New findings shows walnuts may reduce inflammation and risk of colon cancer
New findings published in Cancer Prevention Research show daily walnut consumption may improve markers of systemic inflammation and reduce colon cancer risk. Colon cancer is one of the most common cancers worldwide and accounts for around 10% of total cancer diagnoses.1 Urolithin A (UA), a metabolic byproduct of the plant-derived polyphenols, ellagitannins, found in walnuts, are thought to contribute to these findings.
Researchers at the University of Connecticut analysed the impact of 28g of daily walnut consumption among 39 healthy adult participants, age 50-65, on urinary urolithins and markers of inflammation, immunity and other indicators of colonic health for three weeks prior to undergoing a routine colonoscopy.2 This clinical trial followed a preclinical study by Dr. Masako Nakanishi, an investigator in the Rosenberg lab, who first reported on these effects of walnut consumption on colon cancer.3 In the present study, researchers found that consuming a walnut-containing diet resulted in increased urinary UA levels which were linked to lower levels of several inflammatory markers present in the blood.
In addition, the study found changes in colon polyps that could ultimately prove to be beneficial for preventing the development of some cancers. Urolithins have been studied for their anti-inflammatory properties and may play a role in cancer prevention.4,5 It is thought that higher levels of urinary UA could be responsible for these changes that were observed in polyp tissues, even after a short exposure interval to walnuts.
Dr. Daniel W. Rosenberg, the HealthNet Chair in Cancer Biology and an investigator at the Center for Molecular Oncology at the University of Connecticut School of Medicine, has been studying the properties of walnuts and their anti-inflammatory benefits for more than a decade. “Walnuts are an exceptional source of health-promoting nutrients called ellagitannins. These nutrients, when broken down by the gut microbiome to form urolithin A, are thought to reduce inflammation and may be responsible for reducing risk of colon cancer,” notes Rosenberg.
Beyond their ellagitannin content, walnuts are known for their nutrient composition. Walnuts are the only nut to provide an excellent source of omega-3 ALA (2.5g/oz), which has been researched to support brain health, heart health and more.6 Walnuts also provide 4g of plant-based protein along with a variety of other nutrients in just one handful.7
Reaping the health benefits of walnuts is as easy as incorporating a handful into your meals and snacks. Try some of these recipes to add California walnuts:
Baked Breakfast Walnut Frittata
Ingredients
- 1 tbsp vegetable oil
- 75 g smoked back bacon, trimmed and diced
- 30 g Portabello mushrooms, thickly sliced
- 1 clove garlic, crushed
- 200 g cherry tomatoes, halved
- 75 g California Walnuts, roughly chopped
- 6 medium eggs, beaten
- 50 g reduced fat mature Cheddar cheese, grated
- 1 tbsp chopped flat leaf parsley
Instructions
- Preheat the oven to 180oC, gas mark 4. Grease and line a 22cm square tin with baking parchment.
- Heat the oil in a large frying pan and fry the smoked back bacon, mushrooms and garlic for 4-5 minutes until softened and golden. Add the tomatoes and 50g Walnuts and cook for 1-2 minutes more. Season.
- Transfer to the prepared tin and stir in the eggs. Sprinkle with cheese, remaining 25g Walnuts and the parsley. Bake for 15-20 minutes until golden and set.
- Allow to cool slightly before cutting into 4 squares.
Nutrition
Notes
Smoked Spiced California Walnuts
Ingredients
- 200 g California walnuts
- 1 tbsp extra virgin olive oil
- 1 tsp dried rosemary
- ½ tsp garlic granules
- 1 tsp sweet smoked paprika
- A pinch of chilli flakes
- ¼ tsp sea salt flakes scrunched fine
Instructions
- Toss the walnuts with the olive oil in a mixing bowl. Mix the rest of the ingredients together, then sprinkle over the nuts while tossing them in the bowl so that they get an even coverage.
- Set the air-fryer to 160°C using the ‘Roast’ mode and transfer the coated nuts to the fryer basket. Roast for 6 minutes, giving the basket a shake halfway through.
- Tip the walnuts onto kitchen paper and spread them out into a single layer. Leave to cool completely before serving or storing in an air-tight container.
Nutrition
Notes
Gremolata, Walnut & Pepper Dip
Ingredients
- 300 g fat free cottage cheese
- 100 g California Walnuts chopped
- ½ red pepper finely diced
- Zest 1 lemon
- 2 tbsp chopped chives
- 2 tbsp chopped parsley
- 1 tbsp extra virgin olive oil
- Toasted pitta and vegetable crudites to serve
Instructions
- Place the cottage cheese and half the walnuts in a food processor and blend until smooth. Mix in the remaining walnuts and red pepper.
- In a separate bowl, mix together the lemon zest, herbs and oil, season and stir into the cheese mixture.
- Serve with toasted pittas and vegetable crudites.
Cooks tip
- Try swapping half the cottage cheese for cream cheese for a creamier option.
Nutrition
Notes
California Walnut, Mushroom and Bean Burgers
Ingredients
- 100 g California Walnuts plus extra to serve
- 400 g can kidney beans drained and rinsed
- 100 g mushrooms
- 2 tsp soy sauce
- ½ tsp garlic granules
- 4 spring onions finely sliced
- ½ tbsp olive oil
- 4 brioche burger buns halved
- Lettuce tomatoes and red onion to serve
Instructions
- Place the Walnuts, kidney beans, mushrooms, soy and garlic granules in a food processor and blitz to give a coarse texture. Stir in the spring onions and season. Divide into 4 and mould into burger shapes.
- Brush the burgers with a little oil and place on a BBQ or griddle pan and cook for 2 minutes each side.
- Toast the buns on the BBQ or griddle pan until golden, top the base of the buns with lettuce and tomato and then add the burgers, finish with red onion and extra Walnuts adding the top half of the buns to serve.
Nutrition
Notes
More research is needed as this was a relatively small and short-term study and it is unclear whether the observed effects of consuming walnuts would persist over a longer period of time or in a larger population. Additionally, the study was not a randomised control trial.
References:
- World Health Organization. Colorectal cancer. World Health Organization website. Accessed May 2, 2025. Updated July 11, 2023. https://www.who.int/news-room/fact-sheets/detail/colorectal-cancer
- Moussa MR, Fan N, Birk J, et al. Systemic inflammation and the inflammatory context of the colonic microenvironment are improved by urolithin A. Cancer Prev Res (Phila). 2025;18(4):235-50.
- Nakanishi M, Chen Y, Qendro V, et al. Effects of Walnut Consumption on Colon Carcinogenesis and Microbial Community Structure. Cancer Prev Res (Phila). 2016 Aug;9(8):692-703. doi: 10.1158/1940-6207.CAPR-16-0026
- Fan N, Fusco JL, Rosenberg DW. Antioxidant and anti-inflammatory properties of walnut constituents: Focus on personalized cancer prevention and the microbiome. Antioxidants. 2023;12(5):982.
- Mandalari G, Gervasi T, Rosenberg DW, Lapsley KG, Baer DJ. Effect of nuts on gastrointestinal health. Nutrients. 2023;15(7):1733.
- Sala-Vila A, Fleming J, Kris-Etherton P, Ros E. Impact of alpha-linolenic acid, the vegetable omega-3 fatty acid, on cardiovascular disease and cognition [published ahead of print February 16, 2022]. Advances in Nutrition. doi.org/10.1093/advances/nmac016.
- Food Standards Agency (2002), McCance & Widdowson’s The Composition of Foods, Seventh summary edition. Cambridge: Royal Society of Chemistry
