Zinc is an essential mineral that must be obtained from the diet and has several vital properties for athletes. Nutritionist Rob Hobson explains.
What does zinc do?
Zinc is required by almost 100 enzymes to carry out vital chemical reactions in the body. It is also involved in creating DNA; cell growth; wound healing; processing carbohydrate, fat, and protein in food; and maintaining a healthy immune system.
A study published in the American Journal of Clinical Nutrition showed that athletes who do endurance and other forms of strenuous activity are at greater risk of zinc deficiency. This may be due to the exclusion of certain foods from their diet, or a lack of overall food intake in order to maintain a low bodyweight.
These factors can put them at risk of reduced endurance, muscle mass loss, and greater risk of osteoporosis. In addition, low zinc levels reduce muscle strength and power, so inadequate zinc could affect performance during both endurance exercise and exercise that requires strength and power.
How much zinc do athletes need?
The UK recommended daily zinc intake is 9.5mg for men and 7mg for women. Men have a higher requirement than women because zinc is vital for male reproductive health. There are no specific guidelines for athletes regarding zinc, although it has been suggested that they may need more given losses from sweat.
According to the UK National Diet and Nutrition Survey (NDNS), current daily intakes are 9.5mg for men and 7.6mg for women. The survey has also shown that 6% of men and 7% of women do not get enough zinc in their diet, putting them at greater risk of deficiency.
How does zinc impact athletic performance?
Zinc is required for enzymes used in the immune system. A deficiency in this mineral can result in impaired immunity. Maintaining a healthy immune system is a crucial concern for athletes, as it can impact training and competition.
Upper respiratory tract infections (URTI) are athletes' most-reported acute illnesses. Studies have shown that they are ubiquitous among those involved in endurance sports. Infection is thought to be related to heavy periods of training and prolonged bouts of exercise. The problem has been attributed to suppressing the immune system through physical activity.
A Cochrane review has shown that zinc acetate lozenges (75mg daily) can decrease the duration of a common cold when taken within 24 hours of the onset of symptoms and continued for the period of infection.
Improved strength and lean muscle mass
Recent research demonstrates the role zinc has in raising the levels of three important anabolic hormones in the body: testosterone, insulin-like growth factor (IGF-1), and growth hormone (GH). Studies have also found that low zinc levels correlate with lower serum testosterone, which can significantly affect many aspects of performance, such as strength, body fat percentage, and recovery.
A study of 40 males, half of whom were sedentary and the other half regular weight trainers, was divided into four groups, half of whom received a zinc supplement. Testosterone levels were measured at the start of the study then six weeks later at the end of the training program.
It was found that testosterone levels increased depending on training and supplementation. In other words, the group involved in weight training and supplementation had the most significant increase, implying that this combination contributes to performance and muscle strength. More research is needed to confirm the benefit of zinc as an ergogenic aid, but the findings are fascinating.
Sleep quality has positive effects on athletic performance, but a lack can be detrimental. Several issues can arise from poor sleep that could jeopardise performance. These include decreased accuracy and reaction times that could impact sports like tennis or badminton; quicker times to exhaustion, which could impact endurance athletes; poor-decision making, which could affect all sports; and an increased risk of injury and illness.
Several micronutrients have been linked to sleep. Although there is not a tremendous amount of research on this topic, it still seems that there is a positive association between sleep duration and micronutrients, including iron, zinc, and magnesium. Athletes should ensure they get plenty of foods rich in these nutrients into their daily diet to help ensure the quality of their sleep.
What foods contain zinc?
There are plenty of zinc-rich foods you can include in your diet. Here are some examples and how much zinc they contain.
|Zinc-rich foods|| Amount of zinc
|Offal (liver, kidney)||14.2mg/100g|
|Nuts and seeds (especially pumpkin seeds)||6.6mg/100g|
|Wholegrains (oats, brown rice, brown bread)||2.3mg/100g|
|Beans, lentils and pulses (black beans, chickpeas and red lentils)||1.5mg/100g|
Is all zinc absorbed in the same way?
Phytic acid, or phytate, is found in plant foods such as beans, nuts, seeds, and whole grains. This substance can inhibit the absorption of zinc, which is why it is harder to get zinc from plant-based sources. Vegetarians and vegans should bear this in mind when planning their diet and may need to include plenty of zinc-rich foods to get an adequate intake.
Animal proteins are rich in zinc, which is more readily absorbed in the body from this source. The consumption of animal protein has also been shown to counteract the adverse effects of phytates, thus improving the uptake of zinc from plant-based foods in the same meal.
|Zinc-rich meal|| Amount of zinc
|Two scrambled eggs, 100g spinach, two slices of wholegrain toast||3.6mg|
|100g lean beef stir fry (green veggies) and 180g cooked brown rice||7.4mg|
|Mixed bean chilli (150g), 30g cheese served, and 180g cooked brown rice||4.7mg|
Focus on diet
To maintain performance, athletes should focus on their overall diet as a priority. The more varied this diet, the greater the chance athletes have of gleaning everything they need to support their needs. If an athlete feels that their diet is not up to scratch, or if there is a chance of deficiency, such as in the case of endurance athletes, then taking at least a multivitamin and mineral supplement can help to ensure an adequate micronutrient intake.