zinc

What can high-zinc foods do for you?

• Help balance blood sugar
• Stabilize your metabolic rate
• Prevent a weakened immune system
• Support an optimal sense of smell and taste

What events can indicate a need for more high-zinc foods?

• Impaired sense of taste or smell
• Lack of appetite
• Depression
• Growth failure in children
• Frequent colds and infections

Very good sources of zinc include: calf's liver, mushrooms and spinach.

For serving size for specific foods, see Nutrient Rating Chart below at the bottom of this page.

Description Function Deficiency Symptoms Toxicity Symptoms Cooking, storage and processing Factors that affect function

Drug-nutrient interaction Nutrient interaction Health conditions Supplements Food Sources Public Recommendations References

Description

What is zinc?

Zinc is a micromineral needed in the diet on a daily basis, but only in very small amounts (50 milligrams or less). The other microminerals that all humans must get from food are arsenic, boron, cobalt, copper, chromium, fluorine, iodine, iron, manganese, molybdenum, nickel, silicon, vanadium, and zinc.

The first research studies to demonstrate the zinc's important in the diet focused on the issue of growth. When foods did not supply sufficient amounts of zinc, young men in Iran and Egypt were found to have impaired overall growth as well as impaired sexual maturation. These initial studies on zinc reflected some of the key functions served by this mineral, including regulation of genetic activity and balance of carbohydrate metabolism and blood sugar.

How it Functions

What is the function of zinc?

Regulating genetic activities

Zinc is an important regulator of many genetic activities. The cells of our body each have a special compartment called the nucleus, and inside the nucleus are approximately 100,000 genes. These genes provide instructions for the cell, and the cell has to decide which instructions to read. Zinc is essential for reading genetic instructions, and when diets do not contain foods rich in zinc, instructions get misread, or not read at all. (In biochemistry terms, the gene-reading process that requires zinc is called gene transcription.)

Supporting blood sugar balance and metabolic rate

Insulin, a hormone made by the pancreas, is often required to move sugar from our bloodstream into our cells. The response of our cells to insulin is called insulin response. When the foods in our diet do not provide us with enough zinc, insulin response decreases, and our blood sugar becomes more difficult to stabilize. Metabolic rate - the rate at which we create and use up energy - also depends on zinc for its regulation. When zinc is deficient in the diet, metabolic rate drops (along with hormonal output by our thyroid gland).

Supporting smell and taste sensitivity

Gustin is a small protein that is directly involved in our sense of taste. Zinc mus be linked to gustin in order for our sense of taste to function properly. Because of this relationship between zinc and taste, and because taste and smell are so closely linked in human physiology, impaired sense of taste and smell are common symptoms of zinc deficiency.

Supporting immune function

Many types of immune cells appear to depend upon zinc for optimal function. Particularly in children, researchers have studied the effects of zinc deficiency (and zinc supplementation) on immune response and number of white blood cells, including specific studies on T lymphocytes, macrophages, and B cells (all types of white blood cells). In these studies, zinc deficiency has been shown to compromise white blood cells numbers and immune response, while zinc supplementation has been shown to restore conditions to normal.

Deficiency Symptoms

What are deficiency symptoms for zinc?

Because of the link between zinc and the taste-related protein called gustin, impaired sense of taste and/or smell are common symptoms of zinc deficiency. Depression, lack of appetite, growth failure in children, and frequent colds and infections can also be symptomatic of insufficient dietary zinc.

Toxicity Symptoms

What are toxicity symptoms for zinc?

Zinc toxicity has been reported in the research literature, and in 2000 the National Academy of Sciences set a tolerable upper limit (UI) of 40 milligrams for daily intake of zinc. (This limit applies to all individuals age 19 and over.) A metallic, bitter taste in the mouth can be indicative of zinc toxicity, as can stomach pain, nausea, vomiting, cramps, and diarrhea mixed with blood.

Impact of Cooking, Storage and Processing

How do cooking, storage, or processing affect zinc?

Like most minerals, zinc is present in many different forms in food, and can vary greatly in its response to cooking and processing. In some foods, where a greater percent of zinc is found in water-soluble form and contact with water is great, high losses of zinc can occur.

