Can plant protein help you live longer?

Welcome to the fifteenth episode of Vegetarian Health and Longevity from Hurry The Food Up and Sports Nutritionist James LeBaigue.

A new study in February 2024 suggested that plant protein could help you grow older in a healthier fashion, reducing the risk of certain diseases and the risk of mental and physical deterioration.

In today’s episode I’m going to give you the real truth behind this study, whether its results are something that you can believe and and what you need to be aware of before you start telling your best friend over coffee to start eating more plants.

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The Battle of Plants vs Meat Continues – But We Like Facts

While there’s a constant battle between plant-based advocates and meat eaters, especially when it comes to protein, I like to take a more balanced approach.

I want to use evidence from both sides and see what the research is actually saying about different foods, diets, weight loss strategies, and whatever else it looks at.

There is an overwhelming amount of data to support eating lots of plants in a diet.

They provide fiber, which is incredibly helpful regardless of your goal because it can help reduce the risk of various problems such as gastrointestinal tract cancers and heart disease.

Plants are full of micronutrients which our bodies love, and components like polyphenols and antioxidants get a lot of press because of their health-promoting effects too – and these are well founded.

So there is definitely benefit from certain components of plant-based foods and this is indisputable, but protein is often a sticking point.

Can plant protein actually be good for you, or could it even be better than animal protein?

The Importance of Protein in Healthy Aging

Now these are big wide questions that really aren’t defined enough.

Is it better for health? Is it better for athletic performance? Is it better for building muscle?

Well, today I’d like to narrow it down to the topic that was the focus of a new study in February 2024, and that was on the effect of protein on healthy aging in middle-aged female nurses in the US.

It’s a fascinating study, and it investigated whether protein intake could influence whether females aged without developing chronic disease or deterioration in their mental and physical capabilities.

I’m gonna run through this study with you now but for anyone who is interested, I’ve linked the study in the show notes so you can access it yourself too.

Now this study has caused quite some commotion online because of the results that it showed, and I can see why.

The short, headline message is that dietary protein, especially plant protein, seemed beneficial for healthy aging in middle-aged females.

But as with most things, there’s a little bit more to this and it requires a bit of exploration into it to really understand the results.

Study Design and Participant Details

How many people were included in the study, and was it reliable? We need to start with the design of the study and the number of participants included.

The most reliable studies are usually randomized controlled trials, or RCTs. In an RCT, participants are randomly split into groups to test an intervention against a control, aiming for standardized and unbiased results.

Sometimes, participants may even switch groups during the study to further validate the findings. For instance, let’s consider a study on protein intake.

Imagine we have a group of people who primarily get their protein from meat. We would measure various health parameters of these individuals and then randomly split them into two groups.

One group would continue consuming mostly meat protein, while the other group would switch to predominantly plant protein for a set period.

After this period, we would re-test their health parameters and compare the results within each group and between the two groups.

These are considered the most reliable studies because, when performed correctly, researchers can control things like food intake and other factors that might affect the results.

The downside to these RCTs is that they are often expensive and difficult to run, and the participant size is often smaller meaning the results are harder to generalize to the wider population.

Non-Randomized and Observational Studies

Next up you have controlled trials, such as non-randomized controlled trials, which do not involve this random allocation.

Participants might self-select into intervention groups based on their preferences or other criteria. So this might be that individuals who prefer plant-based diets might choose to be in the plant protein group, while those who prefer meat might choose the meat protein group.

This self-selection introduces potential biases, as the two groups may differ in significant ways beyond just their protein sources, such as in their overall health, lifestyle choices, or socio-economic status.

After this, you have observational studies, which is what the study we’re talking about today was.

The study observed and collected data on dietary habits and health outcomes without any sort of manipulation or testing; so it’s based on historical data.

The study first collected data in 1984 and followed participants until 2016, so it spanned around 30 years.

In 1984, 81,702 participants returned the initial questionnaire, but the end study participant number was 48,762.

This is because people were excluded from the study at the start and end, for example, for not being suitable based on the study criteria or not returning the final questionnaire.

Participant Numbers and Data Reliability

But over 48,000 participants is a pretty huge number of people.

This sort of number for a study is fantastic because it means you’re more likely to get reliable results simply because of it strengthening the data; if more people have the same outcome with whatever pattern it is you’re investigating, the more you can be sure of the results.

Now these sorts of studies, where you simply look at data and outcomes and try to find correlations, can be difficult to manage because you have to factor in things which might influence the outcome, and we call these confounding variables.

For example, in an imaginary study, those who ate a higher amount of plant protein might be less likely to smoke compared to those who ate more animal protein, and if this isn’t accounted for then it might mean that plant protein seems unfairly positive because smoking is causing a lot of health problems that are seen, rather than the animal protein.

In this study, the researchers accounted for variables such as smoking, exercise, body weight, physical activity level, and medication use to try and reduce their influence, and focus on their main objective which was the effect of consuming protein in middle-aged females on healthy aging.

They defined this healthy aging as being free from various diseases such as cancer, type 2 diabetes, heart bypass surgery or heart attacks, strokes, and a couple of others.

Defining Healthy Aging

As well as that, it also meant being free from mental or physical impairment, based on different scoring systems and self-reported abilities.

Overall, I thought this definition was sound and a reasonable way to measure how well someone aged.

What were the results of the study? So let’s go through the results.

The first time the researchers ran their statistical tests they found that total protein and animal protein were associated with decreased odds of healthy aging, while plant protein was significantly associated with improved odds of healthy aging.

They then adjusted for BMI, which means they specifically took BMI into account to ensure that participants’ BMIs were not influencing the results.

