In This article
- Everything you need to know about vitamins and minerals
- Fat-soluble versus water-soluble vitamins
- The big, the tiny, and the necessary minerals
Now that you’re familiar with the macronutrients, it’s time to introduce you to the little guys. Micronutrients are a group of essential substances required in small quantities for normal metabolism. Even though you need only a trivial amount of these nutrients, they’re an extremely critical component of your day-to-day functioning.
Thirteen vitamins quietly hide in the foods you consume, awaiting absorption in the GI tract so they can kick into gear and perform their jobs. Vitamins are divided into two categories: water-soluble and fat-soluble. They are separated based on their physical properties and how they act inside the body. Of the 13, 4 are fat-soluble vitamins, while the remaining 9 are water-soluble.
The Food and Nutrition Board of the National Academy of Science’s Institute of Medicine sets the Recommended Dietary Allowances (RDA). These guidelines suggest the dietary intake level sufficient to meet the nutrient requirements of nearly all (97 to 98 percent) healthy individuals in a particular life stage and gender group. After an explosion of nutrition discoveries, an additional group of guidelines was established in 1998 called the Dietary Reference Intakes (DRIs). DRIs include RDAs as the target intake, adequate intake (AI), tolerable upper limit (UL) of certain nutrients, and estimated average requirement (EAR). All these recommendations are based on the objective of “minimizing risk for chronic disease.”
Fat- Versus Water-Soluble Vitamins
Fat-soluble vitamins, which include A, D, E, and K, require fat for absorption, hence the name. They’re stored in your body’s tissues and are excreted via the feces. Excessive doses can lead to toxicity, and deficiency is possible if inadequate fat is consumed or absorbed.
Water-soluble vitamins, on the other hand, consist of the eight B-complex vitamins and vitamin C. They can be dissolved in water, are not stored in the body, and are eliminated in the urine. Therefore, you need to replenish them every day. Similarly, they’re easily destroyed and washed out during storage, preparation, and cooking, so they need to be cared for delicately.
To reduce their destruction, avoid overcooking foods high in water-soluble vitamins, and steam these foods instead of boiling them. Also be sure to consume raw sources regularly. The moment a fruit or vegetable is exposed to oxygen, the vitamins begin to degrade, so use freshly picked produce as often as possible. (Purchase your produce from a farmers’ market or community-supported agriculture, buy frozen, or grow a garden of your own—and consume it as quickly as possible!)
Let’s take a look at each of the vitamins in a little more detail, starting with the fat-soluble vitamins.
Vitamin A refers to a group of compounds essential for growth, vision, reproduction, and immune function. Preformed vitamin A is found only in animals, but provitamin carotenoids, found abundantly in fruits and vegetables, can be converted into vitamin A. Even though at least 600 of them exist in nature, only about 50 can be converted into retinol, the active form of vitamin A. Beta-carotene is the most active and most commonly known of these carotenoids. Carotenoids come in a spectrum of reds, oranges, and yellows in pigment; however, they can be found hidden by the dark-green chlorophyll color in leafy green vegetables.
Carotenoids are powerful antioxidants. Lycopene, one of the most potent antioxidants in the carotenoid family, is known to prevent and treat prostate cancer. It’s also effective against other cancers, heart disease, and age-related macular degeneration. Cook your lycopene sources (found abundantly in tomatoes) to enhance its availability.
Similarly, high doses of lutein and zeaxanthin—other carotenoids—reduce the risk of age-related macular degeneration and cataracts. These carotenoids, also found in leafy green vegetables, require fat for absorption. If you’re following a low-fat diet or have any issues with absorption, you may be at risk for deficiency of these important nutrients. We suggest eating your leafy greens and tomatoes with a bit of fat, like nuts, seeds, or avocados.
Beta-carotene, one of the most well-known carotenoids, is found in foods with orange and yellow hues. This carotenoid works synergistically with vitamin E to support health protection. High doses can lead to a yellowing of the skin, a harmless condition. However, when taken in high doses via supplements, beta-carotene increases the risk of cancer and heart disease in people who smoke or drink alcohol excessively.
