. Overall, the USDA recommends that you keep your total fat intake under 30% of your total calories.
Even though you can go weeks to months without food, you cannot survive long without water. The body is made up of 2/3 water, and it is required to perform virtually all functions in the body.
The age-old adage of drinking 8-8oz glasses of water daily still applies. If you work or exercise intensely you should consume more water to replace what you lose through perspiration.
Vitamins and Minerals
Often referred to as micronutrients because they are needed in relatively small amounts compared to the essential macronutrients listed above, vitamins and minerals are still necessary for life. There are 13 vitamins and 22 minerals that we need to get from dietary sources.
Most people who eat a wide variety of food from all groups listed on the USDA’s Food Pyramid are likely to get adequate levels of vitamins and minerals without requiring supplements.
The Bottom Line
“Thank goodness good nutrition is not a ‘one shot’ deal – one ‘bad’ meal won’t do you in.” People need to stop labeling foods as ‘good’ or ‘bad.’ “All foods can fit into a healthy diet.”