TYPES OF NUTRIENTS

Let’s discuss the familiar nutrients first:  carbohydrates, fats, and proteins.  These three nutrients provide our bodies with calories.  Calories are used quickly by our bodies in energy metabolism, or they are stored in the form of glycogen or adipose (fatty) tissue.

Carbohydrates

Carbohydrates are various combinations of sugar units, or saccharides and are the major energy source for the body.  Each gram of carbohydrate contains 4 calories.  Since the average person requires approximately 2000 calories per day and about 60% of our calories come from carbohydrates roughly 1200 calories per day come from carbohydrates.

Carbohydrates occur in three forms, depending on the number of saccharide (sugar) units that make up the molecule.  Those that contain only one saccharide unit are classified as monosaccharides (glucose, or blood sugar), those with two units are disaccharides ( sucrose, or table sugar), and those with more than two units are polysaccharides (starches).

Americans now consume about 150 pounds of sweeteners each year – usually in colas, candies, and pastries, which few additional nutritional benefits.  For years, excess sugar intake was blamed for a number of serious health problems, including obesity, mineral deficiencies, behavioral disorders, dental cavities, diabetes mellitus, and cardiovascular disease.  However, with the exception of dental cavities, current scientific data do not confirm that sugar itself directly causes any of these health problems.  Today, it is recommended that no more than 10% of our total calories come from simple sugars.

Much of the sugar we consume is hidden.  For example, it is an ingredient in food such as ketchup, salad dressing, cured meat products, and canned vegetables and fruits.  High-fructose corn syrup, often found in these items, is a highly concentrated sugar solution.

Starches are complex carbohydrates composed of long chains of sugar units.  However, these starches should not be confused with the adjective “starchy.” When people talk about starchy foods, they usually mean complex carbohydrates, or “heavy” foods.  True starches are among the most important sources of dietary carbohydrates.  Starches are found primarily in vegetables, fruits, and grains.  Eating true starches is overall very nutritionally beneficial because most starch sources also contain much needed vitamins, minerals, plant protein, and water.

Fats

Fats (lipids) are an important nutrient in our diets, as they provide a concentrated form of energy (9 calories per gram).  Fats provide a feeling of satiety and keep us from feeling hungry.  Because fats take longer to leave your stomach than either carbohydrates or proteins do, our stomachs feel full for a longer period of time, decreasing our appetite.  Fat also helps give food its pleasing taste, or palatability.  Fats carry the fats soluble vitamins A, D, E and K.  without fat, these vitamins would quickly pass through the body.  Fat also insulates our bodies to help us retain heat.

Dietary sources of fat are often difficult to identify.  The visible fats in our diet, such as butter, salad oils, and the layer of fat on some cuts of meat, represent only about 40% of the fat we consume.  Most of the fat we eat is hidden in the food.

At the grocery store, the fat content of some foods is expressed as a percentage of the product’s weight.  For example, the different type of milk available include skim milk (no fat), low-fat milk (½%), reduced-fat milk (1% to 2%), and whole milk (3% to 4%).  The labeling term “reduced-fat” for 1% and 2% milk was introduced in 1997 to indicate that these types of milk are no longer considered “low-fat.”

The current recommendation is that no more than 25% to 30% of our calories come from fat.  Children under 2 years of age, however, need a certain amount of fat in their diets for growth.  Check with your doctor before restricting you are the amount of fat in a young child’s diet.

All dietary fat is made up of combination of three forms of fat: saturated, monounsaturated, and polyunsaturated, based on chemical composition.  Paying attention to the amount of each type of fat in our diet is important because of the know link to heart disease.  Not all fats are created equal.  Saturated fats, including those found in animal sources and vegetable oils to which hydrogen has been added (hydrogenated), becoming trans-fatty acids, need to be carefully limited in a healthy diet.

Concern over the presence of trans-fatty acids (an altered form of a normal vegetable oil molecule) is associated with changes detrimental to the cell membrane, including those cells lining the artery wall.  Among the changes being suggested is an increase in calcium deposits.  This could result in a rough surface, leading to plaque formation.

Processing can change the structure of fat, making it more saturated.  As a result, the oils become semisolid and more stable at room temperature.  The term trans describes the chemical makeup of a fatty acid.  Most trans fatty acids come from hydrogenated oil, which is found in foods such as stick margarine, peanut butter, and crackers.  They are popular in food manufacturing because they can extend the shelf life of the food: the oil stays mixed in the food and doesn’t rise to the top, and the food doesn’t become too soft at room temperature.  Many foods are fried with these fats in the fast-food industry.

