Maybe you have considered going vegetarian or vegan for the health benefits. Or maybe you feel an ethical or even spiritual obligation to it, but, at the same time are wondering if you are really able to follow it in a healthy manner.
First, and foremost, I want to make sure that everyone reading this piece understands that I respect and appreciate anyone who makes an ethical choice and thinks deeply about their health and/or social or spiritual impact of the food choices they make, even if it’s not my personal choice.
However, I am solely here to bring forth information based on science about the true impact of one’s food choices in relationship to their body, metabolism and over-all health and wellbeing.
Many choose a vegetarian diet because they’re under the impression that it’s a healthier choice from a nutritional perspective. It is this very presumption that I’d like to address in this particular article.
The fact is, for the last 50 plus years, we’ve been told to cut back on and/or eliminate meat, eggs, and animal fats from our diet because they are bad for us and we will live longer and enjoy superior health if we minimize or avoid them.
This idea has been so ingrained in us that few people even question its validity any longer.
In fact, I’m nearly certain that if you asked the average person whether a vegetarian or vegan diet is a healthier option than an omnivorous or meat-eating diet, they’d most likely say yes.
However, is this really an accurately assumption?
Well, let’s dive in to find out the truth!
Plant-based diets emphasize vegetables, which are quite nutrient dense, and fruits, which are somewhat nutrient dense.
They also typically include large amounts of grains (refined and unrefined) and legumes, both of which are low in bioavailable nutrients and high in anti-nutrients like phytate.
Most importantly, vegetarian and vegan diets avoid meats, eggs and fish, which are among the most nutrient-dense foods we can eat. (1)
Vegetarian diets and more so vegan diets, are almost completely devoid of certain nutrients that are crucial for our body’s biological function.
And deficiencies in these types of diets can take months or even years to develop, and many are easily missed due to not being routinely tested for in primary care settings.
Several studies have shown that both vegetarians and vegans are prone to deficiencies in:
- Vitamin B12
- Calcium
- Iron
- Zinc
- Long-chain fatty acids EPA and DHA
- Fat-soluble vitamins like A and D
Let’s take a closer look at each of these nutrients…
Vitamin B12
Vitamin B12 deficiency is especially common in vegetarians and vegans. In fact, the most recent studies using more sensitive techniques for detecting B12 deficiency have found that up to 77 percent of vegetarians and 92 percent of vegans are B12 deficient, compared to just 11 percent of omnivores. (2, 3, 4, 5)
Vitamin B12 works together with folate in the synthesis of DNA and red blood cells. It’s also involved in the production of the myelin sheath around the nerves and the conduction of nerve impulses.
Vitamin B12 deficiency can cause numerous noticeable symptoms, including:
- Fatigue
- Lethargy
- Weakness
- Memory loss
- Neurological issue
- Anemia
- And much more …
It’s a common myth among vegetarians and vegans that it’s possible to get B12 from plant sources like:
- Seaweed
- Fermented soy
- Spirulina
- Brewer’s yeast
These plant-based foods don’t actually contain B12. They contain B12 analogs, called cobamides, which, in turn block the intake of, and increase the need for, true B12. (6)
Calcium
Calcium is not only a major contributor for bone health, it’s also essential for muscle and nerve function and is involved in blood clotting.
On paper, calcium intake is similar in vegetarians and omnivores (probably because both eat dairy products). Vegans, however, are often deficient. (7, 8, 9)
This is because calcium bioavailability from plant foods is affected by their levels of oxalate and phytate, which are inhibitors of calcium absorption, thus decreases the amount of calcium the body can extract from plant foods. (10)
So, while leafy greens like spinach and kale have a relatively high calcium content, the calcium is not efficiently absorbed by the body during digestion.
In fact, one study suggests that it would take 16 servings of spinach to get the same amount of absorbable calcium as a single eight-ounce glass of milk. (11)
That would equal 33 cups of baby spinach or around five or six cups of cooked spinach.
This suggests that trying to meet your daily calcium needs from a plant-based food perspective alone might not be a great strategy.
For those who don’t tolerate dairy well, fish with edible bones like sardines are great sources of calcium, protein and Omega 3 fatty acids.
Iron
Vegetarians and omnivores often have similar levels of serum iron, but levels of ferritin, the long-term storage form of iron, is systematically found to be lower in vegetarians than in omnivores. (12, 13)
This is significant, because ferritin depletion is the first stage of iron deficiency.
Additionally, although vegetarians often have similar iron intakes to omnivores on paper, it is more common for vegetarians (and particularly vegans) to be iron deficient.
For example, this study of 75 vegan women in Germany found that 40 percent of them were iron deficient, despite average iron intakes that were above the recommended daily allowance. (14)
And this study among Australian men, iron intake among vegetarians and vegans was 29 to 49 percent higher than omnivores, but their serum ferritin concentrations were barely half that of omnivores. (15)
Despite similar iron intakes, a recent 2017 study showed vegetarians and Vegans having low ferritin levels. (16)
So, why is this?
