Home » Health and Nutrition » Zinc: Vegetarian Nutrient of Concern #5

Zinc: Vegetarian Nutrient of Concern #5

Jennifer Hanes MS, RDN, LD

Zinc is a nutrient that you probably never think of.  We don’t learn about it in health class. There’s not a zinc section on MyPlate. This is because deficiency of this mineral is relatively rare. 

However, major sources of zinc come from animal sources, mostly meat, so vegetarians and vegans can be at risk of deficiency if they’re not careful.

This is the 5th in my series of nutrients of concern for vegetarians, based on my blog post, “The 7 Habits of an Unhealthy Vegetarian.

Understanding Zinc

Function

Like many of the other nutrients in our series, zinc serves a number of functions for us. 

It is required in over 100 enzymatic activities in our cells.  

Other roles include wound healing, immune system function (this is why you always see it added to cough drops), protein and DNA synthesis, and cell division.

Zinc maintains the structure of some proteins and can affect the expression of some genes.

For children and pregnant women, it promotes normal growth.

Finally, zinc is required for you to smell and taste!

Newer research has linked zinc deficiency to worsening symptoms of major depressive disorder and ADHD, as well as increased aggression and violence!

This is interesting information in light of some research that suggests vegans (and sometimes vegetarians) may have higher rates of depression than other populations. We’re getting off-topic, but this can be the focus of a future blog post!

Unfortunately, you don’t have a zinc storage system in your body, so you have to have a regular daily intake to meet your needs.

Unfortunately for vegetarians, the most prominent sources of zinc come from animal sources. In fact, 7 of the top 10 sources of zinc are animal flesh, but more on that later!

Recommended intake

Men and pregnant women need 11 mg per day. Lactation adds another 1mg to your daily needs. Women who are not pregnant or breastfeeding only need about 8mg per day.

Vegetarian sources of zinc are not as bioavailable, meaning we don’t absorb as much of it. Because of this, a vegetarian may need more total intake compared to an omnivore. Some estimates actually recommend 50% more zinc intake in this population!

However, other sources indicate that vegetarians may adapt to this zinc binding by becoming more efficient at absorption than their omnivorous counterparts. Some studies have found similar serum zinc levels in vegetarians and omnivores. However, we must remember that there isn’t much in our blood, so a deficiency cannot be diagnosed based on blood levels.

Vegetarian Sources of Zinc

Vegetarian sources include:

  • Hemp seeds, 3 Tbsp – 3 mg
  • Fortified breakfast cereal, 1 cup – 2.8 mg
  • Roasted pumpkin seeds, 1 oz – 2.2 mg
  • Tofu, 1/2 block – 2 mg
  • Tempeh, 1 cup – 1.9 mg
  • Whole grain pasta, 1 cup cooked – 1.9 mg
  • Oats, 1/2 cup cooked – 1.5 mg
  • Cheddar cheese, 1.5 oz – 1.5 mg
  • Boiled lentils, 1/2 cup – 1.3 mg
  • Greek yogurt, 6 oz – 1.3 mg
  • Roasted peanuts, 1 oz – 0.8 mg
  • Cooked brown rice, 1/2 cup – 0.7 mg
  • Canned kidney beans, 1/2 cup – 0.6 mg
  • 1 egg – 0.6 mg
  • Whole wheat bread, 1 slice – 0.6 mg

Challenges for Vegetarians

Phytates, discussed in our article on calcium, can also bind zinc, potentially increasing the amount a vegetarian should eat in a day by 50%.  While there are ways to reduce the impact of phytate-binding, it is important to be aware of the problem.

Fortunately, fiber does not appear to bind zinc.

Strategies to Enhance Zinc Absorption

Humans have very little ability to break down phytates on their own, which can inhibit zinc absorption in our intestines. However, we get some help with this from the bacteria that make up our gut microbiota.  Making sure that your gut is healthy is a great way to maximize zinc absorption, as well as other nutrients.

Certain preparation methods can improve zinc bioavailability. Soaking beans and leavening or fermenting grains, most notably. When cooked, the heat also reduces the phytate levels in foods, increasing your ability to absorb the zinc in your food.

Protein, particularly animal-based proteins, increases your absorption of zinc.  This makes including cheese, yogurt, and eggs in your diet helpful for more than just tasting good!

