Vegan Myths: Plant-based diets are lacking certain nutrients
Written by Keira Edwards-Huolohan
Created Monday, 09 December 2013
This is one that I bet we've all heard, or that perhaps you've said. Vegans are often accused of not getting enough nutrients, looking 'sickly' and pale and 'in need of a good steak'. As it turns out, vegans are actually able to get all the nutrients they need from plants. Except for B12, which I'll explain soon.
Veganism has been around for decades and there are people who have been vegan and healthy for decades. Plant-based diets have been looked at by the Dietitians Association of Australia (n.d.) and found to be healthy if planned correctly. There are, however, concerns and things to think about when moving on to a plant-based diet in regards to absorption, availability and more. In this post I'll cover iron, essential fatty acids, B12, calcium and vitamin D.
I am not a dietitian or a nutritionist and I encourage you to talk to a professional before making changes to your diet. This information is intended to be educational and for general interest only and is not intended to be used as nutritional advice.
Vegans have been found to have higher intakes of iron than non-vegans (Davey et al 2002), while vegetarians have been found to be no more likely to be deficient than non-vegetarians (Saunders et al 2012). However, another study found that although the average intake of iron was over the RDI, many young women were iron deficient (Waldmann et al 2004). Therefore, I think it is something that vegans should be aware of in their diets.
Iron requirements can be higher for people who have absorption problems, don't eat enough vitamin C, are pregnant or menstruating or are athletes. Iron deficiency is common, with 25% of people around the world affected (Saunders et al 2012).
All of the iron that vegans consume is non-haem (Saunders et al 2012). There is a difference between haem and non-haem iron and how much of it is absorbed. Haem iron is found in large quantities in animal-based foods; 55-60% of the iron in animal flesh is haem iron (Iron Disorders Institute 2009). It is absorbed at a rate of “just under one quarter” (Better Health Channel 2011a), possibly as low as between 15 and 18% (Australian Institute of Sport Sports Nutrition 2009). Non-haem iron is found in large quantities in plant-based foods. About 2-8% of non-haem iron is absorbed (Better Health Channel 2011a), although some estimates have it as less than 5% (Australian Institute of Sport Sports Nutrition 2009). Because of this, it is estimated that vegans and vegetarians may have a higher RDI, about 1.8x that of non-vegans and non-vegetarians (Norris 2013; Saunders et al 2012).
*Female here seems to be used to refer to people who menstruate
Some sources of iron for a plant-based diet are listed in the table below. Data for this table were taken from the Queensland Government's (2011) information sheet on Iron.
There are a variety of ways to increase absorption, such as eating food containing vitamin C with meals and cooking your plant foods (Australian Institute of Sport Sports Nutrition 2009; Better Health Channel 2011a). There are also a variety of things that will inhibit absorption, such as drinking tea, wine and coffee with meals, and eating bran or soy (Australian Institute of Sport Sports Nutrition 2009; Better Health Channel 2011a). From this, we can see that plant-based diets definitely contain iron. If you are worried about how much iron you are getting, go to a doctor and ask for a blood test to see. This way you can know for sure and talk about what to do if it's too low or too high.
There are two EFAs that humans need to eat as they cannot produce them themselves; linoleic acid (LA) and α-linolenic acid (ALA) (Saunders, Davis & Garg 2012). These are converted in the human body; LA into arachidonic acid (AA) and ALA into EPA, DPA and DHA (Saunders, Davis & Garg 2012). I'm simplifying the process quite a bit, if you want to know more, check out my references. I've made the diagram below for people who are finding this confusing. I hope it helps.
If you eat too much LA, it can cause the ALA to EPA/DHA/DPA conversion process to be pushed aside in favour of the LA (Saunders, Davis & Garg 2012). Vegans tend to consume more LAs than non-vegans (Saunders, Davis & Garg 2012) and male vegans have lower levels of EPA and DHA (Rosell et al 2005). As EPA and DHA are primarily in marine plants, most vegans are not consuming these directly and have to rely on a conversion of ALA to make them (Saunders, Davis & Garg 2012). But, because vegans tend to consume more LA than ALA, the ALA conversion process is pushed aside in favour of LA to AA production. On top of this, less than 10% of ALA is converted into EPA or DHA (Swanson, Block & Mousa 2012). Why is this a problem? Well EPA and DHA are important for a variety of things, including eye function, brain health, fetal development, cell membranes and lots more (Swanson, Block & Mousa 2012). Luckily, there are ways for vegans to ensure that they are getting EPA and DHA. By far the easiest way is direct supplementation of EPA and DHA, which is in fact recommended (Kornsteiner, Singer & Elmadfa 2008; Saunders, Davis & Garg 2012). Another way is through food. Sources of ALA include canola oil, green leafy vegetables, chia seeds, chia oil and hempseed (Saunders, Davis & Garg 2012). Sources of EPA and DHA are sea vegetables and microalgae (Saunders, Davis & Garg 2012).
Again, it looks as though vegans are able to get everything they need from plants or vegan-friendly supplements. It is important to be aware of the different kinds of EFAs and their sources, regardless of if you eat only plants or include animals in your diet.
