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Friday, June 21, 2013

Got Zinc?

Zinc is necessary for all life forms on the planet. Zinc is a natural component of the earth’s crust and an inherent part of our environment. Zinc is present not only in rock, soil, and plants, but also in air, water and the biosphere. Plants, animals and humans contain and depend upon zinc.
Zinc deficiency is a very real and common occurrence in vegans and vegetarians. As  most of us following a plant-based, vegan diet are aware, you must eat a wide variety of fruits, vegetables, legumes, nuts, seeds, and whole grains to get completely balanced nutrition. It sounds simple enough, but almost too simple, and vegans can fall into a "rut" of eating certain foods or meals and neglecting others. The most commonly overlooked and most common deficiency (along with B12 deficiency, read about that here) essential micronutrient in the vegan diet required for good health is zinc. Zinc used to be plentiful in the soil that our food is grown in, but time, irrigation runoff, high turnover of crops, and especially chemical usage has depleted the soil in America markedly. In short, there is less dietary zinc available in food than ever before! Zinc intakes is also low in omnivore populations of older adults. Data from NHANES III indicate that adults aged 60 years or older from food-insufficient families (sometimes or often not having enough food). had lower intakes of zinc and several other nutrients and were more likely to have zinc intakes below 50% of the RDA on a given day than those from food-sufficient families. 
 Zinc is involved in numerous aspects of cellular metabolism. It is required for the catalytic activity of approximately 100 enzymes and it plays a role in immune function, protein synthesis, wound healing, DNA synthesis, and cell division. Zinc also supports normal growth and development during pregnancy, childhood, and adolescence, and is required for proper sense of taste and smell. A daily intake of zinc is required to maintain a steady state because the body has no specialized zinc storage system. Zinc is highest in animal products, and omnivores usually are not lacking in the mineral, but vegans and vegetarians are very often deficient. Symptoms of deficiency are mild at first, but are cumulative, and can cause serious problems! Zinc deficiency is characterized by growth retardation, loss of appetite, and impaired immune function. In more severe cases, zinc deficiency causes hair loss, diarrhea, impaired athletic performance, delayed sexual maturation, impotence, hypogonadism in males, and eye and skin lesions. Weight loss, delayed healing of wounds, taste abnormalities, and mental lethargy can also occur. Severe zinc deficiency depresses immune function because the body requires zinc to develop and activate T-lymphocytes; this makes a person extremely susceptible to bacterial infections and viruses. Many of these symptoms are non-specific and often associated with other health conditions; therefore, a medical examination is necessary to ascertain whether a zinc deficiency is present.

Vegan Zinc Food Sources
Good vegan sources of zinc include beans, nuts, seeds, whole grains, fortified breakfast cereals. However, Phytates—which are present in whole-grain breads, cereals, legumes, and other foods—bind zinc and inhibit its absorption. Thus, the bioavailability of zinc from grains and plant foods is lower than that from animal foods, although many grain- and plant-based foods are still good sources of zinc. This is why vegans and vegetarians must  make a point of seeking out zinc containing foods several times a day to avoid deficiencies. Vegans and vegetarians sometimes require as much as 50% more of the RDA for zinc than non-vegetarians. In addition, we definitely benefit from using certain food preparation techniques that reduce the binding of zinc by phytates and increase its bioavailability. Techniques to increase zinc bioavailability include soaking beans, grains, and seeds in water for several hours before cooking them and allowing them to sit after soaking until sprouts form. Plant based persons can also increase their zinc intake by consuming more leavened grain products (such as bread) than unleavened products (such as crackers) because leavening partially breaks down the phytate; thus, the body absorbs more zinc from leavened grains than unleavened grains.

Pumpkin/Squash Seeds. A popular food in the Middle East and East Asia, pumpkin and squash seeds contain about 10mg (70% DV) of zinc per 100g serving, 6.6mg (59% DV) per cup, and 3mg (19% DV) per ounce (~85 seeds). If you can't find these in your local supermarket you will surely find them in Middle Eastern or East Asian specialty stores. Alternatively, you can also save any pumpkin and squash seeds you have and roast them in your oven. The seeds are typically eaten by cracking the outer shell and eating the seed inside. 

