Zinc - a comprehensive guide

Summary

Zinc is a mineral we only need in very small amounts, yet it is has many known roles in the body. It acts as a cofactor for around 100 different enzymatic reactions, which break down and produce different substances within the body. It is needed for good immune function, growth and development, vision, and good fertility, amongst others. The best food sources of zinc are oysters, followed by seeds such as pumpkin and sesame, and meat – especially beef.

Primary functions of Zinc

  • Zinc contributes to immune system function. One of its roles is as a signalling molecule between immune cells, i.e. allowing them to communicate with each other as part of the body’s immune response [2]. It may also have anti-inflammatory activity.[3]
  • Zinc is needed for fertility and reproduction. It may be particularly important for male fertility, as adequate levels of zinc are needed for normal sperm function [1].
  • Zinc has a role in vision. It’s highly concentrated in eye tissue, including in the retina; and zinc deficiency is thought to be linked to altered vision and even certain eye diseases [4].
  • Zinc helps to normalise testosterone levels in the blood. For both men and women, lower-than-normal levels of testosterone can cause low sex drive, low energy, and/or loss of muscle mass. Having excessively high levels may also be a problem, especially in women.
  • Zinc contributes to the health of our bones, skin, hair and nails.
  • Zinc supports wound healing and growth [5]. This may be primarily because it is needed for DNA synthesis and cell division.
  • Zinc has a role in the metabolism of carbohydrates, fats and proteins, and is needed for protein synthesis. This means it helps these nutrients to be broken down and made into other substances in the body, including building new proteins.

How much zinc do we need?

The nutrient reference value for zinc in the UK is 10 mg for adults. Nutrient reference values refer to the amount needed to ensure that the needs of nearly all the population (97.5%) are being met.

Food sources

The best common food sources of zinc are:

  • Oysters – they are by far the highest source. 100 grams of oysters can provide over 100 mg of zinc, which can work out to around 70 mg per serving of 6 oysters. So one serving per week is all you would need to get your weekly allowance!
  • Calves’ liver – providing up to 12mg per 100 grams.
  • Beef, lamb and game meat, and other types of liver, providing up to 10mg per 100 grams.
  • Sesame and pumpkin seeds, providing up to 10mg per 100 grams, and smaller amounts in sunflower seeds – around 5 mg per 100g.
  • Nuts: cashews, pine nuts and pecans provide 5 to 6mg per 100 grams.
  • Pulses: aduki beans and lentils provide 4 to 6mg per 100 grams (dry weight).

Deficiency signs and symptoms*

Severe zinc deficiency is quite rare, and marginal or mild deficiency is more prevalent in developing countries. However, certain populations of people even in the Western world are more likely to experience zinc deficiency, including children and adolescents (periods of rapid growth), anyone who has poor nutrient absorption, women during pregnancy and breastfeeding, older adults, and strict vegetarians [6].

Symptoms may include [7]:

  • Poor immunity, or increased susceptibility to infections
  • Infertility or impotence
  • Poor wound healing
  • Acne
  • Poor appetite
  • Loss of sense of smell/taste
  • Rough or dry skin
  • White spots on the finger nails.

Forms and bioavailability / What to look for when buying a supplement

In supplements, like most other minerals, zinc is more absorbable in some forms than others.

  • Zinc oxide may not be as well absorbed as some other forms, and is not considered a good choice to take as a supplement.
  • Zinc citrate and zinc gluconate are also commonly found in supplements, including in zinc lozenges. In a study on young adults, researchers found that these two forms of zinc are significantly better absorbed than zinc oxide [8]. Both are considered good forms to take.
  • Zinc picolinate is also considered a good form for absorption, and may be even better than zinc citrate or gluconate.[9]
  • Zinc methionine – sometimes under the name OptiZinc® – is zinc attached to the amino acid methionine. It too is considered one of the better-absorbed forms of zinc [10], and may be less likely to bind with phytic acid in foods compared to other types of zinc [11] (binding to phytic acid reduces mineral absorption).
  • ‘Food form’ zinc is found in a small number of supplements. It is a natural form of zinc that may be better absorbed and utilised in the body than ‘isolated’ zinc (as found in most supplements).

