Meat Vs Plant Protein

Once again I found myself sitting in a café discussing the format for our next AFTP modules with subject experts. This time it is was Caroline Rymer, lecturer and researcher in the School of Agriculture, Policy and Development whose research focuses on animal science (nutrition, health and welfare, and the contribution that livestock make to livelihoods) and Kate Currie, nutritionist with expertise in body composition and nutritional needs of specific populations. Both are module leads for the AFTP, both are fascinating to talk (listen) to and both work best with coffee in a café.

Part way down the second coffee I remembered that not only had the BBC’s Truth about Meat TV series been all over their website but an article talking about investors trying to persuade food companies to move from meat proteins to plant proteins had hit my inbox, in fact we had posted about it on our Facebook page. Now I confess I don’t have a TV so I haven’t actually seen the programmes but I did read the write up and this article in particular interested me, mostly because when I read the comment they had from Australian Ethical Investment which said, according to the article at least, that “the need to change food production models was essential to help limit climate change” I heard myself yelling at the computer words to the effect of “no brown sticky stuff, Sherlock – what do you think we, and the WHOLE INDUSTRY, have been working on for the last 5 years?” And, I might say making some good progress. Now I have written before about Professor Sir John Beddington’s report, The Perfect Storm, which led to the AFTPs being funded, but where I’m heading here is the ensuing conversation that hit me when I asked Caroline and Kate what they thought about the article.

When they stopped spitting feathers at the sensationalism of it all, Caroline explained that to state that intensive farming equals pollution and negative environmental impact is an over simplification. In fact it completely ignored much that had been, and continued to be, done in sustainable intensification to enhance the welfare status of the livestock and to reduce the environmental impact of livestock production. She explained that intensive livestock production uses less plant protein and produces less greenhouse gases and ammonia per Kg of meat produced than more extensive systems of farming. Now our Sustainable Supply Systems was the first AFTP module I worked on and Caroline delivers a couple of video lectures on this so I was pre-armed. I have been to the university’s dairy farm many times and seen this is action but I confess I still couldn’t quite get it clear in my head how large herds of cattle inside could produce less, well, wind, than a few cows scattered across a field. She patiently explained that the animals grow more quickly and the feed is carefully controlled for optimum animal health and meat or milk quality, something that can’t be done with animals in fields. This bit made us smile as we remember the expressions on participants’ faces when we go to the farm during one of the workshops and listen to the farm manager explain the research that goes on to measure the effects of diet on gas emissions – “you actually measure cows farting?” has been asked every year. Well yes we do, but they produce more gas through burping actually.

Anyway, bringing us back to less juvenile thoughts, she went on to explain that all classes of animals, but ruminants especially, use protein sources in their diet that would be inedible or uneatable for humans and convert them into palatable, high quality (in terms of nutrition) human food. Having said that of course, they do consume some food that would be suitable for human feed. This brought us right into Kate’s world.

Now Kate is a nutritionist of some serious repute – she’s worked with professional athletes, the police force, she is an accredited anti-doping advisor, was based at Loughborough before she came (back!) to Reading and she works with “ordinary” people who need her help. But Kate’s passion is body composition and she is leading a number of our modules on lifelong nutrition. One of these covers the needs of special populations, one of which is ageing. I sense a nervousness here in where on earth could I be heading when, in a few short sentences, I jumped from flatulent cattle to an aging population. Age related muscle loss (sarcopenia) and dietary protein requirements, that’s where. So when Caroline said that the animals convert unusable proteins into usable ones Kate nods in emphatic agreement.

Kate explains what Caroline means here – she says that we humans find it quite easy to convert meat protein into human protein because all the composite bits, the amino acids, are already there in the right proportions. They may be in a different order, which makes them cow (or horse) protein but it’s just a question of shuffling the pieces round and the human body is set up to do that. Plant proteins do not have the amino acids present in the right proportions to make human muscle, and in particular the amino acid leucine, which is so critical in sarcopenia, is much lower in plants. She says you would have to eat much, much more to get the optimum effect.

So what’s so important about leucine and why more so as we get older? Well leucine, she explains, kicks starts a gene called mTor and this gene is responsible for muscle growth. She then quotes some age related facts which made Caroline and I wince. So brace yourself. Muscle loss (atrophy) starts at age 24 with ~1% per year. By age 50 this has risen to 5% per year and by age 70 this has escalated to frightening figures of between 10 and 50%.

We worry about the bone health of our elderly relatives and the high risk of fractures when they fall, but she’s right when she said we don’t give much though to why they fall. Muscle loss means that you can’t support your body - your quality of life is seriously affected. “I guess”, Caroline and I said. Then Kate really rammed it home - loss of muscle from the quadriceps (the thighs) means you can’t get yourself off the toilet…..We need our musculature to be as strong as possible, at all ages.

But – it is totally preventable she said. Weight bearing exercises and protein intake are key factors in switching on mTor. She said “basically the weights area of the gym needs to kick out 20 year old males and fill up with +55 year olds and females who actually need it to get healthy and age-defying responses from their DNA”

There is a synergistic effect between weight bearing exercise and leucine uptake in the diet. Our +55 year olds need to be eating 0.6g of protein per kg of body weight with each of four meals a day to offset age-related muscle atrophy. Meat has more leucine than plants but, she said, for those who do not eat meat, the good news is that “if you know enough about your diet you can combine your foods to get the right proportion of amino acids”. For instance, a legume, pulse or bean mixed with a grain does the job perfectly. So if you have beans on toast and add a dhal and rice all is well, jacket and beans however is not so good and soy protein is not a substitute because you are not switching on your mTor. “What about whey protein? “I asked “yes, that’s a rich source of leucine” says Kate, “but it’s an animal protein” Caroline added.

So, yes the environmental impact of livestock does need to be considered really carefully and indeed it is, but it isn’t as simple as switching from one source of protein to another. Relatively poorly informed pressure groups trying to force the hands of those who can influence the diet of the even less well informed through sensationalistic reporting is really not going to help anyone.

If you have enjoyed reading this and would like to find out more about the topics covered here and the wider implications of food security, sustainability and health then visit


Barbara Mason

September 2016


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