Zinc

Prasad, A. S. (2013). Discovery of Human Zinc Deficiency: Its Impact on Human Health and Disease. Advances in Nutrition, 4(2), 176–190. https://doi.org/10.3945/an.112.003210

What is Zink good for

Zinc is an essential component of a wide range of enzymes. It is also necessary for maintaining and replicating genetic material (DNA and RNA), enabling the body to interpret its genetic information.

This mineral is vital for the normal growth of the body. Zinc plays an especially important role in the development of the ovaries and the testes, and a deficiency in childhood and adolescence impairs growth and sexual development. It is also needed for the efficient functioning of the immune system.

Indeed, zinc is so important to the immune system that even a mild deficiency can lead to an increased risk of infection.

The mineral is therefore especially important to the elderly, who may be particularly vulnerable to a wide range of inflammatory concerns.

Zinc is also necessary for a healthy appetite and assists in our ability to taste foods.

HOW MUCH DO WE NEED

Women need a minimum of 9 milligrams of zinc per day, while males need 11. If you find you’re not able to get enough through your diet, consider a zinc supplement, which affordable and available in multivitamin form or in individual supplement form. You can eat too many zinc-rich foods, but should be sure you’re not supplementing with excessive amounts either. Overall, remember to focus on a balanced diet rich in whole, plant-based foods to take care of your health. This is the number one place to start not just for adequate zinc intake, but also all other micronutrients (and macronutrients) too.

sources of zinc

“Some good plant-derived sources of zinc include mung bean sprouts, pumpkin seeds, sesame seeds, sunflower seeds, wheat grass, and spelt sprouts.”

how to increase absorption

sideeffects of zinc deficiency

A deficiency in zinc has been proven to increase the incidence of colds and flu, prostate illness, and premature graying and loss of hair.”

Good plant sources of zinc are legumes, nuts, seeds, oatmeal, bread, tempeh, and miso. Without supplementation, vegan diets provide roughly the Dietary Reference Intakes (DRI) for zinc (see the table below).

When you’re zinc deficient, your body can’t produce healthy, new cells. This leads to symptoms such as:

unexplained weight loss
wounds that won’t heal
lack of alertness
decreased sense of smell and taste
diarrhea
loss of appetite
open sores on the skin

how to test for zinc

Diagnosing zinc deficiency

Zinc is distributed in trace amounts among the cells in your body, making it difficult to detect zinc deficiency through a simple blood test.

If your doctor suspects a zinc deficiency, they will need to test your blood plasma for an accurate reading. Other tests for zinc deficiency include a urine test and an analysis of a strand of your hair to measure the zinc content.

Sometimes zinc deficiency is a symptom of another condition. For example, some conditions may cause zinc to be processed in your body but not absorbed well. Zinc deficiency can also lead to copper deficiency. Your doctor will be aware of these possibilities. They may do additional testing to get to the root of your deficiency.

Zinc side effects from too much zinc

Sources of zink database USDA
https://ndb.nal.usda.gov/ndb/nutrients/index
https://ndb.nal.usda.gov/ndb/nutrients/report/nutrientsfrm?max=25&offset=0&totCount=0&nutrient1=309&nutrient2=&fg=20&fg=4&fg=9&fg=16&fg=12&fg=11&subset=0&sort=c&measureby=g

Zinc

Zinc is important for immunity. If a vegan finds they’re easily catching colds, taking a modest zinc supplement of about the DRI might solve the problem.

Zinc is an essential trace mineral that plays an important role in the body and is best known for its immunity-boosting and wound-healing qualities. A variety of vegan foods contain zinc.

spinach, beans, legumes, nuts, seeds, and whole grains.
zinc for vegetarians include whole grains, tofu, tempeh, legumes, nuts and seeds
Beans and Legumes. This includes tofu, tempeh, black and green soybeans, kidney beans, black beans, garbanzo beans, lentils, peanuts, etc. …
Nuts and Seeds. …
Oats. …
Wheat Germ. …
Nutritional Yeast.

1. Beans and Legumes
Legumes
Legumes like chickpeas, lentils and beans all contain substantial amounts of zinc.
Legumes contain high amounts of zinc. However, they also contain phytates, which reduce its absorption. Processing methods like heating, sprouting, soaking or fermenting can help improve its bioavailability.

