Fish is highly nutritious and is an important part of the traditional Mediterranean diet. It is rich in proteins, omega 3 fatty acids, vitamin D, vitamin B2 (riboflavin) and is also a great source of minerals such as calcium, phosphorus, iron, zinc, iodine, magnesium, and potassium. Analysis of different case-control and population based studies found that a healthy diet/nutrition including fish such as salmon that is rich in omega-3 fatty acids may help in reducing the risk of specific types of cancer such as breast, endometrial, pancreatic, colorectal and liver cancers. However, more detailed research and evidence are required to establish this fact.
Fish has been a part of the nutrition of all non-vegetarians since ancient times. Mediterranean diet, in particular, includes plenty of fish and seafood that are rich in proteins and low in cholesterol as well as saturated fats. There are different types of fish and shellfish that can be added as part of a healthy nutrition including salmon, trout, sardines, herring, mackerel, tuna and oysters. Fish is packed with proteins, omega-3 fatty acids, vitamin D, vitamin B2 (riboflavin) and is also a great source of minerals such as calcium, phosphorus, iron, zinc, iodine, magnesium and potassium.
Health benefits of eating Fish
Being a great source of omega-3 fatty acids, fish is considered as a healthy food especially because it is good for the heart. Eating fish has numerous other health benefits. Different studies have shown that eating fish as part of our daily nutrition may help in reducing the risk of heart attacks and strokes, improving eye-sight, decreasing the risk of asthma, improving brain health, strengthening and improving memory and preserving a strong immune system. If you are a non-vegetarian or a pescatarian, eating fish helps to strike the right balance in your diet, as it is rich in a variety of nutrients.
Nutritional Benefits of Salmon
Salmon is a tasty and popular oily fish used in our daily nutrition, that is rich in good fats and is considered to be one of the most nutritious types of fish with many health benefits. Salmon is a great source of proteins, omega-3 and omega-6 fatty acids, a variety of vitamins including vitamin B12, vitamin B2, vitamin D, minerals such as selenium, phosphorus, zinc and potassium and other essential nutrients. Salmon is hence recommended by nutritionists to be included as part of a healthy diet/nutrition.
Recently, there were a lot of discussions and debates on whether wild caught salmon or farmed salmon should be included in our nutrition. Though farmed salmon is significantly cheaper and a more affordable option, it has got a bad reputation as these may contain toxic contaminants and lesser omega-3 fatty acids, vitamins and minerals. Hence, for a healthy nutrition, choosing wild-caught salmon would be better.
Fish Intake and Cancer
Apart from Salmon, there are many other types of fish that are rich in omega-3 fatty acids. Some of the examples are cod, halibut, haddock and sardines. Since omega-3 fatty acids intake may reduce the risk of certain types of cancers, many studies and meta-analysis have been carried out in the last few decades to study the association between the intake of fish (which are rich in omega-3 fatty acids as well as many other nutrients including proteins, vitamins and minerals) and the risk of different types of cancers. In this blog, we will elaborate the details of such studies which evaluated the association between fish intake and cancer risk along with their findings.
Fish Intake and Breast Cancer Risk
In an analysis published in 2017, the researchers from Iceland, Massachusetts, Sweden and Maryland in the United States used data from the Reykjavik Study, a population-based cohort study, which was initiated by the Icelandic Heart Association, to evaluate the association between fish intake throughout the lifespan and the risk of breast cancer. They used data on the first residence of 9,340 women born between 1908 to 1935 as well as diet information for different periods of life from a subgroup of the 2882 women who entered the Age, Gene/Environment Susceptibility (AGES)-Reykjavik Study. A total of 744 women were diagnosed with breast cancer, during a mean follow-up of 27.3 years. (Alfheidur Haraldsdottir et al, Cancer Epidemiol Biomarkers Prev., 2017)
The analysis found that a very high intake of fish during early adulthood to midlife may be associated with a reduced risk of breast cancer.
Fish Intake and Prostate Cancer Risk
In a recent study, the researchers evaluated the association between fish intake and prostate cancer risk and mortality in a Danish cohort study which included data from 27,178 men. By 2012, 1690 prostate cancer cases were reported. (Malene Outzen et al, Eur J Cancer Prev., 2018)
The analysis of this study found no strong association between fish consumption and the risk of prostate cancer. However, a higher intake of fatty fish was found to be associated with a higher risk of prostate cancer-specific mortality.
In another meta-analysis published in 2010, the researchers used data from 12 case-control/clinical studies consisting of 5777 cases and 9805 controls and 12 cohort studies with data from 445,820 people based on literature search till May 2009 from databases such as MEDLINE, EMBASE and ProQuest Dissertations and Theses Database. Additionally, there were other studies which investigated the association with only certain fish types. Two such studies included data specifically on nutrition including fatty fish (eg, salmon, herring, and mackerel) and 4 studies on preserved fish which were either smoked, dried, and salted. These were not included in the 12 case-control studies and 12 cohort studies which were analyzed to evaluate the association between fish consumption and prostate cancer incidence and mortality. (Konrad M Szymanski et al, Am J Clin Nutr., 2010)
The study did not find any strong evidence of a protective association of fish consumption with prostate cancer incidence. However, the analysis found a significant reduction in prostate cancer–specific mortality.