As it turns out, it was, because after that, total protein and plant protein were both associated with improved odds of healthy aging, and animal and dairy protein were not positively or negatively associated with healthy aging at this stage – they were neutral.

Comparing Protein Sources

After further adjustment, the researchers compared plant and animal proteins directly, meaning they isolated the individual protein sources to try to understand their roles in healthy aging.

Plant, animal, and dairy protein were all associated with improved odds of healthy aging, with plant protein showing the strongest benefit.

And this is the headline takeaway, that all these types of protein were associated with improved odds of aging healthily but plant protein showed the strongest benefit, followed by dairy protein.

However, there was some nuance in the results. Healthy aging was that term that we defined earlier, and is the umbrella term, which meant being free from various diseases as well as not having any mental or physical limitations.

The researchers also tested the individual components of healthy aging and the effect of protein on these, so being free from chronic disease, as well as mental or physical limitations.

In terms of chronic disease risk, they found that total protein intake and animal protein were significantly associated with a higher risk of chronic disease in all models.

However, dairy and plant protein were associated with higher odds of absence of chronic disease.

Plant and animal protein were associated with a lower risk of physical limitations, and only plant protein was associated with higher odds of having good mental status in later life.

So, in short, plant protein seems to be associated with a higher likelihood of healthy aging and had stronger associations across the different health domains compared to dairy and animal protein.

Study Limitations

What were the limitations of the study? So before we go on to the practical takeaways from this study, it’s worth talking about the limitations, because I like to be balanced here.

Firstly, it’s that the study cohort was middle-aged females in the US who were mostly white.

While I know a lot of our listeners will fit this category and so the results might be applicable, caution always has to be applied when suggesting this would work for someone else.

For example, the results might not be the same in females of Afro-Caribbean or Latin heritage. They might be, and my guess is that they would be, but it just means we should take it with a pinch of salt.

Secondly, the study relied on self-reported food intake as well as self-reported questions around mental and physical health.

These can lead to unmeasured confounding, which means the results might be influenced without the researchers being able to control for this.

It’s well known in nutrition studies that people can dramatically under or overestimate their food intake, and this could mean the results aren’t super reliable.

However, the researchers used food frequency questionnaires which are a validated method for this type of study, and I think they probably did as much as possible to manage this.

Protein Intake Recommendations

Thirdly, it’s that there isn’t really a value for protein intake in these study results based on grams of protein per kg of body weight per day that I can easily give you.

You might know this already, but at Hurry The Food Up we like to base protein intake on this because it means our meal plans and recipes can follow the latest research.

This means I can’t give you any exact values of how much protein you should eat per day according to the study, only that an increased amount of protein over the 0.8 g of protein per kg of body weight minimum daily recommendation seems to be beneficial for healthy aging.

All these limitations are important to consider but my overall feeling towards them is that they don’t significantly affect the results in a negative or positive way and I think the design was robust and we can say that the results are reliable enough to be used for practical takeaways.

Practical Implications

So let’s talk about what the results of this study really mean, and why. The main practical application of this is that plant protein seems to be associated with a higher likelihood of healthy aging, and to a lesser extent dairy protein too.

On top of this, plant protein showed the most benefit in the reduction of the risk of chronic disease, followed by dairy protein, while total and animal protein increased the risk.

This suggests either animal protein, or another factor, is causing the increased risk of chronic disease when animal or total protein intake is considered.

These results mean that recommending someone consumes more protein from plant-based sources compared to animal protein (especially women in mid-life – which was the study cohort) is a potential strategy for increasing the chances of healthy aging and decreasing the risk of developing chronic disease.

However, this does not categorically mean plant protein is healthier than animal protein or that the results are applicable to everyone, but it does suggest there is a higher likelihood of this.

Why Protein Intake Matters

So what I would take away from this study is that if I were eating a large amount of animal protein I would start trying to transition to consuming more plant-based protein, and if I were consuming lots of dairy protein I would try to make a bit more of it come from plants instead.

Why does protein intake seem to benefit healthy aging?

Now if you’re anything like me, you might be thinking why, why is the effect seen in this study? In my mind, the biggest potential mechanism is probably the reduction of sarcopenia, which is the medical term for the loss of muscle mass as we age.

Dietary protein stimulates muscle protein synthesis, which is the term given to the process whereby new muscle tissue is generated.

This is really important as we age because it counters the effect of sarcopenia. By doing this and ensuring muscle protein synthesis stays high, it helps to reduce the risk of falls through better mobility by having more muscle.

It means someone can stay more physically active which is incredibly beneficial for so many reasons.

It can improve someone’s basal metabolic rate due to higher muscle mass, and it means a lower likelihood of obesity, reducing the risks associated with that.

Nutrient Contributions from Plants

I’ve talked about this before, but staying active throughout your life and even more so in later life is so important, and dietary protein is a key contributor to that.

My other suspicion is due to plants containing nutrients such as antioxidants, polyphenols, and fiber. So if someone eats more protein from plants, they’re likely consuming more of those nutrients which will lead to better general health.

The researchers did actually do statistical tests where they accounted for fruits and vegetables, and the positive benefits seen for plant protein were reduced but were still significant, so it seems that this is just a contributor and not the only cause.

Honestly, I think overall there are probably lots of reasons why consuming more plant protein improved the odds of healthy aging in this study, and hopefully more research in the future will look into this topic further.

It’s a super interesting area that has the potential to really influence someone’s health in their later years, and given we can’t turn back the clock, it’s crucial to get it right at the time.

I hope you found this episode interesting, if you did please to remember to give this a quick review on whatever platform you’re listening on, and we’ll speak again soon!

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