Nutrition Epidemiology

269 CHS ( # 2) Basics of nutrition

SCIENCE OF NUTRITION Study of nutrients and other substances in foods and the body’s handling of them. Foundation dependent on other fields: Biology, biochemistry, physiology. Nutritional Genomics: a science studying the relationship between human genome, nutrition and health. It can be divided into two disciplines: - nutrigenetics: studying of how genes affect the activities of nutrients and - nutrigenomics: studying how the nutrients affect the activities of genes Genome: full complement of genetic material in (DNA) in the chromosomes of a cell, carrying hereditary information for an individual organism. The human genome is composed of 23 pairs of chromosomes (46 in total)

97% of the genes known to be associated with human diseases result in monogenic diseases , i.e. a mutation in one gene is sufficient to cause the disease. Modifying the dietary intake can prevent some monogenic diseases. e.g. phenylkenonuria, a genetic disease with a defective phenylalanine hyroxylase enzyme, which is normally responsible for the metabolism of phenylalanine to tyrosine. This results in the accumulation of phenylalanine and its breakdown products in the blood and the decrease in tyrosine, which increases the risk of neurological damage and mental retardation. Phenylalanine-restricted tyrosine-supplemented diets are a means to nutritionally treat this monogenic disease.

In contrast , diseases currently in the world, e.g. obesity, cancer, diabetes, and cardiovascular diseases, are polygenic diseases , i.e. they arise from the dysfunction in a cascade of genes, and not from a single mutated gene. Dietary intervention to prevent the onset of such diseases is a complex and ambitious goal.

Recently , it was discovered that the health effects of food compounds are related mostly to specific interactions on molecular level i.e. dietary constituents participate in the regulation of gene expression by modulating the activity of transcription factors, or through the secretion of hormones that in turn interfere with a transcription factor.

Gene expression is the process by which inheritable information from a gene, such as the DNA sequence, is converted first into messenger RNA and then to a protein (functional gene product) Transcription is the synthesis of RNA under the direction of DNA. RNA synthesis, or transcription, is the process in which genetic information (nucleotide sequence) stored in a strand of DNA is copied into a strand of RNA.

Down Syndrome Haemophilia Sickle cell anaemia Adult bone loss Cancer Infectious diseases Diabetes Hypertension Heart diseases Iron deficiency (anaemia) Vitamin deficiencies Mineral deficiencies Toxicities Poor resistance To disease Less nutrition- related (genetics) More nutrition- related

Basics Food —any substance the body can take in and assimilate Essential for life Derived from plant and animals sources A source of NUTRIENTS and non-nutrients Diet —The foods and beverages a person usually eats and drinks.

FOOD CHOICES Omnivore A person who eats food of both plant and animal origin, including animal flesh Vegetarian A person who excludes from his diet animal flesh and possibly other animal products such as milk, cheese, and eggs

Indispensable: absolutely essential and body can not function without them

Key Point: Nutrients are important in food support growth, maintenance, and repair of the body. Conversely, deficiencies, excess, and imbalances of nutrients lead to diseases of malnutrition

Nutrient Deficiencies Primary Deficiency : Nutrient deficiency caused by inadequate dietary intake. Secondary Deficiency: Nutrient deficiency caused by something other than inadequate intake (i.e. absorption, drug interaction, excretion)

The Known 50 Essential Nutrients for Sustaining Human Life * *Numerous other beneficial substances in foods are also known to contribute to good health. Linoleic acid Linolenic acid Lipids-Fat (fatty acids) (2) A D E K C (Ascorbic acid) B 1 (Thiamin) B 2 (Riboflavin) B 3 (Pantothenic acid) Niacin B 6 (Pyridoxal) Folate Biotin B 12 (Cobalamin) Fe Zn Cu Mn I F B Se Mo Ni Cr V Si As Li Sn Co (in B 12 ) Na K Ca Mg S P Cl Histidine Isoleucine Leucine Lysine Methionine Phenylalanine Threonine Tryptophan Valine Water Carbohydrates Vitamins (13) Micro-Elements (17) Macro-Minerals (7) Protein (amino acids) (9) Water & Energy (2)

What are the nutrients in food? Water ENERGY YIELDING NUTRIENTS ( Macronutrients ) -Carbohydrates -Fats (Lipids) -Protein REGULATOR NUTRIENTS ( Micronutrients ) -Vitamins -Minerals

