Meta-analysis Shows Fish Oils Significantly Reduce Breast Cancer Risk

Breast cancer is one of the most common cancers and is the leading cause of cancer related death in women. 

Not surprisingly, it has been getting a lot of media attention recently, particularly following Angelina Jolie's public announcement that she had a double mastectomy to reduce her risk of developing breast cancer, to which she had a genetic predisposition. 

Arguments could be made from both sides of the fence regarding the decision to have a double mastectomy, and of course individual circumstances will differently influence each situation. 

Some good news on the topic however, is that dietary and lifestyle factors can also play a role in reducing breast cancer risk, without the need for drastic measures. 

In a recent analysis, researchers have confirmed that omega 3 polyunsaturated fatty acids found in fish play a protective role against breast cancer. 


Review Findings

Researchers reviewed 21 independent prospective cohort studies involving approximately 880,000 participants (close to 21,000 of which had breast cancer). 

Among these studies were trials looking at the effects of fish intake in general, intake of omega 3 fats from fish and plant-based omega 3 intake on breast cancer risk. 

The type of review conducted was a meta-analysis, a powerful tool to assess topics which have previously yielded inconsistent research results, as it reviews a far larger amount of data to give a comprehensive overview than individual studies do.

As previous research on the association between breast cancer and fish oils (or omega 3 fats) has produced some mixed results, this meta-analysis looked at all of the existing research on this topic and has finally provided the public with solid evidence of the protective role of fish oils against breast cancer.

The most significant results were found in trials using omega 3 fats from fish, which, when comparing women with the highest intakes to those with the lowest intakes, caused a 14% reduction in risk of breast cancer. 

A more detailed dose-response analysis showed that risk of breast cancer was reduced by 5% per 100mg per day of omega 3 fats from fish eaten. 


Interestingly, this review also confirmed previous research showing that omega 3 fats had a more significant protective effect in post-menopausal women than in pre-menopausal women.

A possible reason for this is that the benefits of omega 3s occur after long term exposure, which could be observed best at the postmenopausal period because breast cancer is a disease with a long latency between exposure and development.


Fish that do not contain high amounts of omega 3 fats and plant-based omega 3 fats were not found to significantly reduce breast cancer risk. 

Researchers believe that omega 3 fats from fish may play a role in decreasing the production of oestrogen and thereby reduce oestrogen-stimulated cancer cell growth in breasts. Omega 3s are also involved in gene regulation and cell growth and signalling processes.

In addition, omega 3 fats from fish oils are potently anti-inflammatory which is another possible reason for their cancer-protective effects, as chronic inflammation is known to promote cancer development. 


In Summary 

To gain a therapeutic effect from dietary omega 3 intake from fish, it is recommended to have at least two servings of fish each week.

However, in this review fish oil supplements were also counted as “omega 3 fats from fish”.


The Best Dietary Marine Omega 3 Choices

The best sources of omega 3 fats from fish are salmon, tuna and sardines. To get the best quality fish, ensure you find a fishmonger who sells wild-caught, fresh fish.

Farmed fish, such as farmed salmon, contains far lower levels of omega 3 fats than wild fish do and have higher levels of pro-inflammatory fats as they are fed with omega 6-rich grains. 

Farmed fish will also contain antibiotic and pesticide residues, so are best avoided. Most supermarket and frozen fish are likely to be farmed – so make sure you do your research before buying your fish. 

Interestingly, the authors of this review speculated that the protective effect of general fish intake might be attenuated or even reversed by other contaminants in fish, such as heavy metals and pesticides so purified fish oils are a great alternative source of omega 3 fats. 


Getting The Best Quality Fish Oil Supplements

It is important to research fish oil supplements before taking them, as not all fish oils are of the same quality, and you may do more harm than good by taking a low-quality fish oil. 

It is important to avoid cheap fish oils that use farmed fish sources, do not properly remove toxic contaminants, do not protect fish oils from becoming oxidised or rancid and are of low concentration. 

To find out more about picking a high-grade fish oil, read on here. 


Are You Getting Enough? 

Due to the high intake of omega 6 fats in the standard Western diet which throw out our omega 3 to 6 balance creating an inflammatory environment in the body, most people will require additional supplementation with fish oils.

Fish oils have been shown to be clinically effective for a range of conditions in addition to cancer prevention, including musculoskeletal health, nervous system health and cardiovascular function. 

If you want to find out exactly how much fish oil you need for optimum health results, get your Essential Fatty Acid levels tested through Emed. 


Further Reading: 



Zheng, J. et al. 2013, Intake of fish and marine n-3 polyunsaturated fatty acids and risk of breast cancer: meta-analysis of data from 21 independent prospective cohort studies, British Medical Journal