Breast cancer is now the commonest cancer in the UK and the most common cancer in women globally. 1in 7 women in the UK will develop breast cancer in their lifetime. Breast cancer is more common in high income countries, in part related to the ‘Western lifestyle’. The genes we inherit are responsible for only 5–10% of breast cancer cases, with the most widely studied genes, BRCA 1&2, implicated in only 1–2% of cases. In contrast, up to 25% of cases could be prevented by addressing a number of lifestyle-related factors.
Cancer in general shares common features. There are 3 main stages of cancer development — initiation, promotion and progression. Damage to cells and DNA occurs all the time during the phase of initiation. However, the body has an amazing capacity to correct this damage or remove the damaged cells. Some cells will linger and if given the correct growth environment they will start to divide and increase in number during the phase of promotion, with some becoming cancerous. At a certain point, these damaged and cancerous cells gain the ability to travel around the body away from their site of origin and lodge in other organs — progression. The main opportunity to prevent cancer is during initiation and promotion, when we can help the body avoid damage to cells and prevent these damaged cells from surviving, dividing and becoming cancerous.
Factors that contribute to cells becoming damaged and cancerous include, low grade chronic inflammation, oxidative stress, an abnormal gut microbiome, increased levels of growth hormones and an immune system that is not functioning adequately. All these adverse factors can be prevented to a significant degree by healthy lifestyle choices. Healthy diet and lifestyle practices can reduce inflammation, promote a healthy gut microbiome and maintain a healthy immune system
So what are the important lifestyle factors that are within our control?
Be a healthy weight: Being overweight or obese is a significant risk factor for developing breast cancer. Although the determinants of body weight are complex and multi-factorial, diet choices are the most important factor. People eating the most plant foods and lowest amount of animal-derived and processed foods tend to maintain a healthier body weight. On a basic level, we all eat the same volume of food everyday — around 4 pounds. The easiest way to maintain a healthy weight is by choosing foods that are low in calories but high in nutrients thus paying attention to the calorie density of foods. Check out the flyer below. If you stick to eating from the foods in green, it will be much easier to maintain a healthy weight.
The good news is that if your weight is higher than it should be but you successfully lose weight, you can significantly reduce your risk of breast cancer. Unfortunately if you are overweight or obese and do develop breast cancer, treatments seem to be less effective and the chances of surviving are lower. You can read more about how to maintain a healthy weight in my previous article.
Eat more fruits and vegetables: Eating more fruits and vegetables is a good way of reducing the risk of cancer in general and specifically breast cancer. We know that the optimal number of portions to eat a day is around 10, or 800 grams. A high consumption of fruits and vegetables could reduce the risk of breast cancer by around 10%. The best choices include cruciferous (kale, cabbage, broccoli, cauliflower..) and yellow/orange vegetables (high in carotenoids) and berries (high in polyphenols), but overall you should aim to eat a wide variety of colourful fruits and vegetables
Increase fibre in the diet: Fibre is an essential component of the diet, yet most of us are not eating enough. Fibre is only found in whole plant foods i.e. fruits, vegetables, whole grains, beans, nuts and seeds — and we should be aiming to eat at least 30g a day. The more the better. For every 10g increase in fibre intake reduces the risk of breast cancer by 4%. An updated analysis confirms the benefit of fibre in the diet, with those consuming the most reducing their risk by 8%. Diets high in fibre are associated with a healthy gut microbiome and a more robust immune system.
Eliminate processed and red meat: In 2015, the WHO classified processed meat as a group 1 carcinogen (causes cancer) and red meat a group 2a carcinogen (probably causes cancer). This classification was based on data related predominantely to the risk of colorectal cancer. However, we know that processed and red meat consumption can increase the risk of several other cancers, including breast cancer. The link with breast cancer is definitely strongest for processed red meat such as bacon, sausages, deli meats etc. but there is also some suggestion that any red meat consumption can increase the risk. Replacing red meat in the diet with beans or nuts can significantly reduce the risk.
