Post date: 20.08.2011 11:40 PM

Zinc is an essential mineral found in cells throughout the body. It has many functions which include helping the immune system fight off invading bacteria and viruses. Zinc also plays a role in the synthesis of proteins and DNA, the genetic material in all cells. During pregnancy, infancy, and childhood, the body needs zinc to grow and develop properly. Zinc also helps wounds to heal and is important for proper senses of taste and smell.

Should you take zinc with other mineral supplements? Let’s see…

• Copper – Taking large quantities of zinc (50 mg/day or more) over a period of weeks can interfere with copper bioavailability. High intake of zinc induces the intestinal synthesis of a copper-binding protein called metallothionein. Metallothionein traps copper within intestinal cells and prevents its systemic absorption. More typical intakes of zinc do not affect copper absorption and high copper intakes do not affect zinc absorption.

• Iron –  Zinc and Iron do not go together. Supplemental (38-65 mg/day of elemental iron) but not dietary levels of iron may decrease zinc absorption. This interaction is of concern in the management of iron supplementation during pregnancy and lactation and has led some experts to recommend zinc supplementation for pregnant and lactating women taking more than 60 mg/day of elemental iron.

• Calcium -  High levels of dietary calcium impair zinc absorption in animals, but it is uncertain whether this occurs in humans. One study showed that increasing the calcium intake by 890 mg/day in the form of milk or calcium phosphate (total calcium intake, 1,360 mg/day) reduced zinc absorption and zinc balance in postmenopausal women, but increasing the calcium intake of adolescent girls by 1,000 mg/day in the form of calcium citrate malate (total calcium intake, 1,667 mg/day) did not affect zinc absorption or balance. Calcium in combination with phytic acid reduces zinc absorption. This effect is particularly relevant to individuals who very frequently consume tortillas made with lime (i.e., calcium oxide).

• Folic acid – The bioavailability of dietary folate is increased by the action of a zinc-dependent enzyme, suggesting a possible interaction between zinc and folic acid. In the past, some studies found low zinc intake decreased folate absorption, while other studies found folic acid supplementation impaired zinc utilization in individuals. However, a more recent study reported that supplementation with a relatively high dose of folic acid (800 mcg/day) for 25 days did not alter zinc status in a group of students being fed low-zinc diets (3.5 mg/day); level of zinc intake did not impair folate utilization in this study.

• Vitamin A -  Zinc and vitamin A are friends. Zinc and vitamin A interact in several ways. Zinc is a component of retinol-binding protein, a protein necessary for transporting vitamin A in the blood. Zinc is also required for the enzyme that converts retinol (vitamin A) to retinal. This latter form of vitamin A is necessary for the synthesis of rhodopsin, a protein in the eye that absorbs light and thus is involved in dark adaptation. Zinc deficiency is associated with decreased release of vitamin A from the liver, which may contribute to symptoms of night blindness that are seen with zinc deficiency.

Okay, now let us take a quick look at Calcium and vitamins…

• Calcium – Getting too much calcium can cause constipation. It might also interfere with the body’s ability to absorb iron and zinc, but this effect is not well established. In adults, too much calcium (from dietary supplements but not food) might increase the risk of kidney stones.

• Vitamin A – Red blood cells need iron to make hemoglobin, the chemical that carries oxygen through the body. Taking vitamin A seems to improve hemoglobin levels in people who have low levels of iron and vitamin A.

• Folate – Beware of the interaction between vitamin B12 and folic acid. Intake of supplemental folic acid should not exceed 1,000 micrograms (μg) per day to prevent folic acid from triggering symptoms of vitamin B12 deficiency. Folic acid supplements can correct the anemia associated with vitamin B12 deficiency. Unfortunately, folic acid will not correct changes in the nervous system that result from vitamin B12 deficiency. Permanent nerve damage can occur if vitamin B12 deficiency is not treated.
  
  It is very important for older adults to be aware of the relationship between folic acid and vitamin B12 because they are at greater risk of having a vitamin B12 deficiency. If you are 50 years of age or older, ask your physician to check your B12 status before you take a supplement that contains folic acid. If you are taking a supplement containing folic acid, read the label to make sure it also contains B12 or speak with a physician about the need for a B12 supplement.

Sources:

“Folate” Office of Dietary Supplements, National Institutes of Health http://ods.od.nih.gov/factsheets/VitaminB12/

“Vitamin A ” Medline Plus. http://www.nlm.nih.gov/medlineplus/druginfo/natural/964.html

“Vitamin B12“. Office of Dietary Supplements, National Institutes of Health http://ods.od.nih.gov/factsheets/VitaminB12/

“Zinc” Linus Pauling Institute. Oregon State University. http://lpi.oregonstate.edu/infocenter/minerals/zinc/

“Zinc” Office of Dietary Supplement, National Institutes of Health. http://ods.od.nih.gov/factsheets/Zinc-QuickFacts/