Do Vegans Get Enough Protein?

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Do vegans get enough protein?

If you’re reading this and you’re vegan, it’s probably a question you get asked… all the time. Or if you’re thinking of trying a vegan diet, it could be a question that’s playing on your mind. And that would be understandable (it was a concern I had myself before I went vegan) because modern society would certainly have us believe that meat, eggs and dairy must be eaten in order to get sufficient amounts of protein.

But, as ever, I wanted to show you what the scientific literature and best evidence says to provide you with the most trustworthy, unbiased information possible, in order to help you make your own decision based on the facts.

What is protein?

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Proteins are large molecules made up of long chains of amino acids (they’re the ‘building blocks’ of protein). There are 20 different amino acids, and proteins have such a varied role in the body because the amino acid combination, structure, size and shape of the protein all influence it’s biochemical activity.  

Why is protein important?

Every cell and tissue in your body contains protein - they’re fundamental structural and functional elements in every cell. Your body also uses proteins to make enzymes and hormones so they’re also involved in a vast range of important metabolic interactions. So protein is essential for growth, repair, and maintenance of general good health.

UK protein guidelines

The UK government recommend a protein intake of 0.75g of protein per kg of bodyweight per day. This equates to around 45g per day for adult women, and 56g per day for adult men. As protein is required for growth, children and pregnant or breastfeeding mothers need a little more, while overweight or obese adults require less (than the 0.75g of protein per kg of bodyweight per day).

Protein deficiency

Severe deficiency is known as kwashiorkor and it’s only ever really associated with starvation and famine in developing countries. The main characteristic is oedema, where fluid accumulates in tissues, often causing a swollen belly, because of insufficient protein in the blood that helps to draw fluid from the tissues into the blood circulation. It can also cause fatty liver disease and problems with hair, skin and nails.

However, kwashiorkor is practically unheard of in the West. The current average intake of protein in the UK is 88g for men and 64g for women, which actually far exceeds the reference nutrient intake for protein.

Let’s consider a simple meal of baked beans on toast – it contains 29g of protein which is around 60% of your daily recommended intake (19g of protein in a can of beans, and 5g protein in each slice of bread). It also contains all of the essential amino acids (the ones our bodies can’t make themselves) making it a complete protein source. Having said that, you don’t actually need to worry about combining foods to make sure you get all the amino acids, as a varied balanced diet will contain all of them.

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In fact, even if you got all your daily calories from cucumber (this is purely hypothetical as you’d need to eat around 50 cucumbers, which would NOT be fun) you’d be getting around 100g protein (approx. 2g of protein per cucumber).

So you can see just how easy it is to reach these targets on a vegan diet. In fact, it’s difficult not to reach those targets, as long as you’re eating a balanced and varied diet.

So why all the hype?

Well, there are two reasons why eating more protein can be useful:

1.      Higher protein intake (up to a point) can help with short-term weight loss

It has been shown that increasing protein intake can help with weight loss in the short-term. This is for two reasons: Firstly, higher protein foods tend to be more satiating, keeping you fuller for longer – in studies, those eating higher protein diets tended to feel fuller and consume fewer calories (1). Secondly, a higher protein intake during weight loss can help minimise or even prevent associated muscle loss (2). Since lean body mass (muscle) uses lots of energy, retaining as much muscle as possible during weight loss maintains a higher energy expenditure, so metabolism is improved, making weight loss easier and more sustainable.

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However, although it’s widely accepted that high protein diets can help with weight loss in the short-term, high quality meta-analysis studies looking at the long-term effects (1-2 years) show no difference in weight between high and low protein diets (4). In fact, some long-term studies, including a large cohort study with 89,432 subjects, found those eating more protein were more likely to gain weight (5,6). However, this difference was only seen with high consumption of animal protein; higher intakes of plant protein does not seem to have the same effect.

Eating too much protein can even cause weight gain in the short-term too. Every gram of protein contains four calories, which is exactly the same calorie content as carbohydrates. So eating an excessive amount of protein will result in the protein being used for energy, with surplus amino acids simply being excreted, and can therefore lead to weight gain.