Tropical Oils

Although all cooking oils (and fats such as butter, lard, margarine, and shortening) have the same number of calories by weight (9 calories per gram), some oils contain high percentages of saturated fats.  All oils and fats contain varying percentages of saturated, monounsaturated, and polyunsaturated fats.  However, the tropical oils- coconut, plan, and palm kernel – contain much higher percentages of saturated fats than do other cooking oils.  Coconut oil, for example, is 92% saturated fat.  Tropical oils can still be found in some brands of snack foods, crackers, cookies, nondairy creamers, and breakfast cereals, although they have been removed from national brands.  Do you check for tropical oils on the ingredients labels of the foods you select?

Cholesterol

There has been a great deal of focus and concern over cholesterol levels.  Cholesterol is white, fat-like substance, found in cells of animal origin.  It is not found in any vegetable product, so products such as peanut butter and margarine that claim they are cholesterol free never had it in the first place.  

Cholesterol is used to synthesize cell membranes and also serves as the cell starting material for the synthesis of bile acids and sex hormones.  Although we consume cholesterol in our diet, in such foods as shrimp and other shell-fish, animal fat, and milk, you don’t need to obtain cholesterol from external sources – the human liver can synthesis enough of the substance to meet of the body’s needs.  It is important to note that some foods high in cholesterol may provide other important nutrients and could remain in a healthy diet on a modest basis.  A high level of cholesterol has been reported to be a risk factor in the development of cardiovascular disease.  There are number of medical conditions that can give rise to high blood cholesterol such as liver disease, kidney failure, hypothyroidism, and diabetes.  Certain medications, (some diuretics, for example) can also raise blood cholesterol, irrespective of diet.  

Considerable evidence suggests that increased intake of saturated fats may increase serum (blood) cholesterol levels.  Nutritionists recommend that people restrict their dietary intake of cholesterol to 300 mg or less per day.  In other words, no more than 30% of your caloric intake should come from fat, with 7-10% from saturated fats, 10-15% from monounsaturated fats, and 10% from polyunsaturated fats.

Trans fats can act like saturated fat, potentially raising LDL blood cholesterol levels and decreasing HDL cholesterol.  In order to reduce your intake of trans fat, make sure you check the labels on foods to see if they list “partially hydrogenated vegetable oil” as one of the ingredients.  Foods such as cakes, cookies, crackers, snack foods, stick margarine, vegetable shortening and fried foods are most likely to have hydrogenated vegetable oil as one of the ingredients.  This also the reason nutritionists encourage us to use butter rather than stick margarine.

Low – Fat Foods

Low fat and low calorie are not the same but often people confuse the two.  Fat-free, low-fat, or reduced-fat foods have been popular for many years with people thinking they can eat as much as they want of these foods.  This is far from true as a fat-free or reduced-fat product may have as many if not more calories per serving than regular products.  For example, two tablespoons of fat-free caramel topping.  Because fat helps you to feel fuller for a longer period of time, individuals tend more of the fat-free foods in order to feel satiated, thus consuming more calories.  In general, the lower the fat the higher the price tag as the food industry recognized that American are willing to pay more for reduced-fat and fat-free labels.  However, this may be changing as people have realized that lower fat with potentially higher calories doesn’t equal weight loss or healthy weight management.  With subway trading in cookies for a fruit roll and soda for a 100 percent juice carton in its kids-pak meals and McDonald’s offering a piece of fresh fruit in lieu of French fries for its Happy Meals and touting salad for adult fare, the fast-food tide seems to be turned from supersized and super fat toward healthier choices.

Proteins

Proteins are found in every living cell.  They are composed of chains of amino acids.  Of the twenty naturally occurring amino acids, the body can synthesize all but nine essential amino acids from the foods we eat.  A food that contains all nine essential amino acids is called a complete protein food.  

