Zinc for Seniors and Magnesium for Teens

Healthy Aging, Zinc and Immunity

Functioning of the immune system declines as we age, and those 55 and older are more susceptible to infections. From a global perspective, this presents a challenge to public health systems as the number of elderly worldwide is expected to double by 2050.

As people grow older, they also tend to eat fewer calories, making it harder to meet their vitamin and mineral needs. Zinc is one of several important nutrients that are essential for maintaining a robust immune response, and low levels of this mineral have been found to occur in seniors. Recently, researchers from the University of Michigan and Wayne State University Medical School teamed up to see whether zinc supplements could help boost immunity in fifty healthy seniors aged 55 to 87 (1).

Fewer Infections, Less Oxidative Stress

At the start of the study, the subjects generally had lower blood levels of zinc and higher levels of oxidative stress than a group of younger adults. Oxidative stress occurs when there are more cell-damaging free radicals than the body's antioxidants are able to eliminate.

Study participants received either 45 mg of zinc or a placebo daily over the next 12 months. At the end of the year, those taking zinc had significantly fewer infections than their placebo-taking counter parts.

Blood samples showed that zinc levels had risen and markers of oxidative stress had decreased markedly in the supplemented group. Those getting zinc also generated fewer cytokines, a group of white blood cells that play a key role in inflammation. These findings make sense since zinc has both antioxidant and anti-inflammatory actions.

Zinc: Sensible Supplementation

While too little dietary zinc can negatively impact immune function, extraordinary high levels have also been reported to impair immune cell function. So it's generally prudent for most healthy people to keep supplemental zinc levels to about 40 mg daily. One common exception would be people with age-related macular degeneration (AMD). Those with AMD can benefit from the 80 mg of zinc and antioxidant combination shown to slow progression of this disease in the AREDS trial.

Magnesium and Healthy Bones for Teens

Just as zinc can bolster immune defenses in older individuals, good magnesium intake may well have long-term benefits for adolescent girls. Women are four times more likely to develop osteoporosis later in life than men. Since adolescence is a key time for achieving peak bone mass, Yale researchers examined whether magnesium supplementation in young girls could improve their bone mineral mass and, perhaps, lower their risk of osteoporosis in later years (2).

Higher Bone Mineral Content

The investigators recruited 120 girls aged 8-14, and enrolled those who were not consuming at least 220 mg of magnesium daily into the trial. Volunteers then received either 300 mg of supplemental magnesium (150 mg. twice daily) or placebo for one year.

At the end of the study, girls in the magnesium group had a significantly greater bone mineral content in their hips - one of the most common fracture sites in women with osteoporosis. While bone mineral content was slightly higher in the spine as well, it did not reach statistical significance. The magnesium supplements were safe and well tolerated.

Higher levels of magnesium than were tested in this study can sometimes cause loose stools in sensitive individuals. Gradually phasing in supplementation can reduce this potential side effect. Good dietary sources of magnesium include green leafy vegetables, whole grains, nuts and low fat dairy.

References

1. Prasad AS, et al. Zinc supplementation decreases incidence of infections in the elderly: effect of zinc on generation of cytokines and oxidative stress. American Journal of Clinical Nutrition 85:837-844, 2007.
2. Carpenter MC, et al. A randomized controlled study of effects of dietary magnesium oxide supplementation on bone mineral content in healthy girls. Journal of Endocrinology & Metabolism 91:4866-72, 2006.