Zinc: Health Benefits, Immune System, Absorption
Zinc is an essential trace element that must be consumed in small amounts through diet. Our organism contains approximately 2 to 3 grams of zinc 1. Zinc is present in every cell of the body. It is found in larger quantities in the muscles (60%) and bones (30%). The remaining 10% is distributed in the skin, hair, toenails, fingernails, organs, as well as red and white blood cells.
Zinc is required at the cellular level for numerous catalytic, structural, and regulatory functions 2. It is a component of over 3,000 proteins in the human body that fulfill physiological functions in the organism 3 4. Furthermore, zinc activates over 300 enzymes (present in all six enzyme classes) as a co-factor, which are involved, among other things, in energy metabolism. They are also important for the metabolism of carbohydrates, fats, and proteins, DNA synthesis, and supporting the immune system.
- is required as an activator of many enzymes involved in carbohydrate, fat, and protein metabolism
- is a component of zinc finger proteins, which interact with DNA and RNA, and are involved in protein folding and protein synthesis, among other functions
- is important for taste and smell
- helps in wound healing
- is involved in the formation of hemoglobin
- is necessary for body growth
- is important for the formation, release, and storage of insulin
- is required for the release of neurotransmitters like glutamate from neuronal synaptic vesicles, thereby playing a role in neural signal transmission and cognitive functions
Zinc is a component of a retinol-binding protein that is needed for the transport of vitamin A from the liver to the organs 10. Zinc also helps convert vitamin A into retinal, which, after further conversion processes, contributes to vision.
Zinc strengthens the immune system
Special T lymphocytes, also known as T cells, which belong to the group of leukocytes (white blood cells), attack viruses and bacteria in the body. Zinc ions are required for the formation of these cells developed in the thymus gland (hence the T) 11.
Even a slight zinc deficiency increases the risk of infections. Studies suggest that zinc stimulates the immune system during inflammation 12. It was initially demonstrated that reduced zinc intake caused faulty immune cell activation and dysregulation of interleukin-6, a protein that regulates inflammatory reactions in cells. Ultimately, zinc is an anti-inflammatory mineral 13.
Zinc is a component of the enzyme Cu,Zn-SOD (also known as SOD1 and Cu,Zn-superoxide dismutase), which is the primary cytoplasmic scavenger of superoxide radicals 14. It protects cells from metabolic waste that can cause cell damage.
In addition, zinc is required for enzyme activation and promotes the antioxidant abilities of numerous enzymes such as Cu,Zn-superoxide dismutase and Mn-superoxide dismutase) 15. Thus, zinc indirectly protects cells against free radicals, which are implicated in various diseases and possibly accelerate the aging process. Zinc is also involved in the regulation of metallothioneins, which have antioxidant effects and participate in various other antioxidant functions 16 17.
Significance for Athletes
Since zinc is involved in energy metabolism and protein synthesis, the body should always have an adequate amount of zinc available to prevent a decline in performance and limitations in muscle building and recovery 18.
Even a slight zinc deficiency has a negative impact on testosterone levels 19. Testosterone has an anabolic effect, meaning it promotes muscle growth.
Furthermore, zinc plays an important role in regulating arterial blood pressure, making the trace element involved in the performance of the cardiovascular system 20.
Preventive Benefits of Zinc
Zinc is used preventively and for the treatment of diarrhea, pneumonia, colds, and respiratory infections 21.
An alteration in zinc status is also associated with neurological damage such as impaired brain development and many neurodegenerative diseases, including Alzheimer's disease and mood disorders, depression, Parkinson's disease, Huntington's disease, amyotrophic lateral sclerosis, prion diseases 22. Therefore, it is important for scientists to understand the mechanisms that control brain zinc homeostasis in order to develop preventive strategies and treatment methods for neurological disorders.
The intake of zinc through diet has been associated with a reduced risk of proximal and distal colon cancer in postmenopausal women 23.
Furthermore, zinc could offer protective benefits against atherosclerosis due to its anti-inflammatory and antioxidant functions 24.
Basic information about zinc intake
Free zinc ions are absorbed through the duodenum and jejunum 25. Zinc can be better absorbed from fluids (60-70%) than from solid food components. Absorption depends on the current zinc status as well as the zinc content and composition of the diet. On average, one-third of the zinc present in plant-based foods is absorbed 26 27.
Furthermore, zinc status also influences zinc absorption. Individuals with lower zinc levels in the body can absorb zinc more efficiently than those following a zinc-rich diet 28. The zinc excretion determines the current zinc status in the body 29. The body can then adjust zinc absorption through various pathways depending on the amount of zinc excreted 30.
Improvement of Zinc Absorption
Hydroxycarboxylic acids such as citric acid, malic acid, and tartaric acid can also improve absorption. They bind to zinc and enhance the uptake of zinc, unlike phytic acid 35. Fruits, in particular, are rich in these acids. Good examples include pineapple, apples, kiwis, cherries, plums, grapefruits, and lemons. ⇒ Citric Acid Foods and ⇒ Malic Acid Foods
The bioavailability of zinc can be improved through fermentation, grinding, soaking for a few hours, and heating the corresponding food 36. The cooking or soaking water should then be discarded. Additionally, the phytic acid is reduced by sprouting beans and grains 37. The sprouts go well with vegan spreads and salads.
Impairment of Zinc Absorption
Zinc absorption is negatively influenced by certain food components such as phytates (phytic acid), which are mainly present in grain products, nuts, and legumes 38 39. They bind chemically very tightly to zinc (chelators), reduce zinc absorption (low bioavailability of zinc), and could even contribute to zinc deficiency 40. For example, only 15% of the zinc contained in unrefined grains is absorbed 41.
Oxalic acid, which is mainly found in rhubarb, spinach, and chard, has an inhibitory effect on absorption similar to phytic acid.
However, these foods should not be avoided entirely, as the negative effects can be reduced through certain processes (cooking and soaking). Furthermore, grains, nuts, and legumes are extremely rich in important nutrients.
The heavy metal cadmium, which is mainly released through the combustion of oil and coal and enters plants through air and precipitation, also reduces the absorption of zinc from food 42.
Vegetarians and individuals with a mixed diet have an additional disadvantage since casein has been shown to have a negative effect on zinc absorption 45.
What should vegans consider
In addition to the mentioned zinc-inhibiting plant compounds, vegans should ensure an adequate intake of zinc-rich foods. According to a large study conducted in 2003, vegans had the lowest zinc intake compared to participants following other dietary patterns 48. A smaller study found that vegans are highly susceptible to zinc deficiency 49. A summary of studies from 2013 confirms that a vegetarian diet has a greater impact on zinc intake, resulting in lower zinc levels and zinc status in the body 50.