In this article we shall look at zinc; its role in performance and health, and how much is required, notwithstanding some excellent food sources.
You may have heard about zinc from science lessons at school, or you may have seen it listed on the nutrients panel of vitamin supplements.
Either way, zinc is a trace element that you can find on the Periodic table of elements as number 30 and represented by Zn, it is found in the earths crust, yet we do not expect you to start digging around looking for some.
Zinc is an essential nutrient, this means your body needs it for survival, yet cannot produce it, therefore you must consume zinc through foods or supplements as you would do with other minerals such as iron.
The America Gastroenterological Association describes zinc as, “…an essential trace element for human nutrition that is an integral part of many enzyme systems…”.
Why is it important?
Like other trace elements found in the body, zinc has a few key physiological functions. These have been outlined by Osamu Wada from the University of Tokyo as being:
- Protein metabolism
- Lipid metabolism
- Carbohydrate metabolism
- Bone metabolism
What does this mean?
All bare one of functions listed above (bone metabolism being the exception) are critical to supporting homeostasis. If you were not sure, homeostasis essentially means to keep the internal environment of your body stable regardless of the conditions outside.
An example of your body managing homeostasis is through temperature regulation.
Therefore, what ever is happening outside, such as a temperature change, your body will adapt to keep the internal temperature stable around 37 degrees/98.6 Fahrenheit which is similar to how a thermostat in a building works as explained by the Britannica encyclopedia.
You may wonder why homeostasis is important, to be put simply, if there is a failure of homeostasis, it can lead to the failure of enzyme functions which can cause inflammation, disease, and in some cases, death of the organism.
For instance, hyperthermia is when the body becomes too hot, this can be caused by a few factors such as weather conditions, illness or too much exercise.
When this happens, the enzymes denature, the cells die, and this results in death for the person.
The role of protein, lipid and carbohydrate metabolism are all essential to life. The metabolism of each from food sources is the process in which they are broken down and absorbed by the body for a variety of needs such as disease prevention, growth, energy and recovery.
In regard to bone metabolism, again, this is a very important function which bone cells cooperate to ensure bone health and structure is maintained. A lack of bone metabolism can lead to fragility and fracture, evidence has demonstrated a key link between the bone and immune system.
Zinc has many roles in the body which helps complete the jigsaw of health and development, these include amongst others:
- Immune function
- Skin and hair
- Antioxidant activity
Research suggests that zinc supplementation may help prevent catching the common cold, it may also help reduce the symptoms of a cold and the duration if zinc is taken within 24 hours of symptoms beginning.
There’s also evidence that zinc may also help delay the onset of age related vision loss.
A study conducted in the Netherlands found that when zinc was combined with antioxidants including vitamin C, E and beta-carotene (an antioxidant that converts to vitamin A) reduced the risk of developing advanced age related vision loss.
What does a zinc deficiency look like?
According to the data, approximately 17% of the global population suffer from a deficiency, that is around 1.32 billion people.
Bear in mind that have just talked about how the body requires zinc for survival and that it contributes to homeostasis which if disrupted could lead to death.
That means, over 1 billion around the world are not getting at least one nutrient that is required for their body to operate properly.
What are the symptoms?
The symptoms of a zinc deficiency can vary, and as such it may not be easy to identify. Additionally, it is difficult to actually measure a persons zinc nutritional status.
With this in mind, let us take a look at some of the tell tail signs that a person is zinc deficient as stipulated by the National Health Service in the UK:
- Loss of taste and smell
- Wounds unable to heal
- Loss of hair
- Rise of infections
- Inflamed oral region
- Lack of appetite which could lead to anorexia
- Irregular periods
- Male prostate issues
- Metallic taste in the mouth
- Weight loss
- Eye and skin lesions
Yet this is just the tip of the iceberg as the Japanese Medical Association Journal also add a few more to the list which includes:
- Growth retardation
- Low testosterone
- Depression and mental lethargy
Who is at risk?
Those who are live in regions that eat a lot of cereal foods and low amounts of meat are particularly susceptible.
In these regions a deficiency can affect up to one third of the population.
These areas include:
- Southeast Asia
- Sub-Saharan Africa
Apart for living in a high-risk region, there are groups of people that are also vulnerable.
This can be due partly to lifestyle or chronic illness and diseases.
People who suffer from a number of different diseases can be at a heightened risk of zinc deficiency, this is particularly true for those living with gastrointestinal and digestive issues.
This is because they cannot absorb sufficient quantities of zinc from their diet.
