What is clinical nutrition?
Clinical nutrition is the study of the relationship between food and the
well-being of the body. More specifically, it is the science of nutrients and
how they are digested, absorbed, transported, metabolized, stored, and
discharged by the body. Besides studying how food works in the body,
nutritionists are interested in how the environment affects the quality and
safety of foods, and how these factors influence health and disease.
What are nutrients?
Nutrients are substances that are involved in the creation of every molecule
in the body. The body needs more than 45 nutrients, and the ways that nutrients
are used are as varied as the molecules, cells, and tissues they help to create.
Carbohydrates, proteins, and fats (called macronutrients) are broken down
(metabolized) to give the body energy. Vitamins and minerals (called
micronutrients) are not themselves metabolized for energy, but they are crucial
in helping the macronutrients convert to energy.
What is the history of clinical nutrition?
The study of human nutrition dates back to the 18th century, when the French
chemist Lavoisier discovered that there was a relationship between our
metabolism of food and the process of breathing. By the early 20th
century, scientists had found that diseases were associated with certain diets
(beri-beri, rickets, scurvy and pellagra). Later it was found that these diets
lacked specific nutrients (namely vitamin B1 [thiamine], vitamin D, vitamin C,
and vitamin B3 [niacin] respectively). By 1912, the Polish chemist Casimir Funk
had found a substance (vitamin B1) that actually prevented beri-beri, and
he named it "vitamine."
In the early 1940s, Recommended Dietary Allowances (RDAs) were established by
the National Research Council. The RDAs define the minimal nutrient intakes
necessary for the prevention of basic deficiency diseases like beri-beri and
rickets. Until recently, these guidelines were used to set nutritional adequacy
standards for the general population.
Researchers and scientists also continue to uncover the therapeutic role of
individual nutrients in the prevention and treatment of disease. For example,
antioxidants like beta-carotene, selenium, vitamin E, and vitamin C,
particularly from foods, appear to protect against the development of heart
disease, cancer, and other chronic degenerative diseases. Dietary Reference
Intakes (DRIs) have been developed to show how much of a nutrient we need every
day to maximize health and lower the risk of chronic disease (in contrast to
RDAs which state the minimal amount to avoid disease secondary to deficiencies).
The field of clinical nutrition has evolved into a practice that is increasingly
incorporated into mainstream medical treatment.
What are nutritional supplements?
The term "nutritional supplement" refers to vitamins, minerals, and
other food components that are used to support good health and treat illness.
For example, plant compounds known as phytochemicals (found abundantly in
tomatoes and soybeans, for example) have powerful disease-battling properties.
While it's possible almost all of the time to successfully incorporate nutrients
into your diet alone, supplementation can help maintain sufficient levels and
produce specific desired effects. For example, supplementation with zinc
supplementation has been shown to reduce the duration of the common cold and
decrease the incidence of acute diarrhea in children.
How do vitamins and minerals work?
Vitamins and minerals play an essential role in the body's normal metabolism,
growth, and development. They do this by helping the body to perform various
tasks. For example, while a vitamin is not a source of energy in and of itself,
it can provide the key the body needs to unlock energy stored in food. Some
vitamins and minerals work together--such as the mineral zinc and vitamin A.
Zinc enables the body to use vitamin A to promote good vision. Deficiencies in
vitamin A may lead to night blindness, a condition in which the eyes have
difficulty adjusting to darkness. Zinc supplementation, therefore, may prevent
this condition by keeping vitamin A functioning normally. Supplementation alone,
however, is not the answer to long-term good health. Combining a healthful diet
with a regular exercise program and a positive mental attitude has been shown,
time and again, to be the best bet for a healthy lifestyle.
What constitutes a healthful diet?
The optimal diet for improving health has to be individualized to meet your
unique needs. The USDA food pyramid suggests that we use fat "sparingly," and
that our daily diet include two to three servings of dairy products; two to
three servings of meat, poultry, fish, eggs, beans, or nuts; three to five
servings of vegetables; two to four servings of fruit; and six to eleven
servings of bread, cereal, rice, or pasta. But the numbers alone don't tell the
whole story. Our food needs are influenced by many factors, including age,
gender, body size, pregnancy, and health. A clinical nutritionist can help you
determine what type of diet is best for you.
What happens during a visit to a clinical nutritionist?
During the initial part of the visit, the clinical nutritionist will ask you
questions about your medical history, family history, and personal lifestyle.