Reduce saturated fat in the diet: Saturated fat is predominately found in animal-derived foods. The link between consumption of saturated fat and breast cancer risk is not consistent — some studies show an increased risk and others don’t. This probably comes down to the quality of the rest of diet. However, what seems to be more certain is that if you do get diagnosed with breast cancer, the chances of surviving are less favourable if you are eating high amounts of saturated fat.
Eliminate processed foods: There is very little data on the link between the consumption of processed and ultra-processed foods and cancer. However, studies are beginning to suggest that processed foods may increase the risk of cancer and in particular breast cancer. One study showed that for every 10% increase in the amount of ultra-processed foods in the diet, there is a 10% increase in the risk of developing breast cancer.
Swap cow’s dairy to soya milk and foods: The link between dairy consumption and breast cancer risk is complex. Intuitively you may think that dairy would increase the risk of breast cancer as it is high in saturated fat, cow’s oestrogens and growth hormones such as IGF-1. However, this is not the case in every study. What does seem to be more certain is that replacing cow’s dairy for soya milk and foods can reduce the risk of breast cancer. For example, regular consumption of tofu can reduce the risk of breast cancer by around 12% when comparing those who eat the most versus those that eat the least. Swapping dairy milk for soya milk could reduce the risk by up to 32%. Consuming dairy in childhood and adolescence can even reduce the risk of developing breast cancer later in life.
Overall healthy diet pattern: It is sometimes more useful to consider the whole diet rather than the individual components. The consensus from the World Cancer Research Fund guidelines for cancer prevention is that the healthiest diet is one that is composed predominately of whole plant foods — fruits, vegetables, whole grains, beans — and may contain some fish and low fat dairy. But avoids red and processed meat, processed foods in general and sugar-sweetened beverages. This sort of diet can reduce the risk of breast cancer by 18%.
Be physically active: Regular physical activty has so many benefits for health, including cancer prevention. For breast cancer, regular physical activity could reduce the risk by 13%, and the more the better. Regular exercise shares all the benefits of a healthy diet, including helping to maintain a healthy weight, reducing insulin resistance, lowering oestrogen and IGF-1 levels, reducing inflammation and oxidative stress, turning off cancer promoting genes and improving the function of the immune system.
Avoid alcohol: Alcohol is a group 1 carcinogen (it causes cancer) and probably contributes directly to around 5.5% all cancers globally each year. The link between alcohol consumption and breast cancer is particularly strong. A large, observational study of 105,986 women suggested that drinking three to six drinks per week increased the risk of breast cancer by 15% compared to women who did not drink. Even ‘light’ drinking (0.5 drinks/day) was found to increase the risk of breast cancer by 9%.
Other helpful additions to the diet: There are a few additions to the diet that are beneficial for general health and may help to prevent breast cancer Green tea is full of anti-oxidant compounds with particularly high levels of the compound EGCG. Some, but not all studies, have shown that drinking green tea regularly, may be several times a day, could reduce the risk of developing breast cancer. Green tea supplements can be harmful so make sure you only drink as a tea. Curcumin, the active compound in the spice turmeric, may also have cancer prevention properties. The best way to consume curcumin is to use turmeric liberally in cooking.
It’s never too late: Changing lifestyle behaviours can have significant benefits even after a diagnosis of breast cancer. In one of the largest nutrition intervention studies of all time, women who developed breast cancer and were eating a reduced fat diet with increased amounts of fruits, vegetables and whole grains had a 21% reduced risk of dying from breast cancer compared to those who had not changed their diet. Similarly, women who undertake regular physical activity after breast cancer can reduce their risk of dying by up to 40%. Adding soya to the diet can improve the chances of staying in remission and survival. Making sure you have adequate vitamin D levels may also increase the chances of surviving cancer and this often requires a daily supplement of 1000IU of vitamin D3, especially in the winter months. Surprisingly, alcohol consumption after a diagnosis of cancer may not adversely affect your changes of survival, but I personally would not take the risk.
To get started on your journey of a healthy diet and lifestyle, check out our Plant-based Eatwell Guide. For more in depth information, I would recommend reading the book Breasts, An Owner’s Manual by Dr Kristi Funk
Footnote: It going without saying that smoking tobacco causes cancer. Breast cancer is no different. Never smoke cigarettes.
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