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Chapter 11

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Biomedical Physio & Kines
BPK 143
Tony Leyland

NO ROOM FOR COMPLACENCY - Main reasons for increased life expectancy are 1) Improved sanitation 2) Improved food safety 3) Antibiotics - Life expectancy for the average American could decline by as much as five years unless aggressive efforts are made to slow rising rates of obesity - Quantity and quality of food are important NUTRITION- ARE YOU CONFUSED YET? 1) Food is complex. We don’t know the thousands of compounds that occur in natural foods. Even one type of food grown in a different area has different chemical properties. 2) The interaction between food and physiology is complex. The way food and human physiology interact is incredibly complicated, and affects hormonal balance—how your phenotype is expressed. 3) Exercise affects the food/physiology interaction. Because exercise affects hormonal balance, how you exercise (or if you do not exercise at all) is a huge factor in the way your body responds to food intake. Many good epidemiological studies have been conducted on sedentary populations. However, because there are complex hormonal responses to exercise and food, the questions are whether these results apply to active populations and, if so, at what level of activity. 4) The way food is grown or reared is vastly different. For example, some research suggests that you should limit the amount of red meat you eat. But is meat from a grass-fed, antibiotic-free, and growth-hormone-free animal the same as meat from a grain-fed animal that is given antibiotics and growth hormone? What about fruits and vegetables grown with or without pesticides? 5) Nutritional information is contradictory. There are numerous contradictory statements from nutritional experts. For example, the general belief is that reducing red meat intake reduces risk of colorectal cancer. But, paradoxically, beef together with whole milk and dairy derivatives are almost the only sources for conjugated linoleic acids (CLAs), which are the only natural fatty acids accepted by the National Academy of Sciences of USA as exhibiting consistent antitumor properties. 6) A lot of advice is contrary to “evolutionary logic.” By this I mean that we evolved eating many foods that we are now told aren’t good for us; we did not evolve eating many of the foods that we are now told are okay to eat in huge quantities, such as grains. Given that evolution is one of the few things in biological science that all scientists agree with, this seems strange. 7) Some long-held beliefs are wrong. There were some very bad conclusions made from poor research a few decades ago and some of it has become mainstream belief. This belief is very hard to shift out of the public psyche. 8) Some research has been conducted incorrectly. Further nutritional research set out to prove what we “already knew,” and this is simply not the way scientific research is supposed to be conducted. 9) There are too many rules for the general public to “digest.” Nutritionists want to be complete in their analysis, but providing too many rules means too much confusion for the general population. 10)Nutritional guidelines are not objective. Food manufacturers were involved in the development of government-sponsored nutritional guidelines. This is far from objective. 11)Manufacturers make unreliable claims. Advertisements from food manufacturers often state that their nutritional claims are based on “scientific studies.” The general population does not have time to investigate these claims and the regulation of such claims appears quite lax. The population is led to believe that these claims must be true, which is not always the case. AN EVOLUTIONARY PRESPECTIVE ON NUTRITION - The problem with the study of human nutrition is that it lacks a universally acknowledged, unifying paradigm - Human nutritional requirement were genetically determined Paleolithic nutrition - There is a strong evidence that the obesity problem has been caused by a heavily reliance on sugar, refined carbohydrate, and other processed foods in our diets , and a sedentary lifestyles and lack of exercises - Cow’s milk (but there is chemical evidence for dairying in the form of residues of dairy fats on pottery around 6100-5500 BC in Britain) - Cereal grains (agriculture started around 10,000 years ago). - Table salt (but excavated ancient saltworks are thought to date back to at lest 6000 BC) - Processed sugar (introduced after 1800). - Highly processed foods (introduced mostly after 1800). - Pesticide residues (introduced after 1930). - Radioactive foods (introduced after 1945). - Artificial/synthetic additives (introduced mostly after 1950). - High-fructose corn syrup (HFCS) (mass produced from 1965). - Genetically modified food (introduced since the 1990s). Paleolithic food pyramid - Stone age humans died ( on average) much earlier than we do because of infectious disease that we have since learned to control PROBLEMS WITH PALEOTHIC NUTRITION - Eating a strict Paleolithic diet is incredibly difficult in our society - Food that would be acceptable on a strict Paleo diet is hard to find, spoils very easily, and is usually expensive What is “the” Paleolithic diet and could you actually eat such a diet today? - No one can agree on what Paleolithic diet is - Most foods that we evolved eating are no longer available to us today, either in type of quantity Food isn’t poison - Modern food isn’t strong poison - Some modern food behave like slow-acting poisons, a heavy reliance on these foods will wreak havoc with our health Humans adapted to a wide variety of foods - Ancestors would also had widely varied diets Epigenetic adaptations - Epigenetic adaptations are changes in phenotype (gene expression) caused by mechanisms other than changes in the underlying DNA sequence - Changes may remain through cell divisions for the remainder of the cell’s life, and may also last for multiple generations - There is no change in the underlying DNA sequence; in effect, non-genetic factors are causing the organism’s genes to behave or “express themselves” differently - Epigenetic marks on DNA change over a person’s lifetime, and the changes are similar in family members - Overall genome health is inheritable and that epigenetic changes that occur during a person’s lifetime may explain why susceptibility to disease increases with age Did Paleolithic humans eat starchy tubers? - Tubers are swollen, underground plant parts that store food - Exp. Potato, turnips, cassava, yams - Cannot be eaten raw - During human evolution, duplication of certain genes occurred that allowed humans to more easily subsist on tubers - Advice to avoid potatoes might not be correct if early humans had developed genes that specifically allowed for better breakdown of starchy food - It requires a reliable supply of sugar to fuel brain growth - Starch may be a natural human food, most hunger-gatherer groups consume predominantly meat - Starchy tubers may have supplemented this diet, providing extra energy, or glucose, needed for brain growth Food Production - We couldn’t sustain the current human population if we all eat Paleo diets - Abundant calories have facilitated human population growth - Agriculture has allowed us to congregate in large cities, which has helped cultural development - There is problem finding natural foods similar to what our ancestors would have eaten - There is issue of pesticides used in growing fruit and vegetables - Organic foods are expensive, but is far more nutritious than ordinary produce, and can help improve health and longevity - You should eat food you believe will help you keep you healthy Support for reducing processed and “new” foods - Traditional, un-processed diets did not cause the health problems that we afflict our society today - Modern processed food, overwhelming amount of sugar, refined carbohydrate, high-fructose corn syrup, fructose, trans-fats, and chemicals in those processed foods, are the main reason – along with lack of exercise- behind the current epidemic of obesity and metabolic derangements POOR RESEARCH AND ANCEL KEYS - The close you can move your diet to Paleo nutrition, the healthier you will be - Nutrition did have a unifying paradigm - Low-fat diets failed d Influential studies - Ancels key charted the consumption of fat in seven countries, relative to their rate of heart disease - The science supporting low-fat diet is weak - When you eat carbohydrates with a high-glycemic index, the body releases excessive amounts of insulin rapidly - The insulin spike is designed to remove blood glucose quickly and the body stores it as fat in the cells - Insulin levels have spiked to a high level, insulin stays in the blood stream for quite some time - Drives blood glucose levels lower than ideal, which causes hunger because the brain thinks that there is no more energy left to use - The result is often that you consume another high-GI meal and repeat this cycle - If you balance the meals and eat low-GI foods, you will not be hungry as soon after the meal - The hormonal response to food means there is more to meal design than counting calories - GL = GI xCarbohydrate (grams) / 100 - Glycemic load (GL) takes into account fibre content and portion size - Soluable fire, fat, acidic foods, and protein lower insulin levels - Low fat high carbohydrate diets provide no added cardiovascular benefits and may actually be harmful in terms of increasing incidence of syndrome X - Hyperinsulinemia: a condition in which excess levels of insulin are circulating in the blood - Reducing carbohydrate intake by lowing triglycerides and favorably altering blood cholesterol profiles can reduce risk of cardiovascular disease - Regulating blood insulin level by lowering carbohydrate intake may reduce the risk of developing syndrome x 1) Promote moderate consumptions of all meat 2) Increase consumption of goods rich in complex carbohydrates 3) Encourage use of skim milk and low-fat cheese - Oscam’s razor: the explanation of any phenomenon should make as few assumptions as possible, eliminating those that make no difference in the observable predictions of the explanatory hypothesis or theory - “ all other things being equal, the simplest solution is the best” - When multiple, competing theories are equal in other respects, select the theory that introduces the fewest assumptions and postulates the fewest entities GOVERNMENT AGENCY ADVICE ON NUTRITION - The government still promotes advice suggesting that grains are good and too much meat is bad - Researchers argue that government-ordained food pyramids is inadequate as health g
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