For example, when navy beans are cooked, 50% of the original zinc is lost. The processing of wheat is another example of the susceptibility of zinc to substantial loss. In 60% extraction wheat flour - the kind that is used to make over 90% of all breads, baked goods, and pastas sold in the U.S., almost 75% of the original zinc is lost.

Factors that Affect Function

What factors might contribute to a deficiency of zinc?

In addition to dietary deficiency, problems in the digestive tract can contribute to zinc deficiency. These problems include irritable and inflammatory bowel disorders, as well as insufficient output by the pancreas that prevents proper digestion of food.

Protein deficiency, and deficiency of one particular part of protein - the amino acid cysteine - can also contribute to zinc deficiency by preventing synthesis of transport and storage molecules that are used to shuttle and store zinc in the body.

Loss of zinc through chronic diarrhea or profuse sweating (as might occur with heavy physical labor or athletic training) can also contribute to deficiency of this mineral.

Drug-Nutrient Interactions

What medications affect zinc?

Thiazide diuretics like Diuril ™ or Enduron ™ and ACE inhibitors like Capozide™ and Lotensin,™ both used to lower blood pressure, can compromise zinc status. The body's supply of zinc can also be reduced by use of antibiotics (like penicillinamine or tetracycline), ranitidine (often sold under the trade name Zantac™ and used as a stomach antacid), and oral contraceptives (birth control pills).

Nutrient Interactions

How do other nutrients interact with zinc?

A Tolerable Upper Limit (UL) for zinc of 40 milligrams per day was set by the National Academy of Sciences in 2000 for all adults 19 years and older. The establishment of this limit was largely related to the ability of zinc - particularly supplemental zinc - to impair the status of other nutrients.

The most important of these nutrients are copper and calcium. Even at moderate doses of 18-20 milligrams that can easily be obtained from food, zinc can compromise the body's supply of copper unless foods rich in copper are also included in the diet. When few foods high in calcium are included in the diet, high levels of zinc intake (usually obtained from supplements) can also decrease absorption of calcium from the intestine into the body.

Although zinc is associated with these potential detrimental effects on copper and calcium, it is also supportive of other nutrients. The best studied of these nutrients in vitamin A. Without zinc, vitamin A cannot be effectively transported around the body, and cannot efficiently be mobilized when it is needed.

Health Conditions

What health conditions require special emphasis on zinc?

Zinc may play a role in the prevention and/or treatment of the following health conditions:

• Acne
• Alcoholism
• Alopecia
• Alzheimer's disease
• Anorexia nervosa
• Atopic dermatitis
• Benign prostatic hypertrophy
• Cervical dysplasia
• Common cold
• Crohn's disease
• Diabetes
• Epilepsy
• Graves' disease
• Herpes simplex
• HIV/AIDS
• Infertility (male)
• Inflammatory bowel diseases
• Influenza
• Macular degeneration
• Osteoarthritis
• PMS
• Psoriasis
• Rheumatoid arthritis
• Seborrheic dermatitis
• Senile cataracts

Form in Dietary Supplements

What forms of zinc are found in dietary supplements?

Zinc cannot usually be absorbed into the body unless it is first linked up with other substances. For this reason, many supplement manufacturers have produced dietary supplements containing zinc in what is referred to as "chelated" form. "Chelated" means connected with another molecule.

In the case of zinc, the most common chelates fall into two categories. The first category is organic acids. These chelates include picolinic acid, orotic acid, citric acid and gluconic acid. The second category is amino acids. This category includes methionine, monomethionine, and aspartic acid. When supplements contain zinc in these chelated forms, the supplement label will usually read: zinc picolinate, zinc orotate, zinc gluconate, zinc monomethionine, and so forth.

Supplemental zinc is also available in what is called inorganic form. Here zinc is provided in a non-chelated form, usually as zinc sulfate or zinc oxide. Research studies on these different forms of zinc show mixed results.

Food Sources

What foods provide zinc?

Calf's liver, crimini mushrooms and spinach are very good sources of zinc.

