Medical contributor:
First revision: Overview
Breast cancer cases contributed to 11.7% of all cancers diagnosed worldwide, making it one of the most common types of cancer. The survival rates of breast cancer have significantly increased over the years due to medical treatment advances. One of the crucial elements in the treatment of cancer is nutrition, as it can lessen side effects and improve the patient's quality of life. More than 30% of cancers could be prevented by changing eating habits and increasing physical activity.1
Flaxseeds have been studied repeatedly by scientists to see their benefits and side effects on breast cancer. This article will break down what flaxseeds do in regard to breast cancer, how to use them safely to get the benefits and some things to consider if you are planning to incorporate them into your diet during conventional cancer treatments.
Nutrients of flaxseeds for breast cancer
Flaxseeds, also known as linseeds, are a good dietary fibre source containing omega-3 fatty acids, including alpha-linolenic acid (ALA), and polyphenols such as lignan. Flaxseeds also contain such nutrients as:
in significant amounts, making them advantageous to health, preventing conditions like cancer and cardiovascular problems.1
The beneficial nutrients in flaxseeds for breast cancer are:1,
- Omega-3 fatty acids: Flaxseeds are the best plant-based source of omega-3 fatty acids. Studies show polyunsaturated fatty acid (PUFA) omega-3 in flaxseeds has anticancer properties, reduction of breast cancer risk, reduction in the body’s oestrogen production (prevents cancer cell growth) and reduction of breast cancer tumours upon consumption of 25g of flaxseeds
- Alpha-linolenic acid (ALA): Alpha-linolenic acid helps with PUFA omega-3 production. ALA showed a reduction in breast cancer tumour size, and growth as well as a decrease in cancer cell division. ALA also showed an increased tumour cell death in animal studies
- Lignan: Lignans are a type of phytoestrogen, a plant nutrient that is chemically quite similar to the female hormone oestrogen. Flaxseeds contain 100 times more lignan than other natural food sources, exerting better antioxidant activity and low/anti-oestrogenic action. These properties help with a reduction in breast cancer risk, reduced breast cancer tumour growth and increased tumour cell death. The studies also showed lignan had the potential to reduce breast cancer spread and had a protective effect in people assigned female at birth
Apart from the beneficial nutrients, the high fibre content in flaxseeds are useful in protecting an individual from possible side effects like heart disease or stroke when undergoing breast cancer treatment.
Benefits of flaxseeds in breast cancer
While receiving conventional treatment, such as chemotherapy, many cancer patients decide to adjust their food habits. Patients take this action in an effort to lessen the treatment's significant adverse effects, such as anxiety, depression, insomnia, headaches, nausea, and vomiting. Flaxseeds are one such superfood an individual can include in their diet to combat the side effects of cancer treatment or cancer itself.
Some of the benefits of flaxseeds for breast cancer are:1,2,
- Improving effect of tamoxifen: Tamoxifen is a drug used to treat (ER+) breast cancers. This type of breast cancer contains positive oestrogen receptors and is managed using hormonal therapy. Tamoxifen acts throughout the body, blocking the effects of oestrogen on tumour cells and inhibiting their growth making it an anti-oestrogenic drug. Studies demonstrated flaxseeds did not have any interaction with the drug but had an additional protective effect when taken along with the treatment. Animal and human clinical studies showed flaxseeds increased the effectiveness of tamoxifen to inhibit tumour growth
- In triple-negative breast cancer: Triple-negative breast cancer (ER-) is a rare type of cancer, with the absence of oestrogen receptors and other growth receptors. A study conducted in 2015 2, showed that alpha-linolenic acid present in flaxseeds caused a reduction in cell growth and induction of cell death. An earlier study showed that lignans from flaxseeds reduced the occurrence of secondary breast cancer tumours (metastasis) and reduced tumour growth3
- Reduces breast cancer risk in both pre and post-menopausal women: Several studies have shown the presence of lignan in flaxseeds to have a protective effect before and after menopause. One study explored the association between flaxseed consumption and a reduction in breast cancer risk.4 The consumption of flaxseed (about 32.5 g) and flax bread (1 unit, around 2.5–5 g of flaxseed) on a weekly and daily basis was linked to a significant 18–24% decrease in the risk of breast cancer
- Reduction in the spread of cancer: The process of cancer cells travelling from the primary tumour (breast cancer tumour) to another part of the body (e.g., lung) via the bloodstream is known as metastasis. In multiple laboratory experiments, diets containing 5 or 10% flaxseed, roughly 25 to 30 g of flaxseed per day decreased the metastasis of triple-negative breast cancer
- Increased cancer cell death, reduction in size and growth of breast cancer tumours: A post-menopausal study5 diagnosed with a type of breast cancer and scheduled for surgery were given flaxseeds in muffins for 5 weeks. When the tumours were removed and studied, they showed a reduction of growth and increased cell death
The majority of experimental research conducted revealed that flaxseeds work on reducing tumour growth, increasing apoptosis (programmed cell death), and inhibiting cell replication. However, additional clinical studies are required to validate the relationship, corresponding effectiveness and benefits of flaxseed in breast cancer.