As with calcium, the bioavailability of the iron in plant foods (nonheme iron) is much lower than in animal foods (heme iron).
Additionally, plant-based forms of iron are also inhibited by other commonly consumed substances, such as:
- Coffee
- Tea
- Dairy products
- Supplemental fiber
- Supplemental calcium
This explains why vegetarian diets have been shown to reduce nonheme iron absorption by as much as 70 percent and total iron absorption by as much as 85 percent. (17, 18)
Zinc
Zinc plays an important role in the immune system, cell division and growth, wound healing and the breakdown of carbohydrates.
You won’t usually see obvious zinc deficiency in Western vegetarians, but their intake often falls below recommendations, probably because red meat, poultry, and fish are the best sources.
This is another case where bioavailability is important, because many plant foods that contain zinc also contain phytate, which inhibits zinc absorption.
Vegetarian diets tend to reduce zinc absorption by as much as 35 percent compared with an omnivorous diet. (19)
Therefore, even when the diet meets or exceeds the RDA for zinc, deficiency may still occur. (20)
In fact, a meta-analysis of 34 studies found that both zinc intakes and serum zinc concentrations were considerably lower in vegetarians than non-vegetarians. (21)
What this suggests is that vegetarians may require up to 50 percent more zinc than omnivores to meet the body’s needs. (22)
Essential Fatty Acids
Plant foods do contain the polyunsaturated fatty acids linoleic acid (omega-6) and alpha-linolenic acid (ALA, omega-3), both of which are essential.
What this means is, an essential fatty acid is one that can’t be synthesized by the body and must be obtained in the diet.
However, increasing research is clear on the benefits of the long-chain omega-3 fatty acids EPA and DHA. These fatty acids play a protective and beneficial role in a wide range of disease prevention including: (23, 24)
- Cancer
- Asthma
- Depression
- Alzheimer’s
- Cardiovascular disease
- ADHD
- Autoimmune diseases, like rheumatoid arthritis
While it is possible for ALA from plant foods to be converted into EPA and DHA, the conversion is extremely poor in humans: between 5 and 10 percent for EPA and mere 2 and 5 percent for DHA. (25).
Although no official recommendation exists, the daily suggested intake of combined DHA and EPA is around 250 to 500 mg.
In theory, this means vegetarians and Vegans would need to consume between five and 12.5 grams of ALA per day to obtain 250 mg of DHA.
In reality, vegetarians and vegans consume merely 0.97 g/day and 0.86 g/day of ALA, respectively, according to a study of over 14,000 Americans. (26)
Therefore, Vegetarians have 30 percent lower levels of EPA and DHA than omnivores, while vegans have 50 percent lower EPA and nearly 60 percent lower DHA. (27, 28)
Furthermore, the conversion of ALA to DHA depends on zinc, iron, selenium, and pyridoxine—nutrients that vegetarians and vegans are less likely than omnivores to get enough of. (29, 30, 31)
Therefore, eating 12 to 16 ounces of cold-water fatty fish per week still remains the best way to get adequate EPA and DHA.
The fish will also provide bioavailable complete protein and selenium.
Vitamins A and D
Perhaps one of the prime drawbacks with a strictly plant-based (vegetarian or vegan) diet, however, is their near total lack of two fat-soluble vitamins: A and D.
Fat-soluble vitamins play a number of critical roles in human health.
- Vitamin A promotes healthy immune function, fertility, eyesight, and skin.
- Vitamin D regulates calcium metabolism, regulates immune function, reduces inflammation, and protects against some forms of cancer.
These important fat-soluble vitamins are concentrated, and in some cases found almost exclusively in animal foods such as:
- Seafood
- Organ meats
- Eggs
- Dairy products
Some obscure species of mushrooms can also provide large amounts of vitamin D, but these mushrooms are rarely consumed and often difficult to obtain.
This may explain why vitamin D levels are often low in vegetarians and even lower in vegans. (33, 34, 35, 36)
The idea that plant foods contain vitamin A is a common misconception.
Plants contain beta-carotene, the precursor to active vitamin A (retinol).
However, while beta-carotene is converted into vitamin A in humans, like calcium, zinc and ALA to DHA and EPA the conversion rate is extremely inefficient. (37, 38)
For example, a single serving of liver (per week) would meet the RDA of 3,000 IU of vitamin A. To get the same amount from plant foods, you’d have to eat two cups of carrots, one cup of sweet potatoes, or two cups of kale (every day).
