Meeting zinc requirements on a plant-based diet
What is zinc?
Zinc is a mineral essential to cell division, playing a key role in growth during pregnancy and from birth through to adolescence. It is also important for the preconception period, as it plays a role in hormone balance and ovulation, and in men it is needed to regulate serum testosterone levels and make new sperm. Zinc is also important for healthy immune function and is needed for wound healing, and the metabolism of proteins, fats and carbohydrates. Without zinc, we would not be able to taste, and it is critical for nerve development. Certain tissues and fluids in the body are dependent on good zinc intakes, as they contain relatively high concentrations. These include sperm and seminal fluid, the iris and retina of the eye, and the prostate.
The recommended daily zinc intake for a woman is 7mg, and for men 9mg. Men’s requirements are higher because they lose zinc with each ejaculate and it is therefore important, particularly for men trying to conceive, to ensure adequate daily zinc intakes.
There are many vegan zinc sources, including seeds (in particular poppy, sesame, chia and sunflower seeds), nuts (in particular almonds, cashew and pine nuts), beans, lentils, peanuts, soy foods such as tofu, tempeh and edamame beans, and the majority of grains. Dark chocolate also contains good amounts.
Risks of deficiency
Zinc deficiency can occur when one’s diet is limited, especially those comprised of mainly whole grains or refined grains. The reason for this is that with whole grains, the zinc is bound in phytates and this makes it less bioavailable for absorption. With refined grains, most of the phytates are lost, but so is most of the zinc. Symptoms of deficiency include poor growth, loss of appetite, impaired immune function, poor wound healing, taste changes, weight loss, and low testosterone levels in males. True zinc deficiency is rare, as the body increases absorption in the same way as it does with non-haem iron, when reserves are low. This means that body losses are reduced. However, it remains important to ensure adequate zinc intakes.
How to optimise zinc intake
There are ways to make zinc more bioavailable so that absorption is increased, and these lie in food preparation. The fermentation process during the making of sourdough reduces phytates, and soaking grains and legumes overnight before cooking them and sprouting where possible means that the phytates are broken down and more zinc is available. Sprouting usually takes between 3-5 days and no special equipment is needed, simply a jar and a lid with holes, or you can secure a cheesecloth around the top of the jar. There are many videos/blogs online showing how to sprout: don’t feel intimidated by sprouting, it really is very simple once you have the hang of it.
Another way of breaking down phytates is by adding foods containing acids, such as garlic. For example, by adding garlic to homemade hummus, the zinc absorption will be increased from the tahini and chickpeas.
Avoid zinc supplementation
Studies have shown that iron has a negative effect on zinc absorption when taken together in the form of a supplement, whereas a meal containing both nutrients has not been shown to have the same effect. It is always preferable to meet zinc needs through a varied plant-based diet, and to avoid supplements unless prescribed by a doctor to correct deficiency.
By Lisa Simon, Registered Dietitian at Plant Based Health Online
Davis. B, Melina, V (2014). Becoming Vegan. Book Publishing Company: USA
Lönnerdal. B (2000). Dietary factors influencing zinc absorption. J Nutr, 130(5S Suppl):1378S-83S.