I thought it would be appropriate to write a post about zinc, since it was the topic of my thesis research (I have a feeling nobody is going to read my thesis, unless for some reason they have to).
Zinc is a very under-appreciated and over-looked nutrient. It is not often the topic of breaking news reports or dinner conversations. I have never heard anyone say, “I should eat some shellfish, I need more zinc in my diet,” or “I love pumpkin seeds! They are an excellent source of zinc!” Although severe zinc deficiencies are rare in developed countries, mild to moderate deficiencies are extremely prevalent, so people actually should think more about their intakes.
Here are some interesting (well, I think so) facts about zinc:
- Zinc is necessary for proper functioning of vitamin A. In one study in Nepal, zinc deficient women that were treated with vitamin A for night-blindness were 4X more likely to respond if vitamin A and zinc supplements were taken together. This is because, without adequate zinc, vitamin A cannot travel from the liver to the tissues where it is needed (such as the eye).
- Zinc from animal sources (eg. meat) is more easily absorbed than zinc from plant sources (eg. whole grains). This is because some plants contain phytates, which bind to zinc and prevent its absorption in the intestine.
- High doses of mineral supplements (such as iron) can prevent absorption of zinc (and vice-versa), because these two minerals compete for the same transporter.
Daily requirements of zinc: Recommended Dietary Allowance= 11 mg for men and 9 mg for women.
Rich food sources of zinc: beef (4.1 mg/100g serving), lamb (3.3 mg/100g serving), some seafood–especially oysters (90 mg/100g!), pumpkin and squash seeds (7.5 mg/100g) and whole grains (wheat: 2.9mg/100g).
Deficiency symptoms: impaired growth (in children), slow wound healing, reduced reproductive function (in men), dermatitis, and increased severity of infections. There is also evidence that zinc deficiency can increase the risk of some cancers (due to its role in DNA repair).
(photo credit: http://periodictable.com/Samples/030.7/s13.JPG)