For a lot of people when they are diagnosed with cancer they feel guilty about the choices they have made and worry that they may have contributed to the diagnosis. One of the more common dietary choices raised is protein and a recent study published looked at the evidence from a review of ten studies.

We hear a lot about the link between red meat and cancer. But is it really the meat itself, the protein, or something else? A large review of the research has just taken a closer look, and the results are interesting.

Just a heads up too on the type of research that is done in nutrition, most often its based on people completing questionnaires about how often they ate certain food over the period in question. These studies are generally considered a lower level of evidence but are helpful to see if there is a risk with certain dietary choices.

The other aspect of these studies that is important to understand is that the participants were generally consuming a moderate amount of protein – in the range of 70-129 g a day. These studies are not relevant to higher protein diets, which may create a problem by replacing other nutrients. Plus 70g of protein is equivilant to the amount in 2 eggs (6g each), a small can of tuna (20g)and a small chicken breast fillet. Most animal sources of meat are about 25% protein by weight.

Is protein itself the problem?

The review looked at protein intake (from all sources) and cancer risk. Overall, eating more protein was not linked to a higher risk of cancer. That includes common cancers like breast, colorectal, ovarian, prostate and pancreatic cancer.

So, protein itself doesn’t appear to be the issue. The real story seems to lie in where the protein comes from.

Red and processed meat – why the concern?

When studies zoomed in on different foods, the picture changed:

• Red and processed meat (like bacon, sausages, ham and steak) have consistently been linked with a higher risk of colorectal cancer. This isn’t because of the protein, but other compounds in the meat. For example:
  • High-heat cooking (like barbecuing or frying) creates harmful chemicals.
  • Processed meats often contain nitrates and nitrosamines, which are considered cancer-causing.
• White meat (like chicken or turkey) doesn’t show the same risks – in fact, some studies suggest it may be protective.

Dairy, soy and plant proteins

• Dairy: While some studies have linked dairy (especially milk) to a slightly higher risk of prostate cancer, dairy foods also seem to lower the risk of colorectal cancer – it was thought in the studies because of the calcium content but it may also be because of the benefit of fermented food in the diet.
• Soy and legumes: These plant-based protein foods may reduce the risk of breast cancer, but this benefit is linked to their phytoestrogens rather than the protein itself.

What about IGF-1?

One theory is that high protein intake raises levels of a hormone called IGF-1, which helps cells grow. The theory is that too much IGF-1 may encourage cancer development. While animal and dairy proteins can raise IGF-1 slightly, the changes are small (estimated at about 1% increase in risk for those eating the highest level of protein versus the lowest) and probably not enough to make a big difference for most people.

The bottom line

Protein is important for good health – it’s an essential nutrient. But the type of protein-rich foods you eat matters:

✅ Enjoy protein from a variety of sources – beans, lentils, soy, nuts, fish, chicken, eggs.
✅ If you eat dairy, it may help protect against bowel cancer. Fermented types are better for your digestion.
❌ Limit red and processed meats – save bacon and sausages for the occasional treat, not a daily habit.
🍽 Focus on a balanced diet full of plants, wholegrains and healthy proteins.

It’s not about cutting out protein – it’s about choosing the right sources most of the time.

For more tips on reducing recurrence risk after cancer treatment you may want to read this recent blog What are the best functional foods to reduce your recurrence risk ?

For more guidance on putting together a plan to reduce your risks of recurrence Christine Pope is at Elemental Health at St Ives and is available for both in person and telehealth appointments. For bookings click here.

(1) Kühn T, Kalotai N, Amini AM, Haardt J, Lehmann A, Schmidt A, Buyken AE, Egert S, Ellinger S, Kroke A, Lorkowski S, Louis S, Schulze MB, Schwingshackl L, Siener R, Stangl GI, Watzl B, Zittermann A, Nimptsch K; German Nutrition Society. Protein intake and cancer: an umbrella review of systematic reviews for the evidence-based guideline of the German Nutrition Society. Eur J Nutr. 2024 Aug;63(5):1471-1486. doi: 10.1007/s00394-024-03380-4. Epub 2024 Apr 21. PMID: 38643440; PMCID: PMC11329548.