Which Vitamins and Nutrients Are Plant-Based Diets Potentially Missing?

How to Get Adequate Vitamin B12 and Iron while on a Vegetarian Diet

By Michael Ormsbee, PhDFlorida State University
Edited by Kate Findley and proofread by Angela Shoemaker, The Great Courses Daily

Although it is more challenging for vegetarians to get adequate protein than it is for meat-eaters, it is not impossible. However, it is not uncommon for plant-based eating to lead to low levels of certain nutrients. Professor Ormsbee explains how to avoid these deficiencies.

Foods high in vitamin B12
Vitamin B12 and iron are essential for maintaining health and come from a variety of food groups, both plant and animal sources. Photo By Tatjana Baibakova / Shutterstock

Avoiding B12 and Iron Deficiencies

One nutrient that plant-based dieters are often deficient in is Vitamin B12 since only animal products like meat, fish, eggs, and dairy products contain substantial amounts of it. You can get B12 from foods like cereals that are fortified with it, but otherwise supplementing might be needed.

Iron is also a nutrient that needs special attention when eating primarily plant-based diets. Heme iron—most readily absorbable—comes from animal products and makes up about 40% of iron in meat. 

Non-heme iron is the less well-absorbed form of iron found in nuts, grains, vegetables, and fruit. Plant-based dieters need almost two times the amount of iron from plant sources to get the same amount of iron as meat eaters.

Research has found that vitamin C helps with absorption of the non-heme, plant-based iron, but calcium and tannins found in drinks like tea and coffee reduce non-heme iron absorption. Since many plant-based eaters consume a good amount of vitamin C from foods like peppers, kale, and broccoli, the absorption of iron might not be an issue at all. It just makes sense to combine iron intake with vitamin C and try to consume calcium supplements or tea and coffee an hour or two before you eat iron-rich foods.

Plant-Based Diets and Other Nutrients

Vitamin D is also a special concern for plant-based eating. Dairy foods are often fortified with vitamin D, meaning that vitamin D is added to the final food or drink during processing. 

Some plant-based eaters avoid dairy as well as meat. Luckily, the best source of vitamin D is sunlight. Thus, if you’re a vegetarian lacking in vitamin D and you don’t get much sun, then you should talk to your health care professional about supplementing with vitamin D. 

Plant-based eaters should also pay special attention to omega-3 fats in their diets. Cold-water fish provide ample supplies of omega-3 fats, but non-fish-eaters can go for walnuts, seaweed, hemp, and flax to take in alpha-linolenic acid (ALA). 

ALA is then converted to docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA)—the types of fatty acids that nutrition experts regard as the heavy hitters of the omega-3-fatty acids. These fatty acids can help with body composition and are also needed for warding off disease.

Unfortunately, the body uses the plant-based sources for omega-3s inefficiently. Thus, once again, supplementation is needed with a DHA or EPA product from fish oil, krill oil, or an algae-based product.

Other needs for plant-based eating include both calcium and zinc. Again, these can be consumed in the diet, but absorption of both tends to be low compared to non-vegetarians. 

While zinc is found in many plant foods like lentils, peanuts, and quinoa, its absorption is lower than it is when you get it from animal products. This just means that plant-based eaters need to take in more zinc to fulfill the same requirements.

Considerations for Athletes

If you are very physically active and training for performance, a few other dietary considerations include traditional sports supplements like creatine and beta alanine. Creatine is made naturally in your body, but you also get some from your diet—if you eat meat and fish, that is. 

Those who only eat plants will have lower levels of stored creatine. Since creatine is used for short, explosive movements—and has shown to have some benefits for cognition, neurological disorders, and muscle mass—it might be needed as a supplement.

Additionally, vegetarians have about 50% less carnosine in their muscle tissues. Carnosine is a protein building block concentrated in muscles when they are working. Due to the link between carnosine concentrations and overall health, as well as evidence for exercise performance advantages emerging in the scientific literature, supplementing with beta alanine for the production of carnosine might be important.

Above all, if you are eating a plant-based diet, make sure to include a combination of plant proteins to meet your dietary goals. Include a good variety of non-starchy vegetables like greens, spinach, arugula, broccoli, and squash and good fats like nuts, seeds, and healthy oils.

Eat fruit, starchy vegetables like corn and peas, and starches like bread, whole grains, and potatoes to complete your energy needs. The health benefits that come from a plant-based diet can be achieved by simply eating more plants. 

Dr. Ormsbee is an Associate Professor in the Department of Nutrition, Food, and Exercise Sciences and Interim Director of the Institute of Sports Sciences and Medicine in the College of Human Sciences at Florida State University.

Michael Ormsbee is an Associate Professor in the Department of Nutrition, Food, and Exercise Sciences and Interim Director of the Institute of Sports Sciences and Medicine in the College of Human Sciences at Florida State University. He received his MS in Exercise Physiology from South Dakota State University and his PhD in Bioenergetics from East Carolina University.

This article was edited by Kate Findley, Writer for The Great Courses Daily, and proofread by Angela Shoemaker, Proofreader and Copy Editor for The Great Courses Daily.
About Kate Findley 439 Articles
Kate is a writer, novelist, and blogger living in Los Angeles. She has been writing for The Great Courses since 2017. It incorporates her two favorite things: writing and learning.