Protein, protein protein it seems to be the wonder macronutrient (macro=large so a nutrient we need in larger amounts) that pops up everywhere when people talk about nutrition, but what about in cancer? In this blog (my 40th BLOG!) We’re going to go through, why you need protein, the different sources, what is the connection between IGR-1, cancer and protein and what you need to know if you have cancer.
What is protein anyway?
Protein is made of single units called amino acids, there are 20 different types of amino acids. Different chains of amino acids create different type of proteins.
9 amino acids are ‘essential’ which means they cannot be made in the body so must come from food.
Essential amino acids (1)
Histidine
Isoleucine
Leucine
Lysine
Methionine
Phenylalanine
Threonine
Tryptophan
Valine
You may already know that protein is essential for helping the body to grow and repair but it is also needed for many different functions such as making hormones and some neurotransmitters. It also a source of energy providing 4kcal per gram of protein.
Protein sources
Protein is found in meat products, plant-based food and dairy products.
Meat and dairy products: chicken, red meat, milk, cheese, yoghurt, eggs
Plant-based products: tofu, soya, beans, pulses, legumes, nuts, seeds
You can see from the image above that the meat-based sources tend to have higher amounts of protein compared to plant-based sources. The other difference is that meat, dairy and eggs contains all amino acids and are described as ‘complete proteins’ however plant-based sources of protein do not contain all the essential amino acids. So, does that mean these sources foods are inadequate sources of protein? No, it doesn’t, you just need to make sure you are including lots of different types of plant-based protein to get the all the essential amino acids.
Should I be eating more meat products?
For cancer prevention it is recommended that you include a mixture of plant-based proteins like pulses and beans and limit your red meat to 3 portion a week and to avoid processed meat. If you want to find out more about red meat and processed meat this read my blog
So how much protein do I need?
Protein requirements are calculated based on a number of facts such as you weight, gender, activity level and whether you are unwell. During active cancer treatment (chemo, radio etc) you may need more protein (1.0-1.5g protein per Kg) because your body requires more nutrition to cope with the demands of treatment. Without increasing your energy and protein intake you risk losing weight and muscle and becoming malnourished. When you stop active treatment or recovered from surgery, you can return to a normal protein intake (0.8-1.2g protein per kg).
An oncology Dietitians can calculate your protein requirements taking into considering all of these factors and can assess your protein intake.
Insulin-like growth factor-1 (IGF-1) and high protein intake
Insulin-like growth factor-1 or IGF-1 for short, is a natural hormone in the body that stimulates cells to grow and divide. It is needed in the body for muscle repair and growth. Some research studies have reported that very high levels of IGF-1 have been linked with increased risk of cancer, such as prostate cancer (2) and breast cancer (3). IGF-1 levels are also influenced by several factors which we cannot control too like age and height but also diet and physical activity (4).
Where does the link come with protein and cancer risk? Some research studies have suggested that high protein intakes (particularly from animals and dairy) potentially could stimulate the productions of IGF-1. But the connection between protein and IGF-1 levels is complicated.
A large study in 2014 which had 2 parts: animal study (rodent) and epidemiological study (i.e. a study which measures how often disease occurs in different groups of people and why) attempted to look into this further (5). This study claimed that higher protein intakes was linked to increased cancer risk. However, this was only observed in people 50-65 and those over 65 had a decreased risk which suggests protein is protective for cancer in over 65s (?). The study also didn’t measure some important factors like exercise level, vegetable intake, weight loss and the sources of protein were not specified (only if they had animal or plant sources). This is quite important as we already know that protein from processed meats are linked with increased cancer risk.
Another study looked at prostate cancer and protein intake. They found that men consuming high intakes of dairy protein (more than 30 grams/day) had an increased risk of prostate cancer (6) but recommends larger studies are needed to confirm this association.
So what do I recommended for people with cancer?
The connection between protein intake and cancer is not clear. What we do know is lower protein intakes during cancer treatment can lead to malnutrition and weight loss which can reduce your ability to cope with treatment and delay recovery. During this time, it is a good idea to have a bit more protein but once active treatment has finished to return to a normal protein intake. Looking at your protein sources is a good idea too- try to include a mixture of meat and plant-based sources- but limiting red meat (3 portions a week) and avoiding processed meat.
A detailed dietary assessment can help to assess your nutritional needs and provide you with detailed advice on what protein sources you should be eating. If you want to learn more about how I can help you get in touch!
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