Watermelon Seeds. Much like the pumpkin and squash, watermelon seeds are popular in the Middle East and East Asia and they should be in specialty stores catering to those cultures. It is also possible to just eat the seeds raw with the watermelon. You can shell them, or just chew them up whole. Dried watermelon seeds provide 10mg (70% DV) of zinc per 100g serving, 11mg (74 %DV) per cup, and 3mg (19% DV) per ounce. 

Dark Chocolate is showing more and more health benefits. Unsweetened baking chocolate provides 9.6mg (64% DV) of zinc per 100g serving (most bars are 50-100 grams). Cocoa powder will provide 6.8mg (45% DV) per 100g, or 5.4mg (39% DV) per cup, 0.3mg (2% DV) per tablespoon. 

Broccoli leaves contain far more zinc than the typically eaten florets, (while the stem contains virtually none) and should not be discarded! Add broccoli leaves to smoothies, salads, soups, and stews. 1/2 cup of broccoli leaves contain 10mg (70% DV) of zinc per 100g serving, 6.6mg (59% DV).

Peanuts are a great source of zinc, 100 grams of oil roasted peanuts will provide 6.6mg (44% DV) of zinc, or 8.8mg (59% DV) in 1 cup chopped, 1.9mg (12% DV) per oz (~39 peanuts). Dry roasted peanuts will provide half as much zinc at 3.3mg (22% DV) per 100 gram serving, or 4.8mg (32% DV) per cup, and 1mg (6% DV) per oz. 

Other foods with zinc listed in order from very good to fair sources: Cashews, crimini mushrooms, shiitake mushrooms, spinach, asparagus, chard, maple syrup, green peas, oats, sesame seeds, and miso. 

The U.S. Department of Agriculture's Nutrient Database Web site  lists the nutrient content of many foods and provides a comprehensive list of foods containing zinc..DV = Daily Value. DVs were developed by the U.S. Food and Drug Administration to help consumers compare the nutrient contents of products within the context of a total diet. The DV for zinc is 15 mg for adults and children age 4 and older. Food labels, however, are not required to list zinc content unless a food has been fortified with this nutrient. Foods providing 20% or more of the DV are considered to be high sources of a nutrient.

Dietary supplements
Supplements contain several forms of zinc, including zinc gluconate, zinc sulfate, and zinc acetate. The percentage of elemental zinc varies by form. For example, approximately 23% of zinc sulfate consists of elemental zinc; thus, 220 mg of zinc sulfate contains 50 mg of elemental zinc. The elemental zinc content appears in the Supplement Facts panel on the supplement container. Research has not determined whether differences exist among forms of zinc in absorption, bioavailability, or tolerability.

In addition to standard tablets and capsules, some zinc-containing cold lozenges are labeled as dietary supplements.

Too much zinc?
Zinc toxicity is probably the least common nutritional defecit in vegans and vegetarians (given that zinc deficiency is the most common!). Zinc is present in several products, including some labeled as homeopathic medications, sold over the counter for the treatment and prevention of colds. Numerous case reports of anosmia (loss of the sense of smell), in some cases long-lasting or permanent, have been associated with the use of zinc-containing nasal gels or sprays. In June 2009, the FDA warned consumers to stop using three zinc-containing intranasal products because they might cause anosmia. The manufacturer recalled these products from the marketplace. Currently, these safety concerns have not been found to be associated with cold lozenges containing zinc.

Zinc is also present in some denture adhesive creams at levels ranging from 17–34 mg/g. While use of these products as directed (0.5–1.5 g/day) is not of concern, chronic, excessive use can lead to zinc toxicity, resulting in copper deficiency and neurologic disease. Such toxicity has been reported in individuals who used 2 or more standard 2.4 oz tubes of denture cream per week. Many denture creams have now been reformulated to eliminate zinc. 



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