Vitamin B12 is essential for proper brain and central nervous system function, DNA synthesis, and cell division (O'Leary & Samman 2010; Zeuschner et al 2012). Vegans have been found to have lower intakes of B12 than non-vegans (Davey et al 2002). High levels of sub-clinical B12 deficiency have been found amongst vegetarians (O'Leary & Samman 2010) and one study found that 50% of vegans were deficient (Zeuschner et al 2012). This is because B12 is found primarily in animal-sourced foods (Zeuschner et al 2012). Nonhuman animals have a bacteria in their gut that synthesises B12, which is then absorbed by them (O'Leary & Samman 2010). There is little evidence to support the hypothesis that there is a reliable source of plant-sourced B12 (O'Leary & Samman 2010; Stabler & Allen 2004), however it seems that further study may be needed. It has been suggested that vegans should rely on fortified products that have B12 added, as well as B12 supplements (Stabler & Allen 2004; Zeuschner et al 2012). As veganism becomes more popular, it is possible that more products will be fortified with B12, reducing the risk of deficiency even further.
For the current RDIs, go here: http://www.nrv.gov.au/nutrients/vitamin%20b12.htm
While there are no plant-based reliable sources of B12, vegans are able to get vegan-friendly B12 in the form of fortified food products (e.g. nutritional yeast and soy milk) and supplements. It should be noted that blood tests for B12 are thought to be not entirely accurate (O'Leary & Samman 2010). If you are concerned, please talk to your doctor.
When you think of sources of calcium, you most likely think of dairy (cheese, milk, yoghurt). There are many different sources of calcium however. Below is a table of various plant sources of calcium.
Calcium is important for teeth, bones, blood clotting and muscle and nerve function. It is estimated that less than half of all Australians get the daily recommended amount of calcium (Osteoporosis Australia 2013). The RDI for calcium is shown in the table below.
*Female here seems to be used to refer to people who menstruate
Things that can lower the amount of calcium in your bones include smoking, high salt diets, low levels of vitamin D, low body weight, high fibre diets, low levels of physical activity and high alcohol and caffeine consumption (Better Health Channel 2011b). Phytates, which are in some cereals and brans, can lower the absorption of calcium from foods that they are eaten with (Osteoporosis Australia 2013). Oxalates, which are in foods like spinach and rhubarb, lower the amount of calcium that is absorbed from the food that they are from (Better Health Channel 2011b; Osteoporosis Australia 2013). High intakes of animal protein and fat also seem to be linked with bone loss (Ho-pham et al 2012).
It has been recommended that vegans (where possible) buy fortified non-dairy products due to their higher calcium content (Lightowler & Davies 1998). Many studies have indicated that there is a lower intake of calcium amongst vegans and some have suggested supplements, especially for children who are at a higher risk (Ambroszkiewicz et al 2010; Davey et al 2002; Kohlenberg-mueller & Raschka 2003; Waldmann et al 2003). This is definitely something that vegans need to be aware of.
Vegan calcium supplements are available if you've consulted with a professional and they have recommended that you take that route. Two brands that I know of are DEVA and Green Nutritionals.
From this, we can see that vegans are able to get all the calcium they need from plant and vegan-friendly sources. With more than half of Australians getting less than the RDI this is a topic for everyone to be aware of.
There are two kinds of Vitamin D that are utilised by the human body; D3 and D2. D3 is synthesised in the skin of human and nonhuman animals, and is present in foods created out of animals (Nowson 2012). D2 is found in small amounts in very specific foods; UV exposed yeast and fungi, including some specially-grown mushrooms (Australian Mushroom Growers 2013; Nowson 2012). Vegans have been found to have lower levels and/or intakes of vitamin D when compared to non-vegans (Davey et al 2002; Ho-pham et al 2012). However, only about 5-10% of vitamin D is obtained from food; the rest most people seem to get from sun exposure (Nowson et al 2012). It is estimated that around 31% of Australians are not getting enough vitamin D (Nowson et al 2012).
It is important to make sure that you're getting enough vitamin D as it helps with bone health and muscle function (Nowson 2012; Nowson et al 2012). If you're someone who doesn't go out in the sun a lot, or covers up when they're out, you may have to take a supplement. Deficiencies are especially common during winter when people are rugged up and trying to stay warm indoors; I had a vitamin D deficiency last winter. Luckily, there are a variety of vegan supplements available. It has been suggested that D3 is better than D2 as it is more effective at raising the levels in the blood (Tripkovic et al 2012), however this is something that you should talk to your doctor about. There are both vegan D3 and D2 supplements and I personally supplement with D2.
Therefore, vitamin D is something that all Australians need to keep an eye on. It can be obtained by getting enough careful sun exposure (Stalgis-Bilinksi et al 2011) or through the use of supplements or a combination of both. Thus, vegans are able to get all the vitamin D they need so long as they are careful.
Wrapping it up
So as you can see from the above, vegans have ways of getting iron, essential fatty acids, B12, calcium and vitamin D. Even if you're not a vegan, hopefully you've learned something that can help you with your own diet. If you're not sure if you're getting enough of these, please contact a nutritionist, dietitian or doctor as soon as possible. I personally try to get myself tested for B12, vitamin D and iron once a year to ensure that I am healthy. I urge you to be careful with supplements as it is possible to get too much of a good thing and harm yourself. Below are some links for you to find professionals to talk to.
This article originally appeared on Keira's website.
Keira Edwards-Huolohan is a recent Sociology graduate. In 2013, Keira completed their Honours thesis, titled "Consumption ethics and poverty: What do vegans do to maintain a commitment to veganism when financially challenged?". They've been vegan since January 2010.
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