The medical history might include questions about your diet, digestion, history
of weight loss or gain, sleep and exercise patterns, and relaxation habits. Some
clinical nutritionists will ask you to bring to your first meeting a 3-day food
diary and list of any herbs, supplements, or medicines that you take regularly.
Laboratory tests might be used to find any deficiencies and test organ function.
This way, a nutritionist will get a full picture of your nutritional
During the second part of the visit, the nutritionist will recommend ways
that you can fill the gaps and reduce the nutritional "overloads" in your diet.
For example, if appropriate, he or she may suggest that you schedule your meals
at different times or cut down on the amount of carbohydrates that you eat. He
or she will also offer advice on specific nutritional supplements if necessary
(see below). The nutritionist will then schedule follow-up visits to monitor the
progression of your health.
What is clinical nutrition good for?
Studies show that eating habits play a major role in the development of
certain chronic diseases (such as heart disease, obesity, cancer, and diabetes).
Dietary changes can help to both prevent and treat these conditions. For
example, lowering fat and cholesterol intake and adding whole grains to the diet
can atherosclerosis (plaque build up in the arteries) which can lead to heart
disease or stroke. Reducing caloric intake can help lower weight. Cutting down
on simple sugars (glucose, sucrose, fructose, and lactose) can prevent diabetes,
and high fiber diets (especially soluble fiber) can help control diabetes.
Scientists have found many other connections to diet and disease. In a study
of 20,000 men, for example, one fish meal per week was linked to a 52% reduction
in the risk of sudden death from a heart attack. Fish is high in omega-3 fatty
acids, which are essential components of cells and can protect the heart from,
for example, fatal arrhythmias (abnormal heart rhythm).
In another study of more than 42,000 women, those who ate lots of fruits,
vegetables, whole grains, low-fat dairy, and only lean meats lived longer. High
intake of fruits, vegetables, and legumes is associated with a lower risk of
developing heart disease.
There are numerous, ongoing studies regarding clinical nutrition. Some
interesting results indicate that:
- high dietary intake of folate (found in leafy greens, dry beans and
peas, fortified cereals and grain products, and some fruits and vegetables) may
lower risk of stroke and heart disease
- eating small amounts of fish in pregnancy may protect against early
delivery and low birth weight infants
- iron supplementation in iron depleted women improves aerobic training
- lutein and zeaxanthin (carotenoids) in the diet may reduce risk of
- lutein from dietary sources (such as kale and spinach) may protect
against colon cancer
- flavonoids (found in broccoli, citrus fruits, apples, onions, and
carrots) may protect against certain types of lung cancer
- vitamin E (in the diet from fruits and vegetables) may reduce the risk
of angina (chest pain) and heart attack in people with
In hospitals, nutrition is used to improve the overall health of patients
with a wide range of conditions. Examples of these conditions are AIDS, cancer,
osteoporosis, lung disease, obesity, burns, metabolic disorders, and kidney,
liver, and pancreatic disorders. Patients who need surgery are also supported
with clinical nutrition.
Is there anything I should watch out for?
Adverse interactions between medications and nutritional supplements can
happen; therefore, it is very important to inform your physician about any
dietary supplements you are considering taking. If taking any supplements
according to label directions unless otherwise advised by a qualified
Be aware that there is little scientific information about the effect of
so-called functional foods - foods to which vitamins,
minerals, herbs, or other dietary substances are added --despite their growing
popularity in the market place and claims of beneficial effects. Examples
include calcium-fortified orange juice or soups
containing Echinacea. .
There are many websites offering nutrition information, but not all are
accurate. Visit the Tufts University Nutrition navigator at
www.navigator.tufts.edu for a
rating guide to nutrition websites.
Some common foods, including nuts, wheat gluten, dairy products, fish,
shrimp, soy, bananas and eggs may trigger allergic reactions. If suspected, your
doctor can test for such possible allergies..
How can I find a certified clinical nutritionist?
To find a clinical nutritionist in your area, contact the American Board of
Nutrition at 205-975-8788, the American College of Nutrition at 212-777-1037,
the Clinical Nutrition Certification Board at 972-250-2829, or the American
Dietetic Association at 800-877-1600 (website: www.eatright.org). Specialists in
many alternative health systems (including Traditional Chinese Medicine,
Ayurveda, and naturopathy) also consider food a vital part of preventing and
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