Zinc is of vital importance to the immune defense, our mental balance, fertility, skin, hair, sense of taste, and numerous other functions. According to a new study that is published in Current Research in Physiology, zinc interacts closely with vitamin D and is important for our cells’ ability to absorb vitamin D. Conversely, vitamin D supports the uptake of zinc in the intestines and supports various zinc-dependent cell functions. According to the new study, lack of one or both nutrients can result in a host of different problems such as infections, poor wound healing, muscle diseases, cardiovascular disease, neurological disorders, osteoporosis, cancer, and many other diseases. This is a problem because zinc and vitamin D deficiencies are rather common – mainly because of unhealthy eating habits, lack of sunlight, ageing, overweight, and the use of certain types of medicine.
Most cells in our body have vitamin D receptors (VDR) that enable vitamin D to influence a host of different genes and intracellular functions. Vitamin D is of vital importance to our bones, immune defense, inflammation control, insulin sensitivity, muscles, circulatory system, brain, mood, and many other things. The type of vitamin D that we get from sun exposure or from supplements is inactive and requires zinc, among other things, to become activated so it can be used in the cells.
Zinc is one of the trace elements that we need in the largest quantities. It supports around 600 different enzymes, various transport ions (ZIPs) in the cell membranes, and over 2,500 transcription factors that make sure the right genes are expressed at the right time. Therefore, zinc is crucial for things such as wound healing, growth, reproduction, metabolism, nervous system, immune system, etc. Zinc also supports the important SOD antioxidants (superoxide dismutase) that protect cells and tissues against free radical damage.
In the new study, which is published in Current Research in Physiology, the scientists took a closer look at the interactions between vitamin D and zinc and why it is important to get enough of both nutrients.
The body’s zinc absorption and zinc status
We do not store a lot of zinc in our body and therefore depend on a daily supply from dietary sources or supplements. The body’s zinc balance it handled by the cells in the intestinal wall that are able to store a certain amount of zinc or, if zinc levels are too high, to get rid of zinc.
We have around 2-3 grams of zinc in our body with 90 percent being found in muscles and bones. In soft tissue such as muscle tissue, zinc is mainly bound to intracellular components. Therefore, measuring levels of zinc in the blood does not really give an accurate picture of the body’s zinc status.
Zinc sources, widespread deficiency, and secondary illnesses
Some of the good zinc sources are oysters and shellfish, meat, liver, seeds, kernels, and beans. Zinc from animal sources has better absorption than zinc from vegetable sources where the zinc is bound to phytates. Lack of zinc can cause growth disturbances, impaired immunity, neurological diseases, impaired fertility, skin problems, hair loss, impaired vision, and reduced sense of smell and taste. There is also a connection between coronavirus infections and zinc deficiencies.
Actual zinc deficiency is most common in underdeveloped countries, whereas sub-clinical zinc deficiency is more common in the industrialized countries. A Spanish study found that 83 percent of the population between 9 and 75 years of age did not get enough zinc from the diet. Zinc deficiency is widespread among older people because they often eat too little, but also because our zinc absorption decreases with age. Vegetarians, vegans, pregnant and breastfeeding women, alcoholics, and patients with diarrhea and other gastrointestinal problems also have an increased risk of being zinc-deficient. If you consume too much calcium or iron or suffer from celiac disease (gluten intolerance) or use diuretics, it may also disturb your uptake and/or excretion of zinc.
The dietary reference intake (RI) for zinc is 10 mg. EFSA has established a safe upper intake level for zinc of 25 mg, but it is safe to ingest even larger quantities for brief periods.
- The large American NHANES III study (National Health and Nutrition Examination Study) shows that 35-45 percent of people older than 60 years fail to get enough zinc from their diets.
Vitamin D sources, widespread deficiencies, and secondary diseases
At our latitudes, the sun during the summer is our main source of vitamin D. We only get a small amount of the nutrient from dietary sources such as oily fish, eggs, and high-fat dairy products.
Our risk of becoming vitamin D-deficient increases with factors like too little sun exposure (including the lack of sunlight during winter), dark skin, overweight, diabetes, and ageing. Vitamin D deficiency is currently a global problem.
