Zinc supplementation

In supplements, it is preferable to use zinc citrate, as it is the most bioavailable salt, while zinc gluconate seems to be the most effective salt for improving the evolution of respiratory problems.

Foods with zinc

The foods that contain the most trace elements (zinc, selenium, chromium, copper, manganese, and molybdenum):

• Nuts (all types).
• Wholegrain cereals.

Foods with zinc. The highest concentrations of zinc are found in red meats, particularly beef and lamb, and in the livers of these animals.

Intake and deficiencies

Zinc deficiency is common in the population.

Zinc is an anti-inflammatory and antioxidant agent (Prasad 2007). Superoxide dismutases, or SODs, (with copper and zinc) are the first line of defense in detoxification of products resulting from oxidative stress (Johnson and Giulivi 2005). Zinc decreases production of pro-inflammatory cytokines and of oxidative stress markers.

• Zinc deficiency is common in the population.
• Low zinc levels are common in diabetes, heart disease, and recurrent respiratory infections.
• In diabetes, heart disease, asthma, and frequent respiratory infections, zinc can help improve their control and prevent complications.
• Zinc needs the“team” of basic nutrients to achieve its maximum therapeutic potential in chronic diseases.

Intake. The zinc concentration depends on external inputs. In the United States, the PRI is 8 mg/day for women and 11 mg/day for men, with the tolerable upper limit being 40 mg/day. Average intake in the United States in 2000 was 9 mg/day for women and 14 mg/day for men.

However, a quarter to a third of the world’s population is at risk of zinc deficiency. This statistic depends on the country, ranging from 40% to 73% of the population (Maret and Sandstead 2006). In Spain, according to the ENIDE survey, the population at risk of inadequate zinc intake, compared to the estimated average requirements, is observed to be 1.5% to 2.7% in women and 15% to 30% in men. These statistics are consistent with those found in other populations, such as the Dutch (Van Rossum et al., 2011), which presents inadequate intakes in 8% to 28% of the population. (AESAN, 2011)

Zinc deficiency would be the fifth key disease factor in the developed world and, although it can be associated with a variety of disorders (Prasad 2003) or occur post-surgery, hypozincemia is normally a nutritional deficiency.

The populations that consume plant-based diets poor in bioavailable zinc often present zinc deficiencies (Sandstead 1991). People who eat little meat and fish are a risk group for zinc and iron deficit due to the fact that the plant-based zinc and iron are much less absorbable.

Nutrients. Plasma levels of zinc have been shown to be dependent on vitamins A and D. This suggests that a deficiency of vitamin A or D can cause a secondary zinc deficiency, and that adequate intake of these two vitamins should be ensured to treat zinc deficiency (Potocnik, van Rensburg et al. 2006). Iron deficiency is often associated with zinc deficiency.

Calcium supplements reduce zinc absorption by up to 50%. Folic acid supplements also reduce zinc.

Drugs. Hormone replacement, oral contraceptives, ACE inhibitors, angiotensin II receptor blockers, thiazides, furosemide, and corticosteroids can accentuate a marginal zinc deficiency.

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Reference values

NRV, PRI, UL for zinc

The NRV is 10 mg. The PRI is 12 mg for women and 15 mg for men.

The UL is 25 mg.

Zinc has low toxicity. However, doses of over 50 mg/day over a long period can lead to copper and iron deficiency (Fosmire 1990). Copper deficiency occurs with zinc intakes of 100–300 mg Zn/day; a recent study found a high number of hospitalizations of elderly persons with intakes of 80 mg/day (Johnson, Munoz et al. 2007). Supplements with more than 75 mg/day can reduce HDL cholesterol (Fosmire 1990). Doses higher than 100 mg/day can cause diarrhea, nausea, vomiting, cramps, etc., and depress the immune system.

NRV: Nutrient Reference Value. These are the daily amounts recommended for vitamins and minerals (micronutrients only) considered sufficient in the European Union to prevent a deficit in most healthy individuals in the population. They are the values used for labeling and claims.

PRI: Population Reference Intake. These are the reference values for a specific population group, defined as the amount of energy and/or nutrients (macronutrients and micronutrients) recommended to cover the nutritional needs of practically the entire population. They refer to healthy population groups. The values are expressed per person per day, as a 15-day average. To account for individual differences in digestive and metabolic processes, the PRI figure used for each nutrient is the average plus twice the standard deviation (except for energy, for which the average is used), thereby including almost all healthy individuals in the group (97.5%).

UL: Tolerable Upper Intake Level: the maximum level of total daily intake of a nutrient in a context of long-term or chronic consumption which does not pose a risk to health.