Zinc is an important trace mineral required as a cofactor for a large number of proteins in mammalian nutrition. In animal models of zinc nutrition, it has been demonstrated that zinc deficiency causes a significant deterioration in the response of T cells (T lymphocytes) and the function of the thymus which negatively affects acquired immunity. However, these deleterious effects are reversible upon supplementation with zinc. In humans, zinc deficiency has also been investigated with regard the effects on immunity and studies show that as with animals, humans experience a deterioration in immune function with poor zinc status, particularly in the response of cell mediated immunity. The investigations into the immune suppressing effects of zinc deficiency are interesting considering studies show a poor zinc status in those who consume a typical Western diet. Such a diet is devoid of meaningful level of many trace elements and this puts the consumer at high risk of developing a zinc deficiencies and immune suppression.
The effects of zinc supplementation on the acquired immune system was demonstrated in one study using healthy human subjects1. Subjects were administered pharmacological doses of zinc sulphate (660 mg) in three doses over a one month period, and their T lymphocyte response to lectins extracted from beans (phytohaemagglutinin and concanavalin A) was assess following blood tests. Zinc supplementation significantly increased the T lymphocyte response to the lectins when compared to the controls. As has been shown elsewhere older women (aged 40 to 60) had lower T lymphocyte responses than younger counterparts, however zinc treatment was effective at improving this response. Zinc is known to be antagonistic to copper metabolism, and so the researchers were interested to know if the zinc supplements negatively affected the levels of copper in the blood. However, there was no evidence that the zinc supplements had any effect on copper levels (although other more sensitive tests were not performed).
These results are interesting because the effect of the zinc treatment was highly dependent on the baseline values of the lymphocyte response. When there was a higher than mean baseline value for the response of the T lymphocytes, values went down on supplementation, whereas when there was a lower baseline value for the response, the values went up. Such modulatory activity in nutrition is not uncommon, but science is yet to understand or replicate the modulatory effects of nutrients and plant phytochemicals on humans. More recent studies2 have suggested that zinc may be able to modulate T lymphocyte response because at low concentrations zinc is able to interact with one set of cellular secondary messengers (such as protein kinase C and lymphocyte protein tyrosine kinase), whereas at higher concentrations zinc might interact with other messengers (such as interleukin-1 receptor-associated kinase (IRAK) and calcineurin). Therefore zinc may modulate T cell activity through a number of different molecular targets.
Dr Robert Barrington’s Nutritional Recommendation: Obtaining an optimal zinc intake is important for the immune system. Low intakes of zinc are associated with poor quality diets such as the typical Western diet. Consuming high quality nutrition based on traditional eating practices, emphasising whole grains and other nutrient dense plant foods, may ensure higher intakes of zinc. However, supplementation is often necessary because of the nutrient deficient soils on which many crops are grown. Athletes and those under high amounts of stress may have a requirement for additional zinc and such individuals will have to rely on supplements.
RdB
