Thinking Nutrition

Nutrient wins and losses on a plant-based diet

April 05, 2022 Dr Tim Crowe Episode 96
Thinking Nutrition
Nutrient wins and losses on a plant-based diet
Show Notes Transcript

Plant-based eating is on-trend and has been for some time. Fuelled by health, environmental and ethical personal choices, we are seeing more people than ever adopt this way of eating. But there is no one ‘right’ way to eat. And even within a framework of ‘mostly plants’, it is possible to do it well and not so well. In this podcast, I’ll look at the latest research comparing different types of plant-based diets to one that includes meat and see how they compare on the nutrient wins and losses scoreboard.

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Plant-based eating is on-trend and has been for some time. Fuelled by health, environmental and ethical personal choices, we are seeing more people than ever adopt this way of eating. But there is no one ‘right’ way to eat. And even within a framework of ‘mostly plants’, it is possible to do it well and not so well. In this podcast, I’ll look at the latest research comparing different types of plant-based diets to one that includes meat and see how they compare on the nutrient wins and losses scoreboard.

Vegan and vegetarian diets are definitely ‘on trend’ with these two terms the most popular searched ‘diets’ on Google in the last two decades. And the word diets here also encompass ‘way of eating’ and not just weight loss. Both these diets fall under the umbrella of ‘plant-based’ which isn’t always a helpful term as it doesn’t tell you what foods it may include outside of pure plants as some animal-based foods can be eaten on occasion and a person still consider themselves plant-based. But that aside, a plant-based diet has a lot going for it on the health front with such diets linked with a lower risk of obesity, type 2 diabetes, heart disease, and some types of cancer as well as increased longevity.

A vegan diet is one of the many popular types of vegetarian diets. It is one that is easy to define too with only plant foods eaten and dairy, fish, eggs and meat off the menu. Some people following a vegan diet may even exclude honey because it is a product of an animal, but I’m not going down the rabbit hole debate in this podcast.

For those contemplating a vegan-style diet, it pays to be well prepared to ensure you meet all your body’s nutritional needs. The good news about a vegan diet is that with good planning, it can meet the nutritional needs of almost anyone. 

But taking a step back to more ‘plant-based’ diets in general, how do they fare as far as overall nutrition goes? And what sort of shortcomings could they have for people to be aware of to help them circumvent it?

While plant-based diets are considered healthier, they need to be balanced and diverse to provide the right amount of nutrients daily required for a healthy life. Previous scientific reviews into this topic have indicated that people who follow a vegetarian or vegans diet may risk vitamin B12, vitamin D, iron, zinc and calcium deficiency as these micronutrients can mostly be found in animal foods or have a lower bioavailability in plant foods. Additionally, the intake of longer-chain PUFAs such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) which are mainly present in fish and seafood is commonly inadequate in people following mostly plant-based diets.

So, the latest step in looking at how a whole range of diets that fall under the umbrella of ‘plant-based’ fare as far as nutrient needs go has just been published. It was a systematic review that included 141 observational and intervention studies from Europe, South/East Asia, and North America. So, it had a more global flavour to the study.

In all cases, the participants in each study were voluntarily following a self-selected diet so they inserted their own definition of what ‘plant-based’ meant for them. Studies on highly restrictive plant-based diets such as raw food diets were excluded, as were diets designed to reduce specific non-communicable diseases. All participants were 18 years or older, and women who were pregnant or lactating, people with specific diseases, and athletes were excluded. So, the study was mostly about the general healthy population and what they were eating. And I’ll link to the study in the show notes. https://pubmed.ncbi.nlm.nih.gov/35010904

In the study, most of the diets that people labelled as ‘plant based’ were vegetarian or vegan. The comparison diet in the studies were people who included meat in their diet.

First protein. Protein intake was lower in vegans and vegetarians compared to meat eaters, but was well within the recommended intake levels. This is a pretty well-known finding and it doesn’t mean that a plant-based diet is protein deficient, only that if you are following a plant-based diet and have higher protein needs such as an athlete in training, then you may need to pay more attention to this. And check out my prior podcast episode 74 where I look more closely at plant protein and muscle gains in athletes.

