Strengthening the Immune System (The Body's Internal Battle: Immune Health)

Some of the more well-known immune boosters are zinc, vitamin C and Echinacea. In a 2008 study, lipopolysaccharide (LPS)-challenged adult male mice were fed a zinc-adequate (40 ppm) or a zinc-marginal (4 ppm) diet for four weeks, and then a bacterial challenge was simulated by intraperitoneal injection of LPS (10 mcg/g body weight) or saline (control).⁸ Diet did not affect body weight and feed intake. The LPS challenge led to decreased voluntary locomotor activity (P<0.05). Moderate zinc restriction led to greater leukocyte infiltration in the lamina propria after the LPS challenge (P<0.05) and higher plasma IL-6 and IL-10 levels 24 hours after the LPS challenge (P<0.01).

In another study published in Vaccine, researchers immunized a sub-cohort of 241 Bangladeshi infants who had previously received three doses of a Hib (Haemophilus influenzae) conjugate vaccine with three doses of the heptavalent pneumococcal protein conjugate (PNC) vaccine at four-weeks intervals beginning at 18 ± one weeks of age.⁹ The infants were supplemented with 5 mg/d of zinc or a placebo from 4 to 33 weeks of age. After three doses of PNC, at 29 weeks of age, geometric mean titres for the pneumococcal serotypes ranged from 3.68 to 13.34 μg/ml. Titres were significantly higher for infants who had received PNC compared to infants who had only received DTP-Hib. Zinc supplementation resulted in higher titres for serotype 9V and 3.33 μg/ml for the zinc and placebo group, respectively, (P<0.05) after three doses, but had no effect on other serotypes. Zinc supplementation enhanced the immune response to only one of the serotypes (9V); however, there was no effect on other serotypes.

A study at the University of Michigan, Ann Arbor found zinc supplementation lowered the incidence of infections, increased plasma zinc, and significantly lowered the generation of tumor necrosis factor alpha (TNF-a) and oxidative stress markers in healthy elderly subjects.¹⁰

Contrary to previous findings, a study published in The Journals of Gerontology Series A: Biological Sciences and Medical Sciences found an intake (diet plus supplementation) of up to 40 mg/d of zinc did not have significant long-term effects on immune status in apparently healthy persons aged 55 to 70 years.¹¹ For six months, 15 mg/d or 30 mg/d of zinc were examined on immune status in healthy individuals. At baseline, zinc concentration was positively associated with lymphocyte subpopulation counts and T-lymphocyte activation. Zinc supplementation of 30 mg/d significantly lowered B-lymphocyte count, at month three only. Lower doses of 15 mg/d of zinc significantly increased the ratio of CD4 to CD8 T lymphocytes at month six.