Dietary factors to consider in breast cancer prevention and helpful hints following a diagnosis of breast cancer

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Introduction

Risk factors predisposing to breast cancer are is mainly hormonal (for example age at menarche, age at first pregnancy, breast feeding history, parity, age at menopause) or familial (pedigree of relatives, age at their diagnosis, breast cancer or related cancer history). The relationship to food and diet whilst often spoken about is not clear. Environmental factors that affect breast cancer or breast cancer-risk are unknown although this clearly exists from clustering of cancers within families, who are likely to do common things and are exposed to the same environments, but where no genetic basis for their cancers can be identified. This is likely to include dietary factors.

 Foods are complex being made up of the same carbon based products, amino acids, essential fatty acids, minerals and vitamins. Controlling for variation, compliance, recollection and total exclusions are difficult in clinical studies. There is often a large lead time between exposure to dietary elements and cancer development even in situations where a clear link is established. Many factors are therefore likely to be at play and to single out individual risk or protective food materials will always be difficult. Nevertheless, dietary control are an invaluable mechanism by which women and patients feel they may have some influence over lifestyle and daily living, and remain an important part of dealing with therapy related effects in breast cancer treatment.

A possible effect in breast cancer prevention

 Although diet may have a clearer causal relationship to other cancers, the link to breast cancer is not as clear. This is a complex area and demographic studies to try to identify individual food products as protective against breast cancer are often speculative. How much one needs to eat to protect against cancer or to raise cancer risk is usually unknown. Patients who have a normal diet are likely to have their nutritional requirements more than adequately met and supplementation may not be necessary. Exercise is important and women particularly when post menopausal are at higher breast cancer risk if the body mass index is high. It is very important that overall diet is balanced. A healthy diet should provide all the protein, energy, fibre, vitamins and minerals that the body needs to function properly. 

 The following are food substances that have been reported to be protective against breast cancer:

1. 1.      Cruciferous vegetables contain two chemicals called isothiocyanates and indole-3-carbinol which may affect breast cancer carcinogenesis by triggering cell death or by shifting estrogen metabolism. Examples of these are Chinese cabbage, bok choi, turnips, broccoli, kale and cauliflower.
2. 2.      Women whose fat intake consist mainly of unsaturated fats have a slightly reduced breast cancer risk.
3. 3.      Tomatoes contain high levels of beta-carotene, an antioxidant that supports the immune system and helps maintain healthy skin and tissue lining. They are high in the  antioxidant lycopene, flavonoids and vitamin E, both of which are essential for heart health, and are a good source of potassium.
4. 4.      Oleic acid found in olive oil is said to be protective against breast cancer
5. 5.      Omega-3 fatty acids in fish oil have been associated with a reduced risk of breast cancer. In particular, the two omega-3 fatty acids, docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) are considered to have more potent anticancer properties than omega-3 fatty acids.
6. 6.      High levels of folate in combination with other vitamin supplements such as vitamin B6 may help reduce the risk of breast cancer. This is naturally available in green leafy vegetables such as spinach, broccoli and asparagus.
7. 7.      Other foods substances often cited include: pomegranates, pumpkin seeds, green tea, goji berries, beetroot, peaches, cherries and berries.

Adverse dietary factors that may increase breast cancer risk include:

1. High alcohol intake has been consistently linked to breast cancer risk and a safe amount is two units or less per day.
2. Some studies have found that women who eat a lot of red and processed meat are more likely to develop breast cancer than other women. Saturated fat from animal products is associated with higher breast cancer risk.
3. A high-starch diet is associated with breast cancer risk.

After a diagnosis of breast cancer

 Diets need to be balanced and contain the necessary components for normal body function. Much of what has been described in the preceding section is likely to be relevant. Your optimum body weight for your height should be maintained.

 Post cancer-treatment fatigue may be a feature. It is helpful to have plenty of rest, a routine to the day and structured exercise arrangements built into the daily schedule. Foods that contain much red meats or fat may take more energy to digest. Food should be carbohydrate based, and also contain fruit, vegetables and oily fish. Too much salt should be avoided. Make sure that adequate fluid intake is maintained.

The treatment may predispose to weight gain and this must be controlled by a combination of diet and exercise.

Phyto-oestrogens or plant oestrogens

Soya foods are a source of plant oestrogens. They have been variously described to be protective of or contributing to breast cancer risk. Their action is much weaker than animal oestrogens. Theoretically they may bind oestrogen receptor in the body and have a lesser effect than animal oestrogens. Many clinical studies have not found a true pharmacological effect in objective measured outcomes, such as improving bone density. Whether phyto-oestrogens help with hot flushes compared with placebo is also controversial. It is important that supplements containing phyto-oestrogens are discussed with your doctor in view of theoretical interactions with breast cancer drugs.

Dairy products

 This is often raised but there is very little evidence to support women avoiding dairy foods. Concerns raised include the presence of oestrogen-like hormones and growth factors (eg insulin like growth factor) that are found in dairy products that may influence tumour growth. Growth factors are needed also in the repair process and milk is a useful source of calcium that is necessary for bone health. Women who choose to avoid dairy products should consider calcium and vitamin D supplementation to help maintain bone health, especially if in drugs such as the aromatase inhibitors that predispose to bone mineral loss.

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