chap 1 nutrition and human development

7/28/2019 Chap 1 Nutrition and Human Development

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NUTRITION AND HUMAN DEVELOPMENT

NUTRITION DEFINED

- Nutrition is a broad interdisciplinary subject

- Nutrition : the study of the interaction between human organism and its food- Nutrition : integrated science, applied science, since it is concerned with solving

practical problems ( Alfred Harper )

- Scope of nutrition and food sciences :1. Disciplines that look within cells or in vitro environment ( analytical

chemistry, biochemistry, cell biology, immunology, molecular biology,

molecular genetics )2. Disciplines that look at specific organs ( clinical sciences, medical genetics,

medical and special foods, pathology, physiology, psycholog, physiological

chemistry )

3. Disciplines that look at entire populations ( anthropology, demography,

ecology, economics, education, epidemiology, food and health policy,political science, sociology )

4. Disciplines that look at food supply ( agriculture, animal husbandry,environmental waste management, food engineering, food processing, food

production, food toxicology )

THE ROLE OF NUTRITION IN GROWTH AND DEVELOMPENT

- Growth : a measurable increase in size ( height, weight, metabolic studies in

which body retention of substances are determined e.g. calcium and nitrogen )- Development : an increse in complexity of function and is characterized by

differentiation and maturation- Cellular growth and differentiation

Tissue growth result from : mitosis and hyperplastic growth, hyperthropic

growth, combination of hyperplastic and hyperthropic

Three general patterns of growth in human tissue :

1. In regenerating tissues : cell continually dying and being replaced by newcell, e.g. skin cell, red blood cell

Germinal cell : cell in a primitive stage of development from which other

cells are grown2. Non regenerating tissues : formed early in life and meant to last for a

lifetime, they are highly specialized and can only divide early in life, e.g.

nerve and muscle cells3. Renewing tissues : they do not continually replace thenselves, but under

special situation such as in response to injury or increased demand, they

can undergo mitosis and proliferate, e.g kidney and many secretory tissues

throughout the body.- Heredity, environment and nutrition

Human growth and development is a result of the continuous and complex

interaction between heredity and environment

Each individual inherits a set of genes from his or her mother and father. Each

gene is a linear portion of the DNA. DNA through the formation of mRNA

directs the assembly of structural and functional proteins from amino acid

precusors. Genes elaborate a master plan that codes for the development of thepersons phenotype, however the final expression of phenotype iss strongly

influenced by the environment.E.g. monozygotic twins and dizygotic twins

Nutrition is a major environmental influence on phenotype, afffecting from

clearly visible characteristics to the mor subtle attributes of blood pressure andconcentration of blood chloesterol.


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Critical period of development :

- describred the time of greatest vulnerability to a specific action of insult.

- Critical periods are typically times of rapid cell division. If cell division islimited during a critical period of organ growth, the final cell number in

the organ can be irreversibly reduced and the organ permanently damaged.

- The embryonic period of human development is a particularly critical timefor aduquate nutrition

- Recovery is usually possible if nutritional deprivation occurs at a least

crucial time in development.- Rapid growth occuring after a period of growth impairmnet is referred to

as catch-up growth

Vitamin A : A paradigm of the influence of nutrient on heredity

- Vitamin A can directly affect gene expression- Vitamin A taken up by cells, combines with specific binding proteins and

passes into cell nuclei. In the nucleus, vitamin A interacts with DNAm

regulating gene transcription ( the production of mRNA from DNA )

- By influencing gene expression, vitamin A promotes the differentiation ofepithelial cells from simpler to more specialized forms.

- The effect of vitamin A begin early in embryogenesis, plays a fundamental

morphogenetic role in the organization of the embryo.- Later in childhood, vitamin A continues to influence growth and

development; inadequate dietary vitamin A impairs functioning of

immune system.- In the later stages of life, vitamin A is a vital component of cellular

mechanisms of maintenance and repair. Adequte vitamiin A status may

reduce the risk of certain cancers, inluding mouth and breast cancers.

Nutrition and Inborn Errors of Metabolism

- Inborn errors of metabolism are inherited diseases caused by impairmentof normal metabolic pathways

- A number of these disorders result form mutations in specific genes. Themutation leads to the deletion or impariment of the protein which is

usually an enzyme. This result in the production of a toxic by product or

the deficienscy of an important metabolite. The diseases have been shownto be amenable to nutritional therapy. E.g. phenylketonuria

OVERVIEW OF HUMAN DEVELOPMENT- Life Cycle versus Lifespan

Human life cycle : fertilized egg ( conception ) development intra uterine birth childhood puberty ( sexual maturity : begin to produce eggs or sperm

that will form next generation )

