In good news for nut lovers, growing research in the area of nuts and cancer suggests that nut consumption may help to reduce the risk of several types of cancer.

Cancer can affect anyone, but some people are at higher risk than others.

Some risk factors, such as older age and having a family history of cancer, can’t be modified. Other factors can be changed to reduce the chance of developing cancer. These include poor diet, excess body weight, physical inactivity, excess sun exposure, smoking and excess alcohol.

How to help prevent cancer

The World Cancer Research Fund (WCRF) and the American Institute for Cancer Research (AICR) have developed recommendations to reduce the risk of cancer and to improve survival after a cancer diagnosis (1).

These recommendations are:

  • Be a healthy weight
  • Be physically active
  • Eat a diet rich in plant-based foods, such as fruit, vegetables, legumes and wholegrains
  • Limit consumption of:
    • fast foods’ and other highly-processed foods, high in fat, starches or sugars
    • sugar-sweetened drinks
    • red and processed meat
    • alcohol
  • Don’t use supplements for cancer prevention
  • For mothers, breastfeed if possible.

A 2020 study, that tracked 50,000 people over 15 years, found those who followed these recommendations had a 12-15% reduced risk of cancer, compared to those whose lifestyle was furthest away from the recommendations (2).

Perhaps not surprisingly, these same recommendations are useful for reducing the risk of heart disease and type 2 diabetes!

Nuts and cancer

Since the WCRF/AICR report was published in 2018, several major studies have added to our knowledge of the benefits of nuts for cancer prevention.

A meta-analysis of 33 prospective studies, published in Cancer Epidemiology, Biomarkers & Prevention in 2020, found that eating tree nuts was associated with reduced cancer risk, particularly for cancers related to the digestive system (3).

Key findings include:

  • Study participants with the highest nut intake had a 10% lower risk of cancer, compared with those who ate the least.
  • A 20g/day increase in nut consumption was linked with a 10% decrease in cancer risk.
  • The protective effect of nuts was especially seen for colorectal, pancreatic and gastric cancers.

Another review, published in Advances in Nutrition in 2020, collated the findings from 52 published papers (4). It found a protective association between total nut and tree nut intake and the risk of cancer and its mortality.

Key findings include:

  • A 5g/day increase in total nut intake was linked with a 3%, 6% and 25% lower risk of overall, pancreatic, and colon cancers, respectively.
  • For cancer mortality, the researchers found an 18% risk reduction with higher intakes of tree nuts.
  • In addition, a 5g/day increase in total nut intake was linked with a 4% lower risk of dying from cancer.

A study, published in Nutrition and Cancer in 2020, examined data from 170 countries, including Australia, to determine links between 23 lifestyle and dietary factors and prostate cancer (5). It found a higher intake of nuts and seeds reduced the incidence, prevalence and mortality rates of prostate cancer.

Key findings include:

  • Each 1g increase in nut and seed intake was associated with a 2.0% lower incidence, 3.2% lower prevalence, and 0.8% lower mortality in prostate cancer.
  • The protective association with nuts and seeds was not seen for any other food groups, including fruits, vegetables or whole grains.

How might nuts be protective?

Researchers suggest the disease-fighting effect of nuts is likely due to the unique nutrients and bioactive compounds they contain.

These may play a role in reducing inflammation and insulin resistance, both of which can be risk factors for some cancers. They may also decrease oxidative stress, which can cause cancerous mutations.

Some beneficial nut nutrients:

  • Vitamin E acts as an antioxidant, and is particularly rich in almonds, hazelnuts and pine nuts.
  • Selenium is an essential part of several antioxidant enzymes, and is particularly concentrated in Brazil nuts.
  • Polyphenols are beneficial plant compounds that have anti xidant properties. Chestnuts, pecans, pistachios and walnuts are the richest in polyphenols.  

Nuts offer a package of nutrients, including plant-based protein, healthy mono- and poly-unsaturated fats, fibre, vitamins and minerals (such as vitamin E, magnesium, phosphorous, iron and zinc), and antioxidants.

Daily nut consumption is associated with a 22% reduced risk of mortality (6).

What about nuts and weight?

