- Zinc Deficiency Symptoms
- Factors Contributing to Zinc Deficiency
- How do you know if you have a zinc deficiency?
- Good Food Sources of Zinc
- Zinc-Rich Recipes
- Can Zinc Deficiencies Cause Lines On Your Fingernails?
- Will Zinc Boost Your Libido?
- How Much Zinc Do We Require Daily?
- Zinc Toxicity Level and Upper Limit
- Zinc Stretch Target
- Availability of Zinc In The Diet
- What Factors Interfere With Zinc Absorption?
- Synergistic nutrients
- Processing Losses
- The Iron:Zinc Ratio
- The Zinc:Copper Ratio
A large portion of the population is at risk of becoming zinc deficient. This results from a combination of factors, including the overconsumption of processed foods, nutrient-poor soils, and weakened digestion.
Low zinc levels have even been linked to autoimmunity and cancer. In addition, because zinc is vital for the health of sperm in men and overall reproductive health in men and women, zinc deficiency can contribute to infertility.
Factors Contributing to Zinc Deficiency
Zinc is found readily in animal products, making deficiency more common in developing countries where these foods are harder to obtain regularly. Insufficient food availability affects an estimated two billion people worldwide.
Plant foods like beans, legumes, nuts, and grains contain phytates (phytic acid) that bind to zinc and other similar minerals, blocking their absorption. Consumption of diets high in phytates and low animal-based foods can further exacerbate zinc deficiency.
The human body requires a somewhat acidic environment in the stomach to kick off protein breakdown and absorb zinc. If stomach acid becomes weak, zinc uptake and protein digestion can decrease. Stress, certain medications, and eating too many processed foods can reduce stomach acidity.
How do you know if you have a zinc deficiency?
Zinc deficiency symptoms include:
- low testosterone,
- poor night vision,
- zinc-deficient acne,
- brittle nails,
- white spots on nails,
- loss of taste, smell, and appetite,
- decreased leptin levels,
- decreased immune function,
- low stomach acid,
- emotional disorders,
- hypogonadism, or the diminished production of sex hormones,
- low sperm counts,
- estrogen dominance,
- premenstrual disorder (PMS),
- slowed wound healing,
- stretch marks and increased scarring,
- increased susceptibility to infections,
- elevated histamine levels,
- hypercholesterolemia, and
- impaired cognitive function.
Good Food Sources of Zinc
Zinc is found in a variety of foods, although it’s most concentrated in animal sources.
Shellfish, liver, and non-starchy green vegetables have been found to have the highest contents of zinc, as listed in our zinc-rich food list below.
Keep in mind here that animal-based sources of zinc are also more bioavailable.
Animal Sources of Zinc
Animal foods are relatively bioavailable sources of zinc. Certain dairy products have higher amounts of zinc, meaning vegetarians can get their fix of zinc, too.
- ground beef
- beef liver
- beefsteak (sirloin, filet mignon)
- parmesan cheese
- whole egg
- cottage cheese
Plant-Based Sources of Zinc
Although nuts, seeds, legumes, grains, and beans contain some zinc, it’s often absorbed poorly from these foods because of their phytic acid content. Green vegetables have some zinc, although levels are not as well-absorbed or high as animal foods.
- pumpkin sedsseeds
Some examples of our most zinc-rich NutriBooster recipes include:
- oyster & anchovy dip
- oysters Kilpatrick (pictured)
- Dom D’Agostino’s breakfast
- P:E burger bowl
- veggie-packed meatloaf
Interestingly enough, your fingernails are a great indicator of varying nutrient deficiencies. Ridges in your fingernails can indicate that your body is low in protein, calcium, zinc, or vitamin A. Small white dots on your fingernails can also hint that you may not be getting enough zinc in your diet.
Zinc supplements are often used as a treatment for erectile dysfunction because zinc is needed to produce sex hormones like testosterone and prolactin.
Our satiety analysis indicates a moderate satiety response when people consume foods and meals that contain more zinc. People who consume more optimal levels of zinc in their diet tend to consume 13% fewer calories.
However, more zinc is not necessarily better, especially when it comes from supplements rather than whole food. Beyond about 35 mg/2000 calories of zinc, energy intake starts to drift back up with more zinc.
The chart below shows the distribution of zinc for our Optimisers, with an intake of 17 mg/2000 calories and the 85th percentile of 25 mg/2000 calories. This surpasses the Estimated Average Requirement of 12 mg/day for men and the Daily Recommended Intake (DRI) of 14 mg/day.
There is no evidence of any adverse effects from high amounts of zinc in foods. Hence, there are no real symptoms of toxicity or side effects.
Nutrients like zinc are hard to ‘overdose’ from whole foods because of the balancing vitamins and minerals naturally in foods. You will quickly excrete any excess zinc in the faeces. However, an Upper Limit of 40 mg has been set for supplemental zinc.
Based on our satiety analysis, we have set a zinc stretch target of 25 mg/day for men and 20 mg/day for women.
