Noel W. Solomons
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foods, and the other two are related to the mobi- lization of synthetic (vitamins) or isolated (trace elements) sources for consumption. These sourc- es are outlined in table 2 .
Vitamins and Trace Elements Intrinsic to Foods It takes a wide variety of different foods in com- bination to obtain the entire range of necessary micronutrients in adequate amounts [1] . Micro- nutrients tend to be less varied, less dense and less available in foods of plant origin than in those of animal origin [2] . To the extent that plants are rich sources of vitamins E, C and K and folate, children should be encouraged to consume whole
grains and green, orange and yellow vegetables and fruits. However, for calcium and riboflavin, milk and dairy products are the richest sources, and iron and vitamins A and B 12 are most dense- ly concentrated in animal foods (meat, organ meat and fish). Cooking, processing and storage destroy or elute nutrients in foods.
An emerging new strategy is biofortification, primarily for public health purposes. This in- volves enhancing the content of specific nutrients during the cultivation of edible plants. It can involve nutrient-enhanced fertilization, cross- breeding/hybridization or genetic modification [3] . One can variously enhance the concentration
Table 1. List of vitamins and beneficial and essential trace elements Vitamins Synopsis of role and function Fat-soluble group
Vitamin A Vitamin D Vitamin E Vitamin K
Retinal light receptors in vision, genetic transcription Calcium absorption, bone mineralization, cell signaling Cell membrane antioxidant protection, cell signaling Blood clotting, bone matrix formation
Water-soluble group Vitamin C Thiamin Riboflavin Niacin Vitamin B6
Pantothenic acid Biotin
Folate Vitamin B12
Antioxidant protection in regeneration of reduced vitamin E As thiamine pyrophosphate coenzyme in metabolism As cofactors FAD and FNM in flavoproteins
As cofactors NAD and NADP in dehydrogenases
Cofactor in transamination and carboxylation of amino acids Component of coenzyme A for mitochondrial energy Cofactor in carboxylases for fats, protein and carbohydrates One-carbon transfer reactions in metabolism
Cofactor in one-carbon transfer reaction, specifically for 5-methyltetrahydrofolate
Trace elements Iron Zinc Copper Iodine Fluoride Selenium Manganese Chromium Molybdenum
Oxygen transfer, oxygen-mediated redox reactions Metalloenzymes, zinc-finger protein transcription factors Diverse metalloenzymes
Thyroid hormone structure Dental and skeletal mineralization Glutathione peroxidase antioxidant system Mitochondrial superoxide dismutase Enhances the cellular action of insulin
In molybdenum cofactor in metabolism of organic acids
FAD = Flavin adenine dinucleotide; FNM = flavin mononucleotide; NAD = nicotinamide adenine dinucleotide; NADP = nicotinamide adenine dinucleotide phosphate.
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of a nutrient (e.g. the provitamin A β-carotene) already in the plant (such as in orange-fleshed sweet potatoes) or introduce the same nutrient where it never existed before (as in rice or cas- sava).
Vitamins and Trace Elements Added to Foods Extrinsic addition of micronutrients usually oc- curs in processing or, occasionally, in the home just prior to consumption. It includes three do- mains: (1) enrichment (returning the nutrients lost in processing); (2) public health-directed for- tification (adding a nutrient or nutrients to a widely consumed item such as salt, sugar, oil or flour to counter a population-level deficit), and (3) market-driven fortification (adding nutrients to commercial products to enhance their appeal, such as adding vitamin C to soda beverages) [4] .
Fortification is a legitimate and effective pub- lic health measure [5] . The major focus in the publication arena had traditionally been iodine in salt, but this has recently shifted to iron, spe- cifically in wheat flours and corn meals (Flour Fortification Initiative), and other nutrients such as retinol in cooking oils and condiments. A cre- ative avenue for young children with nutrition- ally precarious diets has been home fortification
in which multimicronutrient-fortified powders (sprinkles) or spreads are combined with tradi- tional foods to support nutrient intake. The Cen- tral American republics have a several-decade history of vitamin A fortification of sugar, but in- creased sugar consumption is now leading to ex- cessive consumption of the vitamin.
