3. MACRONUTRIENTS
Try these Questions (detailed answers at the bottom):
Q1. An appropriate balance of carbohydrate (CHO), protein (PRO), and fat calories in the daily diet of a child two years of age or older would be:
A. CHO = 15%; PRO = 40%; Fat 45%
B. CHO = 30%; PRO = 30%; Fat 40%
C. CHO = 55%; PRO = 15%; Fat 30%
D. CHO = 75%; PRO = 10%; Fat 15%
Q2. True or False: High Fiber containing diets for children may put a child at risk for protein energy malnutrition.
And these techniques:
1. " Create an OXFAM banquet for ten students. Prepare 10 slips of paper. One slip states "recipient will have meal of choice from a high quality restaurant." Three will permit the students to have "mid level items from a cafeteria or take-out place." Another three will allow students to have the minimal cost sandwich or similar item. Two students will have" only carbohydrate side items (rice would be the best choice)." These two students must serve the one with the highest quality meal. One student would "chose among being hungry, bartering services or begging to eat." He or she must attend. Please feed the student when the joke wears thin. Usually the others take pity, but they may not.
2. Create "mother," "father," "child," and "doctor" groups. The parents and child will play out various parent child interactions to challenge the doctor for his or her skills in addressing problems arising in the scenarios.
3a. Macronutrients--Energy in food and analyses of diet quantity
Energy in food
The first dietary constituents identified, in the 18th century, were those that provided energy. These three constituents are:
** Fat that provides 9 calories per gram,
** Carbohydrate (CHO) which provides 4 calories per gram, and
** Protein (PRO) has the potential to provide 4 calories per gram
when degraded for energy.
Alcohol, when consumed in moderation (<10% of calories), is metabolized by the alcohol dehydrogenase (ADH) system and generates 7 calories per gram. Excessive consumption of alcohol leads to detoxification by the P450 (mitochondrial ethanol oxidation) system that extracts lesser amounts of energy per gram. Alcohol use in pregnancy in excess of what can be detoxified by the ADH system may be a contributor to the Fetal Alcohol Syndrome.
Analyses of diet quantity
All diets are best analyzed by calculating the % of calories from each of the macronutrients (fat, CHO or PRO) with the denominator as the calories expended each day rather than the calories consumed. For example, a protein intake of "1 gram/kg/day" (a commonly used but incorrect specification of need) would be fine for a moderately active person, but there are important differences between the energy needs of an "average" person and those of a chronically ill patient or a ditch digger. A child could consume 30% of calories from fat, as recommended in "prudent diets," but when more energy is consumed than expended, the child becomes obese.
A rough rule to estimate calories required for an inactive child would be:
100 cal/kg of weight for the first 10 kgs; 50 for the second kgs, and 20 for subsequent kgs.
For example, a bedridden 6 year old weighing 23 kg expends/requires 1,000 + 500 + 60 = 1560 calories. For children who are active and growing, calorie requirements per kg of body weight are at least 10% greater. For children with high activity levels, hyper-metabolic states or malabsorption, energy intake must be increased even more to maintain growth.
3b. Macronutrients--Carbohydrates
Though glucose is the obligate fuel for the central nervous system and the preferred fuel for the rest of the body, carbohydrate(s) (CHOs) receive less attention than almost any other nutrient. The need for CHO can be met by the conversion of protein and fat. Recently, the move away from complex CHOs -- those unrefined polysaccharides -- occurring with economic development has been associated with the development of the major degenerative diseases of modern society. There are consequences from maintaining low CHO diets especially when the CHOs that are consumed lack fiber or derive from simple sugars -- "sugar drinks."
Terms
mono-, di-, polysaccharide, disaccharidase deficiency, fiber
Requirements
While no specific requirements for CHO have been written, low CHO diets are, by definition, high in percent of calories supplied by fat. This has been associated with an increased prevalence of obesity. A switch from a mixed diet to one with a high simple sugar -- mostly disaccharides and sugar drinks -- also increases the risk for obesity.
