Previous research has pointed to an association between dietary fat consumption and the risk of colorectal cancer, the world’s third most common cause of cancer-related death.
Omega-3 polyunsaturated fatty acids (n-3 PUFAs) like docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), in particular, are known to impede the development of the cancer by restricting gene expression in colon carcinogenesis, and altering membrane lipid composition.
Furthermore, recent studies have suggested that certain omega-3 fatty acids can act as an adjuvant alongside chemotherapy in managing the cancer.
Based on this information, researchers from Sungshin Women's University compiled a review on the chemopreventive and therapeutic effects of DHA and EPA when combined with chemotherapeutic agents and natural anti-cancer compounds.
Omega-3 and chemotherapeutic agents
The review said: "Dietary intake of n-3 PUFAs has been shown to improve the efficacy of chemotherapeutic agents in the in vitro, animal and clinical studies".
It cited the example of 5-fluorouracil (5-FU), an anti-metabolite used as a chemotherapeutic agent for numerous cancers, including colorectal cancer. When combined with fish oil, the treatment was more effective in inhibiting cancer cell growth than either substance alone.
The combination also "synergistically increased the survival rate of animals and inhibited tumour growth…in a mouse colon cancer model".
Furthermore, fish oil successfully ameliorated gastrointestinal, liver and kidney toxicity induced by 5-FU, evidenced by a significant improvement in the organs' functional and structural alterations.
Separately, DHA enhanced 5-FU's pro-apoptotic ability by downregulating anti-apoptotic proteins, and triggered regulator gene overexpression to induce apoptosis and sensitise cancer cells to 5-FU's therapeutic effect.
EPA, on the other hand, worked with 5-FU and Oxaliplatin (FuOx) to shrink tumours in mice and lower levels of inflammatory mediators in their colons.
Omega-3 and natural anti-cancer compounds
The review stated that dietary fibre consumption increases in the lumen of the colon levels of butyrate, an end-product of microbial fermentation that protects against colorectal cancer.
When combined, DHA and butyrates induced apoptosis in certain colon cancer cells.
The review also noted that dietary fish oil helped repair the colonic epithelium during chronic inflammation when combined with curcumin, which is known to modulate molecular pathways in the carcinogenic process.
It added that DHA combined with curcumin could "block insulin-induced cancer cell proliferation in vitro via suppression of the mitogen-activated protein kinase (MEK) / extracellular signal-regulated kinase (ERK) pathway".
The review concluded that omega-3 fatty acids, especially DHA and EPA (abundant in fish oil), can "prevent colon carcinogenesis through multiple mechanisms", and therefore, they "may be of use as an adjuvant in the therapy" of colorectal cancer.
Source: Clinical Nutrition Research
"Chemopreventive and Chemotherapeutic Effects of Fish Oil derived Omega-3 Polyunsaturated Fatty Acids on Colon Carcinogenesis"
Authors: Ja Young Lee, et al.