Believed to affect as many as one in five people in the UK, irritable bowel syndrome (IBS) comes with a catalogue of debilitating symptoms ranging from abdominal pain to bloating, constipation, nausea, heartburn and fatigue. Most patients with IBS are aware that diet plays a major role in the onset of their symptoms and will actively seek guidance on which foods to consume and which to avoid. Diets that are high in fat often exacerbate the symptoms of IBS, but simply cutting out fat from the diet may have unforeseen consequences, of which many IBS sufferers are less aware. Indeed, more emphasis should be placed on the type of fat in the diet.
Recent evidence suggests that inflammation within the gastrointestinal tract may be of great importance in the development of IBS, and that this inflammation is directly linked to the types of food we eat and the source of fat in our diets.1
Arachidonic acid (AA) is an omega-6 polyunsaturated fatty acid (PUFA) and the precursor to a number of important immune and inflammatory substances such as prostaglandin E2 (PGE2) and leukotriene B4 (LTB4). LTB4 is a potent immune-regulating product that is rapidly generated from cells of the immune system such as neutrophils, macrophages, and mast cells. These cells act in part by attracting other immune cells to the site of action. However, if the signals are not controlled correctly and LTB4 continues to be produced, this can lead to prolonged and unregulated inflammation. Elevated levels of LTB4 have been reported in various immune and allergic diseases, including IBS2; these levels have been related to disease activity and response to treatment. As LTB4 is not stored and released, but synthesised directly from AA, reducing the amount of AA from which LTB4 can be produced offers potential to regulate inflammation.
The fatty acid composition of the body (in other words, the type and distribution of fats that make up our cell membranes) is largely determined by what we put on our plates. Western society consumes a high ratio of omega-6 PUFA compared with omega-3 PUFA, due to excessive intake of omega-6 rich vegetable oils together with low consumption of omega-3 rich foods such as oily fish. This is bad news for people experiencing high levels of inflammation since we know that dietary dominance of the omega-6 family gives rise to pro-inflammatory products, with long-term health consequences. Replacing ‘bad’ fats in the diet with healthful monounsaturated and polyunsaturated omega-3s is essential in order to control levels of inflammation and overall health.
EPA, the long-chain omega-3 fatty acid found primarily in fish and fish oil, has been extensively researched for its potent dual-action anti-inflammatory health benefits. Studies have shown that high doses of EPA not only reduces the amount of AA available for conversion to inflammatory products, but also gives rise to a series of anti-inflammatory products that further reduce the inflammatory state of the gut. Given that approximately one-third of the entire immune system is located in the gastrointestinal tract, it’s not surprising that the fatty acid composition of these immune cells can impact our gut function. We also know that the fatty acid composition of inflammatory and immune cells is sensitive to change according to the fats in our diet, so we are able to manage inflammation by restricting our intake of foods rich in AA, whilst increasing foods rich in EPA.
AA-rich foods to restrict that are inflammatory:
- animal-derived products such as eggs and dairy (in particular those fed on grains)
- red meat, especially if not organic or grass-fed, is particularly rich in AA and in general, the fattier the meat, the more AA it contains
EPA-rich foods to eat more of, for anti-inflammatory benefits:
- oily fish are a direct source of EPA; limiting to two portions weekly, however, may be wise when considering the potential health issues connected to contamination of marine products with heavy metals, dioxins and PCBs. Bear in mind that fish higher in the food chain contain higher amounts of contaminants, whereas short-lived fish tend to be ‘cleaner’. Tuna or swordfish, for example, are best restricted to two portions, whereas sardines or anchovies can be safely eaten more frequently. An alternative to consuming fish or a safe way to increase EPA levels in addition to (or instead of) fish consumption is through the use of purified EPA supplements (encapsulated to protect against oxidation), such as E-EPA 90 and Vegepa E-EPA 70.
Restricting intake of foods known to elevate AA whilst increasing EPA levels can have a positive outcome on immune and inflammatory status, not only for IBS but for overall health. The ratio of AA to EPA within cell membranes is increasingly recognised as an indicator of general health status, and managing the ratio can offer significant long-term health benefits. An AA:EPA ratio of less than 3 but not less than 1.5 indicates a better balance of ’anti-inflammatory’ to ’inflammatory’ products in the body. If the body reaches a ratio of 7 or more, indicating EPA deficiency, this implies that the body is in a state of ‘silent-inflammation’, which is associated with a higher risk of developing inflammatory-based conditions.
Supplementing with EPA can help to restore the natural balance of AA to EPA within the body, with 1g pure EPA daily offering significant health benefits not only for immune and inflammatory status, but also for the regulation of the cardiovascular system and for ensuring optimal brain health.
1. Solakivi T, Kaukinen K, Kunnas T, Lehtimäki T, Mäki M, Nikkari ST. (2011) Serum fatty acid profile in subjects with irritable bowel syndrome. Scand J Gastroenterol. 46:299-303.
2. Clarke G, Fitzgerald P, Hennessy AA, Cassidy EM, Quigley EM, Ross P, Stanton C, Cryan JF, Dinan TG. (2010) Marked elevations in pro-inflammatory polyunsaturated fatty acid metabolites in females with irritable bowel syndrome. J Lipid Res. 51:1186-92.