Plant-based diets - get the low down

Over recent years there has been a massive rise in the number of people choosing to adopt plant-based diets for a number of reasons; sustainability, animal welfare, taste preferences and perceived health benefits. “Veganuary” reports signing up just over 400,000 people this January, 150,000 more than 2019 (1). However, veganism is only one type of plant-based diet, the name actually encompasses a number of different dietary patterns. 🌱

Others include;

✔️ Lacto-ovo vegetarian; which incorporates dairy and eggs but no meat or fish.

✔️ Ovo vegetarian; includes eggs but avoids other animal foods, including dairy.

✔️ Lacto vegetarian; eats dairy but excludes eggs, meat and fish.

✔️ Pescatarian; includes fish but no meat.

✔️ Flexitarian/semi-vegetarian; consumes meat occasionally.

Essentially, as long as the majority of the diet is made up of plant-derived foods (like fruits, vegetables, grains, beans, lentils, nuts and seeds), the rest is up to the individual; there is no one ‘right’ way to eat.

All well-planned, balanced and varied plant-based diets can be very healthy and support an individual throughout their life (2), providing higher amounts of fibre and phytochemicals (beneficial plant chemicals) and lower amounts of saturated fats than a ‘typical’ western diet (3). As a result, plant-based diets have been associated with improved health outcomes including lower levels of obesity, reduced risk of heart disease and lower blood pressure (2-6).

There are however a few nutrients that those choosing to minimise or avoid all animal-derived foods (an exclusively or very nearly exclusively plant-based diet) need to be particularly mindful of (2-3). A recent survey of 1000 vegans and vegetarians across the UK, found that 28% and 13% respectively had been diagnosed with a nutrient deficiency (7). Sadly, advice on diet and nutrition can often come from unreputable and non-evidence-based sources, so few were aware of the need to pay particular focus to these nutrients.

Let’s look at each one in turn:

📌 Vitamin B12 - needed for healthy nerves, red blood cells and building DNA, with prolonged deficiency leading to serious health problems. In over 60 years of vegan experimentation, a few plant foods, such as spirulina and dried nori, have been proposed as vegan sources of B12, however NONE have proven themselves to be capable of supporting optimal health (8). Vitamin B12 is produced by bacteria and found in significant amounts only in animal-derived foods (9-12). So, for those not consuming meat/fish/diary/eggs, you need to attain it from fortified plant-based products or a supplement.

The British Dietetic Association recommends either; (3)

✳️ Eating fortified foods at least twice a day, aiming for a minimum daily intake of 3mcg (micrograms) OR

✳️ Taking a 10mcg supplement daily OR

✳️ Taking a 2000mcg supplement weekly

As the adult requirement for Vitamin B12 is 1.5mcg per day, you may wonder why the above amounts are so high. Put simply, Vitamin B12 absorption significantly decreases as intake increases, therefore the less frequently you consume B12 the higher the total needs to be to give the desired absorbed amount (13-14). If you choose a supplement, it’s best to try one that doesn’t also contain vitamin C and copper as these degrade Vitamin B12 (15). Supplements that are either chewable or dissolve under the tongue may also be best, as it's been shown that some people do not absorb the B12 from pills swallowed whole very well (16).

Fortified foods include; some milk alternatives, vegan spreads, nutritional yeast flakes, yeast extracts and breakfast cereals. If having fortified foods, leave a few hours in-between each sitting to maximise absorption from each product. Cooking and exposure to fluorescent light can also impair Vitamin B12, so it’s important that food products are stored carefully.

📌 Iodine – generally unknown and under-appreciated, yet vital for many important roles in the body; the development of a baby’s brain during pregnancy and early life and the formation of thyroid hormones, which control functions, like our metabolism, body temperature and pulse rate (17). Dairy foods (due to iodine-fortified feed and iodine-containing sterilising compounds), as well as white fish are the biggest food sources (9-10).

Unfortunately, the iodine content of plant foods varies and may be low, secondary to the varying amounts in our soil (17), meaning there is potential for deficiency in the diets of those who don’t consume the above foods. The one exception is seaweed but while one and a half sheets (4g) of nori may provide the recommended daily amount (18), levels of iodine in seaweed vary massively and can be excessively high (particularly kelp). As too much iodine is as problematic as too little, it’s advised not to consume seaweed more than once a week (especially during pregnancy) and actually not using seaweed at all as an iodine source is preferred. Instead, you could consider taking an iodine supplement; 75-150mcg 3-4 times per week (10). Please check with your GP first if you have thyroid disease or have had low iodine intake over many years. Also ensure iodine is in the form of “potassium iodide” or “potassium iodate” and doesn’t exceed the daily adult requirement of 150mcg (17).

Although the fortification of milk-alternatives continues to evolve and improve, many are still not fortified with iodine, so have a look at the label. Examples of fortified milk include M&S soya & almond, mighty pea, Oatly. In some countries, iodine is added to table salt to give “iodised salt” but this isn’t widely available in the UK (17). Furthermore, as many need to reduce their salt intake for health reasons, it’s not a reliable, healthy way to increase iodine intake.

