Plant-Based Nutrition Solutions: Potential Drawbacks of Plant-Based Diets and How to Solve Them
People follow plant-based diets for a myriad of reasons, ranging from environmental concerns to ethical values to pure preferences. But while plant-based eaters typically consume more fiber, fruits, and vegetables, there are also many potential nutritional drawbacks to a plant-based diet—especially a vegan diet, which contains zero animal products.
That said, it is absolutely still possible to meet your nutritional needs on a plant-based diet—you just need to plan ahead to optimize your diet and often add supplementation. In this article, we’ll detail the top nutrients of concern in a fully plant-based diet and ways to ensure optimal intake.
8 Potential Nutritional Drawbacks of a Plant-Based Diet and How to Solve Them
People on 100% plant-based (vegan) diets face the most nutritional challenges, as several essential micronutrients are found primarily in animal foods. Those consuming dairy, eggs, or seafood (like vegetarians and pescatarians) are better able to gain these nutrients through their diets, so this section will speak specifically to vegans. Some nutrients are missing entirely in plant foods (like vitamin B12), while others are less bioavailable, like iron and zinc.
1.Vitamin B12
Anyone on a plant-based diet likely knows the importance of vitamin B12, as it’s a micronutrient found only naturally and in substantial amounts in animal products. As vitamin B12 deficiency can lead to severe neurological symptoms, optimizing your B12 intake as a vegan is vital. Some of the best sources of vitamin B12 are shellfish like oysters, clams, and mussels—therefore, pescatarians have an easier time getting B12 from food.
How to support optimal vitamin B12 intake on a plant-based diet
Vitamin B12 supplementation is necessary if you are a vegan. This could come from a dietary supplement or foods fortified with B12, typically including almond and other nut milk, cereals, nutritional yeast, and some soy products.
The more bioavailable forms of vitamin B12 are hydroxocobalamin and methylcobalamin (rather than cyanocobalamin), especially for people with the genetic SNP variant MTHFR. Getting your serum vitamin B12 levels checked every six months or so can also be beneficial.
2. Choline
Inadequate choline intake is not specific to plant-based eaters—much of the general population is undereating this B-vitamin-like nutrient. As the first recommended intake level for choline was only set in 1998, its importance is still being recognized and researched.
Some of the leading benefits of optimal choline intake include cognitive function, heart health, and liver function. Plus, choline is now thought to be as essential as folate in preventing neural tube defects during pregnancy.
The top dietary source of choline is egg yolks (and liver, a highly undereaten food in the U.S.), so vegans understandably have lower intakes than egg eaters. While some plant foods—like broccoli, beans, and Brussels sprouts—contain choline, it’s in much lower amounts. To put it in perspective, you’d have to eat almost four cups of broccoli to get the same amount of choline in one egg yolk.
How to support optimal choline intake on a plant-based diet
Vegans can boost their choline intake by consuming plenty of broccoli, pinto beans, and Brussels sprouts, and vegetarians can easily meet their choline needs by adding eggs (with the yolk!). However, a choline supplement may be necessary to meet the RDA (550mg for adult men and 425mg for adult women), as a half-cup serving of these plant foods only contains about 30mg of choline—compared to the 150mg found in one egg.
3. Vitamin A (Retinol)
Vegans and vegetarians often eat plenty of provitamin A (carotenoids like beta-carotene), which is found in orange, yellow, and green fruits and vegetables, such as carrots, spinach, sweet potatoes, and bell peppers.
However, plant-based eaters may be low in preformed vitamin A, also known as retinol. While our bodies can convert carotenoids into retinol, the conversion rate is very low—sometimes as low as 3%. This means that even if you consume plenty of beta-carotene-rich fruits and vegetables, you still likely are not meeting your preformed vitamin A needs, which is essential for vision, immunity, lung, and respiratory health.
The only natural source of retinol is animal fat, including grass-fed butter, full-fat dairy, eggs, meat, fatty fish, and liver or organ meats.
How to support optimal vitamin A intake on a plant-based diet
As mentioned, beta-carotene is not well converted into retinol in the body. Some people also have genetic variants that reduce the enzymes necessary to convert beta-carotene into retinol, leading to even lower retinol levels.
However, vitamin A supplementation is also not recommended, as supplements of preformed vitamin A (retinol) can be risky if taken in large quantities, causing vitamin A toxicity and congenital disabilities during pregnancy.
So what should plant-based eaters do? While eating beta-carotene-rich produce is beneficial, it may not be enough. However, combining beta-carotene with fats (like olive oil or avocado) can help increase its bioavailability. If you can get behind it (depending on the reasoning behind your vegan diet), one of the best ways to support optimal vitamin A intake with minimal animal product intake would be to consume a spoonful of cod liver oil per day, which provides about 150% of your daily needs for retinol.
4. Vitamin K2
While vitamin K1 is widely available in a plant-based diet (found plentifully in leafy green and cruciferous vegetables like Brussels sprouts, cabbage, kale, broccoli, and spinach), vitamin K2 is less prevalent. Vitamin K2 is vital for bone and cardiovascular health, as it helps calcium deposit where it needs to (the bones and teeth) and not settle and calcify in the heart and arteries.
How to support optimal vitamin K2 intake on a plant-based diet
The best sources of vitamin K2 are animal foods, including grass-fed butter, egg yolks, and full-fat dairy. However, a few plant foods also contain K2, including natto (a Japanese fermented soybean dish) and sauerkraut. You can also supplement with vitamin K2—a great way is to get a combination vitamin D3-K2 supplement, which can optimize calcium deposition and bone health.
