Breast cancer: Using diet and lifestyle to reduce risk and recurrence

To mark Wear It Pink Day 2021and Breast Cancer Awareness Month, we invited Toral Shah to explore the links between diet and lifestyle factors in reducing the risk and recurrence of breast cancer – the most common cancer in women worldwide. Toral also shares her delicious recipe for a Salmon and Coconut Laksa – a quick and easy meal that’s full of flavour.

Toral Shah, Nutritional Scientist (Nutr Med) is a nutritional scientist (Nutr Med), functional medicine practitioner and health & food writer with her own consultancy, The Urban Kitchen. Toral is passionate about educating society on the lack of diversity in health, which leads to health inequalities and disproportionate death, particularly in cancer and metabolic health. Her clinical work ensures that cultural and socio-economic differences are acknowledged and supported.

Breast cancer risk

Globally, breast cancer is not only the most common cancer for women, but female breast cancer has now surpassed lung cancer as the most commonly diagnosed cancer worldwide. In the developed world,  breast cancer affects one in seven women in their lifetimes. According to WHO[1], there were 2.3 million women diagnosed with breast cancer in 2020 and 68500 deaths worldwide with up to 1% of cases occurring in men. By the end of 2020, there were 7.8 million women alive who were diagnosed with breast cancer in the previous 5 years. From a cost perspective[2], the global impact of breast cancer is $88 billion and causes the highest economic loss of all the diseases with most disability-adjusted life years lost. Early diagnosis and detection decreases treatment costs[3], and benefits our already-stretched public health services.

Breast cancer awareness education

Breast cancer screening and awareness education, along with better treatment, means that 84% of women in the US and 76% of women diagnosed with breast cancer in the UK will live for 10 or more years. Part of this awareness education includes not only educating women and health care professionals of the symptoms of breast cancer but sharing modifiable lifestyle risks for breast cancer. Diet and lifestyle are a determinant of 35% of all cancers, so educating doctors, nutritionists and other health care professionals of nutrition and diet risk factors for breast cancer could not only help with reducing risk and incidence of breast cancer but also reduce burgeoning costs of treatment and the economic impact.

Risk factors for breast cancer

Studies have shown that the risk for breast cancer is due to a combination of factors, with approximately half of breast cancers developing in women who have no other identifiable breast cancer risk factor other than gender (female) and age (over 50 years). Having risk factors doesn’t mean that you will get breast cancer, as not all factors have the same effect. Some risk factors are non-modifiable whilst many are modifiable.

Non-modifiable risks:

  • Age – most breast cancers develop after 50
  • Gender – more likely for females
  • Greater weight at birth
  • Height
  • Family history and genetic mutations
  • Age of menarche and menopause
  • Dense breasts

Modifiable lifestyle risks:

  • Physical inactivity
  • Obesity and being overweight
  • Alcohol consumption
  • Reproductive history – having children before the age of 30 can reduce risk
  • Breast feeding
  • Hormones including HRT and oral contraceptives, which may increase risk
  • Smoking, particularly at menarche

Epidemiological research and recommendations

Pre-menopausal breast cancer and post-menopausal breast cancer have different risk factors associated with diet, lifestyle and physical activity. Many of the recommendations are based on research that comes from 119 studies from around the world by the WCRF[4], compromising more than 12 million women and over 260,00 cases of breast cancer (updated in 2018), and the latest studies from American Institute of Cancer Research.

Pre-menopausal breast cancer

There is some evidence that the following foods decrease pre-menopausal breast cancer risk:

  • Eating a high intake of non-starchy vegetables might decrease the risk of oestrogen-receptor-negative (ER–) breast cancer – potentially due to protective effects of bioactive compounds and fibre
  • Foods containing carotenoids (such as peppers, squash and tomatoes)
  • Dairy products, preferably fermented
  • Diets high in calcium[5] (at least 500mg a day but up to 1000mg)
  • Eating a portion of cruciferous vegetables (such as broccoli and cauliflower) and 2 portions of leafy greens daily[6]
  • Low glycaemic index diet[7]

Being vigorously physically active might decrease risk of breast cancer in younger women. Activity is measured in METS (metabolic equivalents) with 1 MET being the energy required to sit quietly and vigorous activity at 6 METS or more. Vigorous activity could be recreational, occupational or housework, including running at 6mph, cycling at 14-16mph, shovelling, lifting heavy loads or playing single’s tennis.

