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Nutrition
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Nutrition
Overview
What is clinical nutrition?
Clinical nutrition is the study of the relationship between food and a healthy body. More
specifically, it is the science of nutrients and how they are digested, absorbed, transported,
metabolized, stored, and eliminated 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
what influence these factors have on health and disease.
What are nutrients?
Nutrients are substances that the body needs to live and grow. The body requires more than 45
nutrients, and the ways they are used are as different as the molecules, cells, and tissues they
help to create. Carbohydrates, proteins, and fats -- called macronutrients -- are broken down
(metabolized) to provide energy. Vitamins and minerals -- called micronutrients -- are not used
for energy themselves, but are needed to help macronutrients be used for energy.
What is the history of clinical nutrition?
The study of 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 -- such as beri-beri,
rickets, scurvy, and pellagra -- were associated with certain diets. By 1912, the Polish chemist
Casimir Funk had found a substance (vitamin B1) that actually prevented beri-beri, and he
named it "vitamine." Later it was found that these diseases were caused by the lack of specific
nutrients -- vitamin B1 (thiamine), vitamin D, vitamin C, and vitamin B3 (niacin) respectively.
In the early 1940s, the National Research Council set Recommended Dietary Allowances (RDAs).
The RDAs set the minimum amount of a nutrient needed to prevent diseases like beri-beri and
rickets.
Researchers and scientists continue to find out more about how individual nutrients can help in
the prevention and treatment of disease. But they are also learning how whole foods may allow
many nutrients to work together. For example, antioxidants like beta-carotene, selenium,
vitamin E, and vitamin C, when consumed in foods, appear to protect against the development of
heart disease, cancer, and other chronic degenerative diseases.
The old RDAs have been replaced by Dietary Reference Intakes (DRIs), which show how much of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 listed the minimum amount needed to prevent a deficiency). The field of
clinical nutrition is now increasingly incorporated into mainstream medical treatment.
What are nutritional supplements?
The term "nutritional supplement" refers to vitamins, minerals, and other nutrients that are used
to support good health and treat illness. For example, plant compounds known as
phytochemicals (found in tomatoes and soybeans) have powerful disease-fighting properties.
While it's always best to get nutrients through the foods you eat, sometimes taking a supplement
can help. For example, taking zinc supplements has been reported to shorten the duration of the
common cold and lower 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. For example, while a vitamin is not a source of energy by 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. Not getting enough vitamin A may lead to night blindness, a condition in which the eyes
have trouble adjusting to darkness. Zinc supplementation may help prevent this condition by
helping the body use vitamin A. Another example is calcium and vitamin D. Calcium, which is
very important in bone and heart health, is more readily absorbed if vitamin D is also present.
Taking supplements, however, is not the answer to long-term good health. Combining a healthy
diet with regular exercise and a positive mental attitude has been shown to be the best bet for a
healthy lifestyle.
What constitutes a healthful diet?
The United States Department of Agriculture (USDA) food pyramid suggests that we use fat
"sparingly," and that our daily diet include 2 - 3 servings of dairy products; 2 - 3 servings of
meat, poultry, fish, eggs, beans, or nuts; 3 - 5 servings of vegetables; 2 - 4 servings of fruit;
and 6 - 11 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 or nutritionally oriented doctor can help you
determine what type of diet is best for you. No matter what, you can improve your diet by
adding more fruits and vegetables and cutting back on saturated fat and sugar.
What happens during a visit to a clinical nutritionist?
At first, 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 a 3-day food diary and list of any herbs, supplements, or
medicines that you take regularly. Laboratory tests might be used to find out if you are low in
any nutrients and to test your organ function. This way, a nutritionist will get a full picture of
your nutritional lifestyle.
During the second part of the visit, the nutritionist will suggest ways that you can fill the gaps
and reduce the nutritional "overloads" in your diet. For example, your nutritionist may suggest
that you eat your meals at different times or cut down on the amount of carbohydrates that you
eat. The nutritionist will also offer advice on specific nutritional supplements if necessary (see
below). The nutritionist will then schedule follow-up visits to monitor your health.
What is clinical nutrition good for?
Studies show that eating habits play a major role in the development of certain chronic diseases,
including heart disease, obesity, cancer, and diabetes. Making changes to your diet can help to
both prevent and treat these conditions. For example, lowering certain fats and cholesterol and
adding whole grains to your diet can help prevent atherosclerosis (plaque build up in the
arteries), which can lead to heart disease or stroke. Eat fewer calories will help you lose weight.
Cutting down on simple sugars (glucose, sucrose, fructose, and lactose) can help prevent
diabetes, and diets high in fiber (especially soluble fiber) can help control diabetes.
Scientists have found many other connections between diet and disease. In a clinical study of
20,000 men, for example, eating 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 can protect
the heart from fatal arrhythmias (abnormal heart rhythm).
In another clinical 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 many ongoing studies regarding clinical nutrition. Some interesting results show that:
Diets high in 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 when pregnant may protect against early delivery and low birth
weight infants. Some fish may contain higher amounts of mercury, and should only be eaten
in moderation. Ask your obstetrician which types of fish are best for you when pregnant.
Taking iron supplements improves aerobic training ability in iron-depleted women.
Lutein and zeaxanthin (carotenoids) in the diet may reduce risk of cataracts.
Lutein from dietary sources (such as kale and spinach) may protect against colon cancer.
Flavonoids (found in apples, blueberries, broccoli, cabbage, carrots, citrus fruits, onions, and
teas) may protect against cancer.
Omega-3 fatty acids found in cold water fish (such as herring, tuna, and salmon) help reduce
inflammation and help prevent certain chronic diseases, such as heart disease, cancer, and
arthritis.
Vitamin E (in the diet from fruits and vegetables) may reduce the risk of angina (chest pain)
and heart attack in people with atherosclerosis.
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?
Some nutritional supplements can interact with medications; it is very important to tell your
doctor about any dietary supplements you are considering taking. Always take supplements
according to label directions unless otherwise directed by a qualified health care practitioner.
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 marketplace. Examples include calcium-fortified orange juice or snacks
containing Echinacea.
Some common foods, including nuts, wheat gluten, dairy products, fish, shrimp, soy, bananas
and eggs, may trigger allergic reactions. Your doctor can test for such possible allergies if he
suspects you have them.
How can I find a certified clinical nutritionist?
To find a clinical nutritionist in your area, contact:
The American Board of Nutrition: www.acbn.org
The American College of Nutrition: www.amcollnutr.org
The Clinical Nutrition Certification Board: www.cncb.org
The American Dietetic Association: 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 treating illness.
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