Not surprisingly, carotenoid intake tends to be high in plant eaters. The RDA for vitamin A is 900 micrograms for men and 700 micrograms for women. Pregnant women need 770 micrograms a day and 1,300 micrograms when lactating. Excellent plant-based sources of provitamin A include tomato, pumpkin, sweet potato, butternut squash, kale, spinach, cantaloupe, mango, and apricots.
Vitamin D has become the vitamin du jour as studies focus on an almost universal insufficiency. Currently, 70 to 97 percent of the U.S. population is lacking in vitamin D! This shouldn’t be taken lightly. Every cell in the body contains vitamin D receptors, indicating its importance for optimal overall functioning. Two commonly known functions of vitamin D include maintaining blood levels of calcium and phosphorus and supporting the cardiovascular system. Your blood level of 25-hydroxyvitamin D (the appropriate test to request from your doctor) should be at least 20 ng/mL; optimum levels are 50 ng/mL and above.
Normally, skin produces vitamin D when exposed to sunlight. A cholesterol compound in your skin called 7-dehydrocholesterol is activated by UVB sun ray exposure. After a visit to the liver and then the kidneys, this compound is transformed into 1,25-dihydroxyvitamin D, the biologically active form of vitamin D. At this point, vitamin D is acting as a true hormone that gets busy on many fronts performing structural and functional jobs throughout the body.
People who live farther away from the equator have an increased incidence of vitamin D deficiency and are, therefore, at an amplified risk for many chronic diseases. Preformed vitamin D is found only in animal products, specifically in fatty fish and their liver oils, milk, beef liver, and egg yolks. Because vitamin D is hard to come by nutritionally, foods like dairy and plant milks, fruit juices, cereals, breads, nutrition bars, and pastas are fortified with vitamin D.
Plant eaters and meat eaters are at the same risk for vitamin D deficiency, so it’s important for everyone to get their vitamin D levels checked by a blood test. The results can help you determine whether you need to consider properly increasing your sun exposure and/or adding a supplement. Populations with darker skin, breastfed infants, people with limited sun exposure, obese individuals, elderly people, and anyone with gastrointestinal absorption issues are at higher risk for vitamin D deficiency. Low vitamin D levels are consistently associated with most chronic diseases, including many cancers, heart disease, osteoporosis, type 2 diabetes, and autoimmune diseases.
How much vitamin D should you consume daily? The RDA is 600 IU (15 micrograms) per day for all populations from 1 year to 70 years of age. After 71, the RDA increases to 800 IU (20 micrograms). Many leading researchers believe higher doses are necessary to sustain optimal levels of vitamin D.
Vitamin E exists in eight different forms, but alpha-tocopherol is active and can meet human requirements. This form of vitamin E is a potent antioxidant. With deficiency—which is rare, thanks to its presence in many foods—red blood cells become fragile and increased free radical damage occurs, leaving the body susceptible to damage due to oxidation. Although you need oxygen to stay alive, oxygen can cause an imbalance in your cells, where reactive compounds (free radicals) outweigh the presence of antioxidants. High exposure to free radicals and oxidation initiates many disease processes, like heart disease and cancer, and speeds up aging. Antioxidants, like vitamin E and the carotenoids, halt oxidation.
In addition to its antioxidant activities, vitamin E also participates in immune function, regulating gene expression and other metabolic processes. With ample amounts, vitamin E helps keep the inner (endothelial) lining of the blood vessels smooth. This keeps blood cell components from sticking to it, which helps prevent plaque build-up. Another heart-helpful task vitamin E performs is boosting two enzymes that increase the release of a compound called prostacyclin. Prostacyclin prevents blood clots and keeps the blood vessels open and flowing.