Examples are animal products, including milk, meat, cheese, and eggs.  A food source that does not contain all nine essential amino acids is called an incomplete protein food.  Vegetables, grains, and legumes peas or beans – including chickpeas, butter beans, soybean curd [tofu], and peanuts) are principle sources of incomplete protein.  For some people, including vegan vegetarians, people with limited access to animal-based food sources, or those who have significantly limited their meat, egg, and dairy product consumption, it is important to understand how essential amino acids can be obtained from incomplete protein sources.  This requires the careful selection of plant foods in combinations that will provide all of the essential amino acids, as shown in the following list:

·         Sunflower seeds/green peas

·         Navy beans/barley

·         Green peas/corn

·         Red beans/rice

·         Sesame seeds/soybeans

·         Black-eyed peas/rice and peanuts

·         Green peas/rice

·         Corn/pinto beans

When even one essential amino acid is missing from the diet, a deficiency can develop, Soybeans provide the same high quality protein equal to that of animal protein.  Furthermore, soybeans contain no cholesterol or saturated fat  and can actually lower blood lipid levels, reducing the risk of heart disease.

Protein primarily promotes growth and maintenance of body tissue.  However, when caloric intake falls, protein is broken down and converted into glucose.  This loss of protein can impede growth and repair of tissue.  Protein also is primary component of enzyme and hormone structure.  It helps maintain the acid-base balance of our bodies and is a source of energy (4 calories per gram consumed).  Nutritionists recommend that 12% to 15% of our caloric intake be from protein, particularly that of plant origin.  The RDA for adults is 58 grams of dietary protein for men and 46 grams for women each day.

Vitamins

Vitamins are organic compounds that are required in small amounts for normal growth, reproduction, and maintenance of health.  Vitamins differ from carbohydrates, fats, and proteins because they do not provide calories or serve as structural elements for our bodies.  Vitamins are coenzymes.  By facilitating the action of sponses, including energy production, use of minerals, and growth of healthy tissue.

Vitamins can be classified as water soluble (capable of being dissolved in fat or lipid tissue).  Water soluble vitamins include the B-complex vitamins and Vitamins C.  most of the excess of these water soluble vitamins is eliminated from the body in the urine.  The fat soluble vitamins are vitamins A, D, E, and K.  Excessive intake of these vitamins causes them to be stored in the body in the adipose (fat) tissue.  It is therefore possible to consume and retain too many of these vitamins, particularly vitamins A and D.  because excess fat soluble vitamins are stored in the body’s fat, organs that contain fat, such as the liver, are primary storage sites.

Because water soluble vitamins dissolve quickly in water, it’s important not to lose them during the preparation of fresh fruits and vegetables.  One method is not to overcook fresh vegetables.  The vegetables are steamed or boiled, the more water soluble vitamins will be lost.  Some people save the water in which vegetables were boiled or steamed and use it for drinking or cooking.  More vitamins are retained with microwave cooking than with stove top cooking.

To ensure adequate vitamin intake, a good approach is to eat a variety of foods.  Unless there are special circumstances, such as pregnancy, lactation, infancy, or an existing health problem, nearly everyone who eats a reasonably well-rounded diet consumes enough vitamins to prevent deficiencies.  People often think taking mega doses of vitamins such as vitamin C can be health-enhancing, but actually the reverse is true.  Taking large doses of vitamin C from a dietary supplement can put a strain on your kidneys, causing kidney stones and diarrhea.  Too much niacin, vitamin B6, and folate can also be harmful.

Some recommend that supplements be taken with food, since they’re really components of food and help the body metabolize other food components.  The fat-soluble nutrients should be taken with a little oil or fat to enhance absorption.  The water-soluble nutrients are easily absorbed without food, but may work better when taken with meals.  In addition, some people complain of stomach upset when they take vitamins on an empty stomach.

Unfortunately, not all people eat a balanced diet based on a variety of foods.  Recent studies suggest that a somewhat higher intake of vitamins A, C, and E for adults might reduce the risk of developing cancer, atherosclerosis, and depressed levels of high-density lipoprotein (HDL) cholesterol; however, several unanswered questions remain, including the amounts needed for effectiveness.

Consuming an adequate amount of folic acid before and during pregnancy has been shown to reduce the incidence of birth defects.  To ensure adequate folic acid intake (400 micrograms/day), in 1997 the Food and Drug Administration (FDA) began to require that bread and cereal products be supplemented with folic acid.  The goal of this requirement is for pregnant women and women of child-bearing age to receive at least 140 micrograms/day through dietary intake.  Taking a daily multivitamin before and during pregnancy would easily provide the remaining amount of folic acid necessary to promote fetal neural tube closure (thus preventing spina bifida).  Folic acid is also considered important in the prevention of cardiovascular disease.