Good sources include sea vegetables, basil, thyme, spinach, pumpkin seeds, yeast, beef, and lamb.

Good sources include beef, lamb, summer squash, asparagus, venison, chard, collard greens, miso, shrimp, maple syrup, broccoli, peas, yogurt, pumpkin seeds, sesame seeds and mustard greens.

 

Introduction to Nutrient Rating System Chart

In order to better help you identify foods that feature a high concentration of nutrients for the calories they contain, we created a Food Rating System. This system allows us to highlight the foods that are especially rich in particular nutrients. The following chart shows the World's Healthiest Foods that are either an excellent, very good, or good source of zinc. Next to each food name, you'll find the serving size we used to calculate the food's nutrient composition, the calories contained in the serving, the amount of zinc contained in one serving size of the food, the percent Daily Value (DV%) that this amount represents, the nutrient density that we calculated for this food and nutrient, and the rating we established in our rating system. For most of our nutrient ratings, we adopted the government standards for food labeling that are found in the U.S. Food and Drug Administration's "Reference Values for Nutrition Labeling." Read more background information and details of our rating system.

World's Healthiest Foods ranked as quality sources of: zinc
Food	Serving Size	Cals	Amount (mg)	DV (%)	Nutrient Density	World's Healthiest Foods Rating
Calf's liver, braised	4 oz-wt	187.1	10.80	72.0	6.9	very good
Crimini mushrooms, raw	5 oz-wt	31.2	1.56	10.4	6.0	very good
Spinach, boiled	1 cup	41.4	1.37	9.1	4.0	very good
Beef tenderloin, lean, broiled	4 oz-wt	240.4	6.33	42.2	3.2	good
Lamb loin, roasted	4 oz-wt	229.1	4.60	30.7	2.4	good
Summer squash, cooked, slices	1 cup	36.0	0.70	4.7	2.3	good
Asparagus, boiled	1 cup	43.2	0.76	5.1	2.1	good
Venison	4 oz-wt	179.2	3.12	20.8	2.1	good
Swiss chard, boiled	1 cup	35.0	0.58	3.9	2.0	good
Collard greens, boiled	1 cup	49.4	0.80	5.3	1.9	good
Miso	1 oz	70.8	1.14	7.6	1.9	good
Shrimp, steamed/boiled	4 oz-wt	112.3	1.77	11.8	1.9	good
Maple syrup	2 tsp	34.9	0.55	3.7	1.9	good
Broccoli, steamed	1 cup	43.7	0.62	4.1	1.7	good
Green peas, boiled	1 cup	134.4	1.90	12.7	1.7	good
Yogurt, low-fat	1 cup	155.1	2.18	14.5	1.7	good
Pumpkin seeds, raw	0.25 cup	186.7	2.57	17.1	1.7	good
Sesame seeds	0.25 cup	206.3	2.80	18.7	1.6	good
Mustard seeds	2 tsp	35.0	0.44	2.9	1.5	good

World's Healthiest Foods Rating	Rule
excellent	DV>=75%	OR	Density>=7.6	AND	DV>=10%
very good	DV>=50%	OR	Density>=3.4	AND	DV>=5%
good	DV>=25%	OR	Density>=1.5	AND	DV>=2.5%

Public Health Recommendations

What are current public health recommendations for zinc?

The Recommended Dietary Allowances for zinc, set in 1999 by the Institute of Medicine at the National Academy of Sciences, are as follows:

• Males and females, 0-6 months: 2 milligrams
• Males and females, 6-12 months: 3 milligrams
• Males and females, 1-3 years: 3 milligrams
• Males and females, 4-8 years: 5 milligrams
• Males and females, 9-13 years: 8 milligrams
• Males 14 years and older: 11 milligrams
• Females 14-18 years: 9 milligrams
• Females 19 years and older: 8 milligrams
• Pregnant females 18 years or younger: 12 milligrams
• Pregnant females 19 years and older: 11 milligrams
• Lactating females 18 years or younger: 13 milligrams
• Lactating females 19 years and older: 12 milligrams

References

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