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Are high protein diets bad for you?

Updated: Jan 20

You may have heard that protein helps build strong bones and muscles and keep those hunger pangs at bay (yay, protein). But you may also have heard people say that too much protein will cause calcium to leach from your bones, cause kidney damage and increase your risk of cancer. Yikes.


Is there any truth to these claims? And how much protein should we be eating? Read on to find out.


Protein and kidney disease. While it's true that people with existing kidney disease do need to limit their protein intake, high protein diets don't actually cause kidney damage in healthy people.


Higher protein intakes may cause the kidneys to excrete more waste products though, so it’s important to make sure you drink plenty of water to replace those extra fluid losses.


Protein and your bones. There has been a theory floating around for years that eating lots of protein reduces bone density by creating an acid load that causes calcium to dissolve from our bones. I know, sounds awful, right?


In reality though, scientific reviews have concluded that higher protein intakes don't actually make bones less dense. In fact, along with getting enough calcium, making sure we eat enough protein is important for building strong bones. Did you know around 50% of the volume of our bones is made up of protein?


Protein and cancer. Eating protein isn’t generally thought to increase the risk of cancer, although the type of protein matters. For example, protein-rich whole grains and dairy products may reduce the risk of bowel cancer, whereas too much red meat and particularly processed meat may increase that risk.


So maybe step away from the cold cuts platter... or at least go for a bit of cheese instead of the salami.

Healthy protein platter

So how much protein should we be having?

See table below for a comparison of protein recommendations


The recommended dietary intake (RDI) seems to be the most commonly cited recommendation for protein. The RDI for protein is based on the minimum amount our bodies need each day to balance the amount of protein coming in to the body vs. the amount going out.

The thing is - RDI doesn’t consider other health or performance outcomes, or how to have a balanced diet with all of the nutrients our bodies need.


Enter the AMDR. AMDR stands for ‘Acceptable Macronutrient Distribution Range’ and refers to the range of protein, fat and carbohydrate we can eat to make sure we get enough vitamins and minerals and reduce our risk of disease.


When you compare it to the AMDR, you'll see that the minimum RDI for protein is actually very low - well below the lowest AMDR level.


When it comes to fuelling exercise performance and recovery, the International Society of Sports Nutrition (ISSN) also recommends higher protein intakes for exercisers (including us weekend warriors!) who want to optimise their lean muscle. Even higher intakes may be needed to maintain muscle in older people or people who are restricting their calories.

Recommended protein intakes

Check out our blog: Five things about protein that might surprise you


How much protein is ‘too much’?

Some short-term studies have safely provided very high protein intakes to healthy people following a strength training programme (up to 4.4g protein per kg body weight - more than five times the RDI!).


In saying that, it’s important to think about all aspects of health and wellbeing over the long term. To get all of the energy and nutrients our bodies need and reduce the risk of disease, we need to eat a wide range of healthy foods providing fat, carbohydrate and protein as well as all the essential vitamins and minerals.


Getting 25% of daily energy from protein is a reasonable maximum for most of us, as part of a varied diet. Protein intakes above that may be appropriate for certain people, but this may be best done under the guidance of a nutrition professional.


Are we eating too much protein?

On average, adults in NZ are eating more than enough protein to avoid deficiency (good news!) and we are within the AMDR but on the lower end – around 16.5% of daily calories.


In saying that, we may be eating too much of the wrong kinds of protein for our health. In the last national nutrition survey, nearly a third of Kiwi adults said they ate processed meats like sausages, bacon, salami, ham and luncheon three or more times a week. Ideally, we should only be having these foods only occasionally. (Time to make smarter choices with that cold cuts platter, remember?)


Key takeaways

Protein provides a range of health benefits and intakes well above the minimum RDI help you thrive rather than just survive.


Generally, the claims around protein reducing bone density, causing kidney disease or cancer are unproven. However, variety is the spice of life. Making sure you get enough protein in your diet is important; eating so much of it that you don’t have enough room for other nutritious foods is not a good idea.


High protein meal

This blog is intended for information purposes only. Speak to a registered nutritionist or dietitian for nutrition advice tailored for your specific needs.


References


Cuenca-Sanchez M, Navas-Carrillo D, Orenes-Pinero E (2015). Controversies surrounding high-protein diet intake: satiating effect and kidney and bone health. Advances in Nutrition 6: 260–266, 2015; doi:10.3945/an.114.007716.


Ferraro PM, Mandel EI, Curhan GC et al. (2016) Dietary protein and potassium, diet-dependent net acid load, and risk of incident kidney stones. Clinical Journal of the American Society of Nephrology 7; 11(10):183-1844. doi 10.2215/CJN.0150216


National Health and Medical Research Council, Australian Government Department of Health and Ageing, New Zealand Ministry of Health (2006). Nutrient Reference Values for Australia and New Zealand. Canberra: National Health and Medical Research Council.


Pedersen AN, Kondrup J, Borsheim E (2013) Health effects of protein intake in healthy adults: a systematic literature review. Food & Nutrition Research 2013. 57: 21245 - http://dx.doi.org/10.3402/fnr.v57i0.21245


Rizzoli R, Biver E, Bonjour JP et al. (2018) Benefits and safety of dietary protein for bone health - an expert consensus paper endorsed by the European Society for Clinical and Economical Aspects of Osteoporosis, Osteoarthritis, and Musculoskeletal Diseases and by the International Osteoporosis Foundation. Osteoporosis International 29(9):1933-1948.

doi: 10.1007/s00198-018-4534-5.


University of Otago and Ministry of Health (2011). A Focus on Nutrition: Key findings of the 2008/09 New Zealand Adult Nutrition Survey. Wellington: Ministry of Health.


World Cancer Research Fund (2018). Continuous Update Project: Summary of Conclusions [online] Accessed 03.02.21 at https://www.wcrf.org/sites/default/files/Matrix-for-all-cancers-A3.pdf

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