In fact, 100 grams of cooked lentils contain around 12% of a man’s daily recommended intake (10).

However, they also contain phytates. These antinutrients inhibit the absorption of zinc and other minerals.

Heating, sprouting, soaking or fermenting plant sources of zinc like legumes can increase this mineral’s bioavailability (12Trusted Source).

This includes tofu, tempeh, black and green soybeans, kidney beans, black beans, garbanzo beans, lentils, peanuts, etc. All beans and legumes offer great amounts of zinc, however, do be aware that they contain a large amount of phytates on their skin, which are meant to protect them in nature. Phytates, however, have been linked to a reduced absorption of important minerals and occur heavily in beans, legumes, and grains. Be sure you soak your beans and legumes first, or buy from brands that pre-soak theirs first. Then cook them thoroughly until they’re very soft. These steps reduce the phytates, which also makes them easier to digest. You should also rely on more than just beans for your zinc needs. And while not thought of as a bean, cacao and coffee beans are also great sources of zinc and do not need special preparation. However, raw cacao is more nutrient dense than chocolate and cocoa powder, so do keep this in mind.

2. Nuts and Seeds

4. Seeds
Seeds are a healthy addition to your diet and can help increase your zinc intake.

However, some seeds are better choices than others.

For example, 3 tablespoons (30 grams) of hemp seeds contain 31% and 43% of the recommended daily intake for men and women, respectively.

Other seeds containing significant amounts of zinc include squash, pumpkin and sesame seeds (13, 14).

In addition to boosting your zinc intake, seeds contain fiber, healthy fats, vitamins and minerals, making them an excellent addition to your diet.

Including them as part of a healthy diet has also been linked to some health benefits, including reduced cholesterol and blood pressure (15Trusted Source, 16Trusted Source).

To add hemp, flax, pumpkin or squash seeds into your diet, you can try adding them to salads, soups, yogurts or other foods.

3. Oats
Oats are one of the few grains that offers a large amount of zinc. Oats are also great sources of calcium, magnesium, iron, and potassium. Soak your oats overnight to make them easier to digest and assimilate, or cook them throughly on the stove top if you prefer.

4. Wheat Germ
If you’re not gluten-free, wheat germ is also a good source of zinc, protein, and vitamin E. A sprinkle on your oatmeal with some seeds is a nice zinc-rich way to start the day!

5. Nutritional Yeast
Nutritional yeast is a great source of nutrients for plant-based eaters, particularly protein, vitamin B12, and yes, … zinc too! It actually has 20 percent of your needs in just 2 tablespoons. Not a shabby side effect of enjoying a cheesy-flavored delight, right? Nutritional yeast is also great for your blood sugar, with zinc, protein, and B vitamins being just one of the reasons why.

Some Vegetables
In general, fruits and vegetables are poor sources of zinc.

However, some vegetables contain reasonable amounts and can contribute to your daily needs, especially if you don’t eat meat.

Potatoes, both regular and sweet varieties, contain approximately 1 mg per large potato, which is 9% of a man’s recommended daily intake (33, 34).

Other vegetables like green beans and kale contain less, at around 3% of a man’s recommended intake per 100 grams (35, 36).

SUMMARY
Some seeds like hemp, pumpkin, squash and sesame seeds contain significant amounts of zinc. They are also a good source of fiber, healthy fats and vitamins, making them a healthy addition to your diet.

5. Nuts
Eating nuts such as pine nuts, peanuts, cashews and almonds can boost your intake of zinc.

Nuts also contain other healthy nutrients, including healthy fats and fiber, as well as a number of other vitamins and minerals.

If you’re looking for a nut high in zinc, cashews are a good choice. A 1-ounce (28-gram) serving contains 14% of a man’s daily recommended intake (17).

Whole Grains
Whole grains like wheat, quinoa, rice and oats contain some zinc.

However, like legumes, grains contain phytates, which bind to zinc and reduce its absorption (29Trusted Source).

Institute of Medicine, Food and Nutrition Board. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zincexternal link disclaimer. Washington, DC: National Academy Press, 2001.