Strong evidence points to greater ‘body fatness’ (particularly around the abdomen) as a cause of many cancers (1).

Some people are wary of adding nuts to their diet for fear that it will result in weight gain. Despite being naturally energy-dense (due to the healthy fats they contain), nut intake has been linked with a reduced risk of overweight and obesity, and a reduced body weight, body mass index and waist circumference (7-9).

Cancer: Facts and figures

  • One in two Australian men and women will be diagnosed with cancer by the age of 85 (10).
  • The most common cancers in Australia are prostate, breast, colorectal (bowel), melanoma and lung cancer. These five cancers account for about 60 per cent of all cancers diagnosed in Australia (11).   
  • The economic cost of cancer in Australia, in terms of health expenditure, has been estimated at around $10.1 billion (12). In 2015-16, the top four cancers, in terms of health expenditure, were breast cancer, non-melanoma skin cancer, bowel cancer and prostate cancer.
  • Research suggests that nut consumption, as part of an overall healthy eating pattern, may have a role in reducing the risk of three of these ‘top’ cancers – breast, bowel and prostate cancer (3-5,13).

The bottom line

Many risk factors for cancer are modifiable. A healthy diet and living an active lifestyle can go a long way towards helping to protect against cancer.

Research shows that healthy eating, centred around a variety of nutritious foods, will offer the greatest benefits. And a daily handful of nuts is an easy and healthy addition to include in a diet that promotes lower cancer risk and better overall health.



References

  1. World Cancer Reserach Fund and American Institute for Cancer research. Diet, nutrition, physical activity and cancer: A global perspective. Accessed May 2021: https://www.wcrf.org/wp-content/uploads/2021/02/Summary-of-Third-Expert-Report-2018.pdf
  2. Kaluza J, Harris HR, Håkansson N, Wolk A. Adherence to the WCRF/AICR 2018 recommendations for cancer prevention and risk of cancer: Prospective cohort studies of men and women. Br J Cancer. 2020; 122(10):1562-1570.
  3. Long, J. et al. Nut consumption and risk of cancer: A meta-analysis of prospective studies. Cancer Epidemiol Biomarkers Prev. 2020; 29(3):565-73.
  4. Naghshi, S. et al. Association of total nut, tree nut, peanut, and peanut butter consumption with cancer incidence and mortality: A comprehensive systematic review and dose-response meta-analysis of observational studies, Advances in Nutrition, 2020.
  5. Ziouziou I, et al. Association of prostate cancer with nuts, seeds, alcohol and processed meats: A worldwide population-based study. Nutr Cancer. 2020; 5:1-8.
  6. Aune, D., et al. Nut consumption and risk of cardiovascular disease, total cancer, all-cause and cause-specific mortality: A systematic review and dose-response meta-analysis of prospective studies. BMC Med, 2016. 14(1): 207.
  7. Eslami O, Shidfar F, Dehnad A. Inverse association of long-term nut consumption with weight gain and risk of overweight/obesity: A systematic review. Nutr Res, 2019. 68:1–8.
  8. Flores-Mateo G, et al. Nut intake and adiposity: Meta-analysis of clinical trials. Am J Clin Nutr, 2013. 97:1346–55.
  9. Guarneiri LL., Cooper JA. Intake of nuts or nut products does not lead to weight gain, independent of dietary substitution instructions: A systematic review and meta-analysis of randomized trials. Adv Nutr, 2020.
  10. Australian Institute of Health and Welfare 2019. Cancer in Australia: In brief 2019. Cancer series no. 122. Cat no. CAN 126. Canberra: AIHW.
  11. Cancer Council: Facts and figures. Accessed May 2021: https://www.cancer.org.au/cancer-information/what-is-cancer/facts-and-figures
  12. Australian Institute of Health and Welfare 2021. Health system expenditure on cancer and other neoplasms in Australia, 2015–16. Cat. no. CAN 142. Canberra: AIHW.
  13. van den Brandt PA, Nieuwenhuis L. Tree nut, peanut, and peanut butter intake and risk of postmenopausal breast cancer: The Netherlands Cohort Study. Cancer Causes Control. 2018; 29(1):63-75.
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