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January 20, 2017

Tiny But Mighty

This micromineral helps us repair damaged DNA and makes a big difference in our health. Can you guess what it is?

It's easy to understand why zinc is often underrated. It is found in tiny amounts throughout the body, and we only need to eat a little of it. What zinc does for our bodies, however, is crucially important; and a new study suggests that a moderate increase in how much we eat may yield big results.

Zinc is present in every part of the body and is an essential building block of thousands of proteins. Without adequate zinc, the body’s ability to repair damaged DNA is compromised.

This makes it important for proper growth in children, insulin activity, sexual maturation, a healthy immune system and liver function. Zinc also helps limit oxidative stress and inflammation, both of which are linked to chronic cardiovascular diseases and cancers.

Increasing zinc intake by just four milligrams a day reduced oxidative stress and damage to DNA, which improved the health of cells that fight infections and diseases.

DNA carries our genetic information in the form of long, delicate strands of molecules. Damage to these strands is inevitable — whether caused by normal cellular processes or exposure to radiation, drugs, chemical agents or ultraviolet light. Fortunately, cells normally have the ability to repair themselves, but they need proteins to do this, and that's where zinc comes in.

To study the impact of zinc on DNA repair, researchers at UCSF Benioff Children's Hospital Oakland Research Institute (CHORI) looked at DNA damage rather than measuring zinc levels in the blood or other parameters of zinc status.

Simply Increasing zinc intake by four milligrams a day, the researchers found, reduced oxidative stress and damage to DNA. It also improved the health of cells that fight infections and diseases. Four milligrams are about the amount of zinc found in servings of the biofortified crops grown for nutrient deficient populations, where polished white rice or highly refined flours supply adequate calories but not essential micronutrients like zinc, are household staples.

The best food source of zinc is oysters, but red meat, poultry, beans, nuts, whole grains, fortified cereals and dairy foods are also good sources.

“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 researcher, Janet King, in a statement. “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.”

The best food source of zinc is oysters, but red meat and poultry provide the bulk of the mineral in the American diet. Beans, nuts, whole grains, fortified cereals and dairy foods are also good sources (see the list below). The recommended dietary allowance of zinc for adult men is 8 milligrams and for women it’s 11 milligrams.

Since many areas of the world don’t have adequate access to zinc-rich foods, the study results suggest a way to reduce the problem of hidden hunger and malnutrition. Biofortification of foods with zinc could be a long-term solution to the problem of zinc deficiency in vulnerable populations.

Percent of Daily Value of Zinc in Certain Foods

  • Oysters, cooked, breaded and fried, 3 ounces 493%
  • Beef chuck roast, braised, 3 ounces 47%
  • Crab, Alaska king, cooked, 3 ounces 43%
  • Beef patty, broiled, 3 ounces 35%
  • Breakfast cereal fortified with 25% of the DV for zinc, ¾ cup 25%
  • Baked beans, canned, plain or vegetarian, ½ cup 19%
  • Chicken, dark meat, cooked, 3 ounces 16%
  • Yogurt, fruit, low fat, 8 ounces 11%
  • Cashews, dry roasted, 1 ounce 11%
  • Chickpeas, cooked, ½ cup 9%
  • Cheese, Swiss, 1 ounce 8%
  • Milk, low-fat or non fat, 1 cup 7%
  • Almonds, dry roasted, 1 ounce 6%
  • Kidney beans, cooked, ½ cup 6%
  • 1/2 Chicken breast, roasted, skin removed 6%
  • Cheese, cheddar or mozzarella, 1 ounce 6%
  • Peas, green, frozen, cooked, ½ cup 3%

    The study is published in the American Journal of Clinical Nutrition.

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