Post-menopausal breast cancer

There is some evidence that the following foods decrease post-menopausal breast cancer risk:

  • Eating a high intake of non-starchy vegetables might decrease the risk of oestrogen-receptor-negative (ER–) breast cancer
  • Foods containing carotenoids (such as peppers, squash and tomatoes)
  • Diets high in calcium (at least 500mg a day but up to 1000mg)
  • Eating a portion of cruciferous vegetables (such as broccoli and cauliflower) and 2 portions of leafy greens daily
  • Low glycaemic index diet

Being  physically active might decrease risk. This would be activity over 3 METS so activities such as brisk walking (4mph), heavy cleaning or mowing the lawn, light bicycling, double tennis or badminton.

Obesity, body fatness and breast cancer

Whilst there is a relationship between body fat levels and breast cancer, this is complex and requires further studies. There is evidence that being overweight or obese before menopause can reduce the risk of breast cancer[8], probably due to anovulation, whilst being overweight or obese after menopause increases breast cancer risk.

We know that adipose tissue or fat cells release hormones such as circulating oestrogen. Excess circulating oestrogen can increase the risk of breast cancer in postmenopausal women[9], most likely by increasing aromatase expression in adipose tissue. Storing too much fat can cause insulin resistance (where insulin becomes less effective at controlling blood sugar levels), which encourages the body to produce growth hormones. High levels of these hormones can promote the growth of cancer cells. Body fat also stimulates an inflammatory response. Inflammation can promote the growth of cancer by encouraging cancer cells to divide. This inflammatory response may underpin the wide variety of different cancers that have been linked to obesity.

Breast cancer risk is increased in women who have attributes of the insulin resistance syndrome, such as obesity (postmenopausal), central obesity (premenopausal and postmenopausal), high endogenous insulin levels, clinical diabetes and physical inactivity. A Westernised diet and lifestyle[10] – chronic excess energy intake from meat, fat, and carbohydrates and lack of exercise – can increase the development of obesity, chronic hyperinsulinemia, higher production and availability of IGF-1[11]. It can also increase levels of endogenous sex hormones (through suppression of sex hormone-binding globulin), which increases the risk of breast cancer.

Some of the proteins of the immune system seem to stimulate breast cancer cells to grow, especially oestrogen-receptor-positive breast cancer in postmenopausal women.

Breast cancer and diabetes

Type 2 diabetes can increase the risk of breast cancer up to 20% more in postmenopausal breast cancer than older, non-diabetic women[12]. A decreased level of oestrogen as a result of insulin resistance increases the risk of developing cancer in any organ with high levels of oestrogen receptors, including breast, endometrium, and ovaries. Several studies have shown that higher insulin and/or C-peptide levels (a marker of insulin secretion), both of which are linked to insulin resistance, are associated with an increased risk of recurrence and death in women with early stage breast cancer, even in the absence of diabetes.

Physical activity and breast cancer

Vigorous physical activity lowers the risk of premenopausal breast cancer and all types of physical activity (moderate and vigorous) help protect against postmenopausal breast cancer[13]. Physical activity may improve insulin sensitivity and reduce fasting insulin and C-peptide levels, which are associated with reduced risk. Physical activity has also been shown to decrease oestrogens and androgens in postmenopausal women, reducing risk of breast cancer.

The Department of Health and Human Services recommends:

  • At least 150 minutes a week of moderate aerobic activity (US recommended 150 – 300 minutes)  OR 75 minutes a week of vigorous aerobic activity OR a combination of moderate and vigorous activity
  • Strength training exercises for all major muscle groups at least twice a week
  • New evidence shows that South Asians need to undertake at least 230 minutes of moderate intensity physical activity per week. This equates to South Asians undertaking an extra 10–15 minutes of moderate intensity physical activity per day on top of existing recommendations

Breastfeeding and cancer

Breastfeeding protects against breast cancer by lowering the levels of some cancer-related hormones in the body and getting rid of any cells in breasts that may have DNA damage. If mothers can, the recommendation is to exclusively breastfeed for the first six months of life but any breast-feeding is beneficial to reducing cancer risk and supports the long term health of the baby.

