Other vitamins and nutrients may get more headlines, but experts say as many as two billion people around the world have diets deficient in zinc - and studies at Oregon State University and elsewhere are raising concerns about the health implications this holds for infectious disease, immune function, DNA damage and cancer.
Zinc deficiency is quite common in the developing world and is particularly common in countries such as the U.S and the UK, where the population eats a large amount of highly processed cereal and grain proteins rather than alternative high zinc sources of protein. It is estimated that up to 40 per cent of the elderly are affected as a result of inadequate dietary intake and reduced absorption of this essential nutrient due to digestive insufficiency.
Symptoms of zinc deficiency
Low zinc alters the sense of taste which in turn leads to increased cravings for saltier and sweeter foods. Other symptoms associated with deficiency include; low energy, poor immunity, chronic fatigue, infertility, poor memory, slow wound healing, inability to focus, nerve dysfunction, alopecia, eye and skin lesions, diarrhoea, ringing the ears as well as a host of neurological symptoms including ADD.
Here are our top 5 benefits of optimising your zinc intake
Zinc is known to play a pivotal role in the immune system, and people with a deficiency have increased susceptibility to a variety of pathogens including viruses and bacteria as well as autoimmune diseases (1). Studies indicate that zinc affects multiple aspects of the immune system, from the barrier of the skin to gene regulation within lymphocytes. Zinc is crucial for normal development and function of cells modulating non-specific immunity such as neutrophils and natural killer cells.
- Male Reproductive Health and Fertility
Zinc is an essential element required in the production of testosterone. Inadequate zinc has also been linked to low libido. Prostate cancer is the second leading form of cancer death among men. In fact, prostate cells accumulate more zinc than the cells in any other human tissue. However, numerous studies (2,3) demonstrate specific mechanisms by which zinc acts as a tumour suppressor, altering the biology of prostate cells to make them less likely to undergo malignant transformation, and less able to multiply and survive as cancer cells.
A link has also been established between zinc status and the production of follicle-stimulating hormone (FSH), luteinizing hormone (LH) and prolactin.
- Cardiovascular Health
Zinc is vital for the maintenance of cardiovascular cells and the delicate cells that line the blood vessels called the endothelium which plays a major role in the circulation. Low zinc levels can cause a deficiency in this protective barrier potentially leading to conditions such as atherosclerosis (4).
- Diabetes and Insulin Resistance
Zinc has three separate roles in the healthy function of insulin. Zinc binds to insulin to enable it to be adequately stored in the pancreas and then released appropriately when glucose arrives in the bloodstream. Zinc is also an important component of the enzymes involved in allowing insulin to bind to the cell wall and thereby giving glucose access to the cell so that it can be utilized for energy production.
When zinc concentrations fall, insulin secretion is reduced as is cellular sensitivity to insulin. Finally, zinc is an excellent antioxidant that helps to quench free radicals that are responsible for driving inflammation. By keeping inflammatory markers down cellular health is optimised (including the membrane) which ensures the cell is receptive to insulin.
- Brain Function
Zinc plays an important role in the production of dopamine. Dopamine is a neurotransmitter associated with reward and pleasure and is necessary for optimal energy levels, focus, mood and reward-driven learning.
Studies have shown that children with ADHD tend to have lower levels of zinc compared with healthy children and improving zinc status improved impaired social behaviour making subjects less hyperactive and impulsive than placebo controls (5).
Dietary Sources of Zinc
Zinc is naturally found associated with proteins in such meats as beef and poultry, and in even higher levels in shellfish such as oysters. It's available from plant sources such as beans and legumes but poorly absorbed from them, raising additional concerns for vegetarians.
Red blood cell zinc levels are regarded as the most reliable way of assessing status although the zinc challenge test is another viable option that allows you to monitor levels and supplement accordingly.
Finally, a word of warning about intake
Zinc is an essential micronutrient for numerous cellular processes. But taking too much zinc can also be a concern because in excess it can interfere with the absorption of other important nutrients such as iron and copper. The recommended nutrient intake (RNI) is seven milligrams a day for women, nine for men, although higher doses are used therapeutically for repletion dosing, anything over 50 milligrams a day could be considered excessive.
- Costello LC, Franklin RB, Tan MT. A critical assessment of epidemiology studies regarding dietary/supplemental zinc and prostate cancer risk. Open Urol Nephrol J. 2008;1.
- Franklin RB, Costello LC. Zinc as an anti-tumour agent in prostate cancer and in other cancers. Arch Biochem Biophys. 2007 Jul 15;463(2):211-7.