The suggested CHO intake is 50 to 55 percent of energy expended with most of the CHO coming from grains (polysaccharides) and a smaller part (10% of total calories) as disaccharides in fruits, juices and various forms of low nutritional value sugar drinks -- "soda pop," "punches," non-alcoholic "drinks," and an excess of fruit juice. Monosaccharides are rarely found in the diet except for fructose in some fruits.
Definitions
Disaccharides:
** Maltose (glucose-glucose) is found in cereals.
** Sucrose (fructose-glucose) is found in fruits and some vegetables (sugar beets). Common table sugar is sucrose.
** Lactose (galactose-glucose) is found in fresh dairy products
and processed cheeses.
Lactase, the enzyme needed to break the disaccharide linkage of lactose is not found in high concentration in the intestines of most adult people in the world. The exception are the descendants of those whose ancestral home is in northwest Europe -- the immigrants from Germany and the British Isles who developed the food economy of this country. Low lactose dairy products include most aged cheeses, yogurt, "butter" milk (which has no butter), and specially prepared low lactose whole or part skim milk products. "Gassy" children or those who refuse milk products may require evaluation for lactase deficiency.
Infants of all racial and ethnic groups, however, usually have adequate intestinal lactase. Lactose in milk is associated with better calcium absorption.
Deficiencies
Himsworth showed the effects of inadequate CHO intake in the 1930s. The two glucose tolerance curves reflect proportions of macronutrients in the diet.
Diet 1 is high in fat and low in carbohydrates. It produces pseudo- carbohydrate intolerance with administration of 50g of glucose. Diet 7 is high in carbohydrate and low in fat. Now, this same patient does not show carbohydrate intolerance. These studies demonstrated the importance of providing substantial amounts of carbohydrate in the diet before testing for glucose intolerance. (Himsworth HH. Clinical Science 2:67-94, Sept 1935)
Treatment
The proportion of CHO in the diet is 35 to 40 percent in infancy and rises to the recommended 55% at age two years. The sources of CHO should be a varied mix of cereal grains, vegetables and fruits. Of note, the one snack food that everyone seems to accept as nutritious is air popped popcorn -- once the child passes an age where aspiration is a risk (5 years of age).
The Glycemic Index
The Glycemic Index (GI) is a ratio calculated from the area under the glucose tolerance curve of a standard 50-gram glucose challenge (the denominator) and a similar curve formed from the consumption of a specific food (the numerator).
Potatoes, for example, contain quickly absorbed starch . The area under the blood glucose versus time curve for potatoes contains almost the same area as a standard glucose tolerance curve. Thus, the Glycemic Index is high for potatoes. By contrast, meals containing wheat bran tend to have slowly absorbed sugar, less area under the blood glucose curve, and a low GI. Recent studies provide data suggesting that a freely chosen low GI diet is more effective in promoting and sustaining weight loss in obese children than controlled low calorie dieting. Recently, bran cereal meals (low GI) taken in the morning were found to promote less food intake at lunch without regard to nutritional status of the children. In this study, children found high GI breakfasts more palatable on the first days of the study but not thereafter suggesting the importance of resolve in offering nutritious food.
The importance of fiber
The low fiber diet may be symbolic of other alterations in the lives of children. From the role of fiber in promoting intestinal bulk, it can be stated that a low fiber diet makes children prone to constipation and hemorrhoids later in life. Other claims for the relationship of fiber to health are unlikely. Excess fiber can absorb minerals and decrease energy density. In the Middle East, there is a well-known syndrome of iron and zinc deficiency associated with growth retardation and hypogonadism found in children on excessively fibrous diets.
Controversial issues in carbohydrate in the diet are discussed in the Post script, below.
3c. Macronutrients--Fat
The importance of fat
Much maligned fat is needed in the diet of every child (and adult). Fat in the diet provides:
** Linoleic acid (an 18 carbon, polyunsaturated fat) that cannot be produced by the body. At least 2% of total calories must come from linoleic acid. Deficiency results in a refractory dermatitis that is seen in otherwise healthy children whose parents are obsessed with limiting their fat intake.
** Building blocks for hormones and prostaglandins.
** Myelination of neural tissue.
** Source of concentrated energy. In developing countries, the energy densities of foods are often too low; protein-energy malnutrition may be a consequence of inadequate fat in the diet. The "fear of fat" phenomenon seen in the US has the same result.