In a third study published in 2003, the researchers evaluated the association between consumption of fish and marine fatty acids and the risk of prostate cancer based on data from the Health Professionals Follow-up Study in the United States which included 47,882 men. The dietary/nutrition information included data about intake of canned tuna, dark meat fish (mackerel, salmon, sardines, bluefish, and swordfish), other fish dishes and seafood which were taken as the main dish. During 12 years of follow-up, a total of 2482 cases of prostate cancer were reported, of which 617 were advanced prostate cancer which included 278 metastatic prostate cancers. (Katarina Augustsson et al, Cancer Epidemiol Biomarkers Prev., 2003)
The study found that men with a high consumption of fish had a lower risk of prostate cancer, especially for metastatic cancer.
In short, it is inconclusive whether high fish intake may be beneficial for reducing the risk of prostate cancer. However, fish such as salmon may be consumed as part of our diet/nutrition for its other well known health benefits.
Fish Intake and Endometrial Cancer
A study published in 2002 evaluated the association between fish consumption and endometrial cancer risk in Sweden, a country which is well known for a wide range of high fatty fish consumption. Based on the dietary/nutrition data from 709 cases and 2888 controls in a Nationwide Case-Control Study in Sweden, the researchers analyzed the association between the consumption of both fatty fish (such as salmon and herring) and lean fish (such as cod and flounder) with endometrial cancer risk. (Paul Terry et al, Cancer Epidemiol Biomarkers Prev., 2002)
The study suggested that consumption of fatty fishes including salmon and herring as part of daily nutrition may be associated with a reduced risk of endometrial cancer.
Fish and Omega-3 Polyunsaturated Fatty Acid (n-3 PUFA) Intake and Pancreatic Cancer Risk
In a study published in 2015, the researchers investigated the association between fish and omega-3 polyunsaturated fatty acid (n-3 PUFA) intake and risk of pancreatic cancer. The researchers used data from 82,024 eligible participants aged between 45 to 74 years without a history of cancer who were included in the Japan Public Health Center-based Prospective Study (JPHC study). The dietary information was obtained from a validated food-frequency questionnaire that covered 138 items in 1995 for cohort I and in 1998 for cohort II and the participants were followed up till December 2010. During a median follow-up period of 12.9 years, a total of 449 newly diagnosed cases of pancreatic cancer were reported. (Akihisa Hidaka et al, Am J Clin Nutr., 2015)
The study analysis found that a high n-3 PUFA intake may be associated with a reduced risk of pancreatic cancer in a population with a large variation in fish consumption.
Fish Intake and Colorectal Cancer Risk
Another study published in 2015 evaluated the association between the consumption of freshwater fish and sea fish and the risk of colorectal cancer in Chinese population in a large case control study. Dietary intake data was obtained using food frequency questionnaires from 1189 eligible colorectal cancer cases and 1189 controls. (Ming Xu et al, Sci Rep., 2015)
The study found that higher consumption of freshwater fish and sea fish may be associated with a reduced risk of colorectal cancer. However, the study found no significant association between dried or salted fish and shellfish intake and colorectal cancer risk.
Fish and Omega-3 Polyunsaturated Fatty Acid (n-3 PUFA) Intake and Liver Cancer Risk
A study published in 2012 evaluated the association between fish, omega-3 polyunsaturated fatty acid (n-3 PUFA) consumption and liver cancer risk in a population-based prospective cohort study named the Japan Public Health Center Study which included 90,296 Japanese subjects aged between 45 to 74 years. (Norie Sawada et al, Gastroenterology., 2012)
The analysis found that consumption of n-3 PUFA-rich fish or n-3 PUFAs may help in protecting against the development of liver cancer.
The above studies hint that a healthy diet/nutrition including fish rich in omega-3 fatty acids such as salmon may help in reducing the risk of specific types of cancer such as breast, endometrial, pancreatic, colorectal and liver cancers. However, more studies and evidence are required to establish this fact. Apart from omega-3 fatty acids, the health benefits of fish may also be attributed to other nutrients such as different vitamins and minerals. Eating more fish and reducing the intake of red and processed meats may help in reducing the risk of cancers such as colorectal cancer. In short, if you are a non-vegetarian, eating fish such as salmon, as part of your daily diet/nutrition, may be beneficial for your overall health.
Cancer patients often have to deal with different chemotherapy side effects which affect their quality of life and look out for alternative therapies for cancer.Taking the right nutrition and supplements based on scientific considerations (avoiding guesswork and random selection) is the best natural remedy for cancer and treatment related side-effects.