Zinc. Not the kind that protected Chris Pringle in the New Zealand cricket team as they won their way through the 90s cricket era, but the inorganic mineral that is (not as) present in our food supply. Close to a quarter of New Zealand adults have inadequate intakes, according to the National Nutrition Survey.
Men over the age of 50 years are at most risk, with over 50% reporting inadequate intakes, and a staggering 90% of men over 70 years not meeting sufficient intakes.
Many athletes who don’t seem to have a lot of resilience to withstand high training loads often present with suboptimal zinc status.
Zinc is one of those nutrients that doesn’t get much air time, so fewer people are aware of any issues associated with deficiency. Zinc, it is one of the first things that people might take when they have a cold or flu, and in fact one of the initial signs of zinc deficiency is a depressed immune system. This is clearly important for any athlete wanting to optimise recovery after a heavy training session.
However, this is just the tip of the iceberg when it comes to functions that it performs. Zinc is second to calcium as being the most abundant metal in the human body and help perform functions including energy metabolism, genetic expression and neurotransmitter production. When lecturing about zinc I always refer to its importance in wound healing, ulcers and male fertility and reproduction, given it has a critical role in testosterone production. Zinc is also responsible for the production of oestrogen in women.
Cardiovascular disease and diabetes are two of the most burgeoning health problems society is experiencing, which athletes are not exempt from. The focus is often on macronutrient intake (i.e. carbohydrate, protein and fat), but micronutrients are just as important in the prevention or progression of these conditions.
The underlying cause of these chronic diseases begins with inflammation, and this is something an athlete experiences in increased amounts by virtue of the training load.
Given the role of zinc in the body, it is no surprise that low zinc levels are associated both with the buildup of plaque on the arteries and insulin resistance. Further, clinical studies have found that zinc helps stimulate the production of hormones that regulate appetite, fat storage and glucose uptake in the body – these are all processes which are compromised in an inflamed state.
It’s not just that our intakes are low, but there can be a double whammy effect with our digestion. Zinc plays an important role in the production of stomach acid, low levels of which will reduce our ability to digest and absorb all nutrients. Reflux can occur when carbohydrates begin to ferment in the gut. This can help explain the prevalence of sub-optimal zinc status among people with gut inflammation and digestive issues.
Athletes who experience recurring gastrointestinal issues would be advised to get their zinc levels tested given the stress the gut is placed under with the physical training combined with an additional sugar load if following a conventional athlete diet.
Finally, the association between zinc and mental health has also been studied, due to its role in serotonin production, one of our ‘feel good’ neurotransmitters which is produced in our gut.
So why are there many people now zinc deficient in a population like New Zealand where we enjoy fresh seafood and good quality meat products that are relatively accessible? Firstly our soil is depleted in minerals such as zinc, and therefore vegetable sources of it are lower than they were in the past. It’s not right to say that only a vegetarian diet is healthier, even though I love the veggies.
The most bioavailable form of zinc in our diet is from protein:
- Oysters have 70mg zinc per 100g
- Beef and lamb comes a distant second with around 12mg per 100g
- Seeds and nuts contain between 5-10mg per 100g depending on type (pumpkin seeds are one of the richest sources)
- Spinach and mushrooms have approximately 1mg per 100g. Much like bread and pasta, these plant-based sources are poorly absorbed compared to oysters, beef and lamb due to the anti-nutrients such as phytic acid present in the food.
So if you aren’t lucky enough to enjoy oysters on a regular basis, and are not consuming that much red meat, how do you know if you need to eat more and – if you are vegetarian – should you be supplementing? As a guide we should be consuming between 8mg to 11mg per day, easily met by 100g of beef or lamb – such as the ginger lamb patties featured below. Vegetarians may like add pumpkin seeds to salads and warm vegetable dishes, such as chickpeas with lightly steamed spinach, roast pumpkin and feta.
My best recommendation is to ask for a blood test from your doctor to establish your serum zinc level. Bear in mind that even if you fall within the ‘normal’ range, there may still be reason to increase zinc intake. If your levels are low (or low ‘normal’), work with a qualified nutritionist or dietitian to optimise zinc intake through diet or supplementation.
- 600 grams Lamb mince
- 2 tablespoon Grated fresh ginger
- 2 Spring onions (greens only) finely chopped
- 0.5 teaspoon Himalayan salt
- 2 tablespoon Coconut oil, melted
- 0.5 cups Tapioca (arrowroot) flour
Preheat oven to 200 degrees and line a baking tray with baking paper. Spread the tapioca flour out in an even layer on a separate board.
Add ginger, onions and salt to the lamb and form 4 even sized burger patties. Brush with coconut oil and roll in a little tapioca flour before putting on baking tray. If you have time, leave for an hour in the fridge to sit before baking 20 minutes or until cooked through.
Mikki Williden [PhD Registered Nutritionist]