Most cells have vitamin D receptors that control different genes, which is why a vitamin D deficiency may cause impaired immunity, cardiovascular disease, metabolic syndrome (overweight and diabetes), neurological diseases, autoimmune disorders, and different cancer forms. It can also result in an increased risk of virus infections (including coronavirus) and serious complications.
The official recommendations for vitamin D are 5-20 micrograms daily. The vulnerable groups should get most, but these intake levels can not guarantee optimal blood levels of vitamin D or that vitamin D will be activated. It is therefore best to aim for levels around 75-120 nmol/L and to get plenty of zinc at the same time.
- An estimated one billion people worldwide are believed to lack vitamin D
Vitamin D synthesis
Vitamin D is a lipid-soluble vitamin that is available in various forms. Humans synthesize vitamin D3 (also called cholecalciferol) through a process where the UVB rays from the sun react with a cholesterol precursor in our skin. This is the same type of vitamin D we get from animal food sources such as oily fish or from supplements. Vitamin D3, however, is not active. First, it must be converted into calcidiol in the liver. This is the form of vitamin D that is measured as 25-hydroxyvitamin D3 in blood tests. When the body needs vitamin D for different functions, it activates calcidiol in the kidneys, in the white blood cells, and other cells by converting it into the active form of vitamin D called calcitriol (1,25-dihydroxyvitamin D3). It is this form of vitamin D that binds to the vitamin D receptors in the cells.
Interactions between zinc and vitamin D
Calcitriol (1,25-dihydroxyvitamin D3), the active form of vitamin D, needs zinc to bind to the vitamin D receptors (VDR). VDR resemble receptors of other steroid hormones, and zinc is a structural component of the VDR. More specifically, zinc is a part of the so-called zinc fingers that consist of one or two zinc ions that are bound to the amino acids, cysteine or histidine.
Zinc is needed for calcitriol to bind to these receptors that enable vitamin D to carry out its different functions inside the cell. In a study of rats that were either fed diets with sufficient amounts of zinc or diets without zinc, it was observed that the zinc-deficient rats had fewer VDRs in their intestinal mucous membrane. This showed that a zinc deficiency clearly affects VDR activity and the related vitamin D functions. Another study demonstrated that higher concentrations of intracellular zinc increase the binding of zinc to the VDR. These observations show that zinc affects VDR interactions and the utilization of vitamin D.
A study of 988 females aged 12-18 years showed that lack of zinc in the blood was related to being vitamin D-deficient. A double-blind, placebo-controlled study has shown that zinc supplementation for eight weeks increases levels of vitamin D in the blood of menopausal women. On the other side, vitamin D also affects both the uptake of zinc from the intestines and the zinc-containing transport proteins (ZIP and ZnT10) that are important for zinc absorption and zinc homeostasis. Scientists seem to be very interested in studying ZIPs.
In their article, the authors refer to several studies of children and adults that have also shown a positive relation between blood levels of zinc and vitamin D.
Lack of zinc and vitamin D have serious and unmanageable consequences
A deficiency of one or both nutrients can result in an array of diseases such as poor wound healing, skin disorders, muscle ailments, cardiovascular diseases, neurological disorders, infectious diseases, overweight, diabetes, autoimmune disorders, and various types of cancer.
There is also an increased risk of virus infections, including coronavirus and life-threatening complications.
The scientific understanding of the interaction between vitamin D and zinc is still relatively new and more studies are needed to understand the exact molecular interactions. This may give better insight into how we can stay healthy and lower the disease burden.
Ashton Amos, Mohammed S. Razzaque. Zinc and its role in vitamin D function. Current Research in Physiology. 2022
William B. Grant. A Narrative Review of the Evidence for Variations in Serum 25-Hydroxyvitamin D Concentration Thresholds for Optimal Health. Nutrients 2022
Debra Sullivan. What are the health benefits of vitamin D? MedicalNewsToday 2019
Lorenzo Lovin et al. Activation of the Zinc-sensing receptor GPR39 promotes T cell reconstitution after hematopoietic cell transplant in mice. Blood, 2022
University of St Andrews. Zinc could be key to new diabetes treatments. MedicalXpress. March 1, 2021
Nikki Hancocks. Diet and supplements: Swiss panel publishes COVID-19 recommendations.
Jan Alexander et al. Early Nutritional Intervention with Zinc, Selenium and Vitamin D for Raising Anti-Viral resistance Against Progressive COVID-19. Nutrients 2020
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