Did You Get Enough Zinc Lately?



A popularity-based ranking of herbs and supplements listed on MedlinePlus[3] (a service of the U.S. National Library of Medicine and the National Institutes of Health) has shown that Zinc maybe is one of the most important nutrients that our body needs.

Let me explain my methodology used in coming up with the ranking first. On MedlinePlus, it lists most of the popular herbs and supplements that have been studied by scientists. For each herb or supplement, it provides a grade which reflects the level of available scientific evidence in support of the efficacy of a given therapy for a specific indication. For example, zinc supplement is used to treat malnourished children with acute diarrhea in multiple studies and it shows that zinc supplement may reduce the severity and duration of diarrhea with strong evidence. Therefore, an evidence grade "A" is assigned to zinc in treating diarrhea among malnourished children.

For each use of herb or supplement in a specific therapy, a grade is given based on an objective criteria. There are 6 grades in the evaluation as shown in the following table:

Level of Evidence Grade Criteria
A (Strong Scientific Evidence) Statistically significant evidence of benefit from >2 properly randomized trials (RCTs), OR evidence from one properly conducted RCT AND one properly conducted meta-analysis, OR evidence from multiple RCTs with a clear majority of the properly conducted trials showing statistically significant evidence of benefit AND with supporting evidence in basic science, animal studies, or theory.

B (Good Scientific Evidence)


Statistically significant evidence of benefit from 1-2 properly randomized trials, OR evidence of benefit from >1 properly conducted meta-analysis OR evidence of benefit from >1 cohort/case-control/non-randomized trials AND with supporting evidence in basic science, animal studies, or theory.
C (Unclear or conflicting scientific evidence) Evidence of benefit from >1 small RCT(s) without adequate size, power, statistical significance, or quality of design by objective criteria,* OR conflicting evidence from multiple RCTs without a clear majority of the properly conducted trials showing evidence of benefit or ineffectiveness, OR evidence of benefit from >1 cohort/case-control/non-randomized trials AND without supporting evidence in basic science, animal studies, or theory, OR evidence of efficacy only from basic science, animal studies, or theory.
D (Fair Negative Scientific Evidence) Statistically significant negative evidence (i.e., lack of evidence of benefit) from cohort/case-control/non-randomized trials, AND evidence in basic science, animal studies, or theory suggesting a lack of benefit.
F (Strong Negative Scientific Evidence) Statistically significant negative evidence (i.e. lack of evidence of benefit) from >1 properly randomized adequately powered trial(s) of high-quality design by objective criteria.
Lack of Evidence Unable to evaluate efficacy due to lack of adequate available human data.


As you can see that grade "A", "B", "C" have been assigned to a herb or supplement for its benefit of a given therapy with the strongest to the weakest positive scientific evidence. In my tabulation, I have counted total number of therapies using a herb or supplement listed on MedlinePlus with a grade "A", "B", or "C". The higher the count is, the more popular that herb or supplement is in the eyes of scientists. Based on the counting, zinc comes up to the top as shown in the following table:

Zinc is necessary for the functioning of more than 300 different enzymes and plays a vital role in an enormous number of biological processes. For example, Zinc
  • Is a cofactor for the antioxidant enzyme superoxide dismutase 
  • Is in a number of enzymatic reactions involved in carbohydrate and protein metabolism
  • Plays a critical role in regulating how neurons communicate with one another, and could affect how memories form and how we learn[2]
  • May lead to symptoms of night blindness[4]
    • Without the proper amount of zinc, vitamin A may not be absorbed as well as it should be
Zinc has gained popularity for its use in the prevention of the common cold. However, we need zinc in only tiny amounts. Most of people eating a zinc-rich diet may not need a supplement. Who needs zinc? Pregnant and breast-feeding women must ensure they are getting adequate supplies of zinc from their diet and/or from supplements, as a lack of this mineral could lead to fetal abnormalities and stunted growth in their babies. Finally, be warned that too much zinc has been linked to a suppression of the immune response.

As I always advocate for getting important nutrients from natural sources — whole foods, not supplements, I'll conclude this article by listing foods that are rich sources of zinc.


Zinc Rich Foods List

Milligrams

Portion
Oysters 25 + 100g
Shellfish 20 100g
Brewers Yeast 17 100g
Wheat Germ 17 100g
Wheat Bran 16 100g
All Bran cereal 6.8 100g
Pine Nuts 6.5 100g
Pecan Nuts 6.4 100g

Ok Sources of Zinc

Milligrams

Portion
Liver 6 100g
Cashew Nuts 5.7 100g
Parmesan Cheese 5.2 100g
Fish 3 100g
Eggs 2 100g


Resources
  1. List of Foods Rich in Zinc
  2. Zinc's role in the brain: Research gives insight into 50-year-old mystery
  3. MedlinePlus - Health Information from the National Library of Medicine
  4. How can I improve my night vision?

Comments