Nutrition

The Community and Nutrition Programs

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Harvard food pyramid

Connections between nutrition and health have probably been understood, at least to some degree, among all people of all places and times. For example, around 400 BC Hippocrates said, “Let food be your medicine and medicine be your food.” Understanding the physiological needs of our cells helps us understand why food has such an impact on overall health. In this chapter we introduce nutrition by examining how cells use different nutrients and then discuss disease conditions that are tied to nutritional problems.

Nutrition and Health in the Community
The nutritional status of people in our communities is a concern not only for quality of life, but  also for economics (treating illness costs far more than preventing it). Various public health agencies are striving to prevent nutritional deficiencies and improve overall health. In the U.S., the government supplies a variety of resources such as state assistance, WIC (Women Infant and Child), and so forth. In addition, there have been many government agencies and voluntary health and scientific associations, such as the American Heart Association, that focus on life style and dietary factors that prevent chronic and life-threatening diseases. The U.S. Department of Agriculture (USDA) and the U.S. Department of Health and Human Services (USDHHS) developed dietary guidelines in 1977 that were compiled and displayed as the food guide pyramid. The food guide pyramid was revised as “My Pyramid,” but this new chart is confusing to most people. Harvard School of Public Health developed an alternative healthy eating pyramid (shown at left) based on long-term nutritional studies. This pyramid differs from the old USDA pyramid in several key aspects: for example, exercise is at the bottom to remind us of its important role in our health. Also, not all carbohydrates are at the bottom (white bread, white rice, and potatoes are now at the top with sugars), and not all oils are at the top (plant oils are at the bottom). Other resource, such as the Recommended Daily Allowance (RDA) have helped people become more aware of nutritional needs, yet obesity and chronic health problems continue to rise.
Nutritional Requirements
Our bodies have both caloric and nutritional needs. Living tissue is kept alive by the expenditure of energy in ATP molecules, which energy came from the break down of food molecules. Caloric need refers to the energy needed each day to carry out the varied chemical reactions in each cell. When looking at a nutritional label, we can easily see how many Calories are in a serving. These Calories (big “C”) are actually kilocalories (1000 calories). Technically, a calorie (little “c”) is the amount of energy needed to raise the temperature of 1 mL of water by 1 °C. How many Calories a person needs daily varies greatly by age, sex, height, and physical activity levels. If the amount of energy taken in exceeds the amount of energy used, then the excess energy is stored as adipose tissue (fat), regardless of the source of the energy. In addition to daily energy needs, there are nutritional needs to prevent the body from losing its own fats, carbohydrates, and proteins. Such molecules are continuously broken
down, and must be replaced regularly. Essential amino acids and essential fatty acids are  particularly important building blocks in replacing these molecules. Vitamins and minerals are not used as energy, but are essential in tissue and enzyme structure or reactions.

