Coronary artery disease is the major cause of death in most Western countries, and blood cholesterol is a major risk factor. Dietary as well as pharmacologic reduction in total and LDL-cholesterol decrease the risk of coronary events, and dietary intervention is the first-line approach.
Increasing dietary fibre, because of the interference with the digestion and absorption processes along the gastrointestinal tract, has been recommended as a safe and practical approach for cholesterol reduction. Several independent studies have documented that oat products have a cholesterol lowering effect in normo- and hypercholesterolemic subjects. In 28 out of 38 studies there was a significant reduction in total cholesterol, with a similar percentage reduction in LDL-cholesterol. Two meta-analyses of controlled trials concluded that consumption of oat products reduces serum cholesterol levels, but the effect is small and variable within the practical range of intake of oat products.
However, these two meta-analyses and a study by Davidson et al. (1991) suggest a dose dependent response in the cholesterol lowering properties of oats found an overall effect of -0.13 to -0.16 mmol/l with an average dose of oat soluble fibre of 3.2 g/d (range 1.1 - 7.6 g/d). In the study by Davidson et al. (1991) there was a statistically significant reduction in total and LDL-cholesterol of mixed linked (1→3)(1→4)-β-D-glucan, the main soluble fibre component in oats. When the level of oat β-glucan exceeded 3 g/d, Brown et al. (1999) calculated a net change on serum total cholesterol of on average -0.037 mmol/l per g soluble fibre. The net change in LDL cholesterol was -0.032 mmol/l per g soluble fibre. The average intake of soluble fibre in these studies was 5.0 g (range 1.5 - 13 g/d).
The mechanism(s) behind the cholesterol lowering effects of oat soluble fibre is not certain but most data suggest that the viscous properties of β-glucan play a key role by slowing absorption of nutrients and increasing bile acid excretion. Modification of rheology of the gut lumen is believed to be responsible for these effects, which means the physiological response is mechanically or physically based rather than biochemically.
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