Overview
Zinc is a mineral that your body uses for fighting off infections and producing cells. It’s important for healing injuries and creating DNA, the genetic blueprint in all of your cells. If you’re not getting enough zinc in your diet, you may have side effects such as hair loss, lack of alertness, and a reduced sense of taste and smell. Zinc deficiency is rare in the United States, but it still occurs in some people.

Absorbtion
Lönnerdal, B. (2000). Dietary Factors Influencing Zinc Absorption. The Journal of Nutrition, 130(5), pp.1378S-1383S.https://academic.oup.com/jn/article/130/5/1378S/4686381

Phytate, which is present in staple foods like cereals, corn and rice, has a strong negative effect on zinc absorption from composite meals. Inositol hexaphosphates and pentaphosphates are the phytate forms that exert these negative effects, whereas the lower phosphates have no or little effect on zinc absorption.

The removal or reduction of phytate by enzyme (phytase) treatment, precipitation methods, germination improves zinc absorption. Iron can have a negative effect on zinc absorption, if given together in a supplement, whereas no effect is observed when the same amounts are present in a meal as fortificants.

Cadmium, which is increasing in the environment, also inhibits zinc absorption. The amount of protein in a meal has a positive effect on zinc absorption, but individual proteins may act differently; e.g., casein has a modest inhibitory effect of zinc absorption compared with other protein sources.

Although the assessment of zinc status is a complicated task (Gibson and Ferguson 1998), supplementation or fortification with zinc has been associated with increased linear growth (Brown et al. 1998), reduction in diarrheal disease (Black 1998), enhanced immune function (Shankar and Prasad 1998) and improved pregnancy outcome (Goldenberg et al. 1995).

Although the cause of suboptimal zinc status in some cases may be inadequate dietary intake of zinc, inhibitors of zinc absorption are likely the most common causative factor. Many staple foods in developing countries, including cereals, corn and vegetables, are relatively good sources of zinc, but even if net zinc intake appears adequate by most recommendations, compromised zinc status is common (Gibson et al. 1998). It is therefore important to identify and evaluate dietary factors that affect zinc absorption. With such knowledge, better advice may be given with regard to avoiding or limiting components with inhibitory effects on zinc absorption and choosing foods or dietary components that enhance zinc absorption. Furthermore, agricultural and food processing methods that reduce the content of inhibitors of zinc absorption may be developed and put into common use.

Dietary factors that influence zinc absorption

Zinc intake.

The amount of zinc in a meal will, in itself, affect zinc absorption (Sandström and Cederblad 1980).
With increasing amounts of zinc in a meal, fractional zinc absorption (%) will decrease.
This has, for example, been shown by Sandström and Cederblad (1980), who administered human adults radiolabeled zinc solutions in water and measured zinc absorption by whole-body counting. When 40 μmol was administered, 73 ± 10% of the dose was absorbed, whereas 46 ± 13% was absorbed when 200 μmol was administered. The amount of zinc absorbed, however, increased from 29 ± 4 to 92 ± 26 μmol.

It is likely that the reduced fractional absorption of zinc at higher doses is due to saturation of the transport mechanisms for zinc.

Zinc absorption has been shown to consist of a specific, saturable carrier-mediated component and a nonspecific, unsaturable diffusion-mediated component (Menard and Cousins 1983, Steel and Cousins 1985).