Meeting Zinc Needs on a Vegetarian Diet

Here’s an example of 1 day of vegetarian meals that includes at least 12 mg of zinc:

Breakfast – 1 cup cooked oats, cooked with milk, 3 Tbsp hemp seeds, 1 cup blueberries

Snack – 6 oz Greek yogurt with 1 oz roasted pumpkin seeds and 1/2 cup strawberries

Lunch – chickpea salad made with 1 cup of chickpeas, vinaigrette dressing, and 1 cup of chopped mixed vegetables

Dinner – Fettucini alfredo with 1 cup cooked whole grain pasta, 1/4 cup fettuccini sauce, topped with 1 Tbsp parmesan, 1/2 cup steamed broccoli

Snack – 1 medium apple with 2 Tbsp peanut butter

Nutrition for this day: 1965 calories, 90 g protein, 42 g fiber (this may be too high for some!), 14 mg iron, 583 mg magnesium, 14 mg zinc, 1013 mg calcium, and 3 mcg vitamin B12.

Symptoms of Zinc Deficiency

Mild deficiency causes loss of appetite, poor immune system function, and delayed growth in children.

As deficiency continues, you can develop hair loss, diarrhea, impotence, hypogonadism in males, lesions on the eyes or skin, unintended weight loss, inflammation, delayed wound healing, difficulty tasting your food, and fatigue, 

Zinc deficiency can be difficult to diagnose, as there are no stores, meaning that the zinc in your body is tied up within your cells rather than floating in your blood or chilling in your liver and muscles.

Infants that are exclusively breastfed past 4-6 months may not get enough zinc to continue growing normally. Introduce some age-appropriate sources in the child’s diet.

Causes of Secondary Deficiency

A common theme in this series, gastrointestinal malfunction can lead to deficiency due to both poor absorption and increased loss.

Chronic liver disease, chronic kidney disease, sickle cell anemia, diabetes, cancer, and chronic diarrhea can lead to poor absorption of zinc

Conditions that increase zinc needs

  • Pregnancy – due to its role in growth women that are pregnant or lactating have higher zinc needs than normal. 
  • Prematurity – infants born too early have poor GI health and increased metabolic rate and needs, requiring higher zinc intakes than full-term babies.
  • Certain medications – some antibiotics, diuretics, and anti-seizure medications reduce your ability to absorb zinc.
  • High protein loss – individuals with conditions that cause them to lose a lot of protein also lose a lot of zinc. These conditions include burns, kidney failure requiring dialysis, chronic diarrhea, liver cirrhosis, and heavy alcohol use.
  • Acrodermatitis enteropathica – a genetic condition that inhibits zinc absorption

Treatments for Deficiency

Treatment for deficiency is dietary modification and supplementation.

Zinc supplementation can cause symptoms of deficiency to improve very rapidly, with diarrhea resolving within 24 hours and skin lesions healing within 1-2 weeks.

Symptoms of zinc toxicity

Short-term toxic levels of zinc can cause nausea, vomiting, loss of appetite, abdominal cramps, diarrhea, and headaches.

Long-term zinc toxicity can lead to copper deficiency (weakness/fatigue, poor memory, sensitivity to cold, premature grey hair, and vision loss), poor iron function, poor immune system function, and reduced HDL (“good” cholesterol) levels.

Treatment for toxicity

Toxicity from dietary intake is rare. Look at your supplements and make sure you’re not taking in more than ~30mg /day from that source.

Another unusual source of zinc is denture adhesives. Normal, recommended use will not cause toxicity. However regular excessive use can.  Toxicity has been reported when an individual uses 2+ 2.4oz tubes of denture adhesive per week.

Should I take a zinc supplement?

Not usually.  There is some evidence that taking zinc supplements at the first sign of a cold may decrease the severity and length of your illness.

Children with sickle cell disease may have better growth and learning capabilities when supplemented with zinc.

What supplementation won’t do

No amount of supplementation will outperform a well-balanced diet.  Obsessively taking supplements is a drain on your pocket and promotes a false feeling of health or wellness.

Any concern for the omnivores?

Not really at all. This one is all ours….

References

National Institutes of Health

Healthline

Medical Journal of Australia

Psychology Today

Psychology Today, part 2

More on Dietitian Jenn

Vitamin B12 and the vegetarian diet.

Should you get nutrition advice from your doctor?

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