Dietary protein is essential in human health. It has many essential roles in the body, including:
Providing the building blocks for growth and repair of skin, muscles, bones, ligaments etc
Building components of the immune system, such as antibodies
Transporting oxygen and nutrients around the body
Being used to build enzymes and some hormones (eg thyroid hormones)
Regulating fluid balance
Reading this, can you tell when we might need more protein than usual in the course of a cancer diagnosis?
In the process of destroying cancer cells, cancer treatments cause collateral damage to our healthy cells. Repair to those healthy cells requires protein. If surgery is required for any reason, cancer-related or other, then additional protein is required for as long as the medical team say that surgical healing process will take.
Risks of not eating enough protein
Inadequate protein in the diet means that your body may have to break down lean tissue mass for their amino acids (amino acids are the building blocks of protein). This is not a situation we want to be in, as loss of lean mass is associated with poorer outcomes across a range of cancer types (1).
Protein is the most satiating of the macronutrients and can therefore play an important role in maintaining a healthy bodyweight. In fact, a model called the “protein leverage hypothesis” proposes that humans’ drive to consume enough protein is so strong that we will keep eating foods that are lower in protein beyond our energy needs in an attempt to eat enough protein (2). In other words, if someone is eating poor quality ultra-processed food that is high in saturated fat and simple carbohydrates, but low in protein, they are likely to overeat this as their body drives them to try to get more protein. Eating enough high-quality protein avoids the problem.
In clinic, I commonly find that when clients start their day with a high protein breakfast, they experience fewer cravings and can regulate their appetite better across the rest of the day.
Importantly, the research tends to show that consuming enough dietary protein after a cancer diagnosis may reduce recurrence risk and cancer specific mortality (3).
Risks of eating excessive protein
A diet that is very high in protein increases the work that the kidneys have to do in eliminating the products of protein breakdown. High protein diets have been linked to an increased risk of kidney stones (4).
Very high protein diets that are based around animal protein may also lead to a high saturated fat intake, or involve foods such as processed meats which we know are not good for our health. Theoretically at least, an excess of any macronutrient, including protein, provides increased building blocks for cancer cells, so more is not always better!
How much protein is enough?
Outside of active treatment (chemotherapy, radiotherapy or immunotherapy), and for people who are exercising regularly, a daily protein intake of around 1g/kg healthy bodyweight is a good aim. This means that if you weigh 60kg, you should be aiming to eat 60g of protein per day. It is best to spread your protein intake out across your meals, including breakfast.
There are some situations in which higher levels of protein might be required. In active treatment and after surgery, daily protein requirements go up to around 1.2g/kg. After more major surgery types, even higher may be required. One study which looked at people going through chemotherapy for lung, head and neck, and oesophageal cancers which have a high risk of sarcopenia (loss of muscle mass, strength and function) found that daily protein intake during treatment needed to be at least 1.4g/kg for muscle maintenance (5). That would equate to 84g of protein for a 60kg woman. Elderly people with cancer may be at higher risk of sarcopenia and require more protein.
Animal or plant protein?
The table below shows some common high protein foods and their protein content.
Food Amount of protein
Skinless & boneless chicken breast fillet, 100g 31g
Wild sockeye salmon fillet, 120g 30g
Venison steak, 120g 28g
Tinned sardines in water, 90g net weight 19g
Mackerel fillet, 100g 17g
Firm tofu, 100g 13g
2 large eggs 12g
Lentils, 100g 9g
Black beans, 100g 9g
Chickpeas, 100g 8g
Cannellini beans, 100g 7.5g
Houmous, 2tbsp 1.5g
Tahini paste, 2tbsp 1.5g
Flaxseed, 2tbsp 3.4g
Sunflower seeds, 2tbsp 3.5g
Quinoa, 80g 3.7g
Jumbo oats, 40g 4.4g
Greek yoghurt, 100g 3.6g (this is an average value, but my top tip is that Yeo Valley Super Thick Creamy Natural Yoghurt contains 9g of protein per 100g!)
You can see that meat, poultry and fish are more concentrated sources of protein than plant foods, although unprocessed soy (such as tofu or tempeh) is a fairly concentrated source of plant protein.
