& Joannie Dobbs Wednesday,
Balanced living keeps senses
The senses of taste and smell are essential for successful evolution and survival of the human species. Both senses are needed for the selection of safe food and to protect against eating foods that are spoiled and toxic. Luckily, the sensitivity of these two senses is remarkable. Only a few molecules are needed for humans to identify many substances.
The perceptions of smell and taste are related. This is especially obvious when a person with a cold finds foods don't taste as good as when smell and taste are normal.
Olfaction (smell) and taste problems are uncommon, however a decrease in sensitivity of either sense can reduce the quality of life and be a sign of various health problems.
Taste sensitivity can vary from one person to another due to genetic differences. Some people actually have a greater density of taste buds than others, resulting in a keener sense of taste. However, a major change in the senses of taste or smell can be an indication of health problems.
Among the most common health problems causing changes in taste and smell are respiratory ailments such as hay fever, asthma and bronchitis. Many medical conditions require medications that can result in major changes in the senses of smell or taste. A loss of the sense of taste or changes in taste sensations makes foods less palatable. Sometimes foods will take on metallic flavors or taste saltier.
Some drugs can cause a decrease in saliva production which also decreases taste sensitivities.
Inadequate intake of several nutrients also can cause sensory problems.
The main nutrients involved in maintaining normal smell and taste sensations are vitamins A and B1 (thiamin) and iron, zinc and copper. Deficiencies of any of these nutrients can cause a decreased ability to enjoy the flavors of food.
Nutrient relationships with the senses of taste and smell are complex. And to complicate matters further, excessive intake of some nutrients can indirectly cause problems with other nutrients and thereby affect smell and taste. For example, zinc lozenges are now sold to decrease the duration of cold symptoms. Most zinc lozenge products contain an average of 12 mg zinc per lozenge (5-23 mg range) and generally the instructions are to take a lozenges every 4 hours.
The U.S. RDA Committee has recommended zinc supplements of less than 15 mg/day to prevent toxic effects such as impaired iron and copper status, anemia and suppressed immune function. If zinc lozenges are taken over a few days to assist with cold symptoms, then toxicity is not likely to occur. However, if symptoms last a couple of weeks or longer and a person is taking the manufacturer's recommended dose throughout that time, negative side effects can occur and affect taste by causing an iron or copper deficiency.
Anecdotally, age has been associated with decreased acuity of the senses of smell and taste, however recent research indicates this decrease is only minimal in healthy older persons.
So it seems the message is, yet again, all about balance. It is important to maintain a good balance of nutrient intake with a wide variety of foods, and to keep use of nutritional supplements balanced as well.
Alan Titchenal, Ph.D., C.N.S. and Joannie Dobbs, Ph.D., C.N.S.
are nutritionists in the Department of Human Nutrition, Food and Animal Sciences,
College of Tropical Agriculture and Human Resources, UH-Manoa.
Dr. Dobbs also works with the University Health Service
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