Zinc

by Jack Norris, RD

Contents

• Essential Information
• Dietary Reference Intakes for Zinc
• Zinc Content of Plant Foods
• Additional Tips
• Zinc Deficiency
• Zinc Absorption and Status of Vegans
• Bibliography

Essential Information

Vegans tend to meet the RDA for zinc, but due to zinc being harder to absorb from plant foods, some vegans might need more than the RDA. If a vegan has found that while on the diet they easily catch colds, develop angular cheilitis (cracks in the corners of the mouth), diarrhea, or hair loss, then a modest zinc supplement of about 50-100% of the RDA might resolve such issues.

Dietary Reference Intakes

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 (USDA National Nutrient Database for Standard Reference).

Additional Tips

Fermenting soyfoods enhances zinc absorption; tempeh and miso are fermented (Messina, 2001).

Regarding supplements, zinc gluconate and zinc citrate are two form of zinc that are well-absorbed; some people don’t absorb zinc oxide (Wegmüller, 2014). There’s evidence, though weak, that zinc picolinate is also absorbed well (Barrie, 1987). Zinc gluconate may be the best choice due to lower levels of cadmium (Krone, 2001).

Zinc Deficiency

A 2020 review summarizes the myriad of conditions that can be associated with zinc deficiency (Hassan, 2020):

A zinc deficiency is characterized by impaired immune function, loss of appetite, and growth retardation. More severe cases of zinc deficiency cause diarrhea, delayed sexual maturation, hair loss, eye and skin lesions, impotence, and hypogonadism in males. Weight loss, taste abnormalities, delayed healing of wounds, and lethargy can also occur.

Zinc is also implicated in some cases of angular cheilitis (cracks in the corners of the mouth; Gaveau, 1987).

Many reputable sources report that zinc deficiency impairs immune function. One source says:

Zinc deficiency has been known for 50 years and is associated with skin abnormalities, hypogonadism, cognitive impairment, growth retardation, and imbalanced immune reactions which favor allergies and autoimmune diseases….

…[A] balanced zinc homeostasis is crucial for either defending against invading pathogens or protecting the human body against an overreactive immune system causing autoimmune diseases, chronic inflammation or allergies (Wessels, 2017).

There isn’t much research studying zinc deficiency and colds; the research mostly focuses on treating colds with therapeutic amounts. But one study on older adults suggests that correcting zinc deficiency can prevent colds and other infections. Prasad et al. (2007, University of Michigan) conducted a randomized, controlled study on zinc supplementation in men and women aged 55 to 87 years. Measurements at baseline suggested that the older participants had, on average, sub-optimal zinc status. The study lasted one year with the treatment group receiving 40 mg of zinc per day. There were 24 people in the treatment group and 25 in the placebo group. At the end of 12 months, fewer participants in the treatment group had experienced infections (29% vs. 88%, P< 0.001), including upper respiratory tract infections (12% vs. 24%, P= 0.136), and common colds (16% vs. 40%, P=0.067).

A study of healthy adults found that eating oysters, which are high in zinc, improved sleep patterns, but it’s not clear if the zinc component of the oysters was responsible (Saito, 2017, Cherasse, 2017).

Zinc Absorption and Status of Vegans

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% (Institute of Medicine, 2001).

Below is a chart showing the zinc intakes of vegans from 4 studies (larger version).

Of the 5 measurements reported, vegans met the RDA except for in the EPIC-Oxford study which found that vegan men had slightly lower zinc intakes than the RDA. The method of determining zinc intake in EPIC-Oxford, by way of food frequency questionnaire, is generally less reliable than are 3-day diet records which were used in the smaller studies in Switzerland and Germany.

These studies showed that on average vegans have lower blood zinc levels than meat-eaters but within the reference ranges. However, in the Switzerland study, 47% of vegans were below the reference range, indicating that vegans should be aware of their zinc intakes and monitor for deficiency symptoms.

Bibliography

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.

Cherasse Y, Urade Y. Dietary Zinc Acts as a Sleep Modulator. Int J Mol Sci. 2017 Nov 5;18(11):2334.

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. Not cited.

Gaveau D, Piette F, Cortot A, Dumur V, Bergoend H. Manifestations cutanées du déficit en zinc dans la cirrhose éthylique [Cutaneous manifestations of zinc deficiency in ethylic cirrhosis]. Ann Dermatol Venereol. 1987;114(1):39-53. French. Abstract.

Hassan A, Sada KK, Ketheeswaran S, Dubey AK, Bhat MS. Role of Zinc in Mucosal Health and Disease: A Review of Physiological, Biochemical, and Molecular Processes. Cureus. 2020 May 19;12(5):e8197.

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

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

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

Prasad AS, Beck FW, Bao B, Fitzgerald JT, Snell DC, Steinberg JD, Cardozo LJ. Zinc supplementation decreases incidence of infections in the elderly: effect of zinc on generation of cytokines and oxidative stress. Am J Clin Nutr. 2007 Mar;85(3):837-44.

Rizzo NS, Jaceldo-Siegl K, Sabate J, Fraser GE. Nutrient profiles of vegetarian and nonvegetarian dietary patterns. J Acad Nutr Diet. 2013 Dec;113(12):1610-9.

Schüpbach R, Wegmüller R, Berguerand C, Bui M, Herter-Aeberli I. Micronutrient status and intake in omnivores, vegetarians and vegans in Switzerland. Eur J Nutr. 2017 Feb;56(1):283-293.

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

Saito H, Cherasse Y, Suzuki R, Mitarai M, Ueda F, Urade Y. Zinc-rich oysters as well as zinc-yeast- and astaxanthin-enriched food improved sleep efficiency and sleep onset in a randomized controlled trial of healthy individuals. Mol Nutr Food Res. 2017 May;61(5).

Sobiecki JG, Appleby PN, Bradbury KE, Key TJ. High compliance with dietary recommendations in a cohort of meat eaters, fish eaters, vegetarians, and vegans: results from the European Prospective Investigation into Cancer and Nutrition-Oxford study. Nutr Res. 2016 May;36(5):464-77.

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.

Weikert C, Trefflich I, Menzel J, Obeid R, Longree A, Dierkes J, Meyer K, Herter-Aeberli I, Mai K, Stangl GI, Müller SM, Schwerdtle T, Lampen A, Abraham K. Vitamin and Mineral Status in a Vegan Diet. Dtsch Arztebl Int. 2020 Aug 31;117(35-36):575-582.

Wessels I, Maywald M, Rink L. Zinc as a Gatekeeper of Immune Function. Nutrients. 2017 Nov 25;9(12):1286.