Zinc availability in the food system has increased since the fortification of breakfast cereals began in the 1930s. The chart below shows a significant jump in zinc fortification in the mid-1970s (data from USDA Economic Research Service).
Despite the sharp increase from fortification, the current average zinc level in the diet still does not meet the Daily Recommended Intake or Estimated Average Requirement and is nowhere near our Optimal Nutrient Intake. Thus, most people need to be attentive to their zinc intake and ensure they’re consuming enough to achieve more ideal levels.
While supplementation and fortification may be helpful if you have deficiency symptoms, our analysis indicates that zinc fortification of otherwise nutrient-poor foods will not provide greater satiety. So simply adding a zinc supplement to a low-nutrient diet will not make you feel any fuller.
Although you may be hitting your stretch target of daily zinc on paper, your body might not be absorbing all of it. Several factors are known to inhibit or lessen zinc uptake in the body.
- The absorption of zinc can be decreased by excess sugar.
- Insufficient stomach acid, inflammatory bowel disease (IBD), and other disorders involving inflammation of the GI tract inhibit the absorption of various vitamins and minerals like zinc.
- Stress is perhaps one of the biggest inhibitors of stomach acid production and therefore can inhibit nutrient absorption across the board.
- Persistent infections like H. pylori are known to decrease stomach acid and inherently affect zinc uptake.
- Prolonged use of drugs like proton pump inhibitors (PPIs) that decrease stomach acid can similarly reduce the body’s ability to absorb zinc.
- Excess calcium intake impairs zinc absorption, as does the consumption of too many phytates from nuts, beans, grains, and legumes.
- Iron and zinc compete for absorption pathways, so excess iron supplementation or fortified foods can negatively impact zinc absorption.
- If your ratio of iron: zinc is greater than 2:1, then your absorption of zinc will be reduced.
- Similar to iron and zinc, copper can also decrease zinc levels if consumed in excess.
- If your ratio of zinc: copper is consistently greater than 10:1 to 15:1, zinc deficiency can appear.
- Absorption from animal sources of zinc is much more readily available than plant sources, so strict vegans should account for an additional 50% of zinc in their diet.
- Exposure to heavy metals like cadmium or mercury can deplete zinc levels.
Zinc is resistant to spoilage, so your food will go bad before the zinc content changes significantly.
Zinc works synergistically with vitamins A, B6, D, E, cysteine, glutathione, copper, magnesium and manganese. Hence, getting your zinc from nutrient-dense whole food sources that typically come packaged with these other nutrients is crucial.
Zinc is also heat-stable, meaning it will not be destroyed through most cooking processes. However, you will lose some zinc via the liquid when cooking vegetables. Soaking and sprouting beans, legumes, seeds, nuts, and grains may decrease phytate content and improve zinc bioavailability in plant foods.
The Iron:Zinc Ratio
Zinc and iron are two essential minerals, but their proportion to one another is important. Because the two minerals are antagonists (inhibit the absorption of one another), consuming too much of one can deplete the other. The two minerals are also synergists, meaning that they need each other to support and reinforce one another’s roles.
Foods high in zinc like seafood and meat also contain iron. Because these nutrients exist in near-perfect ratios in natural foods, it is relatively harder to disrupt this ratio unless you are supplementing either iron or zinc. Fortified foods can also become tricky in this sense as they’re often not supplying balanced nutrients.
While both nutrients are important, our satiety analysis shows that foods that naturally contain more iron than zinc tend to lead to greater satiety. The average zinc:iron ratio of Optimiesrs is 1.3, however it appears that people who consume more iron than zinc consume 8% fewer calories.
The Zinc:Copper Ratio
While getting enough dietary zinc is undoubtedly important, the amount of zinc you’re taking in relative to the mineral copper is arguably just as necessary. Zinc and copper are also synergists and antagonists. Thus, overconsuming copper can contribute to lowered zinc levels.
Getting too much dietary copper and not enough zinc is common in vegan and vegetarian diets because zinc is sparse, and copper is readily found in grains, nuts, and other plant foods.
Studies have shown that an optimal zinc: copper ratio of 10:1 to 15:1 supports optimal health. The average zinc:copper ratio of our optimiesrs is 11.8. However, it appears that consuming more zinc relative to copper aligns with consuming 5% fewer calories.
Nutrient Profile of Zinc Rich Foods
The nutrient fingerprint shows the availability of nutrients in foods that contain the most zinc. It is possible to get adequate levels of zinc from nutrient-dense foods without the use of supplements. Foods high in zinc are generally nutrient-dense, have a lower energy density, and contain significant protein levels.
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Nutrient Density Index
- Vitamin A
- Vitamin E
- Thiamine (B1)
- Riboflavin (B2)
- Niacin (B3)
- Pantothenic acid (B5)
- Vitamin B6
- Folate (B9)
- Vitamin B12
- Vitamin C
- Vitamin D
- Vitamin K1