Therefore, it would be nearly impossible to get an adequate amount of vitamin A from plant foods without juicing or taking supplements. And if supplements aren’t consumed with a fatty meal, the actual absorption will be low at best. (39)
Other Key Nutrients
Vegetarians and Vegans may be missing out on these key nutrients as well:
- Choline
- Creatine
- Taurine
- Methionine
- Glycine
- Selenium
Choline
Vegetarian and vegan diets, along with the Standard American Diet, pose risks of choline deficiency. (40)
Choline is required for:
- Healthy cell membrane function
- Methylation
- Cognitive development in children
It’s so important that the FDA recently set a daily recommended intake of 550 mg for men and 425 mg for women, which should increase to 450 mg during pregnancy and 550 mg during breastfeeding.
Recent research suggests that only 8.5 percent of women meet the daily choline requirement. (41)
With egg yolks and organ meats as the most potent sources of choline, it’s not surprising that even omnivores may not not getting enough.
This is why I encourage giving organ meat dishes like liver a try.
Creatine
Creatine plasma and muscle levels are usually lower in vegetarians than in omnivores, as meat provides the richest source of creatine. (42)
Creatine has also been shown to play an important role in cognitive function.
In fact, a randomized controlled trial found that six weeks of oral creatine supplementation significantly improved vegetarians’ performance on tests of fluid intelligence and working memory.
The difference in scores between groups was enormous. (43)
Another study found that creatine supplementation in vegetarians improved memory, while having no effect on fluid intelligence or working memory in meat-eaters. (44)
These results suggest that vegetarians baseline scores may have been impaired due to low creatine intake.
Glycine
Vegetarians and vegans don’t consume as much glycine as meat-eaters, as the richest sources are the “odd bits” of animal foods, like: (53)
- Skin
- Bones
- Collagen
- Gelatin
Glycine is one of the building blocks of collagen, found in our connective tissues.
In addition to its structural role, glycine can also act as a neurotransmitter, plays a role in blood sugar regulation, and stimulates the production of glutathione, the body’s master antioxidant. (54, 55, 56, 57)
Low choline and glycine intake, common in vegetarians and vegans, can further contribute to high homocysteine levels and increased risk of CVD.
It’s been shown that consuming bone broth on a regular basis can help balance glycine/methionine levels.
Selenium
While a few studies show no difference in selenium status among diet types, most research shows lower intake and/or levels in vegetarians and vegans compared to omnivores.
Selenium has a role in immune function, supports thyroid hormone synthesis, and protects the thyroid from excess iodine damage. (58, 59)
Selenium also helps prevent mercury toxicity. (60)
Selenium deficiency is also common in those with digestive health issues like Crohn’s disease or celiac disease. (61, 62)
The best sources of selenium include:
- Brazil nuts
- Crimini mushrooms
- Sea food
- Chicken
- Eggs
- Lamb
- Turkey
I recommend getting selenium from whole foods instead of supplementing, as it can be quite dangerous and toxic.
Thyroid Health
Thyroid hormone synthesis requires iodine, a nutrient that can be lacking in omnivore and plant-based diets alike.
In a typical mixed diet, the highest sources of iodine are iodized salt and animal products like:
- Dairy products
- Eggs
- Seafood
Therefore, vegetarians and vegans are at risk for low iodine intake. (63)
In fact, several studies of Scandinavian populations confirm that vegans finished last in iodine intake and/or urinary iodine levels. (64, 65,66)
To make matters worse, isoflavones found in soy products, which are sometimes consumed in large quantities in vegetarian and Vegan diets, may worsen iodine deficiency and hypothyroidism. (67)
Sea food and sea vegetables, especially kelp, are the highest sources of iodine ounce for ounce.
Bottom Line:
With careful attention and an insightful approach, I do believe it’s possible to meet almost all of your nutrient needs on a vegetarian diet that includes generous amounts of full-fat dairy and eggs, with the exception of the Omega 3 fatty acids (DHA and EPA).
These long-chain omega fats are found exclusively in marine algae and fish and shellfish, so the only way to get them on a vegetarian diet would be to take a microalgae supplement or bend the rules slightly by incorporating fish oil or cod liver oil into your regimen, as a supplement. (68)
However, I don’t believe it’s possible to meet your nutrient needs on a vegan diet without supplementing wisely.
Vegan diets are low in:
- B12
- Bioavailable iron and zinc
- Choline
- Vitamins A and D
- Calcium
- EPA and DHA
If you’re determined to following a vegan diet, make sure you do your research and understand what supplements you will need to focus on.
It’s worth noting that research points out that there are genetic differences that affect the conversion of certain nutrient precursors (like beta-carotene and alpha-linolenic acid) into the active forms of those nutrients (like retinol and EPA and DHA, respectively).
And these differences may affect how long someone will be able to follow a vegetarian or vegan diet before they develop nutrient deficiencies.
This explains why some people seem to do well for years on these diets, while others develop problems very quickly.
I hope this article can serve as a resource for anyone who has chosen or is looking into the idea of adapting to a plant-based diet. This article is not written to condone or condemn anyone’s chosen path of eating, but rather serve as a resource to help you do so in a purely healthy manner.