Athletes, and persons who lead a very active lifestyle such as soldiers particularly in hot climates are also at risk from a zinc deficiency due to excessive sweat and a variety of other metabolism related functions.
This can lead to complications such as fatigue, a reduction in body-weight, a higher risk of osteoporosis and a negative effect on endurance.
Meat contains bioavailable zinc which the body can utilize as it is highly absorbed. In these cases, people who follow a vegetarian diet may have to increase their recommended daily allowance of zinc by 50%.
Pregnant and lactating women
Lactation can deplete zinc stores and the requirements of the unborn baby are also high, this can place the mother at a higher risk of zinc deficiency.
Sickle Cell Disease
Sickle cell disease is an inherited condition that affects the red blood cells which can increase the risk of infections and anemia amongst other problems.
It is reported that up to 50% of alcoholics suffer from a zinc deficiency because alcohol prevents the absorption of zinc and also increases more zinc to be excreted through urine.
There are some recommended foods that include zinc, however, as already mentioned, if you eat a plant-based diet you may have to increase your zinc intake as legumes and whole grains can inhibit absorption due to phytate which is present.
- Fortified breakfast cereals
Nuts and Seeds
- Pumpkin seeds
Requirements differ between genders and whether a woman is breastfeeding or pregnant, age is also a factor. Also consider your exercise routine and the climate.
This is apparent in an article published by the Military Medicine journal in 2005 which stressed the importance of zinc for the modern war-fighter to improve would healing, cognitive function, behavior, fighting disease and maintaining health.
A further review of the nutritional intake of male athletes saw that there were significant deficiencies across the wider range of vitamins and minerals including zinc, vitamin D, vitamin A and iron amongst many others when they were adhering to the recommended intakes ad standards.
Essentially, the athlete requires more than what is recommended for a regular person.
As a general rule of thumb, you can follow the guide below which follow the guidelines presented by the National Institutes of Health Office of Dietary Supplements.
However, this will most likely need to be adjusted if you are involved in frequent, intense physical activity. This would be a discussion you will need to have with your registered dietitian and nutrition professional.
Any male from the age of 19 has a recommended minimum intake guide of 11mg to an upper tolerable limit of 40mg per day. This means it is advised not to go above that for a long period of time.
Females are also advised to have 8mg daily and not to go above 40mg daily for any long stretch. During pregnancy their minimum intake increases to 11mg and when lactating this demand increases to 12mg daily.
You may think that these amounts are very low. However, bear in mind that a cup of milk only provides 1mg, 1oz/28g of almonds equates to just 0.9mg this is also the same for ½ of a roasted chicken breast.
Even 3oz/85g of crab is only 6.5mg of zinc with the exception being handed to oysters which contain 74mg of zinc.
Is too much zinc bad for you?
We have already touched upon the dire health and performance effects of too little zinc, but can too much of this trace element also cause any problems?
Potentially yes. Again, if you are an athlete or perform regular bouts of intense activity, your requirements may be different.
However, in more normal circumstances, and while we appreciate that there is not always a ‘one-size-fits-all’ solution to nutrition zinc toxicity can occur.
Too Much Zinc Symptoms
Zinc is a mineral that cannot be stored by the body, therefore daily intake is required. It is also excreted mainly in the feces but also through sweat and urine particularly due to high levels of exercise, especially if an individual trains intensively.
Furthermore reviews of the literature demonstrate that humans are able to tolerate high intakes of zinc.
That said, zinc toxicity can lead to unwanted symptoms, such as but not limited to:
- High blood pressure
- Abdominal cramps
- Digestion issues
- Kidney disease
What levels of zinc can cause toxicity?
There is a report of someone vomiting and experiencing severe nausea within 30 minutes of consuming 570mg of zinc and it is considered that a daily intake of 150 to 450mg daily will lead to chronic issues such as a reduced immune function and a reduction of HDL cholesterol (good cholesterol).
Zinc is a very important element that humans need daily in order to survive. A zinc deficiency can lead to many health problems, particularly for child development and pregnant women.
Athletes and military personnel may suffer from performance losses due to zinc deficiencies whilst adequate zinc intake may also reduce age related vision decline and ease the symptoms of the common cold.
Put simply, we need zinc and a large swathe of the global population do not get enough zinc in their daily nutrition intake.
We have identified that an adult male and female can easily tolerate up to 40mg per day, however, we have also referred to publicized articles that state athletes probably require more than what is recommended for the vast majority of the general population.
Any signs of zinc toxicity appear from consuming 150mg to 450mg daily, as such, these high levels should be avoided.
This post was written by Ben - BA(Hons), PGCert Sport & Exercise Nutrition.