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Learn about the best vegan zinc sources and find out if you need a dietary supplement.
Today, the trace element zinc is found more and more frequently as a dietary supplement on drugstore shelves, along with iron, calcium or magnesium. Due to its rather sparse presence in plant foods as well as its lower bioavailability, vegans are said to have a deficient intake. With attention to certain foods and cooking methods, vegans can get enough zinc from a plant-based diet.Trace elements include all those minerals that are found in your body in relatively small quantities compared to the bulk elements. The body’s zinc content is about 1.5-2.5 g and, along with iron, it is one of the most important minerals in terms of quantity. Zinc takes over a multitude of essential metabolic and regulatory functions in your organism and is found to a considerable extent in skin, hair, nails and bone substance.
Functions
As an important metabolic regulator, zinc is involved in numerous biochemical reactions as a so-called cofactor of enzymes. Thus, the substance supports these helpers in and around your cells that implement certain reactions in our metabolism. To date, at least 300 enzymes are known to have zinc as a cofactor (Schuchart and Hahn, 2010). It is important for different physiological areas: the acid-base balance, the detoxification of alcohol, antioxidative and thus cell-protective processes, but also the visual process. In the latter, the trace element intervenes in the synthesis of retinal, a vitamin A compound. This represents a part of the functional protein rhodopsin in your eye, whereby zinc simultaneously interacts with the vitamin A metabolism.
Furthermore, zinc functions at the genetic level in your cells, where it participates in the process of gene expression. This process is responsible for the production of proteins from your genetic material and is the basis of your very individual expression. This can also include the growth or renewal of cells, called cell proliferation, and wound healing. Therefore, you often find zinc in wound ointments or creams that can promote external healing.
This trace element also plays a role in the protective processes of the immune system and in the stabilization of the cell membranes. It supports the production of sperm in men and is involved in the storage of insulin in the pancreas. In this process, it forms a complex with the hormone, which is its storage form in the ß-cells of the pancreas. Only after certain physiological signals, such as a rise in blood glucose levels, is this complex released and insulin released into the bloodstream.
Bioavailability of Vegan Zinc
Comparable to the absorption capacity of iron, the bioavailability of zinc is also considered to be higher in foods of animal origin compared to plant foods. During absorption in the small intestine, interactions with certain food substances can also occur, reducing bioavailability. However, this reduction effect is not as pronounced as with iron. Overall, it can be said that the absorption rate of zinc is around 30 % (Leitzmann and Keller, 2013).
Known inhibitors include phytates, which form a complex with zinc and thus promote its excretion. Phytates are found, for example, in grains, legumes and nuts. In addition, the so-called tannins from coffee and tea, also have an unfavorable effect on zinc absorption. This is counteracted by citric acid from citrus fruits, which improves the bioavailability of zinc from phytate-rich foods. Thus, you can enhance the zinc absorption by the consuming certain fruit or juices to a meal with grain products. However, proteins or certain amino acids can also increase zinc absorption. These form highly soluble complexes with the mineral. Another method of increasing bioavailability is the soaking of legumes or nuts, which can reduce the phytate content by up to 21 % (Gupta et al., 2015).
Likewise, fermentation processes, sourdough fermentation and the germination of cereals and legumes reduce the content of phytate. Thus, ultimately, an adequate intake of zinc is also possible for people eating vegan.
Needs and Status
Due to the already mentioned zinc losses during absorption, nutrition societies have taken a sufficient safety margin for the calculation of requirements into account. The current intake recommendations (PRIs) from EFSA are given gender-specifically and depending on the phytate intake. They range from 7.5 to 12.7 mg (women) and from 9.4 to 16.3 mg (men) daily for phytate intakes between 300 and 1200 mg. It is recommended that women take in 1.6 mg more during pregnancy and 2.9 mg during lactation) (EFSA, 2014). Since phytate intake is usually quite high on a vegan diet, vegans should probably aim for the upper intake levels.
The individual zinc status can be determined via a simple blood analysis of the serum concentration. A range of 60 to 120 µg/dl is considered the reference or normal value. However, this is not a reliable parameter since it is influenced by many factors, including stress or certain illnesses.