The RDA for vitamin E is 15 milligrams per day for both adult men and women. For children age 1 to 3 years, 3 milligrams is recommended, and from ages 4 to 8, the RDA increases to 7 milligrams. Children age 9 to 13 years require 11 milligrams. With lactation, vitamin E RDA increases to 19 milligrams per day. Plant sources of vitamin E include avocados, wheat germ, sunflower seeds, almonds and almond butter, peanuts and peanut butter, pumpkin, soybeans, olives, and leafy green vegetables.
Vitamin K plays an essential role in blood clotting. In fact, its name originates from the German word koagulation, which is what vitamin K helps regulate in the blood. When you get a wound, vitamin K helps the blood clot and begin the healing process. On the flip side, you don’t want to produce unnecessary, potentially fatal clots in your bloodstream because they lead to obstructive heart attacks, peripheral vascular disease, and strokes. Vitamin K regulates coagulation to keep you clotting only when necessary.
With the drug Warfarin (brand name Coumadin), vitamin K becomes a balancing act. If you’re on this drug for anticoagulant purposes, you need to maintain a consistent intake of vitamin K to allow the drug to work properly. Ask your physician to moderate your dosage while allowing you to consume adequate green vegetables to optimize your overall health.
People who are on anticoagulant drug therapy (which inhibits the clotting action of vitamin K) need to monitor their vitamin K intake carefully.
Vitamin K also assists in bone metabolism, mitigating the breakdown of bone minerals by osteoclasts and strengthening the composition of the bone. Low vitamin K levels in the blood are associated with low bone mineral density and higher rates of fractures.
Although deficiency is rare, it can affect breastfed newborn infants (which is why newborns in the United States are given a vitamin K injection right after birth), as well as adults who are suffering from malabsorption or are chronically taking antibiotics. Normally, the bacteria that live in your gut produce vitamin K. That’s why the previously mentioned populations are at risk for inhibiting that process. Deficiency can lead to decreased bone mineral density and bleeding.
There are two forms of vitamin K that are significant in the human diet. Vitamin K1, known as phylloquinone, is omnipresent in the plant kingdom, especially in anything green. Vitamin K2, or menaquinone, is produced by microorganisms and converted from K1 and intestinal bacteria in small amounts. Like the other fat-soluble vitamins, foods rich in vitamin K need to be consumed with some fat. So add nuts, seeds, olives, and/or avocado to your green veggies to enhance absorption.
For adults 19 years and older, the daily adequate intake of vitamin K is 120 micrograms for men and 90 micrograms for women. Leafy green vegetables are excellent sources for vitamin K, as are broccoli, asparagus, lentils, and peas. There is increasing evidence that we may need a direct source of K2, so supplementing may be beneficial.
Thiamin (Vitamin B1)
Now let’s switch to the water-soluble vitamins, starting with thiamin. Also known as vitamin B1, thiamin acts as a coenzyme in the metabolism of carbohydrates and branched-chain amino acids. In other words, it helps convert carbs into energy.
Coenzymes are small, nonprotein molecules that enhance the action of an enzyme.
Thiamin deficiency is common in alcoholics. Many mechanisms contribute to thiamin deficiency in alcoholics, known as Wernicke-Korsakoff syndrome, including decreased intake, impaired absorption and use, and increased demand. Beriberi, a disease caused by thiamin deficiency that can lead to pain, mental confusion, and paralysis, is extremely rare because many foods are fortified with thiamin.
The RDA for thiamin is set at 1.2 and 1.1 milligrams per day in adult men and women, respectively. During pregnancy and lactation, women require 1.4 milligrams a day. Thiamin is found in whole grains such as quinoa, oats, and barley; beans, peas, and other legumes; nutritional yeast; brewer’s yeast; winter squash; and tahini.
Riboflavin (Vitamin B2)
Riboflavin, or vitamin B2, plays a vital role as a coenzyme in energy metabolism. It’s also important for growth and red blood cell formation. Although uncommon, deficiency can lead to mouth sores, a swollen tongue, inflamed and reddened skin, and a rare form of anemia.