It is perfectly possible to meet your protein target as a vegan, although it does require some focus, at least initially. Make high protein foods such as unprocessed soy, pulses or nuts and seeds the focus of every meal. Tracking your protein intake for a few days using an app such as Cronometer can be very enlightening!
With animal protein, what you choose and how you prepare it matters. Due to the associations with cancer, I recommend completely avoiding processed meats such as salami, pepperoni and bacon (6). Red meat contains iron and saturated fat which, in excess, have associations with cancer, so I recommend limiting it to no more than once per week. Cooking meat at high temperatures, by barbecuing, grilling, pan-frying or roasting, can introduce potentially carcinogenic substances (7). Although it’s fine to enjoy a barbecue once in a while, slow cooking or stewing are safer options for everyday cooking.
Oily fish (salmon, mackerel, anchovies, sardines, herring, trout) is an excellent source of animal protein that comes with anti-inflammatory benefits. Eggs are also beneficial for many people.
Putting a Plan Together
There are many dietary patterns which are compatible with eating enough protein. The Mediterranean Diet is one of the most studied for its health benefits (including for cancer survivors) and can be a good place to start. In terms of proteins, it prioritises pulses, nuts and seeds which can be eaten daily. Fish and seafood are recommended at least twice per week, with smaller overall amounts of poultry, eggs, cheese and yoghurt. Meat is not eaten frequently.
I’m a big fan of meal planning – it’s a big help in achieving your nutrition goals. When I plan meals for the week ahead, I always start by choosing the protein sources. This ensures that I eat enough protein with every meal, but it also helps me check that I am including plant proteins on a daily basis, oily fish at least twice a week, eggs a few times a week, and perhaps some organic chicken.
Why not take part in Get Me Back’s June challenge and track your protein?
References
1. Chun-Ming Au, P., Koon-Yee Lee, G., Hoi-Yee Li, G. et al. (2021). “Sarcopenia and mortality in cancer: A meta-analysis”, Osteoporosis and Sarcopenia, 7 S1, ppS28-S33. Available at https://www.sciencedirect.com/science/article/pii/S240552552100008X (Accessed 1 June 2023).
2. Hill, C.M. and Morrison, C.D. (2019). “The Protein Leverage Hypothesis: A 2019 Update for Obesity”, Obesity (Silver Spring), 27(8), p1221. Available at https://www.proquest.com/openview/98a5c65654c7390025faa066305c504c/1?pq-origsite=gscholar&cbl=105348 (Accessed 1 June 2023).
3. Rinninelli, E., Mele, M.C., Cintoni, M. et al. (2020). “The Facts about Food after Cancer Diagnosis: A Systematic Review of Prospective Cohort Studies”, Nutrients, 12(8), 2345. Available at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7468771/ (Accessed 2 June 2023).
4. Delimaris, I. (2013). “Adverse Effects Associated with Protein Intake above the Recommended Dietary Allowance for Adults”, ISRN Nutrition, 2013: 126929. Available at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4045293/ (Accessed 2 June 2023).
5. Capitão, C., Coutinho, D., Neves, P.M. et al. (2022). “Protein intake and muscle mass maintenance in patients with cancer types with high prevalence of sarcopenia: a systematic review”, Supportive Care in Cancer, 30(4), pp3007-3015. Available at https://pubmed.ncbi.nlm.nih.gov/34697674/ (Accessed 2 June 2023).
6. Farvid, M.S., Sidahmed, E., Spence, N.D. et al (2021). “Consumption of red meat and processed meat and cancer incidence: a systematic review and meta-analysis of prospective studies”, European Journal of Epidemiology, 36(9), pp937-951. Available at https://pubmed.ncbi.nlm.nih.gov/34455534/ (Accessed 2 June 2023).
7. Jägerstad, M. and Skog, K. (2005). “Genotoxicity of heat-processed foods”, Mutation Research, 574(1-2), pp156-172. Available at https://pubmed.ncbi.nlm.nih.gov/15914214/ (Accessed 2 June 2023).