NB: Organic milk contains less iodine than conventional, believed to be linked to dairy cows receiving less iodine containing supplementary feed and the feed containing more items that inhibit iodine availability (19).

📌 Iron – I’m sure you’ve heard of this mineral, but did you know that iron deficiency is the most common and widespread nutritional disorder in the world? It’s the only nutrient where deficiency is significantly prevalent in both developing and developed countries (20).

As iron is vital for the formation of haemoglobin, which carries oxygen around our body, we need to ensure we eat plenty of iron-containing foods. Luckily there are lots of plant-based sources available for those eating little to no animal foods. These include beans, lentils, dried fruit, nuts, seeds, tofu, wholegrains, fortified breakfast cereals and green leafy vegetables (21).

On the downside, the type of iron found within plants and eggs (non-haem iron) is not absorbed as efficiently as that found in animal foods (haem iron) (22). This led the United States/Canadian Institute of Medicine to advise that the iron requirement for vegetarians should be 1.8 times higher than that for non-vegetarians/vegans (23). Nevertheless, the strength of the evidence used to make this recommendation is unclear and the UK doesn’t appear to have made a similar statement (24).

We’ve long known that certain factors help to increase iron absorption (e.g. vitamin C) or reduce absorption (e.g. calcium, phytates in wholegrains and legumes, tannins found in tea and coffee) when we look at single meals on their own. However long-term studies have not shown these to change iron status overall (22). Therefore, the importance of a healthy balanced diet that includes a variety of foods containing iron may be more important than focusing on particular inhibitors or enhancers of iron absorption.

Iron fortification of white and brown wheat flour (to replace iron lost during processing) is mandatory in the UK.

📌 Calcium – the most abundant mineral in the body. About 99% is found within our bones and teeth helping to keep them strong, while the remaining 1% is located in our body fluids, influencing functions like blood clotting and muscle contraction (9). The recommended intake for adults in the UK is 700mg per day.

For those not consuming dairy, you’ll be pleased to hear that can still get all the Calcium you need from plant-based sources. Fortified milk alternatives, fortified dairy-free yoghurts and calcium-set tofu are particularly good sources. This is because the calcium they contain is absorbed with a fairly similar efficiency to that within cow’s milk (25). 400mls of fortified plant milk can provide around two thirds of an adults recommended daily intake of calcium, while 100g of tofu may provide nearly half (26). It’s really important you check labels though, as some milk/yoghurt alternatives, particularly organic varieties are not fortified with calcium. Tofu packets should state that they are set with calcium chloride (E509) or calcium sulphate (E516). Always give your carton of calcium-fortified plant-based milk a good shake before opening, as the calcium can settle at the bottom (16).

Several plant foods, such as leafy green vegetables, pulses and nuts contain good quantities of Calcium but its bioavailability (how much your body can absorb) is affected by the plants oxalate and/or phytate level (plant substances that inhibit absorption) (25). For example; the amount of calcium that can be absorbed from high-oxalate vegetables; spinach, Swiss chard and beet leaves is very poor and thus these are not seen as good calcium sources. Low-oxalate vegetables like kale, broccoli, okra and pak choi are better options. Other plant sources include dried figs, chia seeds, almonds, tahini, and bread (by law, white flour/bread must be fortified with calcium in the UK, to replace the nutrients lost during processing).

📌 Vitamin D - helps keep bones, teeth and muscles healthy. People regularly say they’re “just topping up their vitamin D levels” whilst lounging in the sun, so I’m sure you’re already aware that our bodies are capable of making vitamin D when suitable amounts of sunlight hits our skin (exposed hands, face and arms or legs) (17). But what does “suitable amounts” mean? In the UK, sunlight is only strong enough to initiate Vitamin D production between April and September, a time where we also need to be mindful of sun safety. Unfortunately, it’s very difficult to get adequate Vitamin D through food sources alone. Liver, oily fish, egg yolks, sun-exposed mushrooms and fortified foods such as some margarines, breakfast cereals and dairy alternatives contribute some, but these are insufficient to keep up Vitamin D levels during Autumn and Winter.

So the Department of Health recommends: (27-28)

💊 People aged 5 and above, should consider taking a daily Vitamin D supplement of 10mcg (micrograms) during Autumn and Winter. The majority should be able to get adequate levels during Spring and Summer so may choose not to take a supplement during these months.

💊Those who don’t go outside much, wear clothes that cover most of their skin, live in an institution or have darker skin should consider a supplement year-round.

💊Children aged 1-4yrs should take a daily supplement of 10mcg.

💊Babies from birth to 1yr of age should be given a daily supplement of 8.5-10mcg (unless they are having more than 500mls of fortified formula milk a day).

