In the several decades since the need for dietary zinc was discovered, it has proven to be far more important to overall health than initially thought. And deficiency is proving to be common.
You may recall that the phytates of wheat and grains block nearly all absorption of dietary zinc, along with blocking iron, calcium, and magnesium (all positively-charged cations). Just as iron deficiency anemia with hemoglobin values of 7 or 8 g/dl resistant to iron supplementation commonly develops in grain-consuming populations, so a parallel zinc deficiency also develops (although not well reflected by blood levels of zinc, which underestimates tissue levels). Zinc appears to be nearly as important to overall health as iron.
You can also appreciate that there is no shortage of conventional health advice to correct what are nothing more than nutritional deficiencies caused by grain consumption: women take calcium for bone health (a very bad idea), the varied phenomena of magnesium deficiency (e.g., migraine headaches, hypertension, heart rhythm disorders, osteoporosis) are managed with prescription drugs, etc. Zinc deficiency likewise shows itself in many ways, rarely recognized as zinc deficiency but treated, for instance, as IBS, eczema, or pre-diabetes.
Zinc, like magnesium, is an essential cofactor required for thousands of reactions in the body and thereby plays a crucial role in many aspects of health, with zinc deficiency evident in many varied ways. We now appreciate that zinc deficiency, for example, adds to insulin resistance, inflammatory diseases, hormonal disruption, and even cognitive impairment and dementia, and can be responsible for hair loss, diarrhea, impaired growth and development in children, impaired sexual function, skin rashes, and increased susceptibility to viral and bacterial infections. Reflecting the myriad functions for zinc, 3% of the human genome codes for zinc-containing proteins/enzymes.
Note that zinc, like vitamin B12, is obtained primarily from animal products and is therefore one of the major deficiencies that plague people who are vegan/vegetarian. Humans, through our adaptation and substantial reliance on carnivory, have developed reliance on nutrients that are obtained exclusively or primarily via consumption of animal organs and flesh. A listing of zinc-rich sources (from the USDA Nutrient Database):
Zinc is not stored in any organ and regular daily intake is therefore required to maintain all zinc-related functions. The national nutritional NHANES III survey determined that around 45% of Americans do not obtain sufficient zinc, even if they consume foods from the above table.
A quick review of some of the evidence involving zinc:
- Inflammatory markers, c-reactive protein and interleukin-6, were reduced with 30 mg (elemental) zinc as zinc gluconate in obese women with higher starting levels of these markers compared to normal controls.
- The combined data of 6 clinical trials demonstrate reduced measures of insulin resistance with zinc supplementation.
- Zinc supplementation of 30 mg (elemental) as zinc gluconate increased T-cell number and proliferative response as reflections of immune response (with impaired T-cell driven immunity previously demonstrated in other studies).
- In experimental models, zinc deficiency is associated with the pathological hallmarks of dementia, including oxidative injury and accumulation of beta amyloid plaque, the signature abnormality of Alzheimer’s disease.
- Zinc acetate supplementation reduced production of beta-amyloid plaque in the brains of mice.
- People with Alzheimer’s dementia (and Parkinsonism) have lower serum zinc levels compared to controls.
- Blood levels of zinc fall as we age (for unclear reasons).
- Zinc sublingual lozenges (for enhanced delivery to the sinuses) abbreviate the duration of viral illnesses by about one-half if initiated at the start (for total of 75 mg per day during the illness). This presumably reflects improved immunity.
There is plenty we do not yet know about zinc. For example, if zinc deficiency is associated with the hallmarks of Alzheimer’s dementia in experimental models and zinc supplementation reduces the beta-amyloid plaque of dementia, should zinc be a component of any program to prevent human cognitive decline? A human clinical trial has not yet been performed to provide an answer.
Nonetheless, you can appreciate that zinc plays a crucial role in human health and that deficiency—intermittent or chronic—is common. Banishing all wheat and grains from your life is a terrific start, as this alone allows you to absorb the zinc in, say, pork roast or salmon. Because blood levels (both serum and RBC) are such a flawed means of assessing tissue zinc status, we are left with no satisfactory way to assess individual zinc status (though if a serum or RBC level is low, you are indeed profoundly deficient, but a “normal” level can still conceal substantial deficiency), it is worth obtaining zinc in some way, either by being cognizant of your consumption of zinc-rich foods (eat 8 ounces of beef for lunch, for example, and you have obtained your necessary daily intake) and/or including zinc supplementation in your daily routine. Given the RDA of zinc of 11 mg per day in adult males, 8 mg per day in adult females, supplemental intake of only 10-15 mg per day suffices to supplement dietary intake, though greater quantities are necessary if you avoid animal products or are foolish enough to continue consuming phytate-containing grains. Consider zinc supplementation in particular if you are over 60 years old, have struggled with skin rashes or repetitive infections, or have concerns about cognitive decline. At these low doses, there is no toxicity from zinc supplementation.