Dietary fibre is likely a conditionally essential nutrient. Diets containing carbohydrate must contain fibre or they lead to Western lifestyle diseases such as cardiovascular disease, cancer, type 2 diabetes and obesity. In this regard refined crystalline sugars appear to be the most detrimental, but refined starches also play a significant role as drivers of disease. Dietary fibre is important because it delays the absorption of the digestible carbohydrate component of the plant material and this prevents the liver overload syndrome. The cell walls of plants surround the starch and sugars within and this inhibits digestion and absorption, and trickles the energy into the blood in a controlled and manageable manner. The acceptance that carbohydrates refined of their fibre are disease causing agents has been slow to become accepted. This is largely thanks to a clever marketing strategy by the men in expensive suits who work for the powerful food industry. However, the truth will eventually out and even such clever men cannot hide the bodies forever.
Fibre was originally thought to add roughage to the food and little more. However, recent evidence has uncovered a multitude of physiological effect brought about by fibre. Further, while fibre was traditionally grouped into soluble and insoluble fibres, more recently it has become apparent that this gross simplification is not adequate to distinguish the sometimes very different properties of apparently similar dietary fibres. For example, legumes and oats are both excellent sources of soluble dietary fibre, however, they appear to have quite different effect on human physiology. Comparisons of the effects of the soluble fibre from beans and oats have been performed in hypercholesterolaemic men, and generally they both possess a cholesterol lowering ability. In one study1, subjects in a metabolic ward were fed either a high bean diet, a high oat diet or a control diet matched for protein, carbohydrate and fat content for 21 days. A number of parameters relating to lipoprotein metabolism were then assessed by the researchers.
The results showed that those subjects receiving the oat and bean diet both had a 19 % decrease in serum cholesterol concentrations. The oat diet decreases serum low density lipoprotein (LDL) by 23 % and the bean diet decreased serum LDL by 24 %. However, the oat diet increased faecal weight by 43 % but beans had no effect in this regard. In addition, the oat diet also increased faecal bile acid excretion while beans actually decrease faecal bile acid secretion. The bean and oat fibre diets in this study were estimated to provide around 3 times the fibre as the control diet. This was provided in the case of oats by a bowl of porridge and five oat muffins (47 grams total fibre and 17 grams soluble fibre). The bean diet contained pinto and navy beans served in a bean soup and provided the same quantity of fibre as the oat diet. However, despite similar amounts of soluble fibre, there were clear differences in the effects of the fibre from beans and oats. This may relate to the chemical makeup of the fibre in the original plant foods.
Therefore beans and oats both have very similar effects on serum cholesterol levels in hypercholesterolemic men. Neither diet caused a reduction in high density lipoprotein (HDL), and so both beans and oats are able to improve the LDL to HDL ratio in humans. However, beans and oats appear to have differing effect on faecal weight and bile acid excretion. Interestingly and most importantly perhaps, the subjects on the bean and oat fibre diets lost weight, despite the researchers making the diets they consumed adequate in energy for maintaining their body weight. Therefore the cholesterol reducing effects of both beans and oats may derive from their ability to cause weight loss in overweight subjects. This weight loss effects also provides more evidence that it is not the amount of food that is eaten that causes weight gain, but the types of foods eaten. Were these subjects deficient in the conditionally essential fibre before the study started? Is that why they were overweight and unhealthy?
Dr Robert Barrington’s Nutritional Recommendation: Oats and beans are excellent sources of fibre. Studies have shown that they have normalising effects on Western diet induced metabolic dysfunction and can also cause weight loss. Consuming a range of legumes and oats as part of a healthy high quality diet is recommended.
RdB