In summary, our top recommendations are zinc methionine, zinc picolinate or food-form zinc, followed by zinc citrate and zinc gluconate.

Dosages: Lifestyle Labs’ recommendations

Adults: Supplements for adults typically provide between 15 mg and 50 mg of zinc per daily dose. Up to 30mg of zinc is considered safe to take long-term, but copper should generally be supplemented as well (in a ratio of 15:1 zinc to copper – e.g. 30mg of zinc to 2mg of copper). This is because zinc can reduce the absorption of copper, and may result in a copper deficiency with long-term use. A high dosage of 50mg of zinc may typically be recommended for someone who is known to be deficient in zinc or to have very low levels of zinc in their diet. This high dosage would normally be recommended for a fixed period of time, and then reduced to a lower dose. Taking more than 50mg on a daily basis is not advisable unless recommended by a practitioner.

If you’re taking an individual zinc supplement and a multivitamin, check the total amount you are getting each day to make sure you’re not taking too much.

Children: There are small number of zinc supplements on the market suitable for children under 12, which tend to provide up to about 8mg per daily dose. More than this may be recommended by a healthcare practitioner.

Safety

If you are taking any medications or have any medical condition, please consult your healthcare practitioner before taking an individual zinc supplement.  

Zinc is generally a very safe supplement to take for most people. However, as mentioned above under ‘Dosages’, if you are taking an individual zinc supplement on a long-term basis, check you are not taking too much in conjunction with any other supplements, and that what you are taking is balanced with copper.

 

REFERENCES

  1. Fuse H et al. Relationship between zinc concentrations in seminal plasma and various sperm parameters. Int Urol Nephrol. 1999;31(3):401-8.
  2. Prasad AS. Zinc: role in immunity, oxidative stress and chronic inflammation. Curr Opin Clin Nutr Metab Care. 2009 Nov;12(6):646-52. doi: 10.1097/MCO.0b013e3283312956.
  3. Prasad AS. Zinc in human health: effect of zinc on immune cells. Mol Med. 2008 May-Jun;14(5-6):353-7.
  4. Grahn BH et al. Zinc and the eye. J Am Coll Nutr. 2001 Apr;20(2 Suppl):106-18.
  5. Barceloux DG. Zinc. J Toxicol Clin Toxicol. 1999;37(2):279-92.
  6. http://lpi.oregonstate.edu/mic/minerals/zinc [This link leads to a website provided by the Linus Pauling Institute at Oregon State University. Lifestyle Labs is not affiliated or endorsed by the Linus Pauling Institute or Oregon State University.]
  7. Osiecki, H. (n.d.). The Nutrient Bible. 9th ed. Bio Concepts Publishing, p.211.
  8. Wegmüller R et al. 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.
  9. Barrie SA et al. Comparative absorption of zinc picolinate, zinc citrate and zinc gluconate in humans. Agents Actions. 1987 Jun;21(1-2):223-8.
  10. Chien XX et al. Bioavailability, antioxidant and immune-enhancing properties of zinc methionine. Biofactors. 2006;27(1-4):231-44.
  11. Rosado JL et al. Zinc supplementation reduced morbidity, but neither zinc nor iron supplementation affected growth or body composition of Mexican preschoolers. Am J Clin Nutr. 1997 Jan;65(1):13-9.

       

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      Dr. Lifestyle

      Dr. Lifestyle is our own collective of leading health, nutrition and fitness experts. Having several brains makes it really hard to decide what we feel like for breakfast (Chia Coconut Pudding, or a Green Smoothie?), but when it comes to health advice we are an all-knowing, hyper-intelligent, super human.