If you’ve been keeping up with our posts, you may remember a blog from a couple of weeks ago where we were discussing the role of stomach acid in the digestive system. Well as a continuation of that post and with the help of Dr Klaudia Raczko, we’re now looking at how stomach acid (HCl) is not only needed to break down protein but how it helps us absorb certain nutrients – such as zinc.

There are many factors that influence the level of nutrients that are absorbed from our food – but having an adequate level of acid in our stomach is one of the most important. An acidic stomach environment is crucial for the absorption of several micronutrients including iron, vitamin B12 and zinc. If you suffer from Hypochlorhydria (low gastric acid) the release of these micronutrients into the body may be impaired.

Why is Zinc so important?

After iron, zinc is the second most abundant mineral in the body. It’s one of the critical micronutrients predominantly required for growth and adequate functioning of the immune system. Zinc also plays a role in the metabolism of macronutrients like proteins, fats, and carbohydrates as well as the regulation of hormones. It contributes to clearance of oxidative stress, thus protecting DNA from damage.

How much Zinc do we need each day?

Although zinc is the most abundant intracellular microelement (95% is found inside the cells), there is no dedicated storage system in the body and regular intake from dietary sources is required. The UK reference nutrient intake (RNI) for zinc is 9.5 mg per day in males and 7.0 mg per day in females. The overall requirements increase in children, pregnant and lactating women as well as in elderly people.

Zinc Dietary Sources and Absorption

Zinc is best absorbed from animal products, with the highest levels found in oysters, shellfish and red meat. For strict vegetarians and vegans, zinc requirements may need to be increased by up to 50%. Good plant-based sources include nuts, legumes and seeds such as sesame, pumpkin, hemp or sunflower. As zinc is mostly found in the outer layer of the kernel, and so whole grain products tend to contain a higher level of zinc. Any processing mechanism will decrease the amount of this microelement.

But it’s also important to note that phytic acid – which is widely found in the wholegrain and legumes – is one of the zinc absorption inhibitors, known to decrease the bioavailability of zinc (which just means how the body can use it). To combat this, methods such as fermenting, heating, sprouting, soaking as well as leavening grains and legumes are ways to reduce levels of phytic acid and therefore help improve zinc absorption.

Other factors that negatively affect zinc absorption include other microelements such as iron, copper or calcium (as these fight for the same pathways in the body), and oxalates or chlorogenic acid found in tea and coffee, and so zinc supplements should be taken separately.

Zinc is absorbed in the small intestine and an adequately functioning digestive system is essential for its absorption. Zinc is bound to amino acids and a high level of gastric acid is necessary to free it from the protein we eat. Intestinal enzymes (proteases) also contribute to adequate zinc absorption. Factors that enhance zinc absorption include organic acids such as citric acid and also glutathione, the master antioxidant.

Zinc Testing

No single test reliably reflects whole-body zinc status. Measuring plasma (blood) zinc can be the most useful but may not be conclusive as hypozincemia (low zinc level) occurs quite late in deficiency. In addition, the increase of CRP (C-reactive protein) which raises in cases of infection or inflammation can lower the zinc plasma levels – affecting the interpretation of the results.

Urine and hair analysis are often perceived as controversial ways of measuring zinc levels. Zinc deficiency can lead to increased copper (Cu) absorption. Hypercupremia (high copper level) and a Cu:Zn ratio of above 1.5 is considered as a marker of zinc deficiency, and it is suggested that the ratio between zinc and copper may have more significant impact on health outcomes than copper concentration itself. Because of this, the diagnosis of deficiency requires a combination of appropriate tests and clinical assessment.

Diagnosing Zinc Deficiency

Zinc deficiency can be mild or more severe and it may present in many different ways sometimes making the diagnosis quite challenging. Primary zinc deficiency is caused by an inherited condition called acrodermatitis enteropathica , where the body lacks the ability to absorb zinc and it presents with severe rashes. The most common causes of zinc deficiency are insufficient dietary intake and malabsorption (impaired zinc absorption from the digestive tract).

Symptoms and Treatment of Zinc Deficiency

Zinc deficiency may present as skin, hair and nail changes such as alopecia (hair loss), leukonychia (white spots on nails) or skin issues such as acne or rash. Another important sign of zinc deficiency is impaired wound healing or susceptibility to infections, because zinc plays an important role due to its action as an antioxidant and its function in promoting adequate function of immune cells.

Zinc deficiency may also manifest itself in symptoms like loss of appetite, changes in smell and taste, or diarrhoea which can affect food intake.

Zinc affects the vitamin A release from the liver, so a deficiency can impact our night vision or ability to see in the dark as well as our cognitive ability. As this release helps regulate blood sugar, Diabetes has also been linked to low zinc levels.

Zinc also promotes hormonal health in both women and men, so treatment of this deficiency may improve fertility and boost testosterone levels in men.

Zinc can improve increased intestinal permeability problem known as ‘leaky gut’ and it can be found in supplements which aid gut healing. Another important function is its role in stabilising the immune cells responsible for allergic reaction which means it may also help with allergy symptoms.

How to Improve Zinc Levels

With all of this in mind, it’s clear why zinc is such a critical micronutrient and how good levels are necessary for optimal health. By increasing our intake from specific dietary sources and paying attention to the factors which affect absorption, we can help improve the zinc status in our body and prevent the symptoms that signal a zinc deficiency.

If you would like to discuss a potential zinc deficiency and related symptoms with Dr Klaudia Raczko, please book an initial appointment here.

Written by Dr Klaudia Raczko


‘Minerals and trace elements’ in Introduction to Human Nutrition. Gibney MJ, Vorster HH, Kok FJ. 2002, Blackwell, Oxford UK

Livingstone C. Zinc: physiology, deficiency and parenteral nutrition. Nutrition in Clinical Practice 2015;30: 371- 382

Photo Credit: Samuel Alves Rosa