Get Enough Zinc, Iron, and B12 Each Day

 
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Now that we've established that it’s important to focus on three individual nutrients that are more prevalent in animal products (zinc, iron, and vitamin B12) when eating a plant-based diet, it's time to look at ways to get enough of these nutrients.

Red meat and poultry provide the majority of zinc in the American diet. Plant sources of zinc include legumes, nuts and whole grains, however these foods also contain phytates which bind zinc and decrease its absorption in our digestive tract. Vegetarians require as much as 50% more zinc as carnivores for optimum health. Some food preparation techniques reduce the action of phytates and increase zinc bioavailability. For example...

  • Soak legumes, grains and seeds in water for several hours before cooking so that sprouts form
  • Choose more grains that use leavening (anything with yeast, baking soda, or baking powder to make it rise) because leavening partially breaks down phytates

How much zinc do I need?

The RDA for zinc for women age 19+ is 8mg per day and for men age 19+ is 11mg per day. If you’re pregnant you need 11 mg zinc per day, and 12 mg zinc when breastfeeding. If you don’t eat any animal products that are high in zinc (beef, crab, lobster, oysters, pork, chicken) on a regular basis, then increase your daily zinc intake by 50%. That means 12mg zinc per day for women and 16.5mg zinc per day for men who eat a primarily plant-based diet. If you’re pregnant, aim for 16.5 mg zinc and 18 mg when breastfeeding.

To meet your daily zinc needs:

  • ½ cup canned baked beans contains  2.9 mg zinc
  • 1 ounce pumpkin seeds contains 2.2 mg zinc
  • 1 ounce cashews contains 1.6 mg zinc
  • ½ cup cooked chickpeas contains 1.3 mg zinc
  • 1 packet plain instant oatmeal contains 1.1 mg zinc
  • 1 ounce dry roasted almonds contains 0.9 mg zinc
  • ½ cup cooked kidney beans contains 0.9 mg zinc

The iron we can get from foods comes in two forms:  heme and nonheme.

Meat, seafood and poultry contain both heme and nonheme iron, while plants contain only nonheme iron. Heme iron from meat is more absorbable than nonheme iron from plants. Vitamin C increases the absorption of nonheme iron, but once again phytates decrease the absorption. The RDA for iron for vegetarians is 1.8 times higher than people who eat meat because of these absorption issues.

How much iron do I need?  

If you don’t regularly consume animal sources that are good sources of iron (oysters, beef liver, sardines, beef, dark meat chicken) then increase your daily iron by 1.8 times:  32 mg for women age 19-50 and 14 mg for men age 19 and older and women age 50 and older. If you’re pregnant, aim for 48 mg of iron and when breastfeeding 16 mg of iron.

  • Women age 19-50 need 18 mg iron per day.
  • Men age 19-50 need 8 mg iron per day.
  • Women and men age 50+ need 8 mg iron per day.
  • Iron needs increase to 27 mg during pregnancy and 9 mg when breastfeeding.

To meet your daily iron needs:

  • 1 serving breakfast cereal fortified with iron contains 18 mg of iron.
  • 1 cup canned white beans contains 8 mg of iron.
  • ½ cup cooked lentils contains 3 mg of iron.
  • ½ cup cooked spinach contains 3 mg of iron.
  • ½ cup tofu contains 3 mg of iron.
  • ½ cup kidney beans contains 2 mg of iron.
  • ½ cup chickpeas contains 2 mg of iron.
  • 1 medium baked potato with skin contains 2 mg of iron.
  • 1 ounce cashews contains 2 mg of iron.

B12 bioavailability appears to be about three times higher in dairy products than in meat, fish, and poultry, and the bioavailability of vitamin B12 from dietary supplements is about 50% higher than that from food sources. 

How much B12 do I need? 

Men and women age 19 and over need 2.4 mcg of B12 per day. B12 needs increase to 2.6 mcg during pregnancy and 2.8 mcg when breastfeeding.

To meet your B12 needs:

Since Vitamin B12 is not naturally present in any plants, if you don’t regularly consume animal products you’ll need to include fortified nutritional yeast or other foods that often contain added B12 such as breakfast cereal, plant milks (for example almond, soy and rice milk often contain added B12) and foods marketed toward vegans.

By Lynn Grieger, RDN, CDCES, CPT, CHWC

References:

  1. National Institutes of Health. Office of Dietary Supplements. Zinc Fact Sheet for Health Professionals. https://ods.od.nih.gov/factsheets/Zinc-HealthProfessional/  accessed 1-25-22; updated 12-7-21
  2. National Institutes of Health. Office of Dietary Supplements. Iron Fact Sheet for Health Professionals. https://ods.od.nih.gov/factsheets/Iron-HealthProfessional/  accessed 1-25-22; updated 3-30-21
  3. Harvard T.H. Chan School of Public Health. The Nutrition Source. Iron. https://www.hsph.harvard.edu/nutritionsource/iron/  accessed 1-25-22; 
  4. National Institutes of Health. Office of Dietary Supplements. Vitamin B12 Fact Sheet for Health Professionals. https://ods.od.nih.gov/factsheets/VitaminB12-HealthProfessional/   accessed 1-25-22; updated 4-6-21.
  5. Merck Manual Consumer Version. Vitamin B12 Deficiency. Author:  Larry E. Johnson. https://www.merckmanuals.com/home/disorders-of-nutrition/vitamins/vitamin-b12-deficiency  accessed 1-25-22; last review 11-20.
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