Conditionally Essential Nutrients
Research done on animals and premature infants has shown that it is possible to synthesize some essential nutrients from precursors. This then led to a new understanding of the interactions between nutrients representing changes in what is required for humans. It also revealed that some disease states or genetic defects altered essential nutrient needs in those sampled. Therefore, a third category, conditionally essential, has been proposed. For example, in full-term infants, certain nutrients are not required in the same way they would be for a premature infant. For the premature infant to thrive and mature, these nutrients must be added to the diet – even if they are not generally classified as essential nutrients for those infants delivered full-term. The criteria used in determining conditional essentiality of a nutrient include three specific facts:
- Plasma concentrations of the nutrient decline into a range considered low but the body should be able to synthesize the nutrient.
- Chemical, structural or functional abnormalities become apparent, associated with low blood concentrations of the nutrient.
- Dietary supplements of the nutrient are seen to return blood plasma concentrations to normal levels and correct the chemical, structural, or functional abnormalities observed when blood concentrations are low.
Recommended Dietary Allowances and Dietary Reference Intakes
The Institute of Medicine (IOM), Food and Nutrition Board (FNB) of the National Academy of Sciences have revised the methods used when making nutrient recommendations to the general population. The Dietary Reference Intakes (DRIs), having replaced the former Recommended Dietary Allowances (RDAs), were developed by scientists from both Canada and the United States. One of their goals was to provide guidelines that reflect the growing body of scientific evidence suggesting that chronic disease states may alter nutrient requirements. The DRIs include a family of reference values: the Estimated Average Requirement (EAR), the RDA, the Adequate Intake (AI), and the Tolerable Upper Intake Level (UL). These values are determined in a manner that is intended to not only to prevent nutrient deficiency diseases but to also to reduce the risk of chronic diseases through improved nutrition. It is interesting to read the latest recommendations coming jointly from Canada and the United States regarding a focus on some newer keywords used in nutrition… patterns” and “shifts”. The language used in the documentation provided to us as health professionals is rife with these words and indicate a pattern themselves! For now, to bring these concepts together, try to think of the DRIs that follow as an umbrella term that includes the following specific definitions:
RDA (Recommended Dietary Allowance)
Defined as the intake that meets the nutrient requirement of almost all (97.5-98%) of the healthy individuals in a specific age and gender group, the RDAs can help people achieve adequate nutrient intake in order to decrease risks of chronic disease. Values for RDAs are estimates of average requirements plus increases to account for variations within a particular group. Available scientific evidence allowed DRI committees to calculate RDAs for vitamin A, vitamin C, vitamin E, phosphorus, magnesium, copper, iron, iodine, molybdenum, selenium, zinc, thiamin, riboflavin, niacin, vitamin B6, folate, and vitamin B12.
AI (Adequate Intake)
To date, DRI committees have set AIs for vitamin D, vitamin K, chloride, fluoride, pantothenic acid, biotin, choline, calcium, chromium, manganese, potassium, and sodium. The AI values come from experimental or observed intake levels that appear to sustain positive indicators of health. For example, this might include calcium to help in retaining bone, for most members of a population group. Or, it may be the average observed nutrient intake of populations of breast-fed infants defined AIs for infants through one year of age. Individuals should use AIs as goals for intake if there is no RDA presently.
AMDR (Acceptable Macronutrient Distribution Ranges)
When considering essential fatty acids, protein, and carbohydrates, ranges have been established in support of RDI recommendations and these are known as the AMDR. Acceptable ranges will obviously vary by gender and age and, in addition to acceptable range values, carbohydrate and protein have established RDA values based on age and gender, too. Values for daily water intake, total fiber, and essential fatty acids also have established representing AI (Adequate Intake).
Water intake recommendations include the total of all water contained in food, beverages, and drinking water. Tolerable Upper Intake Levels have been established for vitamins A, C, D, E, B6, niacin, and folate, as well as choline, boron, calcium, copper, fluoride, iodine, iron, magnesium, manganese, molybdenum, nickel, phosphorus, selenium, vanadium, zinc, sodium, and chloride.