5. DHA
Docosahexaenoic acid (DHA) is an omega-3 fatty acid found in fatty fish like salmon, sardines, anchovies, and tuna. DHA is essential for cognitive and cardiovascular health, and oily fish is by far the best dietary source.
Foods like flaxseeds, chia seeds, hemp seeds, and walnuts provide another omega-3 fat called ALA. The body can convert ALA into DHA, but the conversion rate is low. It’s estimated that about 2 to 5 percent of dietary ALA gets converted into DHA. Therefore, vegans should consider DHA an essential supplement.
How to support optimal DHA intake on a plant-based diet
Eating ALA-rich foods (flax, chia, hemp, and walnuts) is undoubtedly beneficial, but vegans likely need a separate DHA supplement. If you are already adding cod liver oil for your retinol intake, that would also cover your recommended DHA consumption. If not, there are vegan DHA supplements made from microalgae.
6. Iron
While plenty of plant foods contain iron (especially beans and legumes), it is less bioavailable than the type found in animal foods. Plant-based iron (non-heme iron) is not as well absorbed as animal (heme) iron. Many vegans are on top of their iron intake, as they know that optimal iron consumption is necessary for red blood cell health, immunity, and energy.
How to support optimal iron intake on a plant-based diet
Vitamin C boosts the bioavailability of iron. Therefore, vegans can enhance their absorption of non-heme iron by consuming iron-rich plant-based foods with vitamin C-rich foods. Iron-rich foods include beans, lentils, legumes, tofu, tempeh, nuts, fortified cereals, and dark leafy greens, while vitamin C-rich foods are citrus fruits, bell peppers, tomatoes, and strawberries. Iron supplements are an option, although they are often not well absorbed and can cause digestive symptoms. If you’re unsure whether you’re getting enough iron from your diet, have your doctor check your blood levels through a complete blood count (CBC), including a ferritin test.
7. Zinc
Like iron, zinc is another mineral that is less bioavailable in plant forms. The best plant-based sources of zinc are similar to those rich in non-heme iron: legumes, nuts, seeds, whole grains, and fortified foods.
However, the bioavailability of zinc from plant sources is often lower due to the presence of phytates, a stored form of phosphorus in these foods that can reduce the absorption of nutrients like zinc, iron, and calcium.
Consequently, vegans and vegetarians need to consume about 50% more zinc each day than meat-eaters, who eat zinc from more bioavailable sources. As zinc is vital for immune system health, wound healing, DNA repair, and more, vegans should consider ways to optimize their zinc intake.
How to support optimal zinc intake on a plant-based diet
Vegans and vegetarians should consume adequate amounts of zinc-rich foods (beans, lentils, nuts, seeds, and whole grains) and practice ways to reduce phytate content. The best way to reduce phytates is through their cooking method. For example, soaking beans and legumes overnight in water (and then discarding that water before cooking) can significantly reduce the phytic acid content. Fermentation, sprouting, and pickling of these foods can do the same.
8. Protein
Last but not least, the age-old question that vegans and vegetarians are oh-so-tired of hearing is: “But where do you get your protein?!” While a plant-based diet can provide plenty of protein, vegans do need to ensure they are eating adequate amounts of protein-rich foods daily—just like omnivores.
More research is emerging that the RDA for protein might be too low—especially in older adults. Vegans and meat-eaters alike need to pay attention to their protein intake to support muscle maintenance, immune function, metabolism, weight management, tissue repair, and enzyme and hormone production.
How to support optimal protein intake on a plant-based diet
The best plant-based protein sources include beans, lentils, chickpeas, tofu, tempeh, seitan, edamame, quinoa, nuts, seeds, and certain grains like amaranth and buckwheat. You can also include vegan protein powders or shakes (aim for no-sugar options) when you’re not sure you’re meeting your needs. Although the RDA for protein is 0.8 grams per kilogram (g/kg) of body weight, it’s now thought that this is too low, and 1 g/kg should likely be the new minimum, with some research stating that up to 1.2 to 1.6 g/kg is more ideal.
Key Takeaways
Plant-based diets have plenty of nutritional benefits, including an increased likelihood of meeting the recommended intake of fruits, vegetables, whole grains, and fiber. However, some nutrients can be overlooked, as several vitamins and minerals are not readily available in plants or are not well-absorbed or converted in the body.
The top nutrients to be aware of when consuming a plant-based diet include vitamin B12, preformed vitamin A (retinol), vitamin K2, DHA, iron, zinc, choline, and protein. However, it’s certainly possible to eat a well-rounded and nutritionally balanced plant-based diet—like with all diets, it just requires some planning to ensure you’re checking all of the nutrient boxes.
References:
Niklewicz A, Smith AD, Smith A, et al. The importance of vitamin B12 for individuals choosing plant-based diets. Eur J Nutr. 2023;62(3):1551-1559. doi:10.1007/s00394-022-03025-4
Phillips SM, Chevalier S, Leidy HJ. Protein "requirements" beyond the RDA: implications for optimizing health. Appl Physiol Nutr Metab. 2016;41(5):565-572. doi:10.1139/apnm-2015-0550
Tang G. Bioconversion of dietary provitamin A carotenoids to vitamin A in humans. Am J Clin Nutr. 2010;91(5):1468S-1473S. doi:10.3945/ajcn.2010.28674G