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Deficiency
Inadequate zinc status can manifest itself in a variety of symptoms. As can be seen from the functions, zinc is required in a large number of metabolic pathways. Characteristic symptoms are, for example, a delayed growth process in children and adolescents, a decrease in the sense of taste and smell, and consequently a loss of appetite. But also changes in the skin, cornea and possibly hair loss can indicate a deficiency. The interaction of zinc with vitamin A in the eye can impair the visual process. Furthermore, a zinc deficiency is associated with delayed wound healing. The immune system is weakened, which results in a higher susceptibility to infections. Since zinc is stored with insulin in the pancreas, a deficiency can also lead to reduced glucose tolerance and at the same time to a lowering of insulin sensitivity. In diabetics, zinc deficiency often occurs due to increased excretion of the mineral via the kidney, which promotes the clinical picture (Martin et al., 2007).
Zinc deficiency is not necessarily due to inadequate dietary intake. Increased excretion via the kidneys, for example in dialysis patients, chronic renal insufficiency, alcohol abuse or diabetics, can also be partly responsible for this deficiency. On the other hand, the intestine plays a decisive role in how much is absorbed. If the intestinal mucosa is irritated and damaged due to disease, absorption disorders occur, in which nutrients cannot be absorbed properly through the intestine. However, these causes apply not only to zinc absorption or excretion, but also to other essential nutrients, and should be evaluated by a physician.
Vegan Zinc Sources
Good vegan zinc sources include whole grains and pseudocereals, such as buckwheat. In addition, legumes as well as nuts and seeds can be mentioned. Pumpkin seeds, in particular, can be counted among the zinc-rich foods with a concentration of 7 mg/100 g.
When consuming these products, it is necessary to pay attention to the appropriate methods of preparation (germination, soaking, the combination with organic acids, sourdough fermentation, if applicable) to ensure good bioavailability of the mineral. An example of a zinc-rich meal would be whole-grain bread with chickpea puree (hummus).
Table 1: Vegan Zinc Sources (Elmadfa et al., 2007; BLS)
| Food Items | Zinc |
|---|---|
| (mg/100 g) | |
| High Amounts (> 5 mg/100g) | |
| Spirulina, Powder | 10.0 |
| Sesame | 7.8 |
| Yeast Flakes | 7.4 |
| Pumpkin Seeds | 7.0 |
| Sunflower Seeds | 5.8 |
| Pecan Nuts | 5.3 |
| Medium Amounts (1-5 mg/100g) | |
| Oats | 4.1 |
| Brazil Nuts | 4.0 |
| Peanuts, Roasted | 3.4 |
| Wheat Flour (Typ 1700) | 3.2 |
| Millet, Hulled | 2.9 |
| Rye (Grain) | 2.9 |
| Brown Rice | 1.5 |
| Porcini Mushrooms | 1.5 |
| Low Amounts (< 1 mg/100g) | |
| Soybean Sprouts | 0.96 |
| Alfalfa Sprouts | 0.92 |
| Parsnips | 0.9 |
| Wheat Flour (Type 405) | 0.7 |
| Brussels Sprouts | 0.6 |
| Spinach | 0.6 |
| Dates | 0.4 |
Status on the Vegan Diet
Chronic deficiency of zinc due to inadequate dietary intake has not been demonstrated in industrialized countries. The daily intake of zinc in vegan and vegetarian populations is only slightly lower than that of mixed-food individuals (Ball and Ackland, 2000. Cade et al., 2004. Phillips, 2005). Male vegans were comparable in their intakes to vegetarians, while female vegans were below vegetarian intakes, averaging 7.8 mg daily (Larsson and Johansson, 2002).
A shortcoming in the assessment is the lack of a sufficiently sensitive marker for zinc status. Long-term effects of a minimally lower zinc intake below the intake recommendations have not been sufficiently investigated. Despite this lower zinc intake in vegans, they do not show any impairment in their immune function. It is possible that biochemical mechanisms exist that allow adaptation to lower zinc intakes and thus compensate for potential deficiency (Craig, 2009).
Special attention to zinc intake should be paid not only to people living vegan, but also to at-risk groups: children and adolescents (especially those not eating a lot of meat), women during pregnancy and lactation, and older people.
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Summary
Zinc as an essential trace element is considered a critical nutrient for vegans due to its limited bioavailability from plant foods. To avoid insufficiency, attention should be paid to certain preparation methods of vegan zinc sources, for example sprouting grains, soaking legumes, and sourdough fermentation. In addition, absorption in the intestine can be increased with absorption-enhancing substances, such as citric acid from citrus fruits. With the help of these tips and tricks, you can meet your need with vegan zinc sources.
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