EAR (Estimated Average Requirement)
The EAR is defined as the nutrient intake value that is estimated to meet the requirement of half of the individuals in a specific group or population. This figure is important since it is also used as a basis for developing the RDA. Nutrition policy experts use EARs to evaluate the adequacy of nutrient intakes of a group and to predict and suggest how much the group should be consuming. Consider this example: the RDA for a particular nutrient is calculated as follows: RDA = EAR + 2 SD EAR where SD EAR is the standard deviation of the EAR. If data about the variability in requirements are insufficient to allow calculation of a standard deviation (SD), a coefficient of variation (CV) for the EAR of 10% is ordinarily assumed. Some believe we are fortunate that someone else has done the math for us on this!
UL (Tolerable Upper Intake Level)
The Tolerable Upper Limit (UL) is defined as the maximum intake by an individual that is unlikely to pose risks for adverse health effects to almost all healthy individuals within the general population. The greater intake continues above the UL, the greater the risk of adverse effects. The UL is not intended to represent a recommended level of intake and there is no proven benefit seen in research related to consuming nutrients at levels above the RDA or AI. For most nutrients, the UL refers to total nutrient intake from food, fortified food, and supplements. The language of this descriptor is interesting in that the term “tolerable intake” was chosen to avoid implying a possible beneficial effect from this level of the nutrient.
Balancing the Diet
We probably hear this a lot, but what does it mean when we say that a diet should have “balance?” And how does this balance account for different activity levels? Would a sedentary person have different kilocalorie (or kcal) requirements as someone who is physically active on most days of the week?
The term “balanced diet” is often quoted by nutritionists and dietitians, yet most consumers have little true idea of its meaning or, if they do, they often lack the skills needed to change their diet so that it is more balanced. To help consumers with dietary guidelines and a simple way of evaluating their diets, the U.S. Department of Agriculture (USDA) and the Department of Health and Human Services (USDHHS) initially developed the Dietary Guidelines for Americans and the Food Guide Pyramid as a point of reference. Similarly, the Canadian government has developed Canada’s Guidelines for Healthy Eating and Canada’s Food Guide to Healthy Eating. European countries, Australia, and New Zealand have developed similar guidelines. For example, Switzerland also uses its own variant of Food Guide Pyramid, which factors in the needs of active individuals and athletes.
Before we can truly understand eating strategies for athletes and active clients, we have to understand that The Dietary Guidelines for Americans have evolved over the last 15 to 25 years in an attempt to answer the question “What should Americans eat to stay healthy?” – so this is not for athletes. But the foundation is still set at this point for all in the general public and the pyramid structure remains in use – even for athletes and active clients. So in reality, it doesn’t directly help to know that The Dietary Guidelines — targeting healthy Americans age 2 years and older—provide advice about food choices that promote health, decrease the risk of chronic disease, meet nutrient requirements, and support active lives. Our client or athlete will need more.
The pyramid used before the MyPlate campaign in the United States had its strengths and weaknesses. It provided an excellent way to quickly review the individual dietary intake of the user and then recommend dietary changes that combined food preferences with specific energy and nutrient needs. Variations of Food Guide Pyramids are still in use today. Many locations around the globe have created their own government policies and agencies as they develop dietary guidelines, reference intakes, and even food guide pyramids to meet the dietary needs of the particular population, taking into consideration cultural aspects related to food, eating patterns, and lifestyle factors.
Many countries around the world still look to the pyramid to make nutrition recommendations. Americans now can get used to the new MyPlate design — but this represented a shift from its prior pyramid design, similar to Spain, Australia and Great Britain. In China, Poland, and other parts of the world, one can see a lot of creativity.
We can find some similarities between the methods used by various countries to tell their citizens how to eat — and some notable differences. Most of the guidelines propose suggested intake of proteins, grains, fruits, vegetables, and dairy.
