Shucked open Oysters cooking on a hot chargrill

Are You Getting Enough Zinc?

What is Zinc?

Zinc is a bluish white-grey metal which is essential for survival by all living things. Humans have known about zinc for over 2,500 to 3000 years and can be traced to Palestine, India and Transylvania.1,2,3,4 It wasn’t until 1961 that zinc deficiency was discovered thus it’s importance to human health recognised.5 The world produces approximately 11 million tonnes per year mainly in China, Australia and Peru.1

Zinc is a naturally occurring trace element found in both animal and plant food products. We need a very small amount of it. The body cannot make zinc therefore an adequate diet is required. It is present in every living cell in your body and we lose it daily through the gastrointestinal tract, kidneys, skin, semen and menstruation.6 To say zinc is important greatly understates how essential it is for life. The average body contains about 2-3 grams of zinc7 of which we have no specific system to store it 8 though exists in every cell in the body, predominantly muscle and bone.7  How much zinc we ingest per day differs greatly depending on the diet and deficiencies are not uncommon.

The Role of Zinc

It is imperative each and every human consumes enough zinc to maintain homeostasis of bodily mechanisms.5 Having adequate zinc is imperative for immune function, growth and brain development, sexual maturation and function, nucleic acid synthesis to regulate gene expression, protein metabolism, carbohydrate and lipids(fats) metabolism, cellular function, wound healing, collagen and other tissue deposition and construction, taste sharpness, and preventing functional movement disorders.5,6,8,

  • Immune function
  • 300+ enzyme processes
  • Protein synthesis
  • Cellular division, function and metabolism
  • Growth and development during pregnancy, childhood, and adolescence
  • Brain development and function
  • Nerve function
  • Reproductive health and fertility
  • DNA synthesis
  • Skin health
  • Wound healing
  • Hair health (strength and thickness)
  • Proper taste and smell

Zinc Deficiency

Zinc deficiency can be mild or severe. Mild deficiency can cause low immunity hence more coughs and colds among other things, poor pregnancy, abnormal growth pre- and post-pregnancy and development of children.

A more severe deficiency can result in impaired appetite, diarrhoea, skin irritation, delayed healing, hair loss, delayed sexual development, impotency, eye and skin lesions, loss of smell. Deficiencies may be the result of infection, trauma, stress, poor diet, excessive alcohol consumption and other diseases which can cause zinc deficiency.6

­­Naturally occurring

Your body absorbs it from the diet and also releases it from your reserves. Because it is the most abundant trace element behind iron it is used in many processes. In fact, it is used countless ways in the body. Zinc is involved in all six enzymatic classes of action of ligases, lyases, hydrolases, isomerases, oxidoreductases, and transferases (or seven if you include translocases) therefore extremely important in metabolism, adding up to over 300 enzymatic actions.9

Some groups of people may be at risk of lower zinc serum levels and therefore are encouraged to eat foods naturally high in zinc, fortified or via supplementation. Zinc absorption is greater from a rich animal protein diet compared to a rich plant-based diet. This does not mean a plant-based diet is poor.

Vegetarians

Vegetarians (and vegans) require higher amounts of zinc (~50% more) in their diet as they do not eat from the most abundant sources, being meat (flesh of all animals) which is highly bioavailable zinc.1,10 In a meta-analysis of zinc levels in vegetarians and vegans it was found that vegans had modestly lower levels.10

They concluded that unless the diets contained very high amounts of phytic acid (whole grains, legumes (unfermented, unsprouted) or had lower dietary intakes in general the body does a good job of maintaining zinc levels.  Unfortunately, in some of the studies though vegans were included in the ovo-lacto vegetarian groups which limits the data.

If you are concerned a blood test can confirm your levels. Consuming a zinc supplement or zinc fortified foods would also boost levels.

So, what is phytic acid?

Nonmeat eaters, or very health-conscious people tend to consume more naturally occurring phytic acid or phytate.  Phytate is found in whole grain cereals (including the husk, bran or outer layer), legumes, oil seeds such as sunflower kernels, soybeans, soybean products, sesame seeds, linseeds(flaxseed) and rape seeds, along with nuts.

Phytates (the salt of phytic acid) binds to zinc which inhibits absorption during transition through the small intestine.5,12 What phytate is further broken down is done by fermentation when it reaches the large intestine(colon) but by this time is too late for zinc which needs to be absorbed in the small intestine.11

Phytates also have an affinity with aluminium, calcium, iron, magnesium, cadmium and other heavy metals which means they may help to rid the body of heavy metals12 so trying to eliminate or avoid phytate is not the solution. Phytates have beneficial properties such as anticancer, antioxidative and anticalcification (kidney stones) benefits.11

How to Mitigate Phytates

To reduce phytate, consume sprouted legumes (germinated for 48 hours) as they contain next to no phytates as it is degraded to release phosphorus for the new plant.11 Fermented legumes as in soybean tempeh and fermented tofu would be your second-best bet.