** Flavor. While taste (sweet, salt, sour, bitter, and perhaps "hot") reflects a response of chemical sensors on the tongue and in the mouth, flavors are usually volatile substances that are soluble in and carried by fat. Low fat diets are unpalatable.
** Contribution to satiety. In part this is a reflection of the low energy content of fat free meals. There are, however, enteral hormones that respond to fat with the feeling of fullness or satiety.
** Carrier of fat-soluble vitamins A, D, E, and K.
Body fat is also essential for:
** Production of hormones. The synthesis of estradiol, the active form of estrogen, requires adequate body fat. This contributes to the amenorrhea seen in very lean women with anorexia or who exercise to excess.
** Reserve energy for growth and illness. While the obsession of immigrant mothers that their chubby child "doesn't eat" is a source for jokes, these women have a collective memory of a human history where body fat was needed to survive a long winter and spring before the next harvest or a period of illness. For mothers from developing countries, the chubby baby of affluent families, is a model for a healthy appearance.
Cholesterol
It is abundantly clear, from the response to cholesterol deprivation, that cholesterol is essential for humans. The liver is an engine for the manufacture of cholesterol, which then provides for the production of hormones and for cell integrity. Fat, and thus cholesterol, restriction before two years of age is absolutely inappropriate. Family histories specifically designed to determine histories of coronary heart disease should not be taken, nor should serum cholesterol be measured routinely in young children. Waiting is important to prevent the overly conscientious parent from initiating an overly restrictive diet. Note that human milk and formulae provide 50% of calories from fat. The breast-fed infant has high serum cholesterol, but this should not be confused with "hypercholesterolemia."
Recommendations
Past two years of age, it is suggested that 30% of expended calories be from fat, equally divided between mono-, polyun-, and saturated fat. For children, 30% is a minimum not an average intake. Some parents have a "fear of fat" and "fear of cholesterol" which would reduce the fat content of the diet below acceptable levels. This is to be avoided.
Deficiencies
These are listed above. Note that children with fat malabsorption secondary to biliary or pancreatic disease are at high risk for deficiencies in fat-soluble vitamins and for growth failure secondary to too little energy absorbed.
3d. Macronutrients--Protein
These are the aggregates of amino acids (AAs) which are recombined, in the liver mostly, to build muscle, lay down matrix and collagen in bone, and create new cells in various organs throughout the body. As such, the definition of proteins as "macronutrients" is incorrect. The majority of proteins consumed should not be degraded for energy. The essential function of proteins in the diet is transformation into building blocks.
Terms
Biologic Value (BV), essential and non-essential AAs, specific dynamic action, adaptation, protein-energy malnutrition (p-em) --"kwashiorkor" and "marasmus"
Requirements
The requirement for protein is dependent on the biologic value of the diet, taken as a whole, which in turn is a reflection of the relationship between the distribution of essential and non-essential AAs in the food(s) consumed. The difference between essential and non- essential AAs are that non-essential AAs can be constructed by amination of acids (e.g., pyruvate --> alanine) while essential AAs must be consumed in the diet. The essential AAs are isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. The growing child requires histidine and perhaps arginine.
The BV of a specific food is determined by the ratio of the percent of the least available essential AA/protein in that food (the "limiting amino acid") to the percent of that AA in egg albumin, which is used as a standard of excellence for human dietary proteins. In everyday life, the BV of foods consumed depends on whether foods are mixed. Mixing rice (low in lysine, high in methionine) with beans (the opposite) raises the BV substantially. Adding a small amount of meat or egg raises the BV close to 1.
When foods of low BV are consumed, that proportion of the protein consumed not containing a complete complex of essential AAs will be used as fuel. Similarly when there is excess AA not used for "building blocks" they are used for fuel. The energy needed to deaminate or otherwise degrade AAs is referred to as specific dynamic activity.
Also influencing requirement for protein is the ability of the body to adapt to lower intake. Within limitations, this occurs without affect on function, growth or response to stress. Thus, an infant consuming human milk during the first four months of life can thrive on a diet containing only 8% of calories from protein. Healthy children on mixed diets require 12 to 15% of calories from protein.