When and how to use flaxseeds for breast cancer
Flaxseeds can be used as a breast cancer preventive measure. Recommended daily amounts flaxseed are one to four tablespoons (15-60g). If you are diagnosed with breast cancer and undergoing treatment it is best to discuss supplementary options with your doctor before including flaxseeds in your diet.
Flaxseeds can be consumed in the form of ground powder, oil, or whole seeds. Flaxseed oil is rich in omega-3 fatty acids and can be used as salad dressing and cooking. Any products with whole flaxseeds on bread, muffins, crackers, or cereals made from flaxseeds are good for consumption to get its nutrients. It is equally important to have a well-balanced diet containing vegetables, fruits and a source of protein (chicken, fish, beef or plant-based). It is important to wait for an hour or two after taking any prescription before consuming flaxseeds as they are rich in fibre content, which can reduce how much of the drug you absorb.
Risks and considerations
Flaxseeds must be gradually added to one’s diet, especially when consumed raw. There are no major risks associated with flax seed consumption. However, whether it is safe for breast cancer patients to consume high levels of the lignans contained within flaxseeds is an ongoing debate. The phytoestrogens contained in lignans have the potential to cause an increase in oestrogen levels, which could be linked with increased breast cancer risk. Although other reports on lignans and breast cancer suggest lignans do not promote, instead may inhibit, tumour growth.
Other possible side effects of flaxseeds:
- Diarrhoea (flaxseed oil)
- Intestine blockage
- Stomach soreness and cramping
- Constipation
- Flatulence (gas)
- Allergy to t flaxseed proteins.
It is best to avoid flaxseed computation in any form if you have pre-existing conditions such as high cholesterol, bleeding disorders, Crohn's disease, ulcerative colitis, or irritable bowel syndrome as the high fibre content can cause the above-mentioned symptoms. If you are supplementing your diet with flaxseeds, ensure you consume a moderate amount ie. 2-3 tablespoons per day if ground (powder) or 15-30 ml per day if it is in oil form.
Although there are no any known negative drug interactions caused by consuming flaxseed products it is advisable to consult your doctor/oncologist so they can assess your usage, in accordance with your conditions, to avoid any undesired side effects if you are a breast cancer survivor or still undergoing treatment.
Summary
Flaxseeds are a nutritional superfood that primarily contains omega-3 fatty acids, alpha-linolenic acid (ALA) and lignan. These components possess anti-cancer properties and are extensively studied in relation to breast cancer. In certain studies, consuming omega-3 fatty acids has been linked to a decline in breast cancer.1 Studies on animals revealed that ALA could reduce breast tumour cell size, development, and cell proliferation while increasing cancer cell death.2 Studies also showed it enhanced the activity of the cancer drug tamoxifen in primary and secondary breast cancer.1
Despite its benefits for breast cancer it is safer to be consumed in moderate amounts as it can cause other side effects. Prior to adding flaxseeds to your diet check with your GP/oncologist to avoid any complications.
References
- Calado A, Neves PM, Santos T, Ravasco P. The effect of flaxseed in breast cancer: a literature review. Frontiers in nutrition. 2018 Feb 7;5:4.
- Wiggins AKA, Kharotia S, Mason JK, Thompson LU. Α-linolenic acid reduces growth of both triple negative and luminal breast cancer cells in high and low estrogen environments. Nutr Cancer. 2015;67(6):1001–9.
- Lowcock EC, Cotterchio M, Boucher BA. Consumption of flaxseed, a rich source of lignans, is associated with reduced breast cancer risk. Cancer Causes & Control. 2013 Apr;24:813-6.
- Velentzis LS, Cantwell MM, Cardwell C, Keshtgar MR, Leathem AJ, Woodside JV. Lignans and breast cancer risk in pre-and post-menopausal women: meta-analyses of observational studies. British journal of cancer. 2009 May;100(9):1492-8.
- Thompson LU, Chen JM, Li T, Strasser-Weippl K, Goss PE. Dietary flaxseed alters tumor biological markers in postmenopausal breast cancer. Clinical cancer research. 2005 May 15;11(10):3828-35.