Phytates are heat stable to approximately 100°C and only about ¼ is degraded under normal home cooking methods.11 That is boiling, pressure cooking, refrying. Just to make things more confusing soaking and cooking reduces both phytate and zinc levels13 while adding salt or organic acids (vinegar, citrus juice) to foods may help trace element bioavailability.12

Zinc (Sulfate) Taste Test

If you Google ‘Zinc Taste Test’ you will find many sites speaking of its efficacy, but science has shown mixed results due to subjectivity of the measurement protocol.

Gruner (2012)14 calls it somewhat inaccurate and warrants more research, while Zdilla (2015) mentions its cost effectiveness but with limitations15 even though there were statistically significant positive correlations (2016).16 Unfortunately a correlation does not equal causation and in my opinion having a blood test though less cost effective and more invasive would be far more beneficial and give a myriad of data.

­­­­­­Too Much Zinc

There are no adverse effects of consuming too much zinc from foods naturally high in zinc.6 Too much zinc can suppress your immune response and interfere with absorption of other minerals, particular iron and copper and further deplete copper stores. Too much can also reduce your beneficial high-density lipoprotein (HDL) cholesterol. It can also reduce magnesium and calcium absorption. On the other hand, too much iron in supplements can reduce zinc absorption. Too much zinc is usually the effect of over supplementation.6

Normal serum zinc is 0.66 to 1.10 mcg/mL.

Zinc Supplement

As always consult a qualified practitioner to justify supplementation for you as an individual. If you think you may be low in zinc boosting food sources should be your first choice. Some supplements which are high doses suggested for cold and flu season and required to only be taken at onset for a number of days in a row not ongoing. Some are lower does allowing for more frequent long-term use while others are not recommended for daily use so read the label carefully.

Zinc for The Common Cold

There is very mixed data that supports taking zinc acetate supplementation in the form of lozenges to treat the common cold. Older studies have shown that ≥75mg (up to 100mg) zinc acetate with in 24 hours of cold onset and continuing for the duration of the cold can reduce duration but not the severity of symptoms.17,18 However the most recent study19 (2020) showed no difference in recovery in a randomised, double blind, placebo-controlled trial of 253 men and women in Finland of which 87 were included in the analysis.

Food Fortification

Foods may be fortified by permission of the Food Standards Code which means the addition of synthetic vitamins or minerals that boost the nutritional content of that food. Food fortification can help individuals improve their nutrition if their diet is insufficient.

Food fortification with zinc in Australia is not compulsory like it is with folic acid, thiamin, fluoride or iodine. Many foods are fortified. Fortification with zinc is voluntary and may be found in breads, cereals, biscuits, cereal flours, pasta, plant-based meat substitutes, and other plant-based yogurts and cheese products. The manufacturer must identify zinc on the label if it has been added.20     

There are many forms of zinc both naturally occurring on synthesized for food fortification. Essentially they all do the same job, provide elemental zinc. The differences are dosage or for mode of delivery to aid in absorption. As always if supplementing read the label and follow the directions precisely.

Supplement Warning

Always be aware when taking supplements. Read the label, any warnings and get qualified practitioner advice to make sure it is right for you. Supplements can cause adverse reactions and interfere with medications.

Some people notice an immediate or short-term difference with supplement usage, especially Zinc. It is not recommended to take zinc continuously unless it is a small dose. Some supplements are a therapeutic dose, meaning a larger dose. This means they can be taken for shorter periods of time to help alleviate or speed a cure. (check with your qualified practitioner, pharmacist, dietician or nutritionist).

How Much Do We Need?

Recommended Daily Intake (RDI) (These values are for an Australia population)

RDI Zinc

Adult men 14mg/day

Adult women 8mg/day; pregnancy10-11mg/day; lactation 11-12mg/day

Naturally occurring zinc in food (not fortified) is safe. However total zinc from all sources including naturally, supplemental and fortification of foods should be kept below the upper limit.

UL (Upper Limit) Zinc

Adults 40mg; pregnancy & lactation 14-18 yr. 35mg/day, 19-50 yr. 40mg/day

Too much zinc can deplete copper and cause a range of other symptoms. Remember all vitamins and minerals work together in many ways so altering the balance can have adverse effects.


COVID-19

There are few trials and many anecdotes on zincs effect on COVID-19 disease. COVID-19 is responsible for the disease called Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). As of the 8th of December 2020, a quick PubMed search came up with 154 results searching for “COVID-19, zinc”.