The capacity of the saturable transport mechanism to absorb zinc has been investigated in experimental animals and humans. Coppen and Davies (1987) found that when dietary zinc was increased from 5 to 40 mg/kg, fractional zinc absorption decreased, whereas the amount of zinc absorbed increased linearly at higher dietary levels, which would be consistent with a diffusion process. In humans, intestinal perfusion studies with solutions containing increasing concentrations of zinc showed linear increases in zinc absorption from 0.1 to 1.5 mmol/L zinc, with rates leveling at higher concentrations (Lee et al. 1989). Sandström (1992) calculated that the zinc concentration in the duodenum after a meal in a human is likely to be <2 mg/L (30 μmol/L); thus, in the presence of dietary ligands, the concentration of “free” zinc is likely to be considerably lower. Therefore, zinc is likely to predominantly be transported via the saturable, specific transport mechanism. It is likely that zinc absorption also is homeostatically regulated by intestinal excretion of zinc; considerably lower quantities of endogenous zinc were excreted when infants were fed a low zinc formula than when a formula with a regular level of zinc was fed (Ziegler et al. 1989). Long-term zinc intake, i.e., zinc status, can also affect absorption of dietary zinc. Although the long-term use of zinc supplements does not appear to cause any down-regulation of zinc absorption compared with normal, healthy subjects not taking any supplements (Sandström et al. 1990), low zinc intake and zinc status do affect zinc absorption. Istfan et al. (1983) fed young men a formula diet containing either 1.5 or 15 mg zinc/d and measured zinc absorption in a fasted state after 6 d. Zinc absorption was 92% from the low zinc diet and 81% from the high zinc diet. Wada et al. (1985) performed similar stable isotope studies in young men and found that zinc absorption from the diet was 53% when the zinc intake was 5.5 mg/d and that it decreased to 25% when 16.5 mg/d was fed. Similarly, August et al. (1989) found that young adult subjects absorbed 64 ± 5% of zinc from the diet when it contained 2.8–5 mg/d but only 39 ± 3% when it contained 12.8–15 mg/d. Differences were also found in elderly subjects (43 ± 7% versus 21 ± 1%), but as can be seen, the extent of zinc absorption was lower in this age group. We used infant rhesus monkeys and radioisotopes and found that zinc absorption rapidly increased from ∼40% when a formula with the current level of zinc fortification (4 mg/L) was fed to ∼60% when a formula with lower zinc content (1 mg/L) was fed (Polberger et al. 1996). Thus, it appears that feeding low zinc diets increases zinc absorption in all age groups and that homeostatic mechanisms up-regulate zinc absorption and retention. Previous zinc intake may therefore have an effect on studies on zinc bioavailability. Protein quantity and quality. The amount of protein in a meal is positively correlated to zinc absorption (Sandström et al. 1980). When compiling results from several studies with humans to whom various protein sources and amounts had been administered, fractional zinc absorption increased in a linear fashion with increasing protein content (Sandström 1992). It should also be emphasized that protein is a major source of dietary zinc that results in an increased zinc intake with increased protein content of the meal. Thus, in general, increased dietary protein leads to increased zinc intake and a higher bioavailability of the zinc provided. The type of protein in a meal will also affect zinc bioavailability. Animal protein (e.g., beef, eggs, cheese) has been shown to counteract the inhibitory effect of phytate on zinc absorption from single meals (Sandström and Cederblad 1980), but this may be due to amino acids released from the protein that keep the zinc in solution (see later) rather than a unique effect of animal protein as such. Casein in milk has been shown to have a negative effect on zinc absorption (Lönnerdal et al. 1984). Phytate and fiber. The finding of zinc deficiency in human subjects in the Middle East suggested that phytate can affect zinc status in humans as well (Halsted et al. 1972), and subsequent studies confirmed that this was the case. Because staple foods in most part of the world contain phytate (e.g., corn, cereals, rice, legumes), it is obvious that both zinc and iron status may be compromised in significant portions of the population. By using radioisotopes and whole-body counting, we found very low zinc bioavailability from soy-based infant formula compared with milk formula and human milk (Sandström et al. 1983). When the phytate was removed from soy protein isolate by a precipitation process, zinc absorption was significantly improved (Lönnerdal et al. 1988). Thus, any reduction in dietary phytate content is likely to result in an improvement in zinc absorption. There are several methods available to reduce the phytate content of various foods. Leavening of bread was shown early to decrease its phytate concentration (Nävert et al. 1985), and fermentation in general also achieves the same effect, resulting in enhanced zinc absorption (Gibson et al. 1998, Svanberg and Sandberg 1988). Germination and milling can also reduce the phytate content of legumes and cereals (Gibson et al. 1998,Svanberg and Sandberg 1988). Recently, the treatment of foods with food-grade commercial phytase or the addition of phytase to the diet has been shown to effectively reduce the phytate content of various foods, with a subsequent beneficial effect on mineral absorption (Sandberg et al. 1996, Türk and Sandberg 1992). Phytate in food is composed of a mixture of different phosphorylated forms of inositol phosphate (Sandberg and Ahderinne 1986); the hexaphosphate is usually the major form, but pentaphosphates, tetraphosphates and triphosphates are also present. Because various types of processing can alter the proportions of these inositol phosphates, it is important to evaluate their individual effects on zinc absorption. We found that the hexaphosphate and pentaphosphate forms inhibited zinc absorption in a rat pup model, whereas the tetraphosphate and triphosphate forms had no significant effect (Lönnerdal et al. 1989). Subsequent studies in human subjects confirmed these findings (Sandström and Sandberg 1992). It thus becomes evident that “total phytate” of a meal or a diet is too crude of a measure when evaluating zinc bioavailability; instead, methods that specifically quantify the various forms of inositol phosphates are needed when assessing the effects on zinc absorption (Sandberg and Ahderinne 1986). Fiber is often implied as having a negative effect on zinc absorption. However, this is usually due to the fact that most fiber-containing foods also contain phytate. Knudsen et al. (1996) recently reported low zinc absorption from a fiber-rich diet, but the diet was also high in phytate. Reducing the phytate content of bread by leavening considerably increased zinc absorption to a degree similar to that from white bread (low fiber), suggesting that fiber in itself has no or little effect on zinc absorption (Nävert et al. 1985). Studies on isolated fiber components such as α-cellulose (Turnlund et al. 1982) show no significant inhibitory effect on zinc absorption. It is therefore unlikely that fiber has any negative effect on zinc nutrition of humans. Calcium. Several authors have suggested that the phytate-to-zinc molar ratio can be used to estimate zinc bioavailability from the diet (Davies and Olpin 1979, Lo et al. 1981, Morris and Ellis 1980), and it is possible that this ratio in general may have more predictability than the ratio that includes calcium as a variable. The calcium content of the diet may, however, affect zinc absorption from phytate-containing meals. It has been postulated that the formula [Ca] × ([phytate]/[Zn]) ratio can be used as a predictor of zinc bioavailability (Fordyce et al. 1987). The reason for this is that calcium has the propensity to form complexes with phytate and zinc that are insoluble and consequently have an inhibitory effect on zinc absorption. Although there certainly are studies that support this concept, the interaction is complex, and it is possible that this ratio may be of limited predictive value. For example, we added calcium to a soy-based infant formula (1300 versus 550 mg/L) and found that zinc absorption increased significantly compared with regular soy formula, even though an increased [Ca] × [phytate]/[Zn] ratio would predict lower zinc absorption. We hypothesized that a larger proportion of calcium bound to phytate in the gastrointestinal tract, thereby making more zinc available for absorption (Lönnerdal et al. 1984). Iron. The potential interaction between iron and zinc has caused concern. Iron deficiency is the most common single-nutrient deficiency in the world, and many fortification and supplementation programs have been launched to improve iron nutrition. However, with an increasing awareness that marginal zinc deficiency also may be common, a negative impact of iron provision on zinc absorption and status could further exacerbate zinc status. We found a significant reduction in zinc absorption in the fasting state when iron was added to the zinc dose in water solution at a 25:1 molar ratio but not at a 2.5:1 ratio, which is similar to the ratio used in the study by Solomons and Jacob (1981). Thus, the interaction appears much less pronounced when zinc intake is closer to a “physiological” level. It is hypothetically possible that the administration of iron supplements during a longer period of time could cause mucosal loading with iron, which in turn may affect mechanisms of zinc uptake and transport. However, we gave iron drops (30 mg/d) to infants for 6 mo and found no effect on zinc status as assessed by plasma zinc (Yip et al. 1985). Furthermore, we gave 50 mg iron/d to human adults for 2 wk and found no significant effect on zinc absorption using whole-body counting (Sandström et al. 1985). Thus, it appears that the long-term use of iron supplements does not impair zinc absorption or zinc status. Amino acids. Histidine is a good chelator of zinc (Schölmerich et al. 1987). However, high doses of histidine enhance the urinary excretion of zinc (Henkin et al. 1975). infants fed formula with a high protein concentration had lower plasma zinc concentrations than infants fed formula with less protein (Lönnerdal and Chen 1990) because they also had higher urinary losses of histidine and zinc.


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