Micronutrient Supplements
The advances in pharmaceutical chemistry from the second half of the 20th century allowed high concentrations of vitamins and trace elements to be formulated as capsules, tablets and syrups. In a public health context, various forms of micronu- trient supplementation are used – generally when 40% of the child population shows evidence of nutrient deficiency. This is exemplified by the pe- riodic distribution of high-dose vitamin A cap- sules [6] and intensive courses of daily dosing of iron and folic acid [7] .
Beyond the prevention of micronutrient defi- ciencies, some parents may be motivated to sup- plement themselves and their children with the motivation to decrease the risk of occurrence of chronic diseases such as cancer, cardiovascular diseases and cognitive decline; an analysis of the current scientific evidence does not support such an effect [8] . In fact, adverse outcomes from chronic multimicronutrient supplementation have been documented.
Factors Affecting Vitamin and Trace Element Nutrition
Primary vitamin and trace element undernutri- tion is the result of the oral intake of nutrients from any combination of the aforementioned sources not meeting the recommended amounts.
This is seen not only with poverty, famine and di- saster but also widely in cases where the nutrient density of the diet does not sustain nutrient re- quirements when energy needs are fulfilled. This is an especial concern with regard to complemen-
Table 2. Sources of micronutrients for human consump- tion
Intrinsic micronutrients
Nutrients contained within the tissue matrix and fluid of edible items from the animal and plant kingdoms Extrinsic (added) micronutrients
Nutrients are added to foods as enrichment, in mass fortification by public health mandate and/or with discretionary fortification, as in commercial foods or with nutrient mixes added to complementary foods in the home
Supplemental micronutrients
Nutrients taken in pharmaceutical preparations (chewable candies, tablets, elixirs) in individual or combined forms
Koletzko B, et al. (eds): Pediatric Nutrition in Practice. World Rev Nutr Diet. Basel, Karger, 2015, vol 113, pp 62–67 DOI: 10.1159/000367871
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tary foods during the weaning process [9] . Of course, in individuals receiving part or all of their nutrition via the intravenous parenteral route, at- tention must be paid to perfuse micronutrients as well to avoid deficiency [10] .
Secondary micronutrient undernutrition is re- lated to the failure to absorb, to utilize or to retain the nutrient in the body once ingested with the diet or a supplement. Table 3 classifies and illus- trates the factors affecting micronutrient disposi- tion. These factors come into interplay in severe diseases commonly seen in pediatric practice, such as repeated or chronic diarrhea, Crohn’s dis- ease [11] , untreated celiac disease or cystic fibrosis.
There is a narrow spectrum of situations in which there is excessive absorption or retention of certain trace elements, leading to progressive accumulation and eventual overload. This oc- curs with iron in conditions called hemochro- matosis and hemosiderosis due to disruption of the intestinal regulation of its uptake. It also oc- curs with copper in that the absorbed metal can- not be normally exported from the cells after its uptake due to a genetic mutation. In both in- stances, these metals accumulate in selected or- gans, producing oxidative and degenerative damage.
Theoretical and Practical Precautions and Caveats regarding Vitamin and Trace Element Nutrition
On the one hand, considerations based on cli- mate, environmental conditions and endemic in- fectious diseases may modify the conventional re- quirements of certain micronutrients, usually in- creasing the demand to support nutrition and growth. Even ethnic origin can be seen as an emerging factor, as genetic polymorphisms that influence micronutrient handling are increasing- ly being recognized [12] .
On the other hand, pathogenic viruses, bacte- ria, protozoa and fungi have their own specific requirements of certain trace elements such as iron, zinc and manganese. The malarial organ- ism (Plasmodium) and pathogenic amoeba (e.g.
Entamoeba histolytica ) and their influence on the iron status of the host are cases in point. In situ- ations in which sanitary or antimicrobial control cannot stem parasitic transmission, individuals having lower reserves of iron may be relatively protected against the proliferation of these patho- gens.