Will zinc provide immunity to COVID-19? Nobody can conclusively say yes. (yet)

Are vitamins D, A, C, Folate, B6, B12 and minerals zinc, iron, copper and selenium essential for the proper functioning of the immune system? Absolutely yes.21

Photo credit: Huang Yikai

The Best Sources of Zinc from Food

It’s easy to search for best food sources of zinc. Unfortunately, they are practically incomplete and don’t tell the full picture. Zinc is contained in almost any food. We also maintain adequate levels of nutrients by the total volume of food we eat. That is to say we eat a wide variety of foods to sustain energy, achieve adequate micronutrients and maintain a healthy weight. Focusing on just one food group or omitting one food group will lead to deficiencies without supplementation, so eat a wide variety of unprocessed food.

Many foods do not contain zinc or in such low levels they would never make any list. These include:

Alcohol, soft drinks, high sugar foods, margarine, butter, oils, low egg mayonnaise (all store bought), dressings, tea, coffee, egg whites, white bread, white chocolate, and confectionary.

Foods to Provide Zinc

Oysters (Best source)

Pipi (Goolawa Cockle, Surf Clam) (Best source)

Herring

Crab (very good source)

Sardines

Lobster (very good source)

Mussels (very good source)

Kangaroo tail

Echidna

Yabby

Beef (very good source)

Mutton (very good source)

Lamb (very good source)

Turkey

Pork chop

Cheese

Liver

Anchovy

Poultry

Protein powder

Bacon (eat only occasionally)

Salami (eat only occasionally)

Pâté (eat only occasionally)

Photo credit: Sorin Gheorghita

Non-Meat Sources of Zinc

Sundried tomatoes (very good source)

Cocoa powder (very good source)

Lentils (good source) – see phytate

Pumpkin seeds (good source)

Sunflower seeds (good source)

Tahini

Cashews

Almond meal

Peanuts (good source)

Peanut butter (good source)

Fortified breads, cereals and cereal products (If the food claims to be fortified on high in zinc it will be included in the ingredient label)

Tofu

Split peas – see phytate

Oats

Hazelnuts

Beans – see phytate

Chickpeas (Garbanzo beans) – see phytate

Walnuts

Chia seeds

Ground linseed

Hemp seeds

Pumpkin seeds

Wholemeal bread – see phytate

Quinoa – see phytate

The volume of these foods would be substantial to achieve adequate intake of zinc. Remember the total food intake supplies your nutrients. Therefore, if you were to drink a 500ml soft drink you would already be over calories for the day if you ate enough food to get zinc. Vegans need to be diligent in attaining a very focused nutrient dense diet.

More Tips for Vegans

Eating sprouted legumes (chickpeas, mung beans) that have germinated for 48 hours reduces phytates allowing for higher zinc.

Fermentation is your next best option, like Tempeh or fermented tofu.

Soaking and cooking has a small effect at reducing phytates even at pressure cooking. Cooking bean burgers on a flat grill may destroy more phytate.

Eat more sprouted legumes to allow for the loss of zinc.

Discarding soaking and cooking water during preparing and cooking legumes has a minor effect.

Don’t always eat whole unhulled legumes, brown rice, black sesame seeds, etc. Pair them with other high zinc sources and splash with an acid like vinegar or lemon juice.

Eat bread which has had the base culture fermented (sourdough is better than yeast fermented). Better still look for zinc fortified bread.

My Conclusion

Enjoy life and eat a variety of low processed fresh foods with a plentiful rainbow of vegetables, two pieces of fruit a day, some meat, some fish, some oysters and crustaceans, only occasional whole grains (or none at all), while limiting processed foods, soft drinks, confectionery, high salty snacks, high sugar, high fat, and high additive foods. Eat freshly cooked or prepared foods. Most importantly eat to live not solely for fun and excitement.  Still appreciate and enjoy the amazing world of food without suffering the consequences of excessive consumption.

Yours in health and fitness

Jerome

References

[1] Royal Society of Chemistry. Zinc [Internet]. 2020. Available from: https://www.rsc.org/periodic-table/element/30/zinc#:~:text=chills’%20can%20occur.-,Natural%20abundance,and%20calamine%20(zinc%20silicate).

[2] PubChem [Internet]. Bethesda (MD): National Library of Medicine (US), National Center for Biotechnology Information; 2004-. PubChem Element Summary for AtomicNumber 30, Zinc; [cited 2020 Nov 20]. Available from: https://pubchem.ncbi.nlm.nih.gov/element/Zinc

[3] McDowell L. Mineral nutrition history: The early years. First Edition Design Publishing 2017. 774 p.

[4] Craddock, PT. The early history of zinc. Endeavour [Internet]. 1987 [cited 2020 Nov 20]; 11(4) 1987:183-191. Available from: https://doi.org/10.1016/0160-9327(87)90282-1

[5] Roohani N, Hurrell R, Kelishadi R, Schulin R. Zinc and its importance for human health: An integrative review. J Res Med Sci. 2013 Feb;18(2):144-57. PMID: 23914218; PMCID: PMC3724376.