Carbohydrates
Macronutrient
An energy-yielding nutrient. Macronutrients are those nutrients that together provide the
vast majority of metabolic energy to an organism. The three main macronutrients are
carbohydrates, proteins, and fat.
Micronutrients
Microminerals or trace elements, are dietary minerals needed by the human body in very
small quantities (generally less than 100mg/day) as opposed to macrominerals which are
required in larger quantities.
Functions
Glucose it is the most easily used by the body. It is a simple carbohydrate that circulates
in the blood and is the main source of energy for the muscles, central nervous system, and
brain (the brain can also use ketone bodies).
Carbohydrates are made of organic compounds carbon, hydrogen, and oxygen.
There are three sizes of carbohydrate and they are distinguished by a classification of two
that is, simple carbohydrates (mono saccharides and disaccharides) and complex carbohydrates
(polysaccharides). Polysaccharides are the most abundant carbohydrate in the body along
with glycogen.
The break down of polysaccharides goes as follows: Polysaccharides are digested into
monosaccchorides including glucose which goes into the intestinal epithelium and into the
bloodstream. The molecules of glucose are taken by glucose transporters and delivered into
the cells of the body. While glucose is in the cells it can be oxidized for energy or provide
substrates to other metabolic reactions or of course into glycogen for storage.
A. Monosaccharides = Single carbohydrate unit such as, Glucose, Fructose, and Galactose.
B. Disaccharides = Two single carbohydrates bound together such as, Sucrose, Maltose,
and Lactose.
C. Polysaccharides = Have many units of monosaccharides joined together such as, Starch
and Fiber.
Fiber
Fiber is carbohydrates that cannot be digested. It is in all eatable plants such as fruits
vegetables, grains and Legumes. There are many ways of categorizing fiber types. First,
from the foods they come from such as grains, which is called cereal fiber. Second, if they
are soluble fiber or insoluble fiber. Soluble fiber partially dissolves in water and insoluble
fiber does not.
Adults need about 21-38 grams of fiber a day. Children ages 1 and up need 19 grams a day.
On average Americans eat only 15 grams a day.
Fiber helps reduce the chances of having the following conditions: colon cancer, heart disease,
type 2 diabetes, diverticular disease, and constipation.

Glycemic Index
Glycemic Index is a new way of classifying carbohydrates. It measures how fast and how far
blood sugar will rise after consuming carbohydrates. Foods that are considered to have a
high glycemic index are converted almost immediately to blood sugar which causes it to rise
rapidly. Foods that are considered to have a low glycemic index are digested slower causing
a slower rise in blood sugar. Examples of high glycemic index foods are potatoes, white rice,
white flour, anything refined, anything with a lot of sugar which includes high fructose corn
syrup. Examples of low glycemic index foods are whole grains (brown rice, 100% whole
wheat bread, whole grain pasta, high fiber cereals), high fiber fruits and vegetables, and
many legumes. According to the Harvard School of Public Health, “The most comprehensive
list of the glycemic index of foods was published in the July, 2002, issue of the American
Journal of Clinical Nutrition.

 Proteins
Functions
Protein forms hormones, enzymes, and antibodies. It is part of fluid and electrolyte
regulation, the buffering effect for pH, and transporter of nutrients. A good example of a
protein is the oxygen carrying hemoglobin found in red blood cells.
Proteins are made of carbon, hydrogen, oxygen, and nitrogen, an inorganic molecule, the
thing that clearly distinguishes them from the other macronutrients.
A. Amino acids are the building blocks of proteins.
B. Polypeptide are a group of amino acids bonded together 10-100 or more.
The body requires amino acids to produce new body protein (protein retention) and to
replace damaged proteins (maintenance) that are lost in the urine.
Proteins are relatively large molecules made of amino acids joined together in chains by
peptide bonds. Amino acids are the basic structural building units of proteins. They form
short polymer chains called peptides or longer poly-peptides which in turn form structures
called proteins. The process of protein synthesis is controlled by an mRNA template. In
this process tRNA transfers amino acids to the mRNA to form protein chains.
There are twenty standard amino acids used by cells in making proteins. Vertebrates,
including humans, are able to synthesize 11 of these amino acids from other molecules. The
remaining nine amino acids cannot be synthesized by our cells, and are termed “‘essential
amino acids'”. These essential amino acids must be obtained from foods.

The 9 Essential Amino Acids have the following names: Histidine, Isoleucine, Leucine,
Lysine, Methionine, Phenylalanine, Threonine, Tryptophan, Valine

The 11 Non-essential Amino Acids are as follows: Alanine, Arginine, Aspartic acid, Cysteine, Asparagine , Glutamic acid, Glutamine, Glycine, Proline, Serine, Tyrosine

N.B. |  histidine is not essential for adults while cysteine, tyrosine, histidine, and arginine are
required for infants and growing children. Some amino acids are also essential for specific
subpopulations, e.g., tyrosine for individuals with PKU.

