Plant-Based Nutrition: Episode # 3 – Vitamins

Are you wondering how to optimize your vitamin intake on a plant-based diet? 

Our previous episode of the Plant-Based Nutrition series focused on all-things Omega-3’s! In this episode we focus on how to optimize your vitamin intake, specifically vitamins B12 and D, on a plant-based diet! 

Although plant-based diets are rich in many vitamins, they often tend to be lower in vitamins B12 and D [1,2]. For this reason many people find it challenging to get enough of these nutrients in their diet from just plant-based sources. But it doesn’t have to be hard! Read below to learn more about vitamin B12 and vitamin D and how to easily overcome these nutrient deficiencies!   

What are Vitamin B12 and Vitamin D?

Let’s start with a brief overview of vitamins! 

Vitamins are micronutrients, which means our body only requires them in limited quantities. Yet, even those small amounts are crucial for your health. 

There are 13 essential vitamins ( vitamins A, C, D, E, K and 8 types of B vitamins) that we require for optimal health and functioning. Plant-based diets are often rich in many of these vitamins, with the exception of vitamin B12 and vitamin D, which are mostly found in animal sources of food [3]. 

Vitamin B12 is the largest and most complex of all vitamins. It is water-soluble and found naturally in large quantities only in animal sources. It is also added to certain fortified foods, such as plant-based milks and breakfast cereals. Vitamin B12 is important for many cellular processes including normal brain function, production of DNA and keeping your blood and nerve cells healthy [4,5]! 

Vitamin D is a fat soluble vitamin naturally found in a few foods and used in food fortification. It serves many functions in our body and is critical for keeping our bones strong and healthy. The two forms of vitamin D are vitamin D2 and vitamin D3. Vitamin D2 is found in plant sources, while vitamin D3 is found in animal sources of food and can also be synthesized in human skin upon exposure to sunlight [6,7]! 

Dietary Recommendations?

The recommended dietary allowance (RDA) for vitamin B12 is 2.4 micrograms (μg) per day for healthy adults [8]. 

The RDA for vitamin D is 600 international units (IU) (or 15 μg) per day for healthy adults. But this value is based on the assumption of minimal direct sun exposure. So, you can obtain at least some of your vitamin D needs this way [8]! 

Dietary Sources of Vitamin B12 and Vitamin D 

Vitamin B12 is naturally present in animal foods, such as fish, meat, poultry, eggs and dairy. Although vitamin B12 is not readily found in plant-based sources, certain fortified foods can help achieve the recommended RDA for those on a plant-based diet. These may include fortified [4]:

• Breakfast cereals
• Tofu 
• Fruit juices
• Plant-based milks

Only a few foods contain vitamin D naturally. These include egg yolk, fatty fish, beef liver and wild mushrooms that are grown in the sun. Much of the vitamin D in our diet comes from fortified foods such as [5]: 

• Plant-based soy milk 
• Orange juice
• Cereals 

Considerations?

Getting enough vitamins on a plant-based diet is important for keeping your body healthy! 

Here are a few things you should keep in mind:

Unbalanced plant-based diets are at a greater risk of vitamin D and vitamin B12 deficiency, since these foods are lacking in plant sources of food. 

But, luckily for those on a plant-based diet, there are still ways you can meet the RDA’s for these nutrients! 

Fortified foods may be a good place to get vitamins B12 and D in your diet. Of note, in the case of vitamin D, fortified foods generally only contain vitamin D2, not vitamin D3. However, studies suggest that vitamin D3 is better at improving vitamin D status, compared to vitamin D2 [9]. So, it may be a good idea to obtain vitamin D3 through other methods (discussed below) to ensure you are optimizing your vitamin D status! 

Since your body naturally makes vitamin D3 when your skin is exposed to sunlight, make sure to get regular sun exposure! But, sun exposure alone may not be enough to meet the body’s requirements of vitamin D. The amount of vitamin D that can be obtained through this way depends on many factors including [10]:

• Where you live
• Skin colour and sensitivities to sunlight 
• Amount of skin exposed
• Duration of exposure
• Season 
• Wearing sunscreen 
• Time of day
• Levels of ultraviolet radiation 

For example, in northern regions or during the cooler seasons, the levels of ultraviolet radiation from the sun are too low for every skin type to get adequate vitamin D solely from exposure to sunlight. Also, when smaller areas of the skin are exposed, more time under the sun is required to meet vitamin D needs through this method. Another important thing to keep in mind is that since people with darker skin make vitamin D more slowly, they may find it difficult to meet the recommended dose of vitamin D while adhering to sun protection guidelines [10]. 

Despite these considerations, sun exposure can help your body obtain at least some vitamin D naturally. But, remember that too much sun exposure is not good either!  

And finally, supplementing with vitamin B12 and vitamin D3 is the most effective way for those on a plant-based diet to ensure you are consuming adequate levels of these nutrients! 

The Bottom Line?   

Obtaining natural sources of vitamins B12 and D is difficult on a plant-based diet. Therefore, knowing how to get enough of these nutrients is critical for overall health and body function. Simply make sure you are optimizing these nutrients by identifying and eating the right plant-based fortified foods and supplementing when necessary! 

Want to learn more about other nutrients to improve on a plant-based diet? Look out for our blog on Minerals!

References

1. Rizzo, G., Laganà, A. S., Rapisarda, A. M., La Ferrera, G. M., Buscema, M., Rossetti, P., Nigro, A., Muscia, V., Valenti, G., Sapia, F., Sarpietro, G., Zigarelli, M., & Vitale, S. G. (2016). Vitamin B12 among Vegetarians: Status, Assessment and Supplementation. Nutrients, 8(12), 767. 

2. Chan, J., Jaceldo-Siegl, K., & Fraser, G. E. (2009). Serum 25-hydroxyvitamin D status of vegetarians, partial vegetarians, and nonvegetarians: the Adventist Health Study-2. The American Journal of Clinical Nutrition, 89(5), 1686S–1692S. 

3. HealthLink BC. (2019). Vitamins: Their Functions and Sources. Healthwise. 

4. Harvard School of Public Health. (2019). Vitamin B12. The Nutrition Source. 

5. National Institutes of Health (2020). Vitamin B12. Office of Dietary Supplements. 

6. Harvard School of Public Health. (2020). Vitamin D. The Nutrition Source. 

7. National Institutes of Health (2020). Vitamin D. Office of Dietary Supplements. 

8. Health Canada. (2010). Dietary Reference Intakes. 

9. Shieh, A., Chun, R. F., Ma, C., Witzel, S., Meyer, B., Rafison, B., Swinkels, L., Huijs, T., Pepkowitz, S., Holmquist, B., Hewison, M., & Adams, J. S. (2016). 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, 101(8), 3070–3078. 

10. Gill, P., & Kalia, S. (2015). Assessment of the feasibility of using sunlight exposure to obtain the recommended level of vitamin D in Canada. Canadian Medical Association Journal, 3(1), E258-E263.