Riboflavin is sensitive; it can be destroyed by sunlight, and substantial amounts can be lost in cooking water during boiling. So keep your produce refrigerated and use that cooking water again for soup!
The adult RDA for riboflavin is 1.3 milligrams for men and 1.1 milligrams for women. The daily requirement increases to 1.4 milligrams during pregnancy and 1.6 milligrams during lactation. Sources include nutritional yeast, fortified cereals and plant milks, barley, soybeans, mushrooms, spinach, sea vegetables, and beet greens.
You know when you take a multivitamin and your urine is fluorescent yellow? You can thank riboflavin for that!
Niacin (Vitamin B3)
Niacin, or vitamin B3, also contributes to energy by metabolizing glucose and fatty acids. (You can see why all these vitamins are in the same B family!) Used in therapeutic doses (think large), niacin helps raise HDL cholesterol levels. Niacin is also necessary in the production of DNA.
Pellagra is the disease associated with a deficiency of niacin. Symptoms of pellagra include confusion, delusion, diarrhea, inflamed mucous membranes, and scaly skin sores.
RDA for niacin in adults is 16 and 14 milligrams per day for men and women, respectively. An increase to 18 milligrams during pregnancy and then down to 17 milligrams per day for lactation is recommended. Plant-based niacin sources include fortified cereals, nutritional yeast, barley, rice, peanuts and peanut butter, brewer’s yeast, tahini, tempeh, mushrooms, avocados, peas, and potatoes.
Vitamin B6 is comprised of three compounds (pyridoxine, pyridoxal, and pyridoxamine) that are all converted to its active forms, pyridoxal phosphate and pyridoxamine. B6 functions as a coenzyme for more than 100 different enzymes that are primarily involved in amino acid metabolism. It’s also essential for red blood cell metabolism and for keeping blood sugar levels stable. Vitamin B6 may even have antioxidant properties. This vitamin is required for optimal function of both the nervous and immune systems. Maintaining an adequate consumption of B6 also protects against heart disease.
Older people and individuals on a poor-quality diet may have suboptimal vitamin B6 nutritional status. Symptoms of vitamin B6 deficiency don’t appear until later, when intake has been very low for an extended time. Signs of vitamin B6 deficiency include dermatitis (skin inflammation), glossitis (a sore tongue), depression, confusion, and convulsions.
Adult RDA values vary according to age: from 1.3 milligrams for men and women age 19 to 50, 1.7 milligrams for men over 50, and 1.5 milligrams for women over age 50. During pregnancy, women need 1.9 milligrams daily and 2.0 milligrams daily when lactating. B6 is found in a wide variety of foods, including fortified cereals, bananas, figs, raisins, chickpeas, lentils, sweet potatoes, tomato juice, avocados, soy products, and brewer’s yeast.
Folate’s major role is to help produce and maintain new cells. It also helps make our genetic keys, DNA and RNA, and prevents changes in the DNA that could lead to cancer. (Folate is the form of the B vitamin that occurs naturally in foods. Folic acid is the synthetic version found in supplements and used to fortify foods.)
Folate is named for the Latin word folium, which means “leaf”—perfect because the greatest source of folate comes from leafy green vegetables.
Pregnant women, or those who have the potential to become pregnant, are advised to maintain adequate doses of folate because deficiency, especially in the first three months of pregnancy, can lead to neural-tube defects, premature birth, and/or low birth-weight babies. Prenatal vitamins typically provide the RDA for folic acid, the synthetic form of folate.
However, recent evidence suggests that supplemental folic acid actually increases the risk for breast, colorectal, and prostate cancers, along with the risk of dying from those diseases. Studies also link folic acid supplements to an increased risk for childhood asthma and respiratory infections.
