4 28 14 8 16 AM pdf version of lecture Learning Objectives Explain RDA s Why we have them How we determine them How to use them How not to use them The last material discussed why people eat This material deals with how much do you need and how do we know NUTRIENT NEEDS In the United States the nutritional needs of the public are estimated and expressed in the Recommended Dietary Allowances RDA These were initially established during World War II to determine in a time of possible shortage what levels of nutrients were required to ensure that the nutrition of the people would be safeguarded At the start of the war a priority was to determine how many men must remain at home to provide essential services This included providing food for those in the US as well as the soldiers overseas To estimate the need it was required that some information be available regarding what amount of food was necessary to provide enough nutrients to keep people productive but not in excess Nutritionists realized they did not know the answer National Academy of Science The RDA are established by the Food and Nutrition Board of the National Research Council whose members come from the National Academy of Sciences the National Academy of Engineering and the Institute of Medicine While established by an act of congress the National Academy is not an arm of the government and acts independently of congress The National Academy appoints a group of scientists to establish or update RDAs At one time the RDA for all nutrients was determined by the same group and published as one document More recently they have been changed to RDI see below and there are several groups that work in more specialized teams RDA The RDA are the levels of intake of essential nutrients considered in the judgment of the Food and Nutrition Board on the basis of available scienti c knowledge to meet the known nutrition needs of practically all healthy persons The NAS NRC recognizes that diets are more than combinations of nutrients and should satisfy social and psychological needs as well Over the years RDA been revised a number of times Recently there have been political considerations RDA have been replaced with RDI The RDI are more or less same as the RDA values In 1997 new standards evolved and Dietary Reference Intakes DRI became the norm and include AI Acceptable Intake when enough data does not exist to set a high goal or when a high goal could be harmful for toxic nutrients an acceptable intake is established RDA Recommended Dietary Allowance a high goal see below https carmen osu edu content 1144 FDSCTE 2200 fdscte 2200 su2 ssionVal 8KMB32UCTXaqzANqxsQZoSNda ou 11349922 d2l body type 3 Page 1 of 12 EAR Estimated Average Requirement an estimate of the average requirement UL Tolerable Upper Limit the most of a nutrient that should be consumed 4 28 14 8 16 AM This gure shows an idealized response of of an organism to a given nutrient At some level there may not be enough to support life As the level of intake increases the health of the organism will increase until it gets to some marginal level Additional intake will increase health until some optimal level is reached Additional intake will not enhance health but will cause no harm At some level of intake there will be marginal toxicities and at even higher levels death may result from an overdose The RDA as will be documented below is a high goal to aim for when establishing diets for populations The EAR is an estimate of what the average persons requires The UL is an important recent addition It is the most of a nutrient a person should consume in a day Those who feel they need more of everything should become familiar with these values They are especially important for children The top two causes of poisoning of children under the age of three are consumption of excess iron and vitamin A usually from adult supplements For some nutrients we do not have enough information to establish a requirement or a goal We know we need a little but it is dif cult to determine how much Some of these trace minerals are very toxic at amounts not too much higher than the requirement In these cases it would be irresponsible to establish a high goal that could be toxic For these nutrients AI or acceptable intake levels are established They are usually a lower and upper range that have been observed to provide adequate nutrition without toxicity Requirements Requirement is the minimum intake that will maintain normal function and health Best data would be from human studies Problems with this approach https carmen osu edu content 1144 FDSCTE 2200 fdscte 2200 su2 ssionVal 8KMB32UCTXaqzANqxsQZoSNda ou 11349922 d2l body type 3 Page 2 of 12 4 28 14 8 16 AM Because it is not often possible to do the types of testing that would be required to determine an absolute requirement with people we must use a number of other techniques Determining Requirements Collection of data on nutrient intake from apparently normal healthy people Determinations of the amount of nutrient required to prevent disease states generally epidemiological data Biochemical assessments of tissue saturation or adequacy of molecular function Nutrient balance studies Studies of subjects on diets containing marginally low or de cient levels of nutrient followed by correction of the de cit with measured amounts of nutrient Animal studies It is dif cult to obtain an accurate estimation of the requirement for a population For example if you were asked to determine the height of the goal posts at Ohio Stadium you could nd a number of ways of accurately doing so If you were asked to determine the height of the football team this would be more dif cult While you could determine the height of any given player with great precision the team would have a range of heights Now try to determine the amount of body fat of the average OSU student This could be done with great accuracy for any given student if you were able to grind them up and extract the fat Given that you cannot do that you will have to use a variety of indirect methods These methods will all relate to fat content but the values will not be accurate for all people On top of this uncertainty we must realize that not all people are the same and their needs will vary Estimation of nutritional needs have similar uncertainties for similar reasons Because it would not only be dif cult but also unethical to conduct long term nutritional studies with humans data must be collected from