The Carbohydrate Hypothesis Part 1: From Good Calories, Bad Calories by Gary Taubes
The carbohydrate hypothesis goes though why we label carbs as either good or bad and how certain carbs are linked to many diseases due to the western diet. We will dive into the science, carbs and salt and blood pressure. Next week, we’ll touch on sugar and insulin as well as a bit more on cholesterol. Get ready, you’re in for a doozy.
The Science:
Investigators starting in the 1900’s were led to believe that many western diseases such as obesity, diabetes, cardiovascular disease, hypertension, stroke, cancer, cavities, periodontal disease, appendicitis, peptic ulcers, diverticulitis, gallstones, hemorrhoids, varicose veins, and constipation had a single common cause: the consumption of easily digestible, refined carbs. By the late 1920’s, the meat eating hypothesis had given way to the notion that it was overnutrition in general, in conjunction with modern processed foods, lacking the vital elements necessary for health that were to blame. These are foods that need conservation or refrigeration, artificial preservation and coloring, or processing to keep from spoiling. As a result of these modern processed foods, far reaching changes in bodily function and metabolism are introduced which, extending over many years, can be detrimental to your health. The nutritional debate over the excessive refining of flour and sugar had always been about whether the benefits of digestibility and the pleasing white color outweighed any potential disadvantages of removing the protein, vitamins, and minerals. This led to the suggestion that even diseases like cancer could be a kind of deficiency disease caused by vitamin deficiencies. At least 70-80% of cancers in the US might be avoidable with appropriate changes to diet and lifestyle. But what about fiber? The results of the 49,000 women dietary modification trial of the women's health initiative published in 2006 confirmed that increasing the fiber in the diet by eating more whole grains, fruits, and veggies had no beneficial effect on colon cancer, nor did it prevent heart disease or breast cancer or induce weight loss. It still holds up in relation to constipation, but as far as a major factor in the common diseases of the developed world, no, fiber is not the answer. The two most important conclusions in their analysis were that (1) man-made chemicals in pollution, food additives, and occupational exposure, play a minimal role in human cancers and that diet played the largest role and (2) clinical trials and large scale studies had demonstrated that the dietary fat and fiber hypotheses of cancer were wrong and similar investigations had repeatedly failed to confirm that red meat played any role. Healthy individuals would be expected to increase their risk of all these conditions by the consumption of refined and easily digestible carbs which inflict their damage first through their effects on blood sugar and insulin and then indirectly through triglycerides, lipoproteins, fat accumulation, and other factors. I’m sure you have all seen on your food labels like “prevents” or “protects against” or “lowers the risk of” but the reality of those claims is just that, claims. These words are used when discussing evidence that is suggestive and hypothesis generating as well as when they are discussing evidence that is as firm as science can make it and you (the public) don’t know which one it is.
Carbs:
When it comes to carbs the more the refining, the whiter the product, and the lower the vitamin, mineral, protein, and fiber content. Carb foods can be transported around the world without spoiling or being devoured by rodents on the way such as sugar, molasses, white flour, white rice. Refined carbs represented the most dramatic change in human nutrition since the introduction of agriculture. Americans replaced a good portion of the whole grains they ate in the 19th century with refined carbs. In most cases, cereal grains, tubers, veggies, fruits, and white flour, sugar, rice and beer were all included under one single category of carb versus two: refined and unrefined. Refined carbs, as we know, can cause the body to lose its homeostasis resulting in disease. Anything that slowed the digestion of these carbs like eating unrefined carbs reduced the strain on the pancreas, the organ that secretes insulin in response to rising blood sugar, or anything that increased the assimilation of glucose without the need for insulin (excessive physical activity) might help prevent diseases of the pancreas. It is believed the concentration of carbs in the refining process did its damage in 3 ways; 1: it led to overconsumption because of the deception of the appetite control apparatus by the density of the carb, 2: exacerbated by the removal of protein from the original product, 3:the refining process increased the rate of digestion of carbs and so the onrush of blood sugar on the pancreas which would explain diabetes. Carb rich diets can cause the body to retain water and so raise blood pressure, it’s not just about salt. Eating carbs prompts the kidneys to hold sodium rather than excrete it, the body retains water to balance out, in doing so removing carbs works like diuretics. Treatment of obesity with very low-carb diets would be met with not complete elimination to maintain fluid balance and avoid large shifts in weight due to water. The water retaining effect of carbs was due to the insulin secreted which in turn induced the kidneys to hold sodium rather than excrete it and that insulin levels were higher in hypertensives than normal individuals. The more carbs consumed, the more insulin is needed to transport the glucose from the carbs into cells where it can be used as fuel. The insulin prompts the liver to synthesize and secrete triglycerides for storage in the fat tissue instead of excrement. If eating a carb rich diet in the presence of insulin resistance will abnormally elevate triglyceride levels, it is hard to avoid the implication that eating a carb rich diet increases the risk of heart disease as well. Carbs are disposed of in 3 sites, adipose tissue, liver, and arterial walls. Complex carbs break down into simple sugars during the process of digestion but they take awhile to do so and if the carb is bound up with fiber the digestion takes even longer. When consuming carbs with a meal the presence of fat and protein in a food decreased the blood-sugar response and so decreased the glycemic index. The more refined the carb, the greater the blood sugar and insulin response. Anything that increases the speed of digestion of carbs will increase the glycemic response (mashing, liquid form, polishing).
Salt and Blood Pressure (BP):
The salt-hypertension hypothesis concludes that when salt is consumed we retain water to balance it out and the kidney’s filter and excrete (cannot be proven). If BP is elevated in pre-hypertension or hypertension, salt reduction would only reduce by 4-5 points versus the 20 points or more BP already is which makes little difference. Eating less salt was a preventive measure that is thought to help the general public and the health organizations and companies used scare tactics to make the public believe that salt equals bad. However, as you read above, eating refined carbs raises BP due to insulin. Other hormonal mechanisms by which insulin raises BP include nervous system stimulation and the same fight or flight response normally produced by adrenaline. Insulin increases heart rate and constricts blood vessels, raising BP. The higher the insulin level the greater the stimulation of the nervous system, and if they remained high the sympathetic nervous system would constantly be working to raise BP.