Alcohol and breast cancer

Alcohol can be metabolised in breast tissue to acetaldehyde, producing reactive oxygen species, which can cause with DNA damage. Alcohol may also increase circulating levels of oestrogen, which we know is an established risk factor for breast cancer. To reduce cancer risk as much as possible, we recommend not drinking alcohol at all as there is no safe limit. If people do choose to drink alcohol, they should follow national guidelines. In the UK, the guideline is to drink no more than 14 units a week, spread over at least three days for both men and women.

Other lifestyle factors

There are other lifestyle factors which can impact overall cancer risk including sleep, stress, optimising the gut microbiome and immune system. Managing these can help to reduce risk. Vitamin D deficiency has been linked to an increased risk of breast cancer (14).

Practical tips to share with patients

When working with patients with a family history of breast cancer or those who want to reduce their cancer risk, we need to remember that patients are individual in their eating preferences and their needs are unique. Cultural sensitivity is important when advising patients about their diet in order to impact their breast cancer risk, with a need to understand their cultural and religious choices for how they eat and what food they choose. Consider that different cultures eat different vegetables and fruits, grains and legumes, and herbs and spices. Help them with principles and discuss how they can adapt much-loved dishes to help them to maintain a healthier diet.

Adding in extra portions of fruit, vegetables, wholegrains, legumes, herbs and spices, nuts, seeds and mono-unsaturated fat such as olive oil and avocado – rather than focusing cutting things – gives an opportunity for patients not to feel like their diet is restricted. To help them maintain this new way of eating, encourage them to create new dishes using healthier cooking methods, including changing the oil they cook with, or adding in more vegetables.

Top evidence-based tips to support reduction of breast cancer risk

  • Eat a diet rich in a variety of vegetables, fruits, herbs, nuts, seeds and plant-based foods, such as in the Mediterranean diet pattern
  • Eat the rainbow!
  • Pile half your plate with non-starchy vegetables to increase fibre content
  • Eat at least two portions of oily fish a week for both omega-3-fatty acids and vitamin D
  • Eat healthy (monounsaturated) fats at each meal such as nuts, seeds, olive oil
  • Avoid red and processed meat, especially grilled/barbequed, to reduce potential nitrates and carcinogens which can cause DNA damage
  • Have a Vitamin D supplement from October to April, as the winter sunlight doesn’t contain enough UVB light to catalyze the production of vitamin D production in the skin
  • Improve gut health by increasing plant-based and fermented foods and probiotic foods to optimise the growth of beneficial bacteria
  • Limit alcohol consumption
  • Reduce free and refined sugar intake and eat a lower glycaemic index diet to reduce insulin resistance
  • Eat unprocessed soy products such as edamame, miso, tempeh, tofu
  • Drink at least two litres of water a day

Summary and Recipe

Ultimately, diet and lifestyle changes can reduce risk but not prevent breast cancer and we do need to ensure that patients don’t feel to blame if they are diagnosed with breast cancer after following these risk reduction suggestions.

Salmon and Coconut Laksa

A laksa is a type of hearty Malaysian soup that contains noodles. The coconut milk and chillies complement each other by masking some of the heat of the chillies with the creaminess of the coconut milk. It is quick and easy to make as an after-work dish. The salmon is great for your skin and brain as it contains lots of omega-3 fatty acids.

Ingredients (serves 4 as light meal)
For chilli paste
  • 2 red chillies
  • 4 cloves of garlic, peeled
  • 6cm thumb of ginger, peeled and roughly chopped
  • 1 tsp ground coriander seeds
  • 1 handful of coriander including roots and stems, all washed
  • 30ml sesame oil
For laksa
  • 500g sustainably sourced salmon fillet, skinned and sliced into 12 slices*
  • 50ml fresh lime juice
  • 1 tin of light coconut milk
  • 1 red pepper, sliced finely
  • 100g broccoli or Tenderstem
  • 100g green beans, sugar snaps or mange tout
  • 1 litre fish or vegetable stock
  • 100g dried rice noodles
  • Small handful of mint, leaves only
  • Small handful of coriander, roughly chopped
  • 4 spring onions, finely sliced
  1. Prepare the chilli paste by adding all the ingredients to a food processor and pureeing to a coarse paste.
  2. Marinate the salmon in the lime juice and leave at room temperature.
  3. Heat a pot and fry the chilli paste for one minute, stirring well.
  4. Add the coconut milk and stock and bring to the boil.
  5. Simmer for 10 minutes and then add the red peppers broccoli and green beans, marinated salmon and noodles.
  6. Continue to simmer until the salmon and the noodles are cooked – this will take approximately 4 – 5 minutes.
  7. Serve the laksa and sprinkle over the mint, coriander and spring onions

