"Functional foods" are those that have health benefits beyond basic nutrition. The term phytochemical for example, refers to the health promoting compounds that come from plant sources. Food components with health benefits that are found in animal sources are increasingly referred to as "zoochemicals." A familiar example is iron consumed in foods such as beef, pork, and chicken. Scientific support for the healthful benefits of many other less well-known zoochemicals continues to emerge and looks very promising.
Zoochemicals—like most zoos—cover a lot of ground; it would require hours to see everything. Here's a quick tour of a few promising examples:
CLA—Conjugated Linoleic Acid
"CLA" stands for "conjugated linoleic acid"—a fatty acid identified in the 1970s by Dr. Michael Pariza, researcher and director of the Food Research Institute at the University of Wisconsin, Madison. Pariza had been investigating the potential for carcinogenic effects in ground beef when he instead discovered a compound that could block the growth of tissues that support cancer. The active compound was identified as CLA—a form of linoleic acid with a differing arrangement of bonds within the molecule—hence the term "conjugated."
Preliminary research suggests that CLA may not only suppress cancer cell development, but may also help reduce risk of heart disease, boost the immune system, build lean muscles, and diminish body fat in animals. CLA is a naturally occurring substance in the guts of ruminant or cud-chewing animals like cows, and is present in particular meat and dairy products. Additional emerging research suggests that livestock eating feed supplemented with CLA may produce more lean tissue; dairy cattle ingesting CLA enriched diets seem to have greater milk productivity.
Lutein and Zeaxanthin
Lutein and zeaxanthin are both phytochemicals and zoochemicals. Whether originating from plant or animal sources, of the more than 600 carotenoids found in nature, only lutein and zeaxanthin are specifically located in the macula and lens of the human eye. These yellow carotenoids appear to shield the eye from harmful blue light (blue being the complementary color to yellow) and may protect against age-related macular degeneration, the leading cause of blindness in people over sixty-five. Lutein and zeaxanthin are usually mentioned together because of their similar chemical structures, however they differ in the placement of one key double bond, which gives each distinct properties.
Blue light, just above the UV spectrum, is the highest energy and potentially most damaging wavelength of light that reaches the retina. The way in which the retina is organized, light must first pass through the highest concentrations of lutein and zeaxanthin before reaching the sensitive rod and cone cells. It is thought that the greater the protective layer containing these compounds, the less damage will occur to the retina. While many food sources of lutein and zeaxanthin are plant based, egg yolk contains a significant amount of these zoochemicals.
Omega-3 Fatty Acids—DHA and EPA
The fat in fish contains a class of polyunsaturated fatty acids called omega-3s. These fatty acids differ from the most common polyunsaturated fatty acids found in vegetable oils, called omega-6s, and have different effects on the body.
Long chain omega-3s—eicosapentaenoic acid (EPA) and docosahexanoic acid (DHA)—are found in abundance in cold-water fish such as salmon, trout, mackerel, and tuna. Fish do not make these fats but obtain them from the plankton they eat; the colder the water, the more omega-3s the plankton contains. Likewise, humans can also consume omega-3s—alpha-linolenic acid (ALA)—from plant sources such as flax and walnuts. However, the human body must convert ALA to EPA and DHA in order to have a similar health impact.
Cardiovascular benefits derived from the consumption of the marine omega-3 fatty acids were first noticed during epidemiological studies in the Greenland Inuits, an Eskimo population that consumed large amounts of traditional marine mammals and fish, and had little mortality form coronary artery disease. Since then, there has been a major expansion of our knowledge on omega-3 fatty acids and their beneficial role in health.
Several recent prospective observational studies have concluded that consumption of one fish serving per week decreased the risk of fatal coronary heart disease by approximately 40% relative to a no fish diet. The beneficial effect of omega-3 fatty acids may be related to their ability to prevent atherosclerosis through several mechanisms, including their lowering effect on serum triglyceride levels and blood pressure, their anti-inflammatory or anti-thrombotic effect, or their ability to prevent cardiac arrhythmias.
Currently, the U.S. Food and Drug Administration (FDA) allows a qualified health claim for omega-3 fatty acids and reduced risk of coronary heart disease for dietary supplements and has indicated that they will prioritize evaluations of qualified health claims for foods. Since omega-3 fatty acids inhibit blood clotting, supplements should not be used by those who have blood clotting disorders or by individuals taking anticoagulant medications. Eating two or three fish meals a week is a reasonable strategy supported by the American Heart Association (AHA).
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Zoochemicals—At A Glance
|
|
Zoochemical
|
Animal-Derived Food Source
|
Potential Health Benefits
|
Type of Scientific Evidence
|
Conjugated
Linoleic Acid
(CLA) |
Beef
Dairy Products
(whole or part-fat,
not skim)
Lamb |
May reduce risk
of breast tumors |
Animal studies
|
| Lutein |
Egg Yolk
|
May reduce risk
of cataracts and
age-related
macular
degeneration
|
Epidemiological
studies |
Omega-3
Fatty Acids
|
Fish and eggs with
omega-3 fatty
acids |
May reduce risk
for coronary heart
disease |
Epidemiological
studies (fish);
Clinical trials
Animal studies |
| Zeaxanthin |
Egg Yolk |
May reduce risk
of cataracts and
age-related
macular
degeneration |
Epidemiological
studies |