Obviously, some recommendations contain regionally specific advice, relevant to the region’s staple food items. But one point that emerges from studying different food intake guidelines is that it dietary images worldwide struggle to find balance between comprehensive but confusing nutrition information. If you look at Germany’s 3D pyramid and compare it Hungary’s simple design, you will see that using a pyramid as a visual aid has endured and the shape is, in fact, used for one of the most referenced food guide pyramids – the Mediterranean Food Guide Pyramid. Our point: Pyramids are still in use and may always be – since they fit the message being sent into a nice graphic or visual aid for the reader. It is also important to note that much of the world looks to the recommendations from the United States to gauge their own. You might consider making individualized pyramids for your clients, as well.
Few pyramids exist that specifically address athletes. The first modifications to the standard 1992 U.S. Food Guide Pyramid included fluids as a new food category at the base of the pyramid, underlining the importance of adequate hydration for athletes. However, the recommendations apply only up to 3,000 kcal/day. As you might imagine, these guidelines do not always suit an active individual’s energy and nutrient needs.
The additional guidelines for athletes had to be sufficient to cover the extra energy and nutrient requirements incurred by the demands of daily exercise training, requiring a lot of planning and science into the design of intake strategies for athletes and active clients. The first step was to determine just what the additional energy requirements were, with exercise factored into kcal suggestions.
For this purpose, the energy requirement of different activities and intensities was averaged to approximately 0.1 kcal per minute of exercise; once this was agreed upon, body mass needed to be factored in.
Volume and intensity had to then be added in for certain activities, for example, running at approximately 5 mph, cycling at 2 W/kg body mass on a cycle ergometer, or the “stop and go” nature of some intermittent styles seen in sports – such as an average basketball or soccer game.
Once volume and intensity were estimated, adjusting the additional energy requirement was divided into the different food groups, with new macronutrient recommendations for activity taken into consideration.
Additional sport-specific foods and fluids such as sport drinks, energy bars, or recovery products also need to be integrated into any plans for active clients. The issue of different energy needs relative to body mass was solved through adjustment of the serving sizes originally established for the general population. It is the duration of daily activity that determines the number of extra servings, whereas the athlete’s body mass determines the serving size. This is important to remember.
How Can Nutrition and Physical Activity Affect the Onset of Chronic Disease?
Although an active client may be more prepared to prevent the onset of chronic disease, you will also be retained by clients who are on the opposite end of the continuum; these are your deconditioned clients and they are usually sedentary. For this group, weight loss (a common goal) and muscular development can sometimes represent secondary goals if the client is primarily at risk for chronic disease due to inactivity or poor nutrition. The role that nutrition and physical activity play in reducing chronic disease risk factors is well established. Often times, we read that Americans are largely sedentary, overweight, and eat too many calories – often high in saturated fat and sugar or other refined, processed foods. They rarely consume enough whole fruits, vegetables, grains, and lean protein sources. In reality, obesity is pandemic.
Since diet and exercise have been proven to play an important role in health, exercise, and the reduction of chronic disease risk factors, we all need to understand how this applies to exercise or physical activity and our client. Sound nutrition strategies can improve exercise performance, decrease recovery time from strenuous exercise bouts, prevent fatigue (and injuries from fatigue), and provide the fluids and fuels needed for high-intensity training. Coaching clients about their nutrition needs also involves understanding how maintaining ideal body weight and composition for one’s lifestyle or activity level.
Throughout the world, different agencies have identified essential dietary nutrients, recommended appropriate nutrient intakes, and defined goals for nutrition and exercise for the general populations of their regions. In the United States, as well as in other parts of the developed world, the use of educational tools (interactive websites, pyramids) to help implement these recommendations in our daily lives is only a start … if we are going to be physically active, everything changes. The goal then becomes learning how to motivate individuals to make positive nutrition changes. Although this is a significant challenge, your understanding of what follows includes the tools necessary to help you coach clients how to make healthy lifestyle changes.
You have choices for nutrition education and certifications: