If you're considering a plant-based or vegan diet you may wonder whether it's smart to also take a vitamin or supplement to ensure that you are getting all the necessary vitamins and minerals, such as iron, vitamin D, and vitamin B12. After all, plant-based diets are considered the key to longevity and studies tell us you can elongate your life expectancy by over a decade by going plant-based early in life so why would you need to take a supplement?

And if you’re following a plant-based diet, there’s no hiding the fact that there are several major food groups (meat, poultry, eggs, fish, seafood, dairy) that you won’t be consuming on a regular basis, which means you’ll miss out on certain vitamins and minerals.

As a clinical nutritionist, I generally recommend that all my adult clients, no matter their dietary plan, age, or sex, take a regular multivitamin-mineral supplement. That’s primarily because today’s modern farming practices, which successfully provide food for millions around the globe, often resort to using harsh chemicals and overproduction techniques that deplete the topsoil — and leave our plant foods (both conventional and organic) not nearly as nutrient-dense as in the time of our great-grandparents.

Add to that the fact that researchers estimate 50 percent of the world’s population is deemed vitamin D insufficient, and that humans have less exposure to sunlight and dirt than in any prior century, and we’re coming up short.

A good quality supplement that is taken daily – or at least a few days per week – can help you bridge the gap to achieving your personal health and wellness goals, without a ton of effort.

Here are the seven primary nutrients to supplement on a plant-based diet: Read on for more about what to take depending on your life stage.

Note: As some supplements may interact with certain medications, check with your doctor first before starting any new supplement regimen.

1. Vitamin B12

Naturally found in animal products, including meat, fish, poultry, eggs, and milk, vitamin B12 is a water-soluble vitamin necessary for nervous system support and the creation of red blood cells. Even though it’s water-soluble, stores of the vitamin can circulate for years throughout the body, which means that deficiencies may take up to five years to develop.

The vitamin is produced by bacteria found in dirt — thus when animals consume grass or other plants, they’re consuming the B12 that then gets passed onto humans who eat animal products. It’s true that if you don’t wash and peel your root veggies, you might get a tiny bit of B12, but, thanks to sanitization standards and the topsoil nutrient depletion noted above, this isn’t really a stable or sustainable source of the vitamin.

Certain plants, such as some seaweed and mushrooms, may have a small amount of B12 but aren’t adequate or consistent enough for long-term sustenance. Strict vegans who don’t supplement will possibly consume enough B12 to prevent a true deficiency but definitely won’t get enough to benefit from the vitamin’s brain- and nerve-protective effects. Many vegan foods are now fortified with a highly absorbable, crystalline form of B12, but fortified foods would need to be consumed two to three times per day to reach the recommended amount—a supplement just makes things simpler.

The recommended dietary allowance (RDA) of vitamin B12 is:

  • 2.4 mcg for males and females
  • 2.4 mcg for teens
  • 2.6 mcg for pregnancy
  • 2.8 mcg for lactation

B12 deficiency could lead to lasting nervous system damage or anemia, and so generally speaking, those following a plant-based diet should take a supplemental form of B12 as part of a daily multivitamin or on its own. If taking as a singular supplement, look for the B12 form methylcobalamin in a sublingual spray, which doesn’t rely on stomach acid to metabolize the nutrient and results in better bioavailability (a.k.a. absorption in the body).

2. Vitamin D

Essential for bone health and immune function, vitamin D is a fat-soluble vitamin that acts as a hormone in the body, promoting calcium absorption, supporting optimal blood pressure levels, and healthy heart function.

Vitamin D is present in very few plant or animal foods, including a few fatty fish, eggs, and mushrooms, but the primary source is via direct sun absorption on large swaths of skin (think: thighs and belly) for 20 to 30 minutes per day. However, if you regularly wear sunscreen or live in a climate that doesn’t get great sun exposure year-round, you should supplement — whether you eat meat or not, as it’s difficult to meet the RDA from food alone.

The recommended dietary allowance (RDA) of vitamin D is:

  • 600 IU for males and females
  • 800 IU for adults over 70
  • 600 IU for teens
  • 600 IU for pregnancy/lactation

A deficiency in vitamin D could lead to brittle bones, depression, and an increased risk of cardiovascular disease. Many foods are now fortified with the vitamin in its D2 or D3 form, but for best results, seek out a supplement of vitamin D3. Standard versions typically originate from lanolin, a sheep byproduct, but vegan versions stemming from lichen are also available.

Where to Buy Online: Thrive Market Vitamin D3 Plant-Based 2000 IU, $15, thrivemarket.com

3. Iron

Prevalent in both plant and animal foods, iron is necessary for carrying oxygen in the blood and for forming new DNA. It’s also used in energy metabolism and is essential for growth.

There are two classifications of iron: heme (from animals) and non-heme (from plants). Heme iron is more bioavailable for humans, which is why experts recommend that strict vegans may require more iron (up to 1.8 times) if the main source of iron is from plants. Also, it’s now known that meat, poultry, and seafood consumption can increase non-heme iron absorption–so if you don’t consume those foods, you’re still at a disadvantage.

However, there are numerous plant sources of iron, including lentils, beans, peas, cruciferous veggies, nuts, seeds, and dried fruit. To help with the absorption of non-heme iron, combine iron-rich plant foods with a vitamin C source (strawberries, lemon, and kiwi are good options) to maximize bioavailability. Additionally, cooking in a cast-iron pan can add a small amount of iron content to food.

The recommended dietary allowance (RDA) of iron is:

  • 8 mg for males
  • 18 mg for females age 19-50
  • 8 mg for post-menopausal people
  • 11 mg for non-menstruating teens
  • 18 mg for menstruating teens
  • 27 mg for pregnancy
  • 9 mg for lactation

Iron deficiency can lead to anemia and fatigue. Plant-based athletes, menstruating teens, and pregnant people should seek out supplements, as they’re the groups in need of extra iron. However, due to iron’s status as an oxidant (the opposite of an antioxidant), over-supplementation may be even more dangerous. Your personal supplementation needs are best determined with the help of a healthcare professional who can assess your hemoglobin and ferritin status via bloodwork.

Where to Buy Online: Mary Ruth's Liquid Iron, $30.95

4. Iodine

A trace mineral, iodine is essential for optimal thyroid function and is a critical component of thyroid hormone, which is responsible for protein synthesis, myriad enzyme reactions, and for the nervous system and skeletal system development in babies.

Many people following a strict vegan diet are considered at high risk for iodine deficiency, as the predominant sources of iodine are fish, shellfish, and dairy products.

The primary plant source of iodine is seaweed, though the amounts vary greatly by type. Nori (the seaweed wrap most often used in sushi preparation) has the lowest iodine content (around 11 percent of the RDA), whereas kelp or kombu has the highest (around 2000 percent of the RDA). Some fruit and vegetables can be good sources of iodine, but the consistency varies, as it depends on the iodine content of the soil. However, iodized salt can also cover your daily needs at just half a teaspoon per day.

Iodine is especially critical for pregnant and breastfeeding mothers and can lead to birth defects if not sufficiently supplied. Iodine deficiency can also lead to hypothyroidism or goiter in adults and may have serious repercussions on metabolism and energy production.

The recommended dietary allowance (RDA) of iodine is:

  • 150 mcg for males and females
  • 150 mcg for teens
  • 220 mcg for pregnancy
  • 290 mcg for lactation

Look for dulse or kombu flakes to sprinkle on top of foods, or supplement with a multivitamin or prenatal vitamin with at least 150 mcg of iodine.

Where to Buy Online: SmartyPants Prenatal Complete Daily Gummy Vitamin, $14, amazon.com

5. Zinc

An essential mineral required for optimal immune function, hormone support, sense of smell and taste, and regular growth, zinc is used in more than 100 different enzyme reactions throughout the body. There is no internal storage site for zinc, however, so consistent daily intake of the mineral is key. There’s a high prevalence of zinc deficiency in the U.S., especially among vegans.

Zinc is primarily found in oysters, red meat, crab, and poultry, but is also found in pumpkin seeds, cashews, baked beans, chickpeas, and some fortified foods, such as breakfast cereals. As animal products enhance zinc absorption, the bioavailability of zinc in plant-based diets may be lower than in non-vegetarian/vegan diets.

Additionally, beans and legumes, a staple of plant-based diets, contain anti-nutrients called phytates that bind zinc and prevent absorption. As a result, strict vegans may need up to 1.5 times the RDA for zinc, according to some experts. One way to reduce the phytate content of beans and legumes is to soak and sprout them first before cooking or to cook them with a strip of kombu, which can help break down the phytates. Leavening also breaks down phytate: meaning that breads may be better sources of zinc than unleavened grain products such as crackers.

The recommended dietary allowance (RDA) of zinc is:

  • 11 mg for adult and teen males
  • 8 mg adult females
  • 9 mg for teen females
  • 11 mg for pregnancy
  • 12 mg for lactation

Symptoms of zinc deficiency include depressed immune function, fatigue, delayed wound healing, and slower growth in infants and children. Supplementation with zinc picolinate is the ideal form, as it’s easier to metabolize than other forms. However, supplementation dosage should not exceed 30mg daily, and zinc status should be assessed via bloodwork after three months before continuing.

Where to Buy Online: Thorne Zinc Picolinate, $11, thorne.com

6. Omega-3 Fatty Acids

The human brain and eyes are made primarily of DHA—and so this nutrient is crucial for pregnant and nursing mothers. It’s also been found to be helpful in the prevention of breast cancer, depression, and ADHD.

Primary plant sources of omega-3s include flaxseed, chia seeds, and walnuts, however, these plant foods only contain the ALA form of omega-3, whereas fatty fish such as salmon, herring, sardines, and mackerel are excellent sources of EPA and DHA. As less than 15 percent of ALA is converted to EPA and then to DHA, a supplemental source is helpful for those who don’t eat seafood.

The recommended dietary allowance (RDA) of omega-3s is:

  • 1.6 g for adult and teen males
  • 1.1 g for adult and teen females
  • 1.4 g for pregnancy
  • 1.3 g for lactation

There are several vegan algae-based forms of omega-3 on the market today. Small studies show that the bioavailability of algal oil-derived EPA/DHA is equal to that of cooked salmon.

Where to Buy Online: Nordic Naturals Algae Omega 715 mg, $30, nordicnaturals.com

7. Calcium

There are plenty of plant foods rich in calcium, such as broccoli, kale, bok choy, and some grains, nuts, and seeds, but you’d have to eat cups upon cups every day to meet the RDA. For example, 1 cup of cooked kale has 94 mg of calcium, but the RDA for adults is a whopping 2500 mg. Dairy foods such as milk, yogurt, and cheese are the primary natural sources of calcium, which is why a plant-based diet often comes up short.

  • 2500 mg for males and females
  • 2000 mg for adults over 70
  • 3000 mg for teens
  • 2500 mg for pregnancy/lactation

Calcium is essential for bone formation, muscle function, nerve transmission, and blood pressure, so it’s super important to find a good source of calcium. It’s also worth noting that vitamin D is essential for calcium absorption, so these two nutrients go hand-in-hand and are ideally supplemented in tandem.

However, recent research has shown that a high intake of calcium supplements may increase the risk of kidney stones, cardiovascular disease, heart attack, or stroke, especially in women over 50, and so I generally don’t recommend calcium supplementation for most. However, vegans who consume less than 525 mg of calcium daily were found to be at higher risk for bone fractures. Your best bet is to eat a wide variety of calcium-rich plant foods and fortified foods such as calcium-fortified tofu and soy/nut milks — and to possibly include a small amount of dairy on occasion.

Sources: National Institutes of Health: Office of Dietary Supplements Health Professionals Fact Sheets for Iron, Calcium, Iodine, Zinc, Vitamin B12, Vitamin D, Omega-3 Fatty Acids.