In general, there are 2 main diets recognised in scientific studies to have anti-cancer properties. The first, and most important, is the Mediterranean diet. It is based on the dietary patterns of people living in olive growing areas around the Mediterranean up until the 1960s:

• High intake of vegetables, legumes, fruits and nuts.
• High intake of minimally processed cereals.
• High intake of monounsaturated fats coupled with low intake of saturated fats.
• Moderately high intake of fish.
• Low to moderate intake of dairy products.
• Low intake of meat products.
• Regular but moderate intake of alcohol.

The second diet, which may have some anti-cancer properties, is the Nordic diet. Although it is high in fat and sugar, there is a range of traditional products with anticipated health-promoting effects:

• Fish
• Cabbage
• Rye bread
• Oatmeal
• Apples
• Pears
• Root vegetables.

It seems sensible to adopt as many of these foods into your diet as possible especially as both of these diets are also associated with weight loss, reduced risk of cardiovascular disease (heart attacks and strokes) and reduced risk of diabetes.

The European Prospective Investigation into Cancer and Nutrition (EPIC) study investigated the impact of diets rich in carbohydrates (including sugar) with high gycaemic incices and the risk of breast cancer. They found that there was an association between diets with a high glycaemic load and an increased risk of developing hormone receptor negative breast cancer in post-menopausal women. In mice, a sucrose (sugar) intake similar to what is typically seen in a Western diet led to increased tumour growth and cancer spread. Again, it seems sensible to limit your sugar intake and try to stick to unrefined carbohydrates where possible as these tend to have a lower glycaemic index (GI).

There is consistent evidence suggesting that moderate alcohol intake is associated with an increased risk of breast cancer. The effect may be increased in post-menopausal women taking HRT. The UK Chief Medical Officer recommends that you drink no more than 14 units per week to keep the health risks from alcohol at the lowest level but you may want to reduce this even more.

Overall, folate (vitamin B9) intake is not associated with breast cancer risk (even in women with increased alcohol consumption). The EPIC study showed that a higher folate intake might be associated with a lower risk of hormone receptor negative breast cancer in pre-menopausal women.

The EPIC study indicated that diets rich in dietary fibre (particularly fibre from vegetables) may be associated with a small reduction in breast cancer risk whether you are pre or post-menopausal.

The EPIC study showed that there is no evidence for an association between vitamin D and calcium intake and breast cancer risk, but a French study found a decreased risk of breast cancer in women (especially younger women) with higher circulating vitamin D levels. After a diagnosis and treatment for breast cancer, more robust studies found a link between low circulating vitamin D and breast cancer recurrence. We get most of our vitamin D from our own skin, which makes the vitamin with the help of sunlight. We can also get vitamin D from our diet. As many of us wear sunscreen all year round, we can have low circulating vitamin D levels without knowing it. It is sensible to get your vitamin D levels checked (especially if you have had breast cancer) and then use a supplement if necessary to get back into the ‘normal-range’.

In general, obesity does not seem to increase the risk of breast cancer in pre-menopausal women but in post-menopausal women it is estimated that obesity increases the breast cancer risk by 30-50%. In pre-menopausal women, obesity is related to hormone receptor and Her-2 negative breast cancer (triple-negative breast cancer) and obesity is associated with increased breast cancer recurrence and death.