The overall balance between micronutrients, both in the diet (on the plate) and in the body (in tissues and organs), has implications because a series of recognized nutrient-nutrient interac-
Table 3. Factors conditioning the absorption and utiliza- tion of dietary micronutrients
Inhibition of intestinal uptake
Environmental enteropathy under unsanitary conditions
Dietary constituents that interfere with nutrient absorption, such as dietary fibers and phytic acid Intestinal parasites (Helicobacter pylori, protozoa and
helminths)
Active acute, recurrent or chronic persistent gastroenteritis
Impairment of nutrient utilization
Lead exposure interferes with the incorporation of iron into hemoglobin, leading to anemia
Inflammation, chronic illness and, specifically, renal disease disrupt the mobilization of diverse nutrients to the red cells, leading to anemia
Menkes disease impairs the cellular utilization of copper Enhanced destruction of vitamins
As organic compounds, vitamins can be denatured or metabolized, as happens with vitamin E in the presence of oxidants
Tobacco smoking destroys vitamin C
Note: inorganic substances (trace elements) cannot be destroyed
Increased nutrient wastage
The metabolic consequences of a systemic
inflammatory response leads to excessive urinary excretion of nitrogen, zinc and vitamin A
Abuse of cathartic laxatives induces excessive losses of water, sodium, potassium, magnesium and calcium
66 Solomons
tions between vitamins, between trace elements and between vitamins and trace elements are rec- ognized. These are quite common for vitamin A with its interactions with vitamins D and E and assorted elements such as iodine and iron [13] . The competition between iron and zinc is notable for its potential consequences in public health in- terventions [14] .
Excessive exposure to certain vitamins and virtually all of the trace elements can have ad- verse effects on children. For 7 of the vitamins and all of the inorganic elements, certain daily dietary amounts pose the risk of the adverse con-
sequences of overload and even toxicity if exceed- ed. These so-called upper tolerable intake levels have been established by agencies such as the Food and Nutrition Board of the USA and the European Food Safety Authority. The interplay between essential risks of dietary deficiency and public health interventions to enhance the mi- cronutritional status can lead to paradoxical situ- ations. Increasingly, this also takes place at the interface of the low nutrient content of the diet selected and the sum of fortification and self-sup- plementation sources. Table 4 illustrates a selec- tion of these paradoxes.
Table 4. A listing of some pertinent paradoxical associations and precautions related to dietary exposure to micronutrients
The tolerable upper intake levels for zinc in toddlers and preschool children may be too low, as they are lower than the average amounts of zinc consumed by apparently healthy children in the USA
The traditional ideal is that all members of a family unit share the majority of meals as a family.
In this regard, the tolerable upper intake level of preformed vitamin A for children under 6 years is lower than the recommended daily intake of total vitamin A for pregnant or lactating women in the same household
The currently recommended intake levels for vitamin D, especially for adolescents and for individuals from darkly pigmented ethnic groups living in temperate latitudes such as Europe, North America and southern Australia, may not be sufficient to maintain protective circulating levels of the vitamin. Pediatric dermatologists and nutritionists are at odds about the value of sun exposure. The dermatological community advocates maximal sunscreen protection to avoid skin damage and malignancy risk, whereas pediatric nutritionists realize that maximizing vitamin D formation in skin in temperate latitudes requires some relaxation of solar exposure avoidance measures
An upward spiral of market-driven fortification, with multiple manufacturers adding micronutrients to make their products more attractive and ‘nutritious’, runs the risk of providing child consumers with several times the daily recommended amounts of some vitamins and minerals
Folic acid is a synthetic and totally oxidized form of folate. Folic acid fortification is mandated in many countries for the prevention of neural tube defects in the pregnancies of susceptible women. These higher folic acid intakes may have additional benefits for adults through the prevention of stroke and vascular disease. However, in adults with established dysplastic changes in the large bowel mucosa, higher folic acid exposure accelerates the progression to colorectal cancer. Limited evidence for a similar scenario exists for prostatic neoplasia. We have little understanding of these beneficial versus harmful effects for the pediatric population Epidemiological evidence is accumulating that the consumption of preformed vitamin A from animal sources and food fortification weakens bone mineralization. The extent and importance of such a process in childhood merit research attention
Koletzko B, et al. (eds): Pediatric Nutrition in Practice. World Rev Nutr Diet. Basel, Karger, 2015, vol 113, pp 62–67 DOI: 10.1159/000367871
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Conclusions
• Vitamins and trace elements get into the child via natural foods and beverages, fortified prod- ucts and oral micronutrient supplements;
sometimes a combination is needed to achieve an adequate diet
• The weaning period for infants and toddlers is a challenging period in which to satisfy micro- nutrient nutriture
• In the community setting, antinutrient sub- stances in the diet and recurrent gastrointesti- nal infections can interfere with micronutrient adequacy
• Overconsumption of certain vitamins and trace elements is an emerging problem due to the overlapping of self-supplementation and market-driven fortification in the pediatric context
11 Alkhouri RH, Hashmi H, Baker RD, Gel- fond D, Baker SS: Vitamin and mineral status in patients with inflammatory bowel disease. J Pediatr Gastroenterol Nutr 2013; 56: 89–92.