Consequence of deficiency
The two diseases associated with protein deficiency are called "kwashiorkor" and "marasmus." A better terminology is protein-energy malnutrition (p-em) with edema ("kwashiorkor") and p-em without edema ("marasmus"). P-em with edema was (and is) said to occur when protein intake is inadequate but caloric intake is acceptable. It has been taught that p-em without edema is found when the diet is inadequate in all macronutrients. In fact, both conditions occur with inadequate energy intake, and both conditions can occur in the same family with the same diet.
Diet is not the critical issue in distinguishing the two phenomena. Stress responses affecting protein production (including serum albumin) or more commonly increased catabolism caused by infection (e.g. measles, diarrheal disease) cause the hypoalbuminemia and edema seen in some of the children with p-em.
Finding p-em in one family member suggests the likelihood of malnutrition in others. P-em, like other forms of malnutrition, does not occur in isolation from other nutritional, social and economic problems in the affected community and family. For example, protein deficient children may develop pellagra because of the deficiency of tryptophan, which is degraded to niacin (see Section 4e and addendum on protein energy malnutrition).
In childhood in the United States, p-em usually shows itself as growth failure or failure-to-thrive.
Treatment
As noted above, protein-energy malnutrition is not simply a reflection of inadequate food intake. In the United States, failure-to-thrive is a consequence of multiple failures in the family as well as the society taken as a whole. Further discussion is beyond the scope of these notes -- see reference material and the module on Failure to Thrive.
Controversial issues in protein energy malnutrition are discussed in the Post script, below.
The answers
A1. The answer is C. The recommendations are for sufficient fat in the diet to maintain growth, carry nutrients, and provide satiety. 30% of calories does that well. We suggest long chain polysaccharides with fruits and vegetables and bran providing fiber.
A2. The answer is True. As shown in studies in Egypt and Iran, excessive fiber intake may limit availability of sufficient energy in growing children. While iron and zinc content of these high fiber diets are adequate, the absorbtion is low. Iron and zinc deficiencies contribute to the growth retardation. (Prasad)
The techniques
I've never had the nerve to put on that version of the OXFAM (Oxford Famine Relief) banquet.. Please contact me if you do.
All sorts of scenarios can be worked out. Think of the elements of the diet history. Change one or the other to see how the interview plays out. Don't be too cruel to the "physician." Be sure to break from the roles at end.
ADDENDUMS ON CARBOHYDRATES AND PROTEINS
These topics are controversial. I've chosen to use stanard referencing techniques, so that readers may develop their own understanding.
CARBOHYDRATES
Q. Is there a place for a "low-carb" diet?
A. The answer "generally not" requires an explanation.
A great transformation occurred in Sumer about 8 to 10,000 years ago. (Kramer, 1981) Prior to that time, humankind gathered food from naturally occurring sources, hunted animals and perhaps each other. (Harris, 1975) With that change, dependence on mono-agriculture raised the level of carbohydrate intake to higher than that experienced over the million years of primate and our own homo sapiens history of about 150,000 years. The question "how well have we adapted to this change?" is incomplete without also addressing the environment in which that change has occurred.
The anthropologist Peter Farb points out that semi-starvation is the natural state of humankind. (Farb, 1978) Food was usually plentiful in our ancestors' world of hunters and gatherers, in the "Garden of Eden" of west Africa, but even there, the plenty in one season of the year but not in others. This was accentuated with migrations to the less hospitable climates of the temperate and sub-Artic zones. One group of Native Americans, for example, named the moon of autumn after the harvest while late spring was named "hunger." (Farb. 1978) Animals were still in hibernation while fruits and berries had not formed. Variation in diet and the consumption of raw food, however, did provide protection for hunter-gatherers against micronutrient deficiency.