Fortunately, the natural food source (folate) does not pose any health risk and is found in abundance in the plant world. Pregnant women and everyone else can get plenty of folate without these concerns just by eating more leafy green veggies and beans. In addition, plant-based eaters tend to have superior folate intakes and status compared to omnivores!
The RDA for folate is 400 micrograms a day for both male and female adults and 600 for pregnant and 500 for lactating women. Choose spinach, asparagus, collard greens, turnip greens, beets, lentils, pinto beans, black beans, kidney beans, and black-eyed peas for deliciously rich sources of nature-made folate. There should be no reason for folate supplementation if you are regularly consuming folate rich foods, but it is important to check your multivitamin to make sure it’s not an unhealthy source of folic acid. Recognizing increasing visibility of this health issue, some vitamin labels actually list folate in the dosing, but folic acid is still in the itemized ingredient list.
Cobalamin (Vitamin B12)
Cobalamin, famously known as vitamin B12, is a wildly popular topic of discussion when it comes to following a plant-based diet because it’s the only nutrient not directly available from food or sunlight (as with vitamin D).
B12 is made by microorganisms, bacteria, fungi, and algae. Plants and animals cannot synthesize B12. Because animals don’t wash their food before eating it, they ingest these microorganisms. Ruminant animals (such as cows, goats, and sheep) have enough bacteria living in their rumen to provide adequate B12. They also absorb some of the B12 produced by the bacteria in their intestines. Some plant foods may contain B12 from contamination by those B12-producing bacteria in the soil, but it’s unlikely in developed countries due to rigorous food washing and safety practices.
Vitamin B12 assists with several roles in the body, including red blood cell formation, neurological function, and DNA creation. It’s unique because it requires intrinsic factor, made by the stomach, to be absorbed. With any stomach issues (as with pernicious anemia, an autoimmune disease) or intestinal issues, deficiency of vitamin B12 is possible. Similarly, as we age, it becomes harder to absorb the vitamin. This may lead to megaloblastic anemia and neurological disorders.
You may not realize you have a deficiency until it’s too late. Symptoms include decreased sensation, dementia, difficulty walking, loss of bladder or bowel control, weakness, optic atrophy, and depression. Early detection is key to preventing irreversible neurologic damage, although this can be impossibly tricky. The liver is efficient at storing vitamin B12 and it may take up to five to ten years before the liver becomes depleted; however, without repletion—or for those with an inability to absorb B12— deficiency will ensue. Be forewarned that during this period of time, blood test results may be skewed by other variables and irreversible damage may occur before the deficiency is caught.
While the RDA for B12 is 2.4 micrograms per day for adult men and women, 2.6 micrograms per day during pregnancy, and 2.8 micrograms per day with lactation, absorption varies depending on the dose and the individual. Plant-based sources include nutritional yeast and fortified plant-based milks, cereals, and meat substitutes. However, because of possible issues with absorption, it is recommended that anyone eating a plant-exclusive diet and anyone over the age of 60 use supplements to avoid deficiency. For maximum absorption, supplement with B12 (ideally in the cyanocobalamin form) in one of these three possible dosing schedules: 50 micrograms twice daily, 150 micrograms daily, or 2,500 micrograms once per week.
Please note that sea vegetables, algae, and spirulina act as vitamin B12 analogues and can actually promote deficiency. Because they look like B12, they can attach to your B12 receptors and take up space where real B12 needs to be. However, these analogues have no biological activity and interfere with the absorption of the real deal.
If you don’t take a B12 supplement or use consistent amounts of fortified products (like nutritional yeast or fortified plant milks), deficiency is also probable. Please be steadfast and cautious about your vitamin B12 intake.
Biotin serves as a coenzyme during the synthesis of glucose and fatty acids and for the metabolism of amino acids. Biotin deficiency is rare but will manifest as anorexia, glossitis, depression, nausea, and vomiting.
Limited data are available to form RDAs. Thus, the adequate intake for biotin is 30 micrograms per day for adults and 35 for lactating women. Excellent whole-food sources include oat bran, oatmeal, almonds, peanut butter, lentils, black-eyed peas, mushrooms, and spinach.
