Signs of Zinc Deficiency: Symptoms, Who Is at Risk and Zinc-Rich Foods

The signs of zinc deficiency are getting ill more often than usual, cuts and grazes that are slow to heal, hair thinning, a dulled sense of taste and smell, a scaly red rash around the mouth, nose and on the hands, diarrhoea, poor appetite and, in children, slow growth.^{1, 2} Zinc is needed by hundreds of enzymes and the tissues that turn over fastest, immune cells, skin, gut lining, hair and taste buds, show the shortage first. In the UK, true deficiency is uncommon on a mixed diet, because meat, fish, dairy, eggs, pulses, nuts and wholegrains all supply it; the people who run short are vegans and vegetarians with high-phytate diets, heavy drinkers, people with gut disease or after bariatric surgery, older adults eating little, and pregnant and breastfeeding women.^{2, 3} The reference intake is 9.5 mg a day for men and 7 mg for women, and the fix is food first, with a modest supplement to close the gap, because zinc above 25 mg a day for months causes a copper deficiency that looks like the thing you were trying to treat.

• Signs: frequent minor illness, slow healing, hair thinning, poor taste and smell, rash around the mouth and on hands, diarrhoea, poor appetite, slow growth in children
• Not a sign: white spots on nails, which are almost always minor nail-bed injuries
• Who runs short: vegans and vegetarians, heavy drinkers, coeliac, Crohn's or bariatric surgery, older adults, pregnancy and breastfeeding, some diuretics
• Intake: 9.5 mg men, 7 mg women; up to 25 mg a day from supplements long term
• Richest foods: oysters, beef, lamb, crab, pumpkin seeds, cashews, cheese, lentils, wholegrains

What zinc does, and why these signs

Zinc contributes to the normal function of the immune system, the maintenance of normal skin, hair, nails and bones, normal vision, normal fertility and reproduction, normal cognitive function, normal DNA synthesis and cell division, normal acid-base and carbohydrate metabolism and the protection of cells from oxidative stress.⁴ Read that list against the symptoms and the pattern is clear: when zinc runs short, the tissues that renew fastest and the immune cells that multiply on demand are the first to falter. Taste buds renew every ten days or so and need zinc to do it, which is why a flat or metallic taste is an early sign. Zinc is not stored in any depot, so intake has to be regular, and the body adapts to low intake by absorbing more and losing less, which is why mild shortfall is slow to show and hard to measure.³

The signs in detail

Getting ill more often. More colds and infections, and slower recovery; zinc deficiency impairs the cells that fight them.¹

Slow wound healing. Cuts, grazes, mouth ulcers and pressure sores that linger; zinc is needed for the cell division and collagen work of repair.

Skin. A dry, scaly, sometimes crusted red rash around the mouth and nose, on the hands and feet and in skin folds; in severe deficiency it is unmistakable, in mild cases it looks like eczema that does not respond to the usual creams.

Hair. Diffuse thinning and shedding, reversible with correction; zinc is one of the few nutrients with good evidence in hair loss, alongside iron.²

Taste and smell. Food tastes flat or metallic, appetite falls, and weight can drop; older adults who stop enjoying food deserve a zinc thought.

Gut. Diarrhoea, which both results from and worsens deficiency.

Eyes. Poor night vision, because zinc is needed to use vitamin A in the retina.

Children. Slow growth and delayed puberty, which is how zinc deficiency was first recognised.³

Mood and mind. Irritability, low mood and poor concentration are reported and improve with correction in deficient people; zinc contributes to normal cognitive function.

What is not a sign of zinc deficiency

White spots or flecks on the nails. They are almost always small injuries to the nail bed, knocks and pressure that happened weeks before the mark grew out, and they are not a nutritional sign of anything. Brittle or ridged nails have many causes, zinc rarely among them. Acne is sometimes linked to low zinc in studies and zinc is used in some acne treatments, but acne is not a sign of deficiency in itself.

Who runs short in the UK

Vegans and vegetarians. Plant zinc is bound by phytates in wholegrains, pulses and seeds, so less is absorbed; vegetarians are advised to aim for around 50% more than the reference intake, which a well-planned diet achieves, and soaking, sprouting and fermenting reduce phytates.⁵

Heavy drinkers. Alcohol reduces absorption and increases urinary loss.

Gut disease and surgery. Coeliac disease, Crohn's disease, chronic diarrhoea and bariatric surgery all reduce uptake; lifelong supplementation is standard after bariatric surgery.

Older adults. Smaller appetites, less meat, more medicines, and absorption that falls with age.

Pregnancy and breastfeeding. Demand rises; a pregnancy multivitamin usually covers it.

Some medicines. Thiazide diuretics increase losses; long-term use of some acid suppressants may reduce absorption.

Sickle cell disease and kidney disease, managed by the clinical team.

How is zinc deficiency diagnosed?

