The health benefits of a vegan diet are well documented, but any practicioner of a plant based diet is regularly confronted with a few common objections about its perceived nutrient deficiencies from meat eaters.. In my experience the most common are:
- vitamin B12
These perceived drawbacks are at worst entirely fictional and at best easily gotten around with some simple planning. And most importantly, the benefits of a vegan diet far outweigh any disadvantages that might come from skipping animal products altogether.
But if your experience is similar to mine, then you’ve had quite a few moments when you’re stuck trying to explain to someone why eating a plant based diet will not put them at risk of not getting enough protein, or why such fears are entirely misplaced to begin with.
So my intention for this article is to provide any aspiring vegan evangelist a handy reference guide to use when confronting others about how and why the most common pariahs of the vegan diet are based on false premises.
With that in mind, let’s lay down the gauntlet on these chimeras.
The conventional wisdom is that milk has a lot of calcium, other foods don’t, so in order to have healthy bones you need to drink milk. The well educated vegan ought to reply with the following points:
- Plenty of plants are good sources of bioavailable calcium.
- Vegans generally have lower calcium requirements due to less sodium and sulfur containing proteins found in animal products.
- The link between calcium intake and bone mineral density and osteoporosis is weak relative to other factors
To be fair, it’s true that calcium is absolutely vital to a healthy diet, and dairy is a very potent source of bioavailable calcium. So this line of reasoning has some truth to it.
However, cutting dairy out of your diet hardly restricts your alternatives to dietary calcium. Below is a chart from a study published in the American Journal of Clinical Nutrition that studied different food sources of calcium and their bioavailibility:
Green vegetables that are low in oxalic acid commonly deliver calcium that is more readily absorbed by the body than milk, and per gram often have a calcium content that is very similar.
And what’s more, a plant based diet can lower the body’s need for dietary calcium. Plant foods tend to be more alkaline than meat and dairy products, and calcium is used as a buffer to lower the body’s pH, negatively affecting your body’s calcium balance. Omnivorous diets also tend to be higher in sodium and protein, both of which can increase the amount of calcium that is excreted from the body and lower bone resorption.
The latter point does not diminish the importance of calcium in the diet or the need to get an adequate amount. It just points out the possibility that vegans have a different calcium homeostasis than omnivores. To illustrate my point, a study published in the British Journal of Nutrition found that vegans consumed about 30% less dietary calcium than omnivores, but had an insignificantly different calcium balance.
Calcium is the most abundant mineral in the body, mostly because the body uses it to build bones. So if omnivorous diets are better sources of calcium then people who follow them ought to have better markers for bone health.
However, assuming adequate amounts of calcium are ingested, there is no appreciable difference in bone mineral densities between vegetarians and omnivores. Furthermore, increased intake of animal protein has been shown to be positively correlated with hip fractures and osteoporosis, and lifestyle factors such as bodyweight and physical activity negatively affect bone mineral density, often more so than dietary calcium.
Epidemiological evidence does not support the notion that diets high in dairy increase bone health. In fact it’s just the opposite. American and Nothern European diets have the highest intakes of dairy, and also the highest rates of hip fractures among the elderly. East asian and african populations have the lowest, as can be seen below (Courtesy of Dr. McDougall):
The FAO recommends people get 0.6g of protein per kg of body weight. For most people this amounts to about 35-60 g of protein per day. If your caloric intake is around 2000 calories per day (and for most people it’s more), this means approximately 10-25% of your daily calories should come from protein. Here’s an approximate breakdown of proteins contribution to total calories for different plant foods:
Protein is the building block of all cells. If you consume your calories from real food, you have no choice but to consume adequate amounts of protein as a result. Protein deficiency is all but unheard of in western diets.
Essential Amino Acids
A common argument in favor of omnivorous diets is that animal proteins are “complete”, which usually means they contain greater amounts of essential amino acids than vegetable proteins, which is important to your health.
People who make this argument don’t know what they’re talking about.
- Your body uses essential amino acids very efficiently
- Even though your body can’t synthesize essential amino acids on its own, it can convert non-essential amino acids with similar functional groups into essential amino acids
- Vegetable proteins do provide essential amino acids, albeit in smaller quantities
- Most people get way more essential amino acids then their body knows what to do with….often to harmful effects.
Let’s talk about that last point. Here are the results from a comprehensive longitudonal study conducted by the FAO on protein intake in western diets:
If you look to the right you’ll notice people typically get about four times as many essential amino acids as the body needs.
So, no, you won’t be teetering on the edge of serious deficiency by foregoing animal products.
In fact, you’re probably better off for eating less of it. Your body doesn’t store protein, and eating too much is a more common problem than eating too little. Excessive protein intake over the long run results in undigested amino acid metabolites that can lead to gout, arthritis, kidney stones and high blood pressure over a lifetime.
Vegans and vegetarians often have higher iron requirements than omnivores because the type of iron they typically receive in the diet is non-heme iron, which is not absorbed as well as heme iron, the type found in meat.
However, like all other nutrients, eliminating meat doesn’t leave you stranded in a barren nutritional dessert, destined to the suffocating atrophy of deficiency and deterioriation.
Nuts, beans, legumes, soy products, and iron fortified foods can all give the body enough iron to keep going strong. Vegan diets are also aided by higher levels of vitamin C, which increases iron absorption. When well planned, a whole foods vegan diet does not result in lower rates of iron deficiency than omnivorous ones.
As much as I’m loathe to admit it, when it comes to B12 the meat eaters have a point. Vitamin B12 is a substance that’s only made by bacteria and is stored in the cells of animals but not plants. For this reason plants cannot be counted on to regularly provide vitamin B12, even though fermented foods can provide some in small quantities.
So…..does this finding invalidate the nutritional basis of the vegan diet?
- Your body only needs trace amounts of Vitamin B12 to survive
- Your body typically stores 3-5 years worth of vitamin B12 in your liver
- Fortified foods and fermented foods often provide enough vitamin B12
In order to avoid symptoms of deficiency the body can get by with as little as 3-5 micro grams per day. If you didn’t digest any vitamin B12 from today onward it’d probably be 5 years before you noticed a difference in your body. A large portion of vegan food bought in stores is fortified with B12, and this is typically enough to avoid worst case scenarios for B12 deficiency. However, to be safe, it’s a good idea to use a B12 supplement if you’ve been vegan for more than 3-5 years. And ironically, it’s hard to find a supplement that provides only the amount you need on a day to day basis……they typically provide way more than is necessary.
One might infer that a vegan diet is not what nature intended if it doesn’t naturally provide an essential nutrient. This intuition makes sense, but it neglects the differences in how humans interact with their environment compared to when our nutritional needs were formed.
By far the best source of vitamin B12 in the environment is feces. Bacteria in your colon actually make more than enough B12 to survive on, but because they live south of the ileum not very much is absorbed. In an environment where people are closely connected to the food they grow and not isolated from natural fertilizers growing conditions in the soil are likely to provide more than enough B12, even on a vegetarian diet.
Sometimes the benefits of a vegan diet are hard to articulate, because your explanation has to debunk some typical canons of dietary thought. This is too bad, because it’s prevented me from meaningfully engaging people who were genuinely curious about the benefits of a plant-based diet, but needed to overcome some doubts before trying it out.
I’ve found that people who are fearful of change can’t be nudged into action, they need to be patiently led to the final outcome by overcoming all objections that are floating around in their heads. Only after they’ve been shown that it wouldn’t make sense to not do it does it feel safe to dip your toe into the waters and give it a shot.