With mono crop irrigation agriculture, it became possible to plant fields of wheat and barley as in the middle East. (Farb, 1978; Kramer, 1981) Other forms of single crop predominance include cultivation of rice in Asia, the sweet potato in China, and the white potato in Ireland. Survival depended on the use of a complimentary food to increase the biologic value of the single source, being blessed with "rain that comes in its season," (from Deuteronomy, 28:2) and sufficient variety in the single source to protect against blight. Think draught, war, locusts and the great Irish potato famine to imagine the risk faced by our recent ancestors and us. The availability of these planted grain and tuber crops, however, enabled a major increase in population. The risk of famine, chronic protein-energy malnutrition, and specific nutrient deficiencies, however, continued. (Farb and Harris are the source for this commentary)
The risks from the carbohydrates themselves depend on the nature of the carbohydrate and the environments in which they are consumed. Three forms are presented:
1. whole grains (unrefined)
2. refined grains
3. Simple sugars (di- and mono-saccarides)
The earliest consumers used unrefined whole grain foods. Wheat, for example contains water soluble vitamins and fiber in the shell, oil, protein and fat soluble vitamins in the germ, and calories in the endosperm. Excess grain consumed without supplementary foods could result in the syndrome described by Prasad of iron and zinc deficiency, growth retardation, and delayed sexual maturity. (2002) . This diet, however, when properly supplemented, is not a precursor to the degenerative diseases of Western civilization. Denis Burkitt (1988) saw fiber in the diet as the protector of indigenous African populations from the coronary artery and other diseases of Europeans and assimilated Africans. As noted in the sections on nutritional assessment (Part II, Section 2) and the modules on Type 2. Diabetes Mellitus and hypercholesterolemia, the food mixtures have low Glycemic Indices (GI) and do not stimulate excess insulin secretion.
Refined grains also contain polysaccharides without the fiber or germ. These were at one time foods for the wealthy or powerful. This is no longer so. One must consider. the potential consequences of consumption of refined flour, white rice,, potatoes, corn and other refined foods as they have a high glycemic index. In excess, they have potential consequences when the individual is obese, diabetic, or has a glucose sensitive form of hypercholesterolemia. Leptin levels rise with obesity. Leptin creates insulin resistance as a way, says RH Unger of protecting cells from a lipid toxicity. (2005 -- see the module on pathophysiology of obesity Part III Section 3 for further discussion of the Unger hypothesis) This limiting these forms of carbohydrate would be appropriate. Proponents of high carbohydrate diets recommend use of unrefined grains and the achievement of lean body weight through a combination of diet and exercise.
Di-saccarides as found in fruit and table sugar (sucrose), in dairy products (lactose), and beer (maltose). Mono-saccarides (fructose and glucose) are in honey, fruit and "high fructose corn syrup." Their GI is "1" when consumed in juice, soda, or "drink." In fruit, however, absorption is slowed by fiber content. A limitation to 10% of claries as simple sugars is suggested. This is essentially one serving of fruit as juice. Fructose enters the cell without aide of insulin.
In sum, the current recommendations for a nutritious diet is to encourage 4 to 5 servings of fruits and vegetable, 2 to 3 servings of low fat dairy products, use of whole grains, legumes, and nuts. This will provide 50 to 60% of calories as carbohydrates, a substantial part of which will be in unrefined foods. This is not a "low carb" diet.
A decrease in carbohydrate intake (refined foods and those containing simple sugars) is justified, however, for overweight or obese patients with insulin resistance. A careful assessment of the individual patient is required before making that recommendation.
REFERENCES
Burkitt DP. Dietary fiber and cancer. J Nutr. 1988 Apr;118(4):531-3.
Champagne C. Dietary interventions on blood pressure: the Dietary Approaches to Stop Hypertension (DASH) trials. Nutr Rev. 2006 Feb
Farb P. (1978) Humankind Houghton Mifflin, Boston
Harris M (1975) Culture, People Nature. Cornell University Press, New York
Kramer SN (1981) History Begins at Sumer: Thirty-Nine "Firsts" in Man's Recorded History, 3rd ed University of Pennsylvania Press. Philadelphia
Passmore R, Eastwood MS. (1986) Davidson and Passmore Human Nutrition And Dietetics, 8th ed. Churchill Livingstone, London
Prasad AS. Zinc deficiency. BMJ. 2003 Feb 22;326(7386):409-10.
Unger RH Longevity, lipotoxicity and leptin: the adipocyte defense against feasting and famine. Biochimie. 2005 Jan;87(1):57-64. Review.