[6] National Health and Medical Research Council. Zinc [Internet]. Canberra (AU): Australian Government. 2014 [Updated 2014 Apr 09; cited 2020 Dec 8]. Available from: https://www.nrv.gov.au/nutrients/zinc

[7] Plum LM, Rink L, Haase H. The essential toxin: impact of zinc on human health. Int J Environ Res Public Health. 2010;7(4):1342-1365. DOI:10.3390/ijerph7041342

[8] National Institute of Health. Zinc [Internet]. US Department of Health & Human Services. 2020 [Updated 2020 July 15; cited 2020 Nov 20]. Available from: https://ods.od.nih.gov/factsheets/Zinc-HealthProfessional/

[9] McCall KA, Huang C, Fierke CA. Function and mechanism of zinc metalloenzymes. J Nutr [Internet]. 2000 May [cited 2020 Nov 25];130(5):1437S1446S. Available from: https://doi.org/10.1093/jn/130.5.1437S

[10] 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 [Internet]. 2013 Apr 17 [cited 2020 Nov 23];93(10):2362-2371. Available from: https://doi-org.ezp01.library.qut.edu.au/10.1002/jsfa.6179

[11] Schlemmer U, Frølich W, Prieto RM, Grases F. Phytate in foods and significance for humans: food sources, intake, processing, bioavailability, protective role and analysis. Mol Nutr Food Res [Internet]. 2009 Sep;53 Suppl 2:S330-75. DOI: 10.1002/mnfr.200900099. PMID: 19774556.

[12] Zhang YY, Stockmann R, Ng K, Ajlouni S. Revisiting phytate-element interactions: implications for iron, zinc and calcium bioavailability, with emphasis on legumes. Crit Rev Food Sci Nutr [Internet]. 2020 Nov 16 [cited 25 Nov 2020]. Available from: https://doi.org/10.1080/10408398.2020.1846014

[13] Hummel M, Talsma EF, Taleon V, Londono L, Brychkova G, Gallego S, Raatz B, Spillane C. Iron, zinc and phytic acid retention of biofortified, low phytic acid, and conventional bean varieties when preparing common household recipes. Nutrients [Internet]. 2020 Feb 28 [cited 2020 Dec 1];12(3):658. Available from: https://doi.org/10.3390/nu12030658

[14] Gruner T, Arthur R. The accuracy of the zinc taste test method. J Altern Complement Med [Internet]. 2012 Jun [cited 2020 Dec 4];18(6):541-550. Available from:  https://doi.org/10.1089/acm.2011.0298

[15] Zdilla MJ, Starkey LD, Saling JR. A taste-intensity visual analog scale: An improved zinc taste-test protocol. Integr Med Clin J [Internet]. 2015 Apr [cited 2020 Dec 1];14(2):34–38. Available from: https://search-ebscohost-com.ezp01.library.qut.edu.au/login.aspx?direct=true&db=c8h&AN=109801451&site=ehost-live&scope=site

[16] Zdilla MJ, Saling JR, Starkey LD. Zinc sulfate taste acuity reflects dietary zinc intake in males. Clin Nutr ESPEN [Internet]. 2015 Dec 23 [cited 2020 Dec 6];11, e21 – e25. Available from: https://doi.org/10.1016/j.clnesp.2015.11.004

[17] Singh M, Das RR. WITHDRAWN: Zinc for the common cold. Cochrane Database Syst Rev [Internet]. 2015 Apr 30 [cited 2020 Dec 6]; (4):CD001364. DOI: 10.1002/14651858.CD001364.pub5

[18] Hemilä H, Fitzgerald JT, Petrus EJ, Prasad A. Zinc acetate lozenges may improve the recovery rate of common cold patients: An individual patient data meta-analysis. Open Forum Infect Dis [Internet]. 2017 [cited 2020 Dec 6];4(2) ofx059. Available from: https://doi.org/10.1093/ofid/ofx059

[19] Hemilä H, Haukka J, Alho M, Vahtera J, Kivimäki M. Zinc acetate lozenges for the treatment of the common cold: A randomised controlled trial. BMJ open [Internet]. 2020 Jan 23 [cited 2020 Dec 6]; 10(1)e031662. DOI:10.1136/bmjopen-2019-031662

[20] Food Standards Australia & New Zealand. Vitamin and minerals added to food [Internet]. Canberra (AU). Updated 2016 Jun [cited 2020 Dec 7]. Available from: https://www.foodstandards.gov.au/consumer/nutrition/vitaminadded/Pages/default.aspx

[21] Galmés S, Serra F, Palou A. Current state of evidence: Influence of nutritional and nutrigenetic factors on immunity in the covid-19 pandemic framework. Nutrients [Internet]. 2020 Sep 8 [cited 2020 Dec 7];12(9):2738. Available from: https://doi.org/10.3390/nu12092738

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