Modest increase in zinc intake may reduce 'wear and tear' on DNA

The study’s findings, published in the American Journal of Clinical Nutrition​​, is said to be the first to show that a modest increase in dietary zinc reduces oxidative stress and damage to DNA.

“We were pleasantly surprised to see that just a small increase in dietary zinc can have such a significant impact on how metabolism is carried out throughout the body,”​ said Dr Janet King, Senior Scientist at UCSF Benioff Children's Hospital Oakland Research Institute (CHORI) and lead researcher in the study.

“These results present a new strategy for measuring the impact of zinc on health and reinforce the evidence that food-based interventions can improve micronutrient deficiencies worldwide.”​

Zinc​

Zinc is an essential part of nearly 3,000 different proteins, and it impacts how these proteins regulate every cell in our body. The micronutrient is required for many biological processes, including growth and development, neurological function and immunity. It is naturally found in protein-rich foods such as meat and shellfish, with oysters among the highest in zinc content.

Deficiency of the micronutrient is a global problem.

The 4 mg increase used in the new study is equivalent to what biofortified crops like zinc rice and zinc wheat can add to the diet of vulnerable, nutrient deficient populations.

Study details​

The randomized, controlled, six-week study involved 18 men consuming a diet containing 6 mg of zinc per day for two weeks, followed by four weeks of consuming a diet containing 10 mg of zinc per day.

Results showed that total absorbed zinc increased with increased dietary zinc, but the concentration of zinc in the plasma did not change. The body’s zinc pool also did not change, said the researchers.

DNA strand breaks in leukocytes were decreased with increased dietary zinc, said the researchers, while the dietary zinc increase also restored the level of proteins involved in DNA repair and antioxidant and immune functions.

“The multiple metabolic responses to a marginal increase in dietary zinc that were observed in this study suggest that the framework that is used to evaluate zinc status needs to be modified,” ​wrote the researchers. “Modest changes in dietary zinc, as is typical with changes in the composition of human diets, caused a shift in the serum concentrations of multiple proteins, thereby reflecting several metabolic functions rather than a single, specific biomarker. ​

“Proteins that are associated with preventing DNA damage, oxidative stress, and inflammation changed without any changes in [plasma zinc concentrations]. We suggest that a combination of endpoints that are linked to a key metabolic function (i.e., DNA damage) can be used as bioindicators of the relation between zinc nutrition and a nonspecific functional outcome.”​

According to King, these results are relevant to the planning and evaluation of food-based solutions for mitigating the impact of hidden hunger and malnutrition. The CHORI scientist believes that biofortification can be a sustainable, long-term solution to zinc deficiency.

Source: American Journal of Clinical Nutrition​​
Published online ahead of print, doi: 10.3945/​ajcn.116.135327
“A moderate increase in dietary zinc reduces DNA strand breaks in leukocytes and alters plasma proteins without changing plasma zinc concentrations”​
Authors: S.J. Zyba et al.