Pantothenic acid helps release energy from glucose, manufacture amino acids, and synthesize and degrade fatty acids. Sources are so widespread that no reliable documented deficiencies are recorded!
Adequate intakes are 5 milligrams per day for adults. The AI increases to 6 milligrams for pregnancy and 7 milligrams during lactation. Pantothenic acid can be found in high quantities in papaya, guava, mangoes, oranges, cantaloupe, broccoli, Brussels sprouts, bell peppers, and kohlrabi.
Ascorbic Acid (Vitamin C)
Vitamin C, also known as ascorbic acid, is the other water-soluble vitamin alongside the large B-family. A very busy vitamin, C functions in varied and extensive myriad roles in the body. It helps create collagen, L-carnitine, and certain neurotransmitters. Vitamin C also acts as an antioxidant and helps in protein metabolism, immune function, and iron absorption. Deficiency leads to scurvy, which is nearly impossible on a whole-food, plant-based diet that includes plenty of fruits and vegetables.
Plant-based eaters have no problem attaining the RDA for vitamin C, which is 90 milligrams for adult men and 75 milligrams for adult women. During pregnancy, women should consume 85 milligrams per day and then 120 milligrams when nursing. Fantastic food options include papaya, guava, pineapple, bell peppers, broccoli, Brussels sprouts, cauliflower, kiwi, oranges, strawberries, cantaloupe, kohlrabi, turnip greens, and tomatoes.
Minerals are inorganic nutrients your body requires in continued supply for life, health, growth, and development. Thousands of different minerals exist in nature, but only about 21 have significant impact in your diet:
All minerals are derived from the soil and enter animals or humans via plants. And lucky for those on a plant-based diet, plants are loaded with minerals, including calcium, iron, zinc, and selenium. So the more plants you eat, the more minerals you acquire!
Macrominerals Versus Trace Elements
Minerals are divided into two groups based on whether you need a large amount (macrominerals) or small amount (trace elements, or microminerals).
Macrominerals, also considered “bulk elements,” are minerals your body needs in amounts of 100 milligrams per day or greater. Microminerals, or trace elements, are present in minute amounts in the body’s tissues. For optimal health, growth, and development, you need 15 milligrams per day or less.
Recommendations for intake have been established for nine essential trace elements—chromium, copper, iodine, iron, manganese, molybdenum, selenium, zinc, and fluoride. Recommendations for five potentially essential trace elements—arsenic, boron, nickel, silicon, and vanadium—haven’t yet been determined.
Because you can easily attain adequate amounts of all minerals from a whole-food, plant-based diet, I focus on the three minerals that often have absorption issues: calcium, iron, and zinc. Also, because iodine tends to be low in plant eaters, we will offer some suggestions to prevent deficiency.
Calcium is the most abundant mineral in the body—an adult human contains approximately 1,000 to 1,500 grams! Ninety-nine percent of the calcium in your body is stored in your bones and teeth, and the remaining 1 percent is throughout the rest of your body’s tissues and fluids. Calcium plays an essential role in blood clotting, muscle contraction, nerve transmission, bone and tooth formation, and the secretion of hormones and enzymes.
AI recommendations for calcium in adults vary throughout the lifespan. For age 19 to 50, AI is 1,000 milligrams per day for males and females (even during pregnancy and lactation beyond the age of 19). After age 50, AI increases to 1,200 milligrams per day just for women, but the men increase at 70 years old, too. Whole-plant food sources of calcium include fortified plant milks, leafy green vegetables (especially low oxalate options such as kale, bok choy, lettuce, and cabbage), dried figs, sesame seeds and tahini, almonds and almond butter, chia seeds, beans, soybeans, soy nuts, and calcium-set tofu.