Vitamin B12, vitamin D, iron, zinc, iodine, calcium and bone turnover markers were generally lower in people following plant-based diets compared to meat-eaters. And it was people following a vegan diet who had the lowest vitamin B12, calcium and iodine intake, and also lower iodine status and lower bone mineral density. And while a vegan diet was very favourable for its fibre, what were classed more broadly as a vegetarian diet, had a higher chance of being lower in fibre which was a similar case to the diets of meat eaters. 

But if you look further at meat eaters, it wasn’t all smooth sailing. They were at risk of inadequate intakes of fibre as I mentioned but also polyunsaturated fatty acids, folate, vitamin D, vitamin E, calcium, magnesium, and α-linolenic acid (which is an essential omega-3 fatty found in many plant foods),. So, all dietary patterns had evidence of nutrient inadequacies.

None of these findings I’ve covered means that every person following each diet had the same nutrient profile. Only that on average, some nutrients were more likely to be well represented or less common in certain dietary patterns.

And that’s an important point because sugar is 100 percent vegan, but if your version of a vegan diet was full of highly processed foods and loads of added sugar, then you can’t really expect that great health outcomes. And that was the clear, but very unsurprising finding, of a recent observational study on plant-based dietary patterns and health where plant-based diets were grouped into ‘healthy’ and ‘unhealthy. 

Here, a 'healthy' plant-based diet featured lots of wholegrains, fruits, vegetables, nuts, legumes, vegetable oils, and tea and coffee and this was linked to much more favourable outcomes on the risk of earlier death and the risk of cardiovascular disease compared to people eating an 'unhealthy' plant-based diet which featured lots of fruit juices, sugar-sweetened beverages, refined grains, and sweets and desserts. And I’ll link to the study in the show notes. https://pubmed.ncbi.nlm.nih.gov/34379193

Yes, the findings here pretty much state the obvious, but it is an important signpost to not get sucked into plant-based marketing spin of foods that are still pretty damn average in their nutritional merits.

Nutrients to watch out for

So, let’s give a quick summary of the nutrients to look out for if you’re following a predominantly plant-based diet that is aligning more closely with a vegan diet. Four important ones are iron, vitamin B12, calcium and omega-3 fatty acids.

Iron in plant foods is not as well absorbed as that found in animal foods. So, people following a vegan diet need almost double the recommended amount of iron compared to non-vegetarians. Good plant sources of iron include foods such as legumes, tofu, nuts and seeds, quinoa, dried fruits and dark green leafy vegetables. Having a vitamin C rich food such as citrus fruits or broccoli with meals will help improve iron absorption.

Vitamin B12 is a significant nutrient of concern for people following a vegan diet as it’s generally found only in animal foods. Vitamin B12 is important for nerve transmission and blood cell formation. Eating foods that are labelled as fortified with vitamin B12 such as some soy milks is one way to get B12. Or give close thought to taking a vitamin B12 supplement and have your doctor keep an eye on your blood levels.

Calcium can be another nutrient of concern because of the absence of dairy foods in a vegan diet. Calcium is important not just for bone health, but for vascular, muscle, and nerve function. Good plant sources of calcium include calcium-fortified soy or almond milk, tofu set with calcium sulfate, almonds and green leafy vegetables.

Omega-3 fatty acids are essential for our immune system and because we cannot make them, they are required in our diet. With fish off the menu for a vegan, then plant sources such as walnuts, flaxseeds, canola oil, chia seeds or soybean oil can go some way to meeting a person’s needs. You could also consider taking a vegan omega-3 supplement which is sourced from marine algae rather than fish.

As with any dietary pattern, a plant-based diet can be healthy or unhealthy depending on the types of nutrient-rich or nutrient-poor foods eaten. With some awareness and good planning, a plant-based diet can meet a person’s nutrient needs throughout their life and give a host of health benefits to boot.

So that’s it for today’s show. You can find the show notes either in the app you’re listening to this podcast on if it supports it, or else head over to my webpage www.thinkingnutrition.com.au and click on the podcast section to find this episode to read the show notes.

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I’m Tim Crowe and you’ve been listening to Thinking Nutrition.