At the same time that many health experts are recommending some vitamin supplementation, the FDA has prohibited manufacturers of food supplements, including vitamins, from making unsubstantiated claims for the cure and prevention of disease.  Supplement manufacturers fought against the implementation of this regulation by suggesting to the public that vitamins might become available only by prescription.  This did not happen.  Today, manufacturers of folic acid supplements may make claims about the product’s ability to prevent neural tube defects in infants.

Minerals

Nearly 5% of the body is composed of inorganic materials, the minerals.  Minerals function primarily as structural elements (in teeth, muscles, hemoglobin, and hormones).  They are also critical in the regulation of body processes, including muscle contraction, heart function, blood clotting, protein synthesis, and red blood cell formation.  

Approximately twenty-one minerals have been recognized as essential for good health.  Unlike vitamins, minerals are inorganic and can’t be destroyed by heat or food processing.

Major minerals are those that exist in relatively high amounts in our body tissues.  The RDA recommends taking 250 mg of each one daily.  Examples are calcium, phosphorus, sulfur, sodium, potassium, and magnesium.  Examples of trace elements in body tissues, include zinc, iron, copper, selenium, and iodine.  Trace elements are required only in small quantities, fewer than 20 mg daily of each, but they are essential for good health.  As with vitamins, the safest, most appropriate way to prevent a mineral deficiency is to eat a balanced diet.  However, calcium, a major mineral, can be taken as a supplement to help prevent osteoporosis.

Water

Water may well be our most essential nutrient, since without water most of us would die from effects of dehydration in less than 1 week.  We could survive for weeks or even years without some of the essential minerals and vitamins, but not without water.  More than half our body weight comes from water.  Water provides the medium for nutrient and waste transport, controls body temperature, and functions in nearly all of our body’s biochemical reactions.

Most people seldom think about the importance of an adequate intake of water and fluids.  The average adult loses about 10 cups of water daily through perspiration, urination, bowel movements, and breathing.  Adult require about six to ten glasses a day, depending on their activity level and environment.  People who drink beverages that tend to dehydrate the body (tea, coffee, and alcohol) should increase their water consumption.  To see if you are drinking enough fluid, check your urine.  A small amount of dark-colored urine can be an indication that you are not consuming enough fluids.  Needed fluids are also obtained from fruits, vegetables, fruit and vegetable juices, milk, and noncaffeinated soft drinks.  Excessive water consumption by infants, however, can dilute sodium stores in the body to dangerously low levels, possibly causing death.  Also, dentists are increasingly concerned about the abnormally high number of dental caries (cavities) seen in children who have consumed bottled water rather than fluoridated tap water.

Fiber

Although not considered a nutrient by definition, fiber is an important component of sound nutrition.  Fiber consists of plant material that is not digested but moves through the digestive tract and out of the body.  Cereal, fruits, and vegetables all provide us with dietary fiber.

Fiber can be classified into two large groups on the basis of water solubility.  Insoluble fibers are those that can absorb water from the intestinal tract.  By absorbing water, the insoluble fibers give the stool bulk and decrease the time it takes the stool to move through the digestive tract.  In contrast, soluble fiber turns to a “gel” in the intestinal tract and binds to liver bile, to which cholesterol is attached.  Thus the soluble fibers may be valuable in removing cholesterol, which lowers blood cholesterol levels.  How much fiber do you need? Adults should eat from 25 to 35 g of fiver each day; however, most American adults only eat 11 g per day.  Fiber has many benefits, including helping to curb your appetite and prevent overeating because it is filling, requires more chewing, stays in the stomach longer, and absorbs water, adding to the feeling of fullness.  Fiber also helps to slow the absorption of sugar from the intestines, thus steadying the blood sugar and slowing down the absorption of fat from the foods you eat.  Consuming adequate amounts of fiber has an important effect on reducing serious medical problems because soluble fiber lowers LDL cholesterol and protects against cardiovascular disease while insoluble fiber protects against developing colon cancer.

In recent years, attention has been given to three forms of soluble fiber – oat bran, psyllium (from the weed plantain), and rice bran – because of their ability to lower blood cholesterol levels.

Oat blood can lower cholesterol levels by five to six points in people whose initial cholesterol levels are moderate high.  To accomplish this reduction, a daily consumption of oat bran equal to a large bowl of cold oat bran cereal or three or more packs of instant oatmeal would be necessary.  Oatmeal can also be eaten as a cooked cereal or used in other foods, such as hamburgers, pancakes, or meatloaf.