Description of Nutrients -1 Water Inorganic Indispensable The foremost of the nutrients Constantly lost and replaced Provides environment in which nearly all of the body’s activities are conducted. Not energy-yielding

Where's the Water? 66% of a person's total body weight is from water. 65% of total body water is intracellular. 35% of total body water is extracellular. Well-hydrated muscles are about 75% water. Bones are about 32% water. Fat is essentially anhydrous, having only about 10% water content. Blood is about 93% water. Average males are about 60% water weight. Average females are about 50% water weight. Obese individuals are about 40% water weight. Athletes are about 70% water weight.

Description of Nutrients -2 Energy-Yielding Nutrients : The body can use the energy they contain. MACRONUTRIENTS -Carbohydrates -Fat (Lipids) -Protein

Energy in food Energy is measured in calories (calories, kilocalories, kcalories, kcal) One kcalorie = Amount of heat energy needed to raise the temperature of 1 kilogram of water 1°C

The calorie is a pre-SI (International System of Units) unit of energy, in particular, heat. In most fields, its use is outdated, and the SI unit of energy, the joule, has become accepted. However, it remains in common use as a unit of food energy. It was first defined by Professor Nicolas Clement in 1824 as a kilogram-calorie, and this definition entered French and English dictionaries between 1841 and 1867 . Etymology: French calorie , from Latin calor (heat).

The unit calorie has historically been used in two major alternate definitions that differ by a factor of 1000: The small calorie, gram calorie , or calorie (symbol: cal ) is the amount of heat (energy) required to raise the temperature of one gram of water by 1 °C. The large calorie, kilogram calorie, kilocalorie (symbol: kcal ), or Calorie (capital C ) is the amount of heat (energy) needed to increase the temperature of one kg of water by 1°C, exactly 1000 small calories, or about 4.184 kJ.

The second definition is the one commonly used to express food energy, e.g. when discussing dieting or nutrition plans. Under this definition, 1 g of pure carbohydrate yields about 4 Calories of energy, and the recommended intake for an adult person is about 2,000 - 2,500 Calories/day. Measuring Foods Unit of weight: Gram

Protein requirements The recommended level of protein intake for the general population is 12% to 15% of total calories. Therefore, someone consuming 2,000 calories per day has an energy equivalent of 240 to 300 calories (60 to 75 grams) of protein per day.

Meats and dairy products provide all the essential amino acids (derived only from food as body cannot manufacture. They perform various functions ) in a single food, but plant sources of protein do not. Therefore, vegetarians should be careful to combine foods in a way that optimize essential amino acid availability

Carbohydrate Requirements The Institute of Medicine recommends 130 grams (520 kilocalories) of carbohydrate per day, which is the average minimal usage of glucose by the brain. The desirable range of carbohydrate intake is 45% to 65% of total caloric intake ( also referred to as the Acceptable Macronutrient Distribution Range, or AMDR ), and the Daily Value ( DV ) for carbohydrate on food labels is based on a recommended intake of 60% of total caloric consumption. These recommendations also generally advise that no more than 25% of carbohydrate intake be derived from sugars (mono- and disaccharides)

Fat requirements The American Heart Association and the United States Department of Agriculture recommend that fat intake is limited to no more than 30% of daily calories: 10% or less of calories come from saturated fat, not more than 15% from monounsaturated fat, and less than 10% from polyunsaturated fat. Saturated fats , which are generally solid at room temperature, are the least healthy and tend to increase the level of cholesterol in your blood. Monounsaturated fats have been shown to raise the level of HDL , the 'good' cholesterol that protects against heart attacks. Although polyunsaturated fats come from plants and fish, but they may be more likely to form free radicals and lead to tissue damage.

Description of Nutrients -3 Regulator Nutrients : Do not produce energy Act as regulators and assist in all body processes. Some minerals serve as parts of body structures. MICRONUTRIENTS Vitamins Minerals

-Vitamins are essential for several enzymatic functions in human metabolism -Thiamine was discovered in 1912 and was thought to be a vital amine compound & thus the term vitamin was invented -13 vitamins are known, 4 fat soluble (KEDA) and 9 water soluble (C, Folate and the B group) .

The total mineral content of the body is approximately 4% of body weight. Sixteen essential minerals are required to support human biochemical processes by playing roles in cell structure and function as well as electrolytes. The required minerals are divided into macrominerals and microminerals. Macrominerals are present in the body in relatively larger amounts than micro minerals (thus the name). Microminerals (trace elements) are present in body tissues in extremely small amounts but have critically important roles to play in human nutrition. The required intake of each micromineral is less than 100 milligrams per day, and the total body content of these minerals is less than 5 grams.

Macrominerals include Calcium (an important mineral for bone and tooth structure, blood clotting, and nerve transmission), Phosphorus (combines with calcium-about two parts calcium for every part phosphorus- to produce healthy bones and teeth, plays an important role in energy metabolism), Magnesium (essential for human metabolism and for maintaining the electrical potential in nerve and muscle cells), Sodium (an essential mineral commonly referred to as salt. It is involved in body water balance and acid-base balance and is the major extracellular -outside the cell, including blood and fluid- mineral), Chloride (an extracellular mineral that is essential for the maintenance of fluid balance and, therefore, normal cell function, also it is an important component of gastric juices) , and Potassium (the main mineral found inside cells -an intracellular electrolyte- at a concentration that is 30 times greater than the concentration of potassium found outside cells. It is involved in water balance, nerve impulse transmission, and muscular contractions).

Microminerals include: Iron (needed to form the oxygen-transporting compounds hemoglobin (in blood) and myoglobin (in muscle) and is also found in a number of other compounds involved in normal tissue function), Zinc (helps form a large number of enzymes, many of which function in energy metabolism and in wound healing), Iodine (needed to synthesize a key hormone of the thyroid gland, thyroxin, which is involved in regulating metabolic rate, growth, and development), Selenium (an important mineral antioxidant in human nutrition), Copper (present in many enzymes and in copper-containing proteins found in the blood, brain, and liver), Manganese (involved in bone formation, immune function, antioxidant activity, and carbohydrate metabolism), and Chromium (is also known as glucose tolerance factor (GTF) because of its involvement in helping cells use glucose).

The Challenge of Choosing Foods Well-planned meals can convey pleasure and can be nutritious

Building blocks for Nutritious Diet: -1 1-Adequacy The diet provide all of the essential nutrients, fiber, and energy in sufficient amounts to maintain health and body weight 2-Balance (In proportion to one another) Providing foods of a number of different types in proportion to each other. Such that foods rich in some nutrients do not crowd out of the diet foods that are rich in other nutrients

Building blocks for Nutritious Diet: -2 3-Calorie control -Control of energy intake -A feature of a sound diet plan 4-Moderation -Provide constituents within set limits -Nothing in excess 5-Variety -Provide a wide selection of food -The opposite of monotony

Role of Nutrition in Prevention of Disease

Nourishment Functions Synthesis of Bioactive Compounds Energy Lean Body Mass, Skeletal Mass Fluid, Electrolyte, Acid-Base Balance Regulatory Functions membrane potentials, neuromuscular activity, plasma & cellular fluid volumes enzymes hormones immune substances enzyme activation cell messengers gene induction production, storage, release Structure, functional activities

Determinants of Nutrient Needs Absorption Efficiency Metabolic Demand Excretion Levels

Nutrient Interactions Zinc deficiency interfere with vitamin A metabolism in several ways : It decreases the synthesis of retinol binding protein, which transports retinol to tissues. It decreases the activity of the enzyme retinyl palmitate, which is necessary for release of retinol from the liver. Zn is needed for the enzyme that convert retinol into retinal.

Nutrient Interactions/2 Iron & vitamin A. Vitamin A deficiency may exacerbate IDA ِِ Vitamin A supplementation improves iron status among children & pregnant women. Combining vitamin A with iron controls IDA more quickly & effectively than using iron alone.

Goals of Nutrition in Disease Prevention Optimize cellular activity and tissue/organ function Reduce metabolic burden imposed by environmental factors on cardiac, pulmonary, renal, hepatic, and musculoskeletal systems Support cellular defenses that protect tissue integrity

Optimize Cellular Activity and Tissue/Organ Function Provide sufficient amounts to satisfy daily demands Adequacy of intake Balance and variety in food choices Maintain adequate reserves Habitual diet and dietary patterns Defensive approach

Nutrition Epidemiology

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Nutrition Epidemiology