Zinc is a trace element, a mineral that the body needs relatively little of, in the order of milligrams, and there are about 200 enzymes in the body that require zinc as a cofactor. As a cofactor, zinc serves as a type of “helper molecule” that enables the enzyme to do its work.
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Many of these enzymes are involved in metabolism. In addition, zinc is needed for other bodily processes such as:
- DNA synthesis
- Protein metabolism, wound healing, and growth
- Proper functioning of the defense/immune system
- Development of sexual organs and bones
- Storage, release, and function of insulin
- Structure and function of the cell membrane
- Indirect function as an antioxidant
Furthermore, zinc plays a role in the conversion of vitamin A into its biologically active form (retinol->retinal), which is important for good vision. Zinc also helps in the breakdown of alcohol in our liver.
Zinc sources and requirements
Generally, protein-rich products contain a lot of zinc, such as beef, milk, and poultry. In addition, plant-based sources such as whole grains, peanuts, nuts, and legumes like beans are rich in zinc. Shellfish and crustaceans like shrimp and mussels are also good sources of zinc. In America, 11 milligrams for adult men and 8 milligrams for women are recommended per day. The Nutrition Center advises 10 milligrams for men and 9 for women (1).
How a zinc deficiency occurs
A deficiency in certain minerals and trace elements can occur in several ways:
- Your diet contains too few of these substances
- Your diet contains a lot of refined sugars
- You are unable to absorb sufficient substances
- You may excrete too much of these substances
Certain gastrointestinal diseases can prevent certain nutrients from being properly absorbed. This can lead to a deficiency in certain nutrients such as vitamins and minerals. Another example is that some people take supplements for certain nutrients that can disrupt the absorption of other nutrients. For example, zinc competes with iron and copper for absorption. It was suspected that when someone takes in a lot of iron, the absorption of zinc in the body is reduced. However, this only seems to be the case when both are taken together as a supplement and not when they are taken as part of a meal. Moreover, iron only has a negative effect on zinc absorption when taken as a supplement where the amount of iron is much higher than the amount of zinc (2). In most supplements, this is not the case. Hormone levels also play a major role. An excess of estrogen can counteract the absorption of minerals.
The use of the pill can thus have a negative influence on the absorption of minerals. Stress can also cause minerals and trace elements to be absorbed less effectively. In stressful situations, the liver needs more zinc and extracts it from other organs.
Zinc and obesity
A strict diet, such as a crash diet, is often not a good solution in terms of minerals. During a crash diet, much less is eaten, naturally resulting in much fewer minerals being consumed. A zinc deficiency disrupts insulin production, usually leading to the production of too much insulin. This can make cells less susceptible to insulin, causing them to respond poorly. This is called insulin resistance, which disrupts good glucose metabolism and can lead to obesity, high blood pressure, and diabetes. Insulin also plays a role in transporting glucose to the brain cells. If this system works less effectively, the brain may think that not enough energy is entering the body, resulting in the body sending a hunger signal that prompts eating. This feeling can be misleading, leading to overeating and potentially obesity. Zinc also affects the absorption of tryptophan, an amino acid converted into serotonin, important for brain function, especially in relaxation. Less serotonin increases our craving for sweetness, leading to the consumption of more refined sugars. Additionally, less serotonin can result in less effective relaxation, leading to stress. Stress, in turn, can reduce zinc absorption. Thus, there is a link between all these functions, and disruption can lead to obesity.
Should I take extra zinc?
A zinc deficiency is actually not very common because we need very little of it. Often, it is a combination of multiple causes that can lead to a deficiency. A zinc deficiency can be recognized by a number of symptoms such as abnormalities in the skin, mucous membranes, and skeleton. Other symptoms include stunted growth and development, night blindness, and a weakened immune system. Taking in much more zinc does not help. Moreover, it is often the case that when you consume too much of a certain mineral, other minerals are absorbed less effectively, which can lead to other problems. A healthy and balanced diet should generally provide the right amount of vitamins, minerals, and trace elements.
References
- Nutrition Center: http://www.voedingscentrum.nl/encyclopedie/zink.aspx
- http://jn.nutrition.org/content/130/5/1378S.full
- Contemporary Nutrition, G.M. Wardlaw & A.M. Smith, 2011
