Evidence overwhelmingly supports a role for dietary fibre in human health. Originally fibre what thought to provide roughage and improve the transit of food in the gut, but more recent evidence suggests that fibre is essential to optimal human health. The health benefits of fibre are numerous although the mechanisms by which fibre can provide these benefits has not been fully elucidated in the nutritional literature. However, generally it is though that fibre helps modulate plasma glucose and lipid levels and also is beneficial at causing weight loss. While fibre has traditionally been though to remain undigested, more recent evidence suggests that fibre is digestion by microorganisms in the colon, where fermentation leads to the production of short chain fatty acids. These fatty acids such as propionate and butyrate and acetate can contribute significant energy to humans in a delayed and prolonged manner.
Fibre may be particularly useful for those who are overweight or have metabolic disorder such as with diabetes and metabolic syndrome. This is because these conditions are likely caused by poor quality diets that are devoid of fibre. Adding back in the essential components to the diet allows the body to rebalance, and this provides considerable health benefits. For example, one study published in the American Journal of Clinical Nutrition1 investigated the effects of a high fibre or a regular Western low fibre diet plan of the blood glucose and plasma lipid levels in subjects with type 2 diabetes. The subjects were fed meals consisting of identical macronutrient ratios, which only differed by the amount of fibre they contained. The results showed that fibre consumption caused improvements in fasting blood glucose levels, a decrease in the ratio of low density lipoprotein (LDL) to high density lipoprotein (HDL) and a decreases in plasma triglycerides.
In order to confirm whether the effects were from a single meal or cumulative, the high fibre subjects were given a low fibre test meal. After this solitary meal their improvements in plasma glucose and blood lipids remained, suggesting that their metabolism had been modulated by the fibre content of their diets. Just why fibre is able to cause metabolic changes that improve the health is not known, but it may relate to the ability of fibre to slow the absorption rate of nutrients from the gut. This in turn decreases the nutrients presented to the liver at any one time, and decreases hepatic overload. The resulting decrease in de novo lipogenesis may increase the efficiency of energy utilisation and decrease the flux through metabolic pathways that deal with the storage and processing of excess energy. Fibre is therefore similar to eating smaller amount more frequently, something that has been shown to have similar metabolic effects.