With difficulty. Blood zinc is held steady by the body until deficiency is marked, falls with infection and inflammation regardless of zinc status, and varies with the time of day and the last meal, so a normal result does not exclude a mild shortfall and a low result during illness may not mean deficiency.³ Doctors therefore diagnose on the picture: risk factors, symptoms, and a response to supplementation over a few weeks. Hair and sweat tests sold online are not reliable. If you have several of the signs and a reason to be at risk, ask your GP; the test is worth doing, read with its limits in mind.

Zinc-rich foods, per UK portion

• Oysters, 6: about 30 mg, far above anything else
• Beef or lamb, 100 g cooked: about 4 to 6 mg
• Crab, 100 g: about 5 mg
• Pumpkin seeds, 30 g: about 2.2 mg; cashews 30 g: about 1.7 mg
• Cheddar, 30 g: about 1 mg; milk 200 ml: about 0.8 mg
• Lentils or chickpeas, cooked, 120 g: about 1.5 mg; tofu 100 g: about 1 mg
• Wholemeal bread, 2 slices: about 1.4 mg; porridge oats 40 g: about 1 mg
• Chicken thigh, 100 g: about 2 mg; egg, one: about 0.6 mg

Two eggs a day give about 1.2 mg, an eighth of a man's need, so eggs alone are not enough. Bananas and most fruit carry almost none. A mixed diet with meat or fish, dairy, pulses, nuts and wholegrains reaches 9.5 mg without effort; a vegan diet reaches it with pulses, seeds, nuts, wholegrains and tofu daily.

Supplements, and the copper problem

To close a gap, 7 to 15 mg of zinc a day as a supplement is ample, and the UK guidance level for long-term supplements is 25 mg. Above that, zinc blocks copper absorption, and copper deficiency over months causes anaemia, low white cells and nerve damage with numbness and unsteadiness, a picture that can be mistaken for B12 deficiency.⁶ Case reports almost always involve 50 mg or more a day, often from stacking products. Take zinc with food to avoid nausea, two hours away from iron and calcium supplements and from tetracycline and quinolone antibiotics. Zinc nasal sprays have caused permanent loss of smell and should be avoided. Lozenges for colds are a separate, short-term use; vitamin C and zinc together covers that evidence. Wellgard's vegan vitamin C and zinc supplies 15 mg of zinc with 1,200 mg of vitamin C per two-capsule serving, within the 25 mg guidance; zinc contributes to the normal function of the immune system and the maintenance of normal skin, hair and nails.

When to see a doctor

A persistent rash around the mouth or on the hands, wounds that will not heal, marked hair loss, loss of taste or smell, chronic diarrhoea, or slow growth in a child; and any of these in a risk group. Zinc is one possibility among several, and the GP will think about iron, thyroid, coeliac disease and skin conditions alongside it.

What we don't know

• How common mild zinc shortfall is in the UK. The blood test cannot measure it well, so estimates rest on intake surveys.³
• Whether zinc helps hair, skin or immunity in people who are not deficient. It has been studied mainly in people who were short; evidence in people with adequate intake is limited.

Frequently asked questions

What are the signs of zinc deficiency in females?

The same as in men: frequent minor illness, slow healing, hair thinning, poor taste, a rash around the mouth. Pregnancy and heavy periods with a low-meat diet raise the risk in women.^{1, 2}

Does zinc deficiency show in the nails?

Not as white spots, which are minor injuries. Severe deficiency can cause brittle, ridged nails, but so can many other things.

How much zinc per day?

9.5 mg for men and 7 mg for women from food; vegetarians should aim about 50% higher. Supplements up to 25 mg a day long term.^{4, 5}

Can you take too much zinc?

Yes. More than 25 mg a day for months blocks copper absorption, causing anaemia and nerve damage; high doses also cause nausea and blunt immunity.⁶

Which is better for sleep, zinc or magnesium?

No sleep claim is authorised for either. Magnesium contributes to normal psychological function and normal functioning of the nervous system, and has small sleep trials in older adults with low intake; zinc has not been studied for sleep.

Sources

1. Prasad AS. Discovery of human zinc deficiency: its impact on human health and disease. Advances in Nutrition, 2013. PubMed 23493534.
2. Almohanna HM, et al. The role of vitamins and minerals in hair loss: a review. Dermatology and Therapy, 2019. PubMed 30547302.
3. Saper RB, Rash R. Zinc: an essential micronutrient. American Family Physician, 2009. PubMed 20141096.
4. NHS. Vitamins and minerals: others, including zinc. nhs.uk; Great Britain nutrition and health claims register.
5. Foster M, Samman S. Vegetarian diets across the lifecycle: impact on zinc intake and status. Advances in Food and Nutrition Research, 2015. PubMed 25624036.
6. Expert Group on Vitamins and Minerals. Safe Upper Levels for Vitamins and Minerals, 2003. cot.food.gov.uk.

This article is general information, not medical advice. A persistent rash, wounds that will not heal, marked hair loss or loss of taste need a GP; do not take zinc above 25 mg a day without medical advice.