It is intimately involved in every aspect of reproduction including the production of testosterone. Low levels of this most important hormone are usually associated with zinc deficiency; remove the deficiency, and testosterone levels go back up to normal.
Just one ejaculation can contain up to 5mg of zinc, which shows you how important it is.
Zinc is also vital for fertility in both sexes, is involved in the production of DNA and cell division, and promotes normal development of the fetus. A zinc deficiency during pregnancy can cause congenital abnormalities at birth.
Zinc is an essential trace mineral that acts as a catalyst in over 100 enzyme reactions in the body and is antioxidant, anti-inflammatory and involved in:
- cell division
- building and strengthening bones
- production of DNA
- production of hemoglobin
- production of testosterone
- correcting hormonal imbalance
- as a catalyst in hundreds of enzymatic processes
- insulin activity
- function of adrenals, pituitary, ovaries and testes
- maintaining healthy liver function
- mental alertness
- activation of T-cells (immune system)
- healing wounds
- attacking infected cells
- attacking cancerous cells
- decreasing risk of age-related chronic disease including AMD/ARMD
- fertility in both sexes
- preventing pneumonia
Zinc is vital for the function of many hormones, including insulin. It is also important for the promotion of normal growth in children, both mentally and physically (in the womb as well as after birth).
Zinc is used for:
- fighting free radical damage
- improving athletic performance
- slowing the ageing process
- cold remedies
- high blood pressure
- head injuries
- diarrhea (but see note on dosage)
- Crohn’s disease
- ulcerative colitis
- peptic ulcers
- reduction or loss of taste
- anorexia nervosa
- reducing damage to the heart
- night blindness
- type 2 diabetes
- psoriasis, eczema and acne
- erectile dysfunction
- rheumatoid arthritis
- Hansen’s disease
- Down’s syndrome
- Alzheimer’s disease
- sickle cell anemia and many other inherited disorders
You need to get enough zinc every day, because although the body contains 2-3g at any one time, this is mostly bound up in the liver, kidneys, skin, muscles and bones. The available zinc is therefore insufficient to last for more than a few hours.
The Recommended Dietary Allowance (RDA) for zinc is 11mg for men, 8mg for women, 2mg for babies up to 6 months, 3mg for infants up to 3 years, 5mg up to age 8 and 8mg to age 13. During pregnancy and lactation, the requirement increases to 12mg a day. Some conditions may indicate a requirement for a higher dosage than listed here.
Phytate/phytic acid (found in vegetables and many vegetarian protein sources) can reduce zinc absorption, but can be partially removed by soaking and/or sprouting beans, grains and seeds, or eating grain products which rise during preparation (eg. wholemeal bread).
Only about 20 percent of the zinc in food can be absorbed on average, although zinc in animal/fish sources is more easily absorbed because of high cysteine levels, which are not found in vegetables and fruit. Zinc is often removed unintentionally during the course of processing and refining. eg. 83% of zinc in brown rice is lost in the process of being polished and turned into white rice.
The highest sources of zinc are usually claimed to be animal/fish based, but in fact cashews and pumpkin seeds are also pretty good sources.
The richest source is oysters, which have almost 5 times the content of the next highest, dried brewers yeast (this is undoubtedly the reason for oysters’ reputation as an aphrodisiac in men). As it’s easier to eat 20-25g of oysters than 100g brewer’s yeast, this makes oysters a particularly valuable source, but it’s unlikely you can eat them every day – you’d get heartily sick of them after a while, for a start.
Please refer to the chart below for more information on sources. It includes both vegetarian/vegan sources and others suitable for meat-eaters.
There’s a wide range of products rich in zinc in my online store.
Available zinc from supplements varies. 100mg of each of the following yields the amount of zinc shown:
- zinc amino acid chelate – 19mg
- zinc gluconate – 13mg
- zinc orotate – 17mg
- zinc sulphate – 22.7mg
Some cold remedies which are sold contain zinc, in particular lozenges.
I offer a choice of zinc supplements in my online store.
Deficiency can be caused by phytic acid in grains, legumes (beas, peas and lentils) and vegetables, a high fibre diet, EDTA (used in food processing), large quantities of TVP in the diet, and breastfeeding in infants over 6 months (there is sufficient zinc in breast milk for the first 6 months of life).
Possible symptoms of deficiency include: slow growth and development in children, eczema, frequent colds and other infections, regular stomach problems, slow recovery from exercise, obesity, leaky gut, slow mental processes, post-natal depression, white spots on the nails, consistent diarrhea, chronic fatigue, poor vision esp. slow dark adaptation, lack of concentration, slow healing wounds/bruises, infertility in both sexes, thinning hair, lack of sexual drive or erectile dysfunction in men, lost sense of taste and/or smell, and poor appetite. You don’t need to have all the symptoms to suspect zinc deficiency.
There is also evidence linking zinc deficiency to various types of cancer, including leukemia, prostate cancer, breast cancer, ovarian cancer, lung cancer, colon cancer and skin cancer.
Possible causes of deficiency are a vegan or vegetarian diet, a low protein diet, pregnancy, endurance sport, alcoholism, sickle cell disease, gastrointestinal disease, over-consumption of iron supplements, some diuretics, and eating disorders.
Research into the effects of zinc
1. Studies have shown that men who are deficient in zinc have lower testosterone levels and that supplementation restores testosterone levels to normal.
2. There have been several studies on the effect of zinc supplementation on Age-related macular degeneration (AMD/ARMD).
A study in the Netherlands found a reduced risk of AMD when the diet contained high levels of zinc with beta carotene (vitamin A), vitamin C and vitamin E.
A study in 2007 found no effect on AMD from supplementation with zinc on its own, but the AREDS study found that supplementation with 500mg vitamin C, 400 IU vitamin E, 15mg beta carotene, 2mg copper and 80mg zinc significantly reduced serious deterioration in existing AMD patients. Without the zinc, there was no effect found. They also found that zinc without the antioxidant vitamins reduced deterioration in “subjects at higher risk, but not in the total population”.
A follow-up to AREDS found that 25mg zinc worked just as well as the 80mg administered in the original study. As excess intake is associated with genito-urinary problems, it is helpful that the reduced dose has been shown to be effective.
3. Research has found that children with ADHD tend to have lower levels of zinc than other children. A study of 400 children with ADHD found that they showed improved behaviour and were less impulsive and hyperactive when they were given 150mg a day of zinc sulphate (which would yield about 34mg zinc).
Zinc and medication
Taking zinc at the same time as antibiotics or penicillamine (a treatment for rheumatoid arthritis) reduces the effect of both the medication and the zinc. Leave at least 2 hours between taking zinc and either of these medications.
Some prescribed diuretics may cause zinc deficiency. Talk to your doctor about monitoring your zinc status whilst taking these.