low carb & high fiber Synergistic health benefits
Updated: Oct 2, 2019
Gerald Davies MBBCh
Replacing glycemic carbohydrates with fiber offers combined benefits in the prevention and treatment of obesity, diabetes and most of the non-communicable diseases (NCD): the list includes heart attacks, strokes, cancers, dementias, autoimmune conditions such as arthritis, colitis, asthma, diabetes, celiac disease and multiple sclerosis.
1. Most people consume way too much high glycemic carbs (the root cause)
2. And they don’t get enough fibre (the antidote)
Synergy in this combined approach comes from different and opposing mechanisms for health benefits: Carbohydrates in our staple foods; flour, sugar, rice, potatoes, etc. increases both fat storage and appetite. Replacing these carbs with fibre suppresses appetite, the key to long term weight loss but also improves health via multiple newly discovered mechanisms.
Following is the evidence and links to original articles supporting a low carb, high fibre dietary pattern for weight control, diabetes treatment, regulation of immunity, reduction of inflammation and prevention of NCD’s.
The Case against carbohydrates
Modest amounts of rapidly digested carbohydrates spike glucose levels and produce large increases in insulin secretion after meals but rather than innocuous there is a mountain of evidence that these responses to our staple diet are damaging. The figure below shows glucose and insulin changes in healthy volunteers over 24 hours from foods carbohydrate foods recommended under NHS and FDA guidelines.
High glycemic carbohydrates are associated with increased all-cause mortality and the mechanisms of damage are chronic high blood sugar, fructose toxicity and chronically raised insulin levels leading to insulin resistance. High blood glucose spikes from habitual consumption of rapidly digested carbohydrate increases inflammation and atherosclerosis, even in people without diabetes. Transient increased blood sugar increases glycation throughout body tissues. This tendency is reflected in the stickiness of sugars where a negatively charged sugar molecule becomes bonded to an electropositive protein and the degree of glycation can be routinely monitored by the HgbA1C test. Incidentally, glycated LDL-C lipoprotein levels are associated with coronary disease where LDL levels, the so-called bad cholesterol are not. Insulin secretion increases 10-15 fold after only 50g or so of starch. Insulin has far reaching effects on cells throughout the body, but when produced in excess many of these actions are damaging. Chronically high insulin itself produces insulin resistance. Insulin controls lipogenesis and produces insidious weight gain but also a cell signaling pattern that increases inflammation, impairs immune function, increases risk of cardio-vascular disease, cancer and neurodegenerative diseases and likely accelerates the aging process by multiple mechanisms. Insulin directly inhibits autophagy, the process responsible for protein recycling and maintenance of efficient energy production in mitochondria. Excess insulin signalling may be particularly harmful in brain cells and immune cells involved in tissue repair. Insulin promotes cell growth and division by activating mTOR via PIP3/akt pathway and in this way provides a milieu for cancer initiation and progression.
The Case for Fibre
Protective effects of fibre go way beyond the simple concept of bowel regularity: it is a powerful antidote to diabetes and many other diseases. Levels of short chain fatty acids (SCFAs) increase proportionately with fermentation of fibre by beneficial gut bacteria. Beneficial effects of SCFA are mediated through 2 types of free fatty acid receptors present in cells widely distributed in the body such as CNS, immune cells, fat cells, and insulin producing pancreatic islet cells. SCFA, mainly acetate, propionate and butyrate are essential nutrients for intestinal cells particularly butyrate which provides colonic epithelial cells their main energy source as well as cell signaling effects that improve the integrity, size and function of the whole hind gut including increasing numbers of hormone producing L cells. Colonic entero-endocrine L cells increase in number and increase production of incretin hormones GLP1 and PYY on stimulation by SCFA. GLP1 and PYY suppress appetite and voluntary food intake. GLP1 has multiple beneficial actions across the body but particularly regulating glucose metabolism, pancreatic beta cell function and appetite suppression. GLP1 agonist drugs are widely used for the treatment of diabetes and obesity but endogenously produced GLP1 is largely responsible for the remarkable cure rate of type2 diabetes with gastric bypass surgery. Both GLP and SCFAs are involved with preserving intestinal permeability barrier function vitally important to prevent chronic low-grade inflammation from intestinal contents entering the blood stream. Butyrate and propionate have powerful anti-inflammatory effects and may reduce autoimmune diseases, allergies and promote oral tolerance of potential food allergens. Furthermore, the ‘Leaky Gut’ hypothesis may be a triggering event in inflammatory conditions and autoimmune diseases such as colitis, arthritis, asthma, celiac disease and type 1 diabetes as well as a factor in age-related diseases that are thought to be increased by systemic inflammation such as heart attacks, strokes, cancer, and dementia.
Hydrogen is produced along with SCFA during hind gut fermentation and was recently discovered to have powerful selective anti-oxidant and protective cell signaling effects. Hydrogen makes up over 60% of colonic gas, it rapidly crosses cell membranes, equilibrates throughout body fluids, tissues, cells, lipoproteins and is detectable in expired breath. The graph below is evidence of prolonged hydrogen production in subjects with lactose intolerance from 15g of lactose in 300 ml milk compared to drinking hydrogen dissolved in water. Hydrogen water is being marketed by “nutraceutical” type businesses for perceived health benefits but prebiotic fibre is a far more convenient & effective hydrogen source.
Colonic fermentation of dietary fibre produces prodigious amounts of hydrogen in direct proportion to fibre intake. Centenarians had higher breath hydrogen than controls and higher breath hydrogen had an inverse correlation with oxidized lipids. Another 2018 study showed hydrogen reduced LDL cholesterol oxidation and inflammation. Outside of China and Japan the therapeutic and preventive uses of hydrogen are not well known but the evidence and mechanisms of multiple health benefits of hydrogen are well documented.
Numerous studies have documented decreased risk of all causes of death with higher fibre intake. This figure shows a dose response of increasing protection against heart attack (CHD) with increasing consumption of fibre. The study suggests larger amounts (60-70 g/day) than current nutritional guidelines (25-35 g/day) would be at least as protective as the 30-40% relative risk reduction for CHD claimed for statins.