PROTEINS
Q. True or False. The classic definitions of marasmus and kwashiorkor, the two forms of protein-energy malnutrition, are as follows:
1. Marasmus is a consequence of adequate protein intake with inadequate intake of energy, and
2. Kwashiorkor is a consequence of inadequate intake of both protein and energy.
A. These are currently accepted definitions. Reality, however, is more complex.
These definitions are derive from Cicely Williams' original description in 1933 of "kwashiorkor," a word meaning "the sickness the older child gets when the next baby is born" in the language of the Ga in West Africa. (Williams, 1933; see also Passmore & Eastwood p279). Kwashiorkor has been often translated as "weanling's disease." This misses the impact of having too many infants in too short a time.
Dr. Williams described changes occurring when an adequate intake of breast milk was shifted to an intake of cereal grains. This lead to an assumption that the low protein content, per se, was the cause for the protein-energy malnutrition with edema she named kwashiorkor. The clinical distinction between this disorder and marasmus, which is associated with obvious inadequate energy intake, informed the classic definitions.
Subsequent experiences suggest a more complex set of principles underlying the disorders. In fact, energy intake is inadequate in both kwashiorkor and marasmus; the two coexist in families and communities with identical diets. The figure that follows shows children in the same family, one with kwashiorkor and the other with marasmus.
** Figure 27 from page 18 of the Colour Atlas awaits permission from Dr. McLaren for republication
CAPTION: "Compare the miserable expression, pale hair, generalized oedema and skin changes in the child at left with the marasmic wasting of his older brother. Kwashiorkor often follows acute infection and/or diarrhoea in a child during the weaning period." (McLaren, 1986)
As Widdowson writes, "… protein turnover, which is low in these (severely undernourished) children, is raised with concomitant infection. (in Blaxter & Waterlow, p102) The stable slow growth of a moderately healthy but energy and protein deficient child are disrupted by an increased need following an infection.
"Kwashiorkor is frequently precipitated in epidemic proportions by outbreak of febrile illnesses such as malaria, measles or gastroenteritis." (Passmore and Eastman, p280)
In clinical settings, children may have characteristics of both disorders (marasmic-kwashiorkor) or have precursors such as "wasting" (decreased weight for length or height), or "stunting" (decreased length for age). Further discussion can be found in Part II Section 2 - Assessing nutritional status.
Support for the McLaren, Passmore/Eastman and Waterlow constructs do not detract from Dr. Williams' original proposition. Her description was appropriate for the particular circumstances she observed. Contemporary "hospital malnutrition," often associated with edema, occurs when patients are left on intravenous glucose feedings without attention to global nutrition needs for too long a time. (see Coats, et al)
REFERENCES
Coats KG. Morgan SL, Bartolucci AA, Weinsier RL. Hospital-associated malnutrition: a reevaluation 12 years later. J Am Diet Assoc 1993 Jan;93(1):27-33.
McLaren. Defining marasmus and kwashiorkor. Nutr Rev. 1968 Aug;26(8):256
McLaren DS. (1981 A Colour Atlas of nutrition. Wolfe Medical Publishers. London
McLaren DS. The great protein fiasco revisited. Nutrition. 2002 Apr;18(4):361-3
Passmore & Eastman (1986) Davidson and Passmore Human Nutrition and Dietetics, 8th ed. Churchill Livingstone. London
Waterlow JC. (1986) What do we mean by adaptation (in) Nutritional Adaptation in Man. Baxter K, Waterlow JC. (eds) John Libbey. London
Williams CD. A nutritional disease of childhood associated with a maize diet. Arch Dis Childhood 1933;8:423-33.
Answers
A1. C is correct. Infants require a high fat content in the diet approaching 50% of calories. In the transition to solid foods, the necessary contribution of fat diminishes to about 40% at 12 months of age with ½ of caloric intake coming from whole milk. By 2 years of age, children should received a relatively diminished content of fat. At 30% essential nutrients and satiety will be maintained.
A2. The answer is True. The low caloric density of high fiber diets diminishes caloric intake. It also leads to absorption of essential micronutrients. A syndrome of poor growth and delayed sexual maturity associated with a tuber and grain diet has been reported in Egypt and Iran.
