Zinc is an important trace mineral, required as a cofactor to more proteins than any other mineral in human nutrition. Evidence suggests that zinc intakes have been declining in Western nations as food habits have changed. In particular, the gradual switch to the modern Western diet, that has been occurring over the last century, has lowered the zinc intake of the populations that are living in developed nations. Many studies attest to the poor zinc status of Western populations, and this poor status is reflected in biochemical changes to the systems that rely on the zinc metalloproteins for function. From studies of human subjects it is known that zinc deficiency is able to cause altered taste perception. Studies have reported altered taste sensations in unhealthy subjects as a result of a zinc deficiency secondary to other health issues. However, evidence in the nutritional literature suggests that this altered taste perception can occur in a relatively short time after following a low zinc intake even in otherwise healthy adults.
For example, one group of researchers1 fed healthy subjects a diet containing 15 mg of zinc per day or a depletion diet containing only 0.25 mg of zinc per day. From the data they collected, the authors reported that the taste sensations of sodium chloride (salt) solutions were significantly reduced during zinc depletion compared with the 15 mg per day basal zinc diet. However, this altered perception was only evident at less concentrated solutions. The authors also showed that there were no associations between the altered taste perception for sodium chloride with the salivary concentration of zinc, the length of time to depletion, or the change in the plasma zinc concentration. The salt solutions that were used in this study that altered taste perception ranged from 75 to 150 mM sodium chloride, which in laymen’s terms could be described as moderately salty. Therefore zinc depletion may alter taste perceptions for salt at physiologically and nutritionally relevant intakes of salt.
When the authors fed the depleted subjects a repletion diet containing 15 mg zinc per day, the taste perceptions showed a trend to returning to normal, but were still altered compared to baseline at the end of the two week repletion period. In addition, the authors noted that bitter taste sensations were not altered by zinc depletion, suggesting that the bitter taste buds on the palate are less affected by zinc status than the salt taste buds located primarily on the anterior of the tongue. Evidence suggests that large numbers of Westerners are deficient in zinc and so it is likely that the taste perception of such individuals is dysfunctional. One possible consequence of this may be that ingestion of low quality foods becomes more likely as the normally high salty taste of such foods becomes altered. This could explain part of the reason that such foods tend to be over eaten by certain individuals. Ensuring proper zinc status may therefore be a requirement of successful weight loss through its effects on taste sensation.
Dr Robert Barrington’s Nutritional Recommendation: The requirement of zinc for an adult will depend on biochemical individuality as well factors in the diet such as phytate and iron intakes. A simple way to gauge zinc status is with a zinc taste test or a hair mineral analysis. The zinc taste test (here) is based on the requirement of zinc for correct taste perception, and is a useful way to assess zinc status. Hair mineral analysis uses the mineral content of the hair to assess whole body status and can be a reliable marker for mineral intakes (here). If a deficient status exists, supplementation with an organically bound form of zinc in the 15 mg per day range should be followed before retesting. If no improvements are seen incremental increases in zinc intake should be tried until zinc status is restored. Working closely with a nutritionist is advisable when attempting to redress mineral deficiencies because supplementation of isolated minerals can cause mineral imbalances.
RdB