Macronutrients: 473kcal, 23g carbs, 29g fat, 38g protein

*Tofu is a great subsitute for salmon too

Practical and research resources for HCP

Related MyNutriWeb Content

Breast Cancer and Diet – 60 min webinar with Toral Shah and Rachel Clark from the WCRF

Breast Cancer and Diet Infographic – Download the infographic summarising the key points from the above webinar

 

References

  • [1] https://www.who.int/news-room/fact-sheets/detail/breast-cancer
  • [2] http://phrma-docs.phrma.org/sites/default/files/pdf/08-17-2010_economic_impact_study.pdf
  • [3] : Sun L, Legood R, dos-Santos-Silva I, Gaiha SM, Sadique Z (2018) Global treatment costs of breast cancer by stage: A systematic review. PLoS ONE 13(11): e0207993.
  • [4] https://www.wcrf.org/wp-content/uploads/2021/02/Breast-cancer-report.pdf
  • [5] Kesse-Guyot E, Bertrais S, Duperray B, et al. Dairy products, calcium and the risk of breast cancer: results of the French SU.VI.MAX prospective study. Ann Nutr Metab 2007; 51: 139–45
  • [6] Postdiagnostic Fruit and Vegetable Consumption and Breast Cancer Survival: Prospective Analyses in the Nurses’ Health Studies Maryam S. Farvid, Michelle D. Holmes, Wendy Y. Chen, Bernard A. Rosner, Rulla M. Tamimi, Walter C. Willett and A. Heather Eliassen Cancer Res November 15 2020 (80) (22) 5134-5143
  • [7] Farvid MS, Tamimi RM, Poole EM, Chen WY, Rosner BA, Willett WC, Holmes MD, Eliassen AH. Postdiagnostic Dietary Glycemic Index, Glycemic Load, Dietary Insulin Index, and Insulin Load and Breast Cancer Survival. Cancer Epidemiol Biomarkers Prev. 2021 Feb;30(2):335-343
  • [8] Examining breast cancer growth and lifestyle risk factors: early life, childhood, and adolescence. Clin Breast Cancer.  2008; 8(4):334-42 (ISSN: 1526-8209) Ruder EH; Dorgan JF; Kranz S; Kris-Etherton PM; Hartman TJ
  • [9] Adult weight change and risk of postmenopausal breast cancer. JAMA.  2006; 296(2):193-201 (ISSN: 1538-3598) Eliassen AH; Colditz GA; Rosner B; Willett WC; Hankinson SE
  • [10] Xiao, Y., Xia, J., Li, L. et al. Associations between dietary patterns and the risk of breast cancer: a systematic review and meta-analysis of observational studies.Breast Cancer Res 21, 16 (2019)
  • [11] Nutrition, insulin, IGF-1 metabolism and cancer risk: a summary of epidemiological evidence. Novartis Found Symp.  2004; 262:247-60; discussion 260-68 (ISSN: 1528-2511) Kaaks R
  • [12] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7279688/pdf/cureus-0012-00000008010.pdf
  • [13] Pizot C, Boniol M, Mullie P, et al. Physical activity, hormone replacement therapy and breast cancer risk: A meta-analysis of prospective studies. European Journal of Cancer2016; 52:138-154
  • [14] Atoum M, Alzoughool F. Vitamin D and Breast Cancer: Latest Evidence and Future Steps. Breast Cancer (Auckl). 2017 Dec 20;11:1178223417749816. doi: 10.1177/1178223417749816. PMID: 29434472; PMCID: PMC5802611.