The NHS states not to take more than one supplement containing vitamin D (includes cod-liver oil) as you could exceed 10mcg.

N.B. 10mcg is equivalent to 400IU (international units). Vitamin D2 and lichen-derived Vitamin D3 are suitable for vegans (29).

📌 Zinc – needed for a variety of functions; maintaining a healthy immune system, wound healing, proper sense of smell and taste, as well as growth and development during pregnancy and childhood (9). Good plant-based sources include tempeh, wholegrains, nuts, seeds, beans, lentils, fortified nutritional yeast flakes and soya products, as well as meat, milk, fish, eggs if you eat these (30). Zinc is absorbed less easily from animal-derived foods, as absorption is affected by phytates (found in plant foods, such as wholegrains and beans) and high intakes of copper and iron (25). Bioavailability in vegan diets may be as low as 15-26%. As with iron, procedures like milling, sprouting, soaking, and sour-dough leavening can increase the bioavailability of zinc.

📌 Selenium – an antioxidant that plays a key role in reproduction, immune function and thyroid hormone metabolism among other functions (31). The amount of selenium in any given plant food depends on the amount in the soil that it’s grown. In the UK, levels in soil are low. However, the selenium content of Brazil nuts, although variable, tends to be quite high, so two brazil nuts daily may meet your requirement. Additional sources include grains, seeds and other nuts. Selenium is found in smaller amounts in cereals like rice, bread and lentils.

📌 Protein – made up of amino acids, nine of which are classified as essential, meaning our bodies cannot make them and we must obtain them from our diet. It’s a myth that plant foods are completely without one or more amino acids, as all contain at least some of each one (16). However, as animal-derived foods have a similar ratio of essential amino acids to the proteins found in the human body, these foods are often considered to be "complete". With the exception of soya beans, most plant foods like grains, beans and nuts have a lower percentage of at least one essential amino acid, deeming them "incomplete". There used to be the idea of commentary pairings” of “incomplete” plant proteins i.e. eating rice and beans together, to ensure meals contained adequate percentages of each essential amino acid, however, it is now known that this is unnecessary, as the body maintains its own storage supply. Providing a variety of plant foods are eaten across the day and energy needs are met, adequate amounts of all essential amino acids should be obtained.

Plant-based protein-rich foods, include tofu, seitan, tempeh, beans, lentils, seeds, nuts and their butters. Beans, peas, lentils, peanuts and soya foods are the only good plant sources (with a few exceptions) of the essential amino acid lysine, so they're important in a solely plant-based diet. Soya protein also has a high digestibility (>95%), similar to that of animal proteins. Eggs and dairy are also good sources if you eat these. Quinoa and some milk alternatives can also contribute to protein intake. Be mindful of processed meat substitution products, as these can be high in salt and fat, so it is best to use these in moderation.

📌 Omega-3 - the name given to a group of essential fats whose popularity has grown in recent years. Research tends to focus on three of them; Alpha-linolenic acid (ALA), Docosahexaenoic acid (DHA) and Eicosapentaenoic acid (EPA) (32). A lot of the studies investigating their benefits, revolve around the latter two and their connection with functions, such as; brain and eye development and the prevention of chronic diseases.

Our bodies are unable to make ALA, so we must obtain it from our diet. Whilst the body can convert ALA to EPA and DHA, it’s an inefficient and limited process, which may be further inhibited by other dietary factors (26). Unfortunately though, only ALA is present in useful amounts in plant foods; walnuts, pecans, flaxseed (grinding may help absorption), hemp seeds, pumpkin seeds, chia seeds, soya beans, tofu and hemp/walnut/rapeseed/flaxseed oil (34). EPA and DHA are extremely limited in plant foods, as oily fish is their main provider.

Although the relevance of all this is not fully known, everyone agrees that those predominately or completely eating a plant-derived diet, should ensure they include sources of ALA in their daily diet. The UK currently do not recommend a specific daily amount but around one tablespoon of chia seeds/ground linseed or 6 walnut halves daily meets recommendations by European organisations (33).

Our bodies are unable to make ALA, so we must obtain it from our diet. Whilst the body can convert ALA to EPA and DHA, it’s an inefficient and limited process, which may be further inhibited by other dietary factors (25). Unfortunately though, only ALA is present in useful amounts in plant foods; walnuts, pecans, flaxseed (grinding may help absorption), hemp seeds, pumpkin seeds, chia seeds, soya beans, tofu and hemp/walnut/rapeseed/flaxseed oil (34). EPA and DHA are extremely limited in plant foods, as oily fish is their main provider.

⚠️ Final thoughts…a plant-based diet isn’t automatically healthy. Coconut oil (which is high in saturated fats) and maple syrup (which is high in free sugars) are technically plant foods but you wouldn’t want to include large amounts in a healthy diet. Furthermore, with loads of manufacturers jumping on the ‘plant-based’ bandwagon, there’s been a surge in highly processed products available on the market, so be label savvy.


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