Bone is dynamic and is constantly breaking down and rebuilding. Even though it’s seemingly always solid and hard, bone mass is turned over as much as 15 percent every year. That shows the potential of your diet to influence the strength and density of your bones throughout your lifetime. Remember, you are what you eat!
With calcium, how much you consume isn’t necessarily the issue. What’s more important is how much you absorb. Calcium absorption determines risk of bone fractures and osteoporosis. Many factors influence calcium absorption, including age, how much you need, how much you take in, and other compounds that accompany the calcium when you consume it. Taking effective combinations of calcium and vitamin D improves absorption.
Only minimal research on bone status in strict plant eaters has been conducted so far. However, calcium is plentiful in plants, so you don’t need to reach for harmful animal products to get your daily dose, which—because of their high protein, fat, cholesterol, and sodium content—wreak havoc on your arteries. If you eat your leafy greens and get plenty of exercise, you will have strong bones to last a lifetime.
Iodine deficiency is a global public health concern, affecting nearly one out of every three people worldwide. Characteristics include goiter and cretinism. Brain damage occurs when iodine deficiency happens during fetal or early childhood development, so pregnant women and preschool children in low-income settings are among the high-risk populations. Recent evidence has shown a possible increased risk of deficiency in plant eaters as well, especially raw followers.
Iodine is closely tied with thyroid function. When intake is low, production of thyroid hormones slows down. Adequate intake for infants up to 6 months is 110 micrograms per day and 130 micrograms from 6 to 12 months. The RDA for children ages 1 through 8 is 90 micrograms per day, 120 micrograms per day for children ages 9 through 13, and 150 micrograms per day for adults. Pregnant women require 220 micrograms daily and, while breastfeeding, 290 micrograms daily.
Iodine is hard to find in plant-based food. Because iodine content varies widely in soil, it’s unreliable in plant foods. Sea vegetables can either have a lot of iodine or very little. Iodine deficiency was common in early twentieth-century America until salt was iodized. Salty foods like tamari, kosher salt, and processed items don’t contain iodized salt. A quarter teaspoon of commercial iodized salt contains approximately 68 micrograms, or 47 percent of the adult RDA. However, since it’s not advisable to use salt, you can incorporate sea vegetables (especially dulse and kelp) into your diet and monitor for iodine deficiency.
Ironically, iron is one of the most abundant metals on Earth, yet it’s considered the most common nutritional deficiency worldwide! According to the World Health Organization, approximately 30 percent of the global population has iron-deficiency anemia. However, plant-based diets tend to be higher in iron than other diets. Iron is an essential component of proteins and enzymes that maintain good health, but its most important role is transporting oxygen. Almost two thirds of the iron in the body is found in hemoglobin, the protein in red blood cells that carries oxygen to the cells.
From age 19 to 50, adult men require 8 milligrams per day of iron, while adult women need 18 milligrams per day. After 51 years of age, the RDA is 8 milligrams per day for both men and women.
Diet provides two forms of iron: heme and nonheme. Heme iron is made from hemoglobin and is found in animal flesh. Nonheme iron is supplied by plants, including lentils, kidney beans, navy beans, chickpeas, pinto beans, spinach, Swiss chard, beet greens, turnip greens, pumpkin seeds, tahini, dried apricots, and blackstrap molasses.
Heme sources are absorbed better than nonheme, but this may not be advantageous. More of a good thing isn’t always better, and heme iron is the perfect example of when it’s not. A high blood level of stored iron has been associated with increased insulin resistance and heart disease. Furthermore, iron delivered by animal products comes with saturated fat, dietary cholesterol, steroids, hormones, and antibiotics.
Iron deficiency leads to fatigue, decreased immune function, and glossitis (inflamed tongue). Loss of iron, and its resulting anemia, usually occurs due to small intestinal bleeds or kidney disease. It can also accompany certain periods of life, including age 6 months to 4 years, adolescence, pregnancy, and menstruation. Still, dietary factors impact the absorption of iron—for better and for worse.