Human development includes the entire lifespan : physical growth ceases,

degenerative changes appears, but individuals continue to develop and maturepsychologically and socially

Optimal nutrition, vital for growth and development in early life, continues to be

important in supporting maintenance and repair throughout the lifespan


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- Major Developmental Stages ( used in this book )

Developmental Stage Approximate Age

Prenatal

EmbryonicFetal

0 8 weeks8 weeks birth

Infancy

NewbornEarly infancy

Late infncy

First month after birth1 month 1 year

Second year

ChildhoodEarly ( Preschool )

Late ( School age )

2 5 years

5 10 years

Adolescence

Females

Males

10 18 years

12 20 yearsAdult 18 or 20 to 65 years

Older adult Greater than 65 years

Prenatal period

- Development begins as a single cell ( the fertilized ovum ) and during the first

few days after conception, the rapidly dividing ovum is self-sufficient, livin

off food stored in its yolk sac.- About a week after fertilization the ovum has developed into a blastocyst and

buries itself in the endometrium of the uterus. As the placenta forms, the

embryo becomes completely dependent on nutrition derived from the

maaternal bloodstream.- Growth is modest during the embrionic period, rapid differentiation of all

major organs. The fetal period is characterized by further development and

extraordinary growth.- Simple substrates from maternal diet and maternal stores are transffered in a

continuous stream across the placenta to the fetus.

Infancy

- At birth, the newborn infant must begin to process and assimilate good- Digestion and absorbtion of complex substances must occur before nutrients

are available for energy production and growth

- The ability to digest certain substances varies with age, e.g. starch, lactose

Childhood and adolescence- Physical growth is slow but steady during childhood. Psychological and social

development is brisk, and there is increasing coordination of function asintellect and personality develop.

- Human and primates have a period of accelerated growth in early adolescence.

- Adolescence si characterized by growth spurt, puberty and the attainment of

sexual maturity- Human achive maximum stature after about 2 decades of growth ( about 21

years of males and 17 for females ).

- Muscle mass usually continues to increase into the mid 20-s and skeletal massinto the early 30s.

Adult and older adult- Psychosocial development conitunes through adulthood.

- Nutrient needs for physical frowth cease, but adequate nutrition continues tobe important to support maintenance and repair.

- Senescence, the state of later maturity, is characterized by a gradual loss of

cells from tissue and functional decline in tissues throughout the body.


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- Aging is inherent and genetically determined.

- The rate of aging process is strongly influenced by the environment and diet.

- Many chronic degenerative disesase can be prevented or favorably influencedby diet.

RECOMMENDED NUTRIENT INTAKES AND DIETARY GUIDELINES

- Recommended Dietary Allowances ( RDAS )

The level of intake of essential nutrients that are judged to be adequate to meet the

known nutient needs of practically all healthy persons, on the basis of scientific

knowledge

Established by estimating the average physiological requirement for an absorbed

nutrient by sex and age, adjusted to compensate for variaton in the requirementamong individuals and the bioavailibility of the nutrient in the food supply.

Fairly generous allowances that actually exceed the requirements of most

individuals, except for energy requirement. Only the mean requirement energy is

offered for each age group to avoid the intake of excess energy Purposes :

1. Evaluating the adequacy of food supplies and planning food suplies for

populations

2. Interpreting food consumption surveys3. Establishing standards for food assistance programs

4. Designing nutrition education programs

5. Developming new products in industry

Most appropriate for populations, not individuals.

Comparing long-term individual intakes to the RDAs allows an estimate about the

probable risk of deficiency for that individual

- Dietary Guidelines

Diet annd Health Guidelines by NAS give advice on foods individuals should

include, limit, or avoid to reduce the risks of chronic disease

- Nutrition Objectives of Healthy People 2000

21 objectives that focus on nutrition

Aimed at decreasing the prrevalence of obesity and irondeficiency anemia,

reducing coronary heart disease death rates, reversing the rise in cancer mortality.

Specific dietary changes :

- decreasing consumption of total fat to 30% or less of kcalories, saturated fat toless than 10% of kcalories and cholestorol to less than 300mg daily

- increasing consumption of grains, or starches and othre complexcarbohydrates

- maintain protein intake at moderate level

- limit total daily intake of salt ( sodium chloride ) to 6grams or less- increasing consumption fruits and vegetables,

- maintain adequate calcium intake

- balance food intake nd physical activity to maintain appropriate body weight

- for those who drink alcoholic beverages, limit consumption to the equivalentof less than 1 ounce of pure alcohol in a single day. Pregnant women should

avoid alcoholic beverages- Avoid taking dietary supplement in excess of the RDA in any one day- Maintain optimal intake of fluoride particularly during the years of primary

and secondary tooth formation and growth.


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chap 1 nutrition and human development

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