2.      High protein diets (again, up to a point) can help to promote muscle growth

Studies show that for strength training athletes, almost doubling the recommended intake of protein can increase muscle protein synthesis (MPS – building muscle). However, increasing the protein intake further, to nearly triple the recommended intake, makes no further difference (7). So, just as with weight loss, the effects are only seen up to a point, after which it makes no difference. It’s also important to point out these studies are looking at strength training athletes, who are weight training quite vigorously and frequently. If you’re not regularly strength training, increasing your protein intake won’t promote MPS.

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As well as making no further difference to MPS, excessive protein intake – especially from animal sources – can affect our health negatively in a number of ways (8,9). So not only is consuming too much protein just a waste of money, it can even damage our health.

What about protein supplements? While they’re by no means absolutely necessary, they can still come in quite handy. That’s because they offer a convenient and quick way to consume a high amount of protein, which can be useful before and after exercise to prevent muscle breakdown and to promote MPS (10). Using vegan protein shakes is no reflection on the ability to consume sufficient amounts of protein on a vegan diet, it’s just a matter of convenience – the same reason that protein shakes are so popular among meat eating gym-goers too. 

 

The take home message

So as you can see, increasing protein intake may help in the short-term for those looking to lose weight, and can help with muscle protein synthesis in weight training athletes. But bear in mind that too much of a good thing is not always healthy, and the kind of levels of intake required to see these benefits are very easy to get from a vegan diet.

As with most topics around nutrition, the advice boils down to a very simple message – just make sure you’re eating a balanced, varied, and ideally colourful diet consisting primarily of loads of legumes, pulses, fruit, vegetables, whole-grains, nuts and seeds. Follow this and the rest usually falls into place!  

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References

1.      Weigle DS, Breen PA, Matthys CC, et al.  A high-protein diet induces sustained reductions in appetite, ad libitum caloric intake, and body weight despite compensatory changes in diurnal plasma leptin andghrelin concentrations. Am J Clin Nutr  2005;82:41–8.

2.      https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4892287/

3.      Schwingshackl, L., & Hoffmann, G. (2014). Comparison of High vs. Normal/Low Protein Diets on Renal Function in Subjects without Chronic Kidney Disease: A Systematic Review and Meta-Analysis. Plos One, 9(5), E97656.

4.      Schwingshackl, L., & Hoffmann, G. (2013). Long-term effects of low-fat diets either low or high in protein on cardiovascular and metabolic risk factors: A systematic review and meta-analysis. Nutrition Journal,12, Nutrition Journal, 2013 Apr 15, Vol.12.

5.      J Halkjær, A Olsen, K Overvad, M U Jakobsen, H Boeing, B Buijsse, . . . A Tjønneland. (2010). Intake of total, animal and plant protein and subsequent changes in weight or waist circumference in European men and women: The Diogenes project. International Journal of Obesity, 35(8), 1104-1113.

6.      Bujnowski, Xun, Daviglus, Van Horn, He, & Stamler. (2011). Longitudinal Association between Animal and Vegetable Protein Intake and Obesity among Men in the United States: The Chicago Western Electric Study. Journal of the American Dietetic Association,111(8), 1150-1155.e1.

7.      Tarnopolsky, M., Atkinson, S., Macdougall, J., Chesley, A., Phillips, S., & Schwarcz, H. (1992). Evaluation of protein requirements for trained strength athletes. Journal of Applied Physiology (Bethesda, Md. : 1985),73(5), 1986-95

8.      Tipton, K. (2011). Efficacy and consequences of very-high-protein diets for athletes and exercisers. Proceedings of the Nutrition Society,70(2), 205-214.

9.      https://www.health.harvard.edu/diet-and-weight-loss/when-it-comes-to-protein-how-much-is-too-much

10. Areta, J., Burke, L., Ross, M., Camera, D., West, D., Broad, E., Coffey, V. (2013). Timing and distribution of protein ingestion during prolonged recovery from resistance exercise alters myofibrillar protein synthesis. Journal of Physiology, 591(9), 2319-2331.