12 Leung WC, Hessel S, Méplan C, Flint J, Oberhauser V, Tourniaire F, Hesketh JE, von Lintig J, Lietz G: Two common sin- gle nucleotide polymorphisms in the gene encoding β-carotene 15,15 ′ -mon- oxygenase alter β-carotene metabolism in female volunteers. FASEB J 2009; 23:
1041–1053.
13 McLaren DS, Kraemer K: Interaction of vitamin A and other micronutrients.
World Rev Nutr Diet 2012; 103: 101–105.
14 Fischer Walker C, Kordas K, Stoltzfus RJ, Black RE: Interactive effects of iron and zinc on biochemical and functional outcomes in supplementation trials. Am J Clin Nutr 2005; 82: 5–12.
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6 Palmer AC, West KP Jr, Dalmiya N, Schultink W: The use and interpretation of serum retinol distributions in evalu- ating the public health impact of vita- min A programmes. Public Health Nutr 2012; 15: 1201–1215.
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1 Specific Aspects of Childhood Nutrition
Key Words
Adiposity ã Bone mineral accrual ã Metabolic syndrome ã Fitness ã Strength ã Weight status
Key Messages
• Physical activity (PA) is a behavior that changes with growth and maturation
• Regular PA favorably influences bone mineral accrual, cardiorespiratory fitness, and muscular strength and endurance
• PA has relatively small effects on lipids and adipos- ity and blood pressures in normal-weight and nor- motensive youth, respectively
• PA interventions favorably influence adiposity in the obese, blood pressures in the hypertensive, and components of the cardiometabolic profile in obese youth
• Many indicators of health and fitness, especially metabolic risk, are affected by obesity. A key issue is the prevention of unhealthy weight gain early in childhood and the potential role of PA
© 2015 S. Karger AG, Basel
Introduction
Physical activity (PA) is a behavior. It is the most variable component of energy expenditure. On average, PA declines from late childhood through adolescence, and boys are more active than girls.
From a public health perspective, PA is a be- havior with important implications for health promotion and disease prevention during child- hood, adolescence and adulthood. Emphasis is largely placed on the level of PA associated with health benefits. The role of PA as a medium for learning, enjoyment and social interactions is of- ten overlooked.
Correlates of PA among children and adoles- cents include biological and cultural factors and their interactions. Physical fitness, specifically cardiorespiratory fitness (CRF), is both a corre- late and outcome of PA. Movement skills are also an important correlate of PA. Types and settings (contexts) of PA are often overlooked, and include play, physical education, exercise, sport, transport and chores, among others. Contexts per se and meanings attached to them vary with age and also between and among different cultural groups [1] . Sport is a major context of PA for youth, but regu- lar PA is not equivalent to training for sport.
Outcomes
Two questions, among others, are central to dis- cussions of PA and health of school-age youth:
(1) What are the health and fitness benefits of regular PA?
Koletzko B, et al. (eds): Pediatric Nutrition in Practice. World Rev Nutr Diet. Basel, Karger, 2015, vol 113, pp 68–71 DOI: 10.1159/000360318