Dietary proteins fall into two categories: complete proteins and incomplete proteins. Complete
proteins include ample amounts of all essential amino acids. Examples of foods that
will include these great complete proteins are meat, fish, poultry, cheese, eggs, and milk.
Incomplete proteins contain some but not all of the essential amino acids required by the
human body. Examples of incomplete proteins include legumes, rice, and leafy green vegetables.

Someone who chooses a vegan lifestyle must be careful to combine various plant
proteins to obtain all the essential amino acids on a daily basis, but it can be accomplished.
Ingested proteins are broken down into amino acids during digestion. They are then absorbed
by the villi of the small intestine and enter the blood stream. Our cells use these amino
acids to assemble new proteins that are used as enzymes, cell receptors, hormones, and
structural features. Each protein has its own unique amino acid sequence that is specified by
the nucleotide sequence of the gene encoding that protein (see Genetics and Inheritance1).
If we are deficient in even a single amino acid, then our cells cannot make the proteins they
require.

 Lipids
Macronutrient
Provide 9 Kcalories per gram; it is an energy-yielding nutrient
Functions are stored energy (adipose tissue), organ protection, temperature regulator,
insulation such as myelin that covers nerve cells, lipid membrane around cells, and emulsifiers
to keep fats dispersed in body fluids.
Lipids are made of organic molecules carbon, hydrogen, and oxygen. Fats consist of glycerol
fatty acids joind by an ester bond.
• A. Triglycerides – composed of three fatty acids and one glycerol molecule.
• B. Saturated fatty acid – fatty acid with carbon chains fully saturated with hydrogen.
• C. Monounsaturated fatty acid – fatty acid that has a carbon chain with one unsaturated
double bond.
• D. Polyunsaturated fatty acid – fatty acid that has two or more double bonds on the
carbon chain.
Essential fatty acids part of the polyunsaturated fatty acids
• E. Linoleic acid an essential polyunsaturated fatty acid, its first double bond is at the
6th carbon and this is why it can be called Omega 6.
• F. Linolenic acid an essential polyunsaturated fatty acid, its first double bond is at the
3rd carbon and this is why it can be called Omega 3, and is the main member of the
omega-3 family.
• G. Eicosapentaenoic acid (EPA) , may be derived inefficiently from linolenic acid and is
the main fatty acid found in fish, also called omega 3.
• H.Docosahexaenoic acid (DHE), is an omega 3 fatty acid, is synthesized in body from
alph-linolenic acid, and is present in fish. DHA is present in retina and brain.
Nonessential
• I.Sterols serve a vital function in the body, are produced by the body, and are not
essential nutrients. This structure of a lipid is cholesterol which is a waxy substance that
doesn’t look like a triglyceride. It doesn’t have a glycerol backbone or fatty acids, but
because it is impermeable in water, it is a lipid.

—————————
1 Chapter 16 on page 453

• J.CIS- Trans Fatty acids hydrogenation makes monounsaturated and polyunsaturated
fatty acids go from a state of their original form that is cis to a trans form. Addition
of hydrogen ions will cause vegetable oil to harden. Additionally, they may stimulate
cholesterol synthesis, and are potentially carcinogenic.
Absorption process of triglycerides. This is the fat that your body deals with most of
the time. They are absorbed with the transport of chylomicrons into the lymphatic system
which in turn will pour into the blood stream at the thoracic duct. Once it enters the blood
stream the chylomicrons take the triglycerides into the cells. The triglycerides that are on
the outer part of the chylomicrons are broken down by lipoprotein lipase. Lipoprotein lipase
can be found on the walls of capillaries. It is this enzyme that will break it into fatty acids
and monoglycerides. The fatty acids are taken by the body’s cells while the monoglycerides
are taken to the liver to be processed.
More Info on Lipids:
• 1. Lipids are structural components found in every cell of the human body. That is, they
form the lipid bilayer found in individual cells. They also serve as the myelin sheath
found in neurons.
• 2. Lipids provide us with energy. Most of that energy is in the form of triacylglycerols.
• 3. Both lipids and lipid derivatives serve as vitamins and hormones.
• 4. Lipophilic bile acids aid in lipid solubility.
Recommendations for Fat Intake: Although there are different types of fat the effect
on health and disease, the basic message is simple: leave out the bad fats and replace them
with good fats. Try to limit saturated fats in your diet, and try to eliminate trans fats
from partially hydrogenated oils.Replace saturated and trans fats with polyunsaturated
and monounsaturated fats. As of January 1, 2006, trans fat must be listed on food labels.
More and more “trans-fat” free products are becoming available. Keep in mind, though, that
according to the FDA, a product claiming to have zero trans fat can actually contain up
to a half gram. You may still want to scan the ingredient list for “partially hydrogenated
vegetable oil” and “vegetable shortening,” and look for an alternative product without those
words.

 Vitamins and Minerals

Fruits and vegetables

We all need micronutrients in small quantities to sustain health. Micronutrients include
dietary minerals and vitamins. While all minerals and vitamins can be obtained through
food, many people do not consume enough to meet their micronutrient needs and instead
may take a supplement.
Microminerals or trace elements include at least iron, cobalt, chromium, copper, iodine,
manganese, selenium, zinc, and molybdenum. They are dietary minerals needed by the human
body in very small quantities (generally less than 100mg/day) as opposed to macrominerals
which are required in larger quantities. (Note that the use of the term “mineral” here is
distinct from the usage in the geological sciences.)
Vitamins
Vitamins are organic compounds that are essential for our body to function properly. Most
vitamins are obtained from what you consume, because the body is unable to manufacture
most of the essential vitamins that you need to survive.

Here are types of vitamins and their roles:

Folic acid and cancer prevention
Women of childbearing age are often encouraged to take a folic acid supplement to help
reduce the risk of certain birth defects. Research cited by the Harvard School of Public
Health shows that folic acid may have even more benefits, and not just for the developing
fetus. Their study shows that people who get more than the recommended amount of folic
acid due to diet or supplements can actually lower the risk of developing colon or breast
cancer. Since alcohol blocks the absorption of folic acid and inactivates circulating folate,
this can be especially important to those who drink alcohol frequently (more than one drink
per day). The current recommended intake for folic acid is 400 micrograms per day. There
are many excellent sources of folic acid, including prepared breakfast cereals, beans, and
fortified grains. So if you would like to reduce your risk of colon or breast cancer, be sure to
get more than 400 micrograms per day!
Fat soluble vitamins A, D, E, K
With fat soluble vitamins you need the presence of fat in your diet to absorb them, this is
because the bile will not be secreted to help with emulsification and therefore the fat vitamins
will not be broken down for absorption. Fat soluble vitamins are stored in organs such as
the liver, spleen, and other fatty tissues in the body. Because of this, excessive amounts of
fat-soluble vitamins can accumulate in the body resulting in toxicity, but this rarely comes
from excessive dietary intake but rather from improper use of vitamin supplements. The
other, water-soluble vitamins, do not build up to toxic levels because they are regularly
excreted in the urine.
Minerals
Minerals are atoms of certain chemical elements that are essential for body processes.
Minerals are inorganic, meaning that they do not contain the element carbon. They are
either produced by our body, or we obtain them by eating certain foods that contain them.
They are ions found in blood plasma and cell cytoplasm, such as sodium, potassium, and
chloride. In addition, minerals represent much of the chemical composition of bones (calcium,
phosphorus, oxygen). They also contribute to nerve and muscle activity (sodium, potassium,
calcium). Minerals serve several many other functions as well. There are 21 minerals
considered essential for our bodies. Nine of the essential minerals in the body account for
less than .01% of your body weight. Because of the small amount of these minerals that
our body needs, we call them trace minerals. The 12 most important minerals and their
functions are listed below:

 

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