Dietary variables that inhibit absorption of iron include phytates in whole grains and legumes, tannic acids from tea, calcium in dairy, fiber, coffee, cocoa, and some spices (such as turmeric, coriander, chile peppers, and tamarind). To enhance iron absorption, include a source of vitamin C with your nonheme iron-rich food. For instance, enjoy salsa in your bean burrito or drizzle lemon juice over your leafy greens to maximize absorption. Other organic acids, vitamin A, and beta-carotene may also help with absorption, as does soaking and sprouting grains, beans, and seeds; leavening bread; and fermentation.
What about iron supplements, you might be wondering? They’re pro-oxidative, meaning they promote oxidation. The opposite of antioxidants, they encourage free radicals to perform their mischief, thereby leading to increased risk for cancer, heart disease, aging, and other chronic diseases. Iron supplements should only be used if there’s a deficiency and for as short a period as possible.
Phytates can block iron absorption up to 90 percent, making them significant inhibitors. Because they’re primarily found in whole grains and legumes, phytates are prevalent in a plant-based diet. Fortunately, the higher the phytate content in a food, the higher the iron tends to be. Thus, consuming these products may not impact iron status as much as first thought. Ironically, phytates are also thought to reduce risk of various chronic diseases, including several forms of cancer!
Undoubtedly, the most telling fact about iron status in people who primarily eat a plant-based diet is that there’s not much difference in incidence of iron-deficiency anemia between plant-based eaters and omnivores.
Selenium is an essential trace mineral that is required for thyroid function, reproduction, and DNA synthesis, and acts as a powerful antioxidant, antimicrobial, and anti-inflammatory. While seafood and organ meats are food sources highest in selenium, plant sources vary according to soil quality. Brazil nuts are an excellent source of selenium, providing 777 percent of the RDA with just one ounce (approximately 6 to 8 nuts). When possible, eating one Brazil nut a day is an easy way to meet recommendations. Other plant sources include whole grains, legumes, vegetables, seeds, and other nuts. Adult RDAs are 55 micrograms a day, increasing to 60 micrograms when pregnant and 70 when lactating.
Like the other minerals, zinc is needed in many metabolic processes, including the activity of about 100 enzymes, immune function, wound healing, protein and DNA creation, and cell division. You need zinc every day because your body doesn’t have a special zinc-storing system. Symptoms of deficiency include growth retardation, loss of appetite, immune impairment, hair loss, delayed wound healing, and taste abnormalities.
Adult RDA for zinc is 11 milligrams per day for males and 8 milligrams for females. However, need increases for females to 11 milligrams when pregnant and 12 milligrams during lactation. Animal products contain high doses of zinc, but you can find it in plant sources, too. Cashews, chickpeas, almonds, kidney beans, and peas are all good choices. Similar to iron, zinc absorption is inhibited and enhanced by the same nutrients.
The higher incidence of zinc deficiency in plant-based eaters is due to the fact that the absorption of zinc from plants is somewhat lower than from animal products. The Food and Nutrition Board recommends that plant eaters increase their RDA by 50 percent to make up for these shortcomings.
It also recommends preparation techniques that discourage phytates from binding to zinc and increase its absorption. These techniques include soaking beans, grains, and seeds in water for several hours before cooking them and allowing them to sit after soaking until sprouts form.
You can also enhance your zinc intake by choosing leavened grain products (such as bread) instead of unleavened foods (such as crackers). Leavening partially breaks down the phytate.
The Least You Need to Know
- Vitamin B12 isn’t available from any plant-based food source. To get this vitamin, you need to take a supplement or eat fortified products.
- Vitamin D poses no more a risk for deficiency in strict plant eaters than in omnivores. Although sunshine is the best source, additional supplements may be required.
- Several macrominerals and trace elements have significant impact on your diet and health, and all are available from plants.
- As a plant eater, you need to remain cognizant of the minerals calcium, iron, zinc, and iodine to ensure you meet your daily needs.