Why does the WHO estimate zinc deficiency to be so high? Two main reasons:
1) The best sources of zinc are animal products that people don't eat that much of (red meat and oysters).
2) Most people eat foods which inhibit their absorption of zinc and are capable of depleting the body's zinc reserves. All nuts, grains, seeds and legumes contain something called phytic acid (to varying degrees).
Phytic acid binds to certain minerals in the diet and blocks their absorption. With regards to zinc, phytic acid can even bind to zinc in your digestive enzymes and avoid this zinc being reabsorbed like it usually does (8), thereby causing depletion. That's why in order to maintain a positive zinc balance there is a ratio of zinc to phytic acid that needs to be met or exceeded.
According to a paper from the world’s leading scientific journal (Nature), 76.9% of people in China fall below this ratio with a median (average) daily intake of zinc and phytic acid being 10.6mg and 1186mg respectively (9).
This implies the 76.9% of Chinese people are constantly losing zinc from the body.
This explains why the WHO estimates at least 1 in 3 people are affected by zinc deficiency (10).
To put this into context, you would only need about 50 grams of certain beans (not soaked or fermented) to reach this unfavourable quantity of phytic acid (1186mg) (11).
This is why we think most people must supplement with zinc.
This is why we believe more than 1 in 3 people are affected by suboptimal zinc levels.
Many populations have been shown to have a daily phytic acid intake higher than China; South Korean populations (1676.6mg), Indian populations (1560mg-2500mg), Nigerian populations (2000mg-2200mg) (9). Which is why we think it is especially important for Black and Minority Ethnic (BAME) groups to supplement with zinc.
It should be noted that anybody of any ethnicity can consume high phytic acid foods, but Western diets tend to have lower phytic acid content (12). According to one article, “The average phytate intake in the U.S. and the U.K. ranges between 631 and 746 mg per day; the average in Finland is 370 mg; in Italy it is 219 mg; and in Sweden a mere 180 mg per day” (13).
If deficiency is so common, why aren’t your doctor and the health authorities telling you about this?
Because only really severe cases show symptoms and doctors can’t test for it.
Why?
Because under normal circumstances 84-90% zinc is in the muscles and bones. That’s why experts agree that blood levels aren’t a great way of measuring deficiency (14).
You can see exact quantity of phytic acid from various foods below: