Zinc 2

by Jack Norris, RD

Contents

• Summary
• Dietary Reference Intakes for Zinc
• Zinc Content of Plant Foods
• Zinc Deficiency
• Zinc Absorption and Status of Vegetarians
• Zinc Supplements
• References

Summary

Zinc is not found in large amounts in plant foods, but as far as can be detected, vegetarians have similar zinc status to non-vegetarians (1). Zinc is important for immunity and if you find you’re easily catching colds, a modest zinc supplement of about the Dietary Reference Intake (DRI) might solve the problem.

Dietary Reference Intakes for Zinc

See Daily Needs for the zinc DRI.

Zinc Content of Plant Foods

The common plant foods highest in zinc are legumes, nuts, seeds, and oatmeal. The table below shows the zinc content of selected plant foods (2).

Zinc Deficiency

Symptoms of zinc deficiency include poor growth and delayed sexual maturation in children, poor wound healing, hair loss, impaired immune function, and dermatitis—especially around body orifices (3).

Zinc Absorption and Status of Vegetarians

Phytates, which are commonly found in plant foods, reduce zinc absorption, and some researchers have suggested that this increases the zinc needs of vegetarians by up to 50% (4).

In contrast, a 2013 meta-analysis showed vegans to have only a slightly lower serum zinc level than non-vegetarians, a difference of 1.17 ± 0.45 µmol/l (1). Average serum zinc levels are from 10 to 15 µmol/l (5), so it’s doubtful that the differences are meaningful (absolute values for serum zinc were not given in the analysis).

Protein increases zinc absorption. Because of this, foods high in protein and zinc, such as legumes and nuts, are good choices (6). The leavening of bread (most bread is leavened) and fermenting of soyfoods (tempeh and miso) also enhances zinc absorption (6).

Zinc Supplements

A modest zinc supplement up to 100% of the Dietary Reference Intake (DRI) should be safe for those who are concerned or having symptoms of zinc deficiency. See Daily Needs for the DRI and Upper Limit for zinc.

Zinc gluconate and zinc citrate are two forms that are well-absorbed (7). There’s evidence, though weak, that zinc picolinate is also absorbed well (8).

Some people do not absorb zinc oxide (7).

Zinc gluconate may be the best choice due to lower levels of cadmium (9).

References

Last updated February 2014

1. Foster M, Chu A, Petocz P, Samman S. Effect of vegetarian diets on zinc status: a systematic review and meta-analysis of studies in humans. J Sci Food Agric. 2013 Apr 17.

2. USDA National Nutrient Database for Standard Reference.

3. Groff J, Gropper S. Advanced Nutrition and Human Metabolism, 3rd ed. Wadsworth: 2000.

4. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. (2001) Food and Nutrition Board, Institute of Medicine. Accessed 12/28/2010.

5. Dietary reference intakes: the essential guide to nutrient requirements. National Academy of Sciences. 2006.

6. Messina V, Mangels AR. Considerations in planning vegan diets: children. J Am Diet Assoc. 2001 Jun;101(6):661-9.

7. Wegmüller R, Tay F, Zeder C, Brnic M, Hurrell RF. Zinc absorption by young adults from supplemental zinc citrate is comparable with that from zinc gluconate and higher than from zinc oxide. J Nutr. 2014 Feb;144(2):132-6.

8. Barrie SA, Wright JV, Pizzorno JE, Kutter E, Barron PC. Comparative absorption of zinc picolinate, zinc citrate and zinc gluconate in humans. Agents Actions. 1987 Jun;21(1-2):223-8.

9. Krone CA, Wyse EJ, Ely JT. Cadmium in zinc-containing mineral supplements. Int J Food Sci Nutr. 2001 Jul;52(4):379-82.

Also Reviewed

Dietary Supplement Fact Sheet: Zinc. Office of Dietary Supplements. National Institutes of Health. Accessed 12/15/2010.

Singh M, Das RR. Zinc for the common cold. Cochrane Database Syst Rev. 2013 Jun 18;6:CD001364.