NUTRITIONNUTRITION Dr. Ayyub Patel, PhD CChem MRSC FRSC

Assistant Professor, Medicine KKU KSA

IntroductionIntroduction• Nutrients are the constituents of food necessary to

sustain normal functions of the body• Most of the energy is provided by three classes of

nutrients:

(1) Fats

(2) Carbohydrates

(3) Proteins• These nutrients are consumed in larger amounts,

therefore, they are called ‘macronutrients’ • Those nutrients needed in lesser amounts, such as

vitamins and minerals are called ‘micronutrients’

Classification of NutrientsClassification of NutrientsNutrients are

A).Macronutrients: (Source of energy)

Carbohydrates, Lipids, Proteins

B).Micronutrients :

Minerals & Vitamins

C). Water

Calories per gramProtein 1 Gram = 4 caloriesCarbohydrates 1 Gram = 4 caloriesFat 1 Gram = 9 calories

Energy content of foodEnergy content of food• The energy content of food is calculated from the heat

released during its breakdown. • It is expressed in kilocalories (kcal or Cal) • Joules is the another unit of energy

1 cal = 4.128 J Calorimeter is used to measure the

heat generated from the food under combustion or by either chemical reaction, change of state, or formation of a solution.

Energy requirement in humansEnergy requirement in humans

• Sedentary adults (less activity) require

30 kcal/kg/day• Moderately active adults require

35 kcal/kg/day

• Very active adults require 40 kcal/kg/day

Human energy requirements are estimated from measures of energy expenditure plus the additional energy needs for growth, pregnancy and lactation.

Energy Utilization or expenditure Energy Utilization or expenditure • Energy is required for ; 1. Basal Metabolic Rate (BMR) or resting metabolic rate 2. Thermic effect of food (formerly termed specific dynamic action) 3. Physical activity

Energy balance • It is achieved when input (i.e. dietary energy intake) is equal to output (i.e. total energy expenditure).• Added energy consumed for growth in childhood and pregnancy, or the energy used to produce milk during lactation are maintained. Steady StateWhen energy balance is maintained over a prolonged period, an individual is considered to be in a steady state.

Energy expenditureEnergy expenditure

• 1.The energy expended in a resting, postasorptive state is called resting metabolic rate (RMR) or formerly BMR.

• 2.The production of heat by the body increases as much as 30% above the RMR during digestion and absorption of food. It is called thermic effect of food

• 3.Muscular activity provides physical activity. Sedentary life requires 30 to 50% more than the RMR. Highly active persons require 100% more than the RMR

Energy Balance Energy Balance

• Calories consumed should be equal to calories burned.

• Positive balance : calories consumed is higher than calories burned.

• Negative balance: calories consumed is less than calories required.

Role of different foodsRole of different foods • Adults should consume 45 to 65% of their total

calories from carbohydrates• 20 to 35% calories from fats• 10 to 35 % calories from proteins.• Carbohydrates provide energy and fiber • Fats provide energy and essential fatty acids• Proteins provide essential amino acids for protein

synthesis.• Water forms essential part of diet though it has no

calorific values. • Vitamins and minerals are required for

maintenance of body’s metabolism.

Recommended Dietary Allowance (RDA)Recommended Dietary Allowance (RDA)

• The RDA is the average daily intake level, that is sufficient to meet the nutrient requirements of nearly all (97 to 98%)

• RDA will vary according to the physiological needs. • Pregnant and lactating women need more nutrients. • Growing children will need more of some nutrient than

adults.

Nutrition & DiseaseNutrition & DiseaseNutritional disease may be due to

(A). Deficiencies: eg developmental abnormalities,

Protein energy malnutrition, Mineral deficiencies

and vitamin deficiencies. Malnutrition like Iodine

deficiency, Coelic disease, starvation etc.

(B). Excesses in the diet : eg obesity and uncontrolled

eating disorders, chronic diseases like

cardiovasucular (CVD),hypertension, diabetes,

cancer etc.

Dietary Mineral Toxicity, Hypervitaminosis.

Nutrition & Disease…ContdNutrition & Disease…Contd• Fiber rich diets decreases the risk for constipation• Consumption of saturated fats is strongly

associated with high levels of total plasma cholesterol and LDL cholesterol which result in increased risk of cardiovascular disease

• Consumption of n-6 polyunsaturated fatty acids reduce the risk of cardiovascular mortality

• Kwashiorkor is caused by inadequate intake of protein (Protein energy malnutrution)

• Marasmus results from chronic deficiency of calories (Starvation and protein energy malnutrition)

A child with kwashiorkorA child with kwashiorkor A child with Marasmus

Minerals Minerals

• Minerals are required in amounts greater than 100 mg/day

• Calcium, phosphorus, Sodium, Potassium, Chloride and Magnesium are the important minerals in the body

• They are present in the leafy vegetables, fruits, dairy products and table salts

• Calcium & Phosphorus deficiency produce rickets in children and osteomalacia in adults

Functions of CalciumFunctions of Calcium• Calcium is the most abundant mineral in the

human body• The average content of calcium in an adult is 1

kg of which 99% is present in the bone.Functions of calcium include:• Structural component in bone and teeth.• Controls excitability and release of

neurotransmitters• Initiates muscle contraction• Coