9 Common Nutrient Deficiencies in Vegan Diets
Published: December 2021 | Updated: June 2024
It is common knowledge that fruit, vegetables and other plant-based foods are good for us. Omnivores (people who eat meat and plants) are often told to include more of these plant-based foods in their diet for good health. On the other end of the spectrum are vegans who not only go meatless but exclude foods of animal origin completely. While there are plenty of health benefits to being plant-based, there are some nutrients that are abundant in foods of animal origin that vegans may be lacking.
It is possible to avoid nutrient deficiencies while enjoying the benefits that plant-based diets offer us, but just like other diets that restrict certain foods or exclude food groups entirely, it takes some planning to make sure you are meeting your needs and avoiding common nutritional deficiencies.
What are plant-based diets?
Plant-based diets emphasize getting nutrition from fruits, vegetables, whole grains, nuts, and seeds as primary sources. There are different types of plant-based diets, including varying types of vegan and vegetarian diets. All of the diets listed below, with the exception of the flexitarian diet, exclude meat and poultry from the eating pattern.
- Flexitarian – A primarily vegetarian diet that occasionally includes meat or fish
- Vegetarian – A general term, may or may not include egg or dairy products
- Pescatarian – Includes fish, seafood, eggs and dairy products
- Lacto-ovo-vegetarian – Includes eggs and dairy products
- Lacto-vegetarian – Includes dairy products, but not egg products
- Ovo-vegetarian – Includes eggs and egg products, but no dairy
- Vegan – Excludes all foods of animal origin, and may exclude honey
- Raw vegan – A diet based on vegetables, fruit, nuts and seeds, legumes and sprouted grains. The amount of uncooked food varies from 75% to 100%
Benefits of plant-based diets
Following a plant-based diet benefits your health because many plant-based foods are nutritious. Fruits and vegetables are rich in antioxidants, fiber and other healthy compounds.
People who are vegans and vegetarians are also more likely to have beneficial gut bacteria, maintain a healthy body weight, and are more likely to maintain optimal heart health.
Which nutrients may be lacking in vegan diets?
1. Protein and amino acids
Vegan diet amino acid deficiencies are actually more common than protein deficiencies. Protein is made of amino acids, commonly referred to as the building blocks of protein, and the amino acid profile of a given protein-containing food will vary. When it comes to amino acids, some are considered essential, non-essential and conditionally essential. The essential amino acids cannot be made by the body, so we need to get these from food. Leucine, lysine, and sulfur-containing amino acids such as methionine are the ones that vegans may be lacking. A "limiting amino acid" refers to the specific amino acid in a protein that is present in the lowest proportion of an individual's dietary requirement. Therefore, vegans should be particularly attuned to the exact breakdown of amino acids in their protein sources.
Is it possible to get enough protein from plants?
Yes. However it takes a lot of planning.
Previously it was thought that animal foods are complete protein sources, while most plant foods were considered incomplete sources, meaning they do not contain all nine essential amino acids. Research shows that all plant-based protein sources contain all 20 amino acids, though they may only be present in small amounts.
Also, when it comes to protein, it's not just about quantity (which is typically measured in grams); it's also about quality.
That's because protein from whole grains and legumes has lower digestibility than animal protein. Protein from plant foods is encased in plant cell walls, which are hard to digest. So, for example if a serving of a plant-based protein source is supplying 5 grams of protein, you may not actually be getting the entire 5 grams. On the plus side, plant-based protein typically contains more dietary fiber and less saturated fat than animal-based sources of protein which are cornerstones of a heart-healthy diet.
Consider the Digestible Indispensable Amino Acid Scoring system (DIAAS). A food item can be considered a "good" quality protein source if the DIAAS value is between 75 and 99. Here are a few examples:
| Protein | Score |
|---|---|
| Soy | 92 |
| Potato | 85 |
| Lentils | 75 |
Vegans may benefit from consuming slightly more protein than animal based protein eaters, which can be difficult to obtain if you are following the 1g of protein per kg body weight rule for protein intake (which is slightly higher than the current RDA of 0.8 g/kg). But this is especially important for vegan athletes or vegans who are muscle training regularly as part of their exercise routine. Plus, vegans need to consume a variety of plant-based protein sources to compensate for these foods having less of an anabolic (muscle, growth, and protein building) effect compared to animal proteins due to lower digestibility/utilization. Consider a plant-based protein powder made from peas and brown rice to help you meet your protein & amino acid requirements.
Meals with a variety of plant foods can make up for the limiting amino acids in a single plant protein. These combinations are known as "complementary proteins". For example a combination of cereals and legumes. Legumes typically have low/limiting levels of methionine and high levels of lysine. Cereals have the opposite characteristics. Incorporate at least three servings per day of legumes in meals: 1/2 cup cooked dried beans, peas, or lentils; 1/2 cup tofu, tempeh, or edamame; 1 cup soymilk; 1/4 cup peanuts, and 2 T peanut butter.
- Cereal with soymilk
- Pinto beans and corn
- Black beans or lentils and rice
- Chickpea hummus and pita bread
- Oatmeal and pumpkin seeds
However, studies show complementary proteins do not need to be eaten in the same meal to be effective. Eating them together in a 24-hour period conveys the same complementary benefit as eating them together. Either way, you should get to know the amino acids that are in the protein sources you eat so you can ensure you're getting the protein you need to be at your best.
2. Vitamin B12
Vitamin B12, which is important for the nervous system and more, is found in a variety of foods of animal origin—but only trace amounts are found in plant foods. Some foods, such as cereal and nutritional yeast, are fortified with vitamin B12.
However, eating these fortified foods alone is not enough to meet our B12 needs. Therefore, supplementation of this B vitamin is necessary if following a vegan diet. I always recommend choosing the methylated form: methylcobalamin.
3. Calcium
Although we often think of dairy products when we think of calcium, vegetables and legumes are also sources of this important mineral. Make sure to include broccoli, soybeans, spinach and other leafy greens into your repertoire.
4. Vitamin D
Although our skin can produce vitamin D from sunlight, regardless of your dietary choices, there are some limitations to this such as one’s age, skin color, geographic location and lifestyle habits (indoors, much?).
Animal sources of vitamin D include milk, egg yolks and fatty fish, such as salmon and trout. Fortified cereals and non-dairy milks are vegan options for vitamin D3. Some plants, such as UV exposed mushrooms, provide vitamin D2, but vitamin D3 is well absorbed and supports blood levels of vitamin D more than vitamin D2 does.
Unfortunately though, it can be difficult for vegans and non-vegans alike to obtain vitamin D from food alone. Supplementation is often necessary to support optimal levels for bone health and immune function. Most vitamin D3 (cholecalciferol) supplements are derived from lanolin (sheep’s wool), but if you are looking for a vegan option, algae derived vitamin D3 supplements are available.
5. Iron
Iron is important for red blood cell function, since iron is incorporated into heme, found in hemoglobin, which allows red blood cells to carry oxygen throughout the body. Plant foods provide nonheme iron, whereas meat provides heme iron, and heme iron is more bioavailable than nonheme iron. Because of this, the RDA of iron for vegetarians is 1.8 times higher than for people who eat meat. The good news is that eating vitamin C rich foods along with iron-containing plant foods can help you absorb more nonheme iron.
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6. Zinc
Zinc is important for immune system function, protein synthesis and more. Although a variety of grains and plant foods contain zinc, the bioavailability from these sources are lower than zinc coming from animal sources like beef and seafood. This is because phytates—which are present in whole-grain breads, cereals, legumes, and other foods—bind zinc and inhibit its absorption.
According to the NIH, people who are on plant-based diets sometimes require as much as 50% more of the RDA for zinc than non-plant based. Soaking beans and choosing leavened grains (bread versus crackers) can help inhibit phytates and increase zinc absorption.
7. Iodine
When it comes to this thyroid supporting mineral, the partially good news for vegans is that sea vegetables like seaweed are among the best sources of iodine. The not-so-good news is that seaweed is one of the only food options that both serves as a good source and is suitable for vegan diets.
Some plant foods such as beans and potatoes contain iodine, but are not reliable sources since the amount will vary based on regional growing practices. Using iodized salt is also an option for vegans to get more iodine. Because plant-based options are lacking, vegans are at risk of deficiency and should consider iodine supplementation, especially if pregnant or breastfeeding.
8. Omega-3: DHA
DHA (docosahexaenoic acid) is an omega-3 fatty acid that is important for brain and heart health. It is largely obtained from fatty fish like salmon and sardines. It can be difficult for vegans and non-vegans alike to get enough DHA.
If you are vegan, consider supplementing with algae derived DHA instead of fish oil as your omega-3 supplement to make sure you are getting enough. Nuts (walnuts) and seeds (chia, flax) are vegan sources of an omega-3 called alpha linolenic acid (α-linolenic acid; ALA), but it is a common misconception that ALA will cover your bases. We can convert ALA to EPA (eicosapentaenoic acid) and DHA to some extent, but the conversion efficiency is very low.
9. Vitamin B2
Riboflavin, AKA vitamin B2, plays important roles in energy production, cellular function, metabolism and more.
Lean meat, eggs, dairy, almonds, quinoa, spinach, grains and fortified cereals contain riboflavin. Because riboflavin is soluble in water, some riboflavin content is lost in cooking water when foods are boiled. Interestingly, intestinal bacteria can make some riboflavin. Despite this, vegetarian athletes and vegans are considered to be at risk of riboflavin vitamin deficiency. Exercise produces stress in the metabolic pathways that uses riboflavin, therefore athletes may have an increased need for this nutrient.
How to avoid nutrient deficiencies
DO: Eat a variety of foods
Creature of habit? We all have our favorite foods, or tend to choose ones that are easier to prepare, but variety isn’t just the spice of life—keeping a varied diet will also help to ensure you are getting enough amino acids, vitamins, minerals, and other nutrients. Pairing foods is one strategy (black beans + rice = a complete protein source). But as long as you include a variety of foods in your diet, including plant-based protein sources, you should hit your goals.
DON'T: Rely too much on processed and packaged foods
Just because something is labeled as vegan, doesn't automatically mean it is nutrient dense.
DO: Take lab tests
Want to know exactly where you stand? Here are some valuable testing options beyond what is usually on your annual lab test ordered through your doctor that can help you identify deficiencies:
- Vegan/Vegetarian Panel Blood Test
- Vitamin D, 25-Hydroxy Blood Test
- Omega-3 Index Complete Finger Stick Test
- Nutrient Panel Blood Test
DON'T: Skip supplements
Meeting your nutrition needs from food is ideal, but sometimes supplementation is necessary. In addition to some of the stand-alone vitamin & mineral supplement options, choosing a Plant-Based Multivitamin is a good, vegan-friendly way to help you fill in the gaps from your diet.
References
- Berrazaga, Insaf et al. “The Role of the Anabolic Properties of Plant- versus Anima Based Protein Sources in Supporting Muscle Mass Maintenance: A Critical Review.” Nutrients, August 2019, https://www.ncbi.nlm.nih.gov/labs/pmc/articles/PMC6723444/
- Pawlak, Roman et al. “How Prevalent Is Vitamin B(12) Deficiency among Vegetarians?” Nutrition Reviews, February 2013, https://pubmed.ncbi.nlm.nih.gov/23356638/
- Shieh, Albert et al. “Effects of High-Dose Vitamin D2 versus D3 on Total and Free 25-Hydroxyvitamin D and Markers of Calcium Balance.” The Journal of Clinical Endocrinology and Metabolism, August 2016, https://www.ncbi.nlm.nih.gov/labs/pmc/articles/PMC4971338/
- Tomova, Aleksandra et al. “The Effects of Vegetarian and Vegan Diets on Gut Microbiota.” Frontiers in Nutrition, April 2019, https://www.ncbi.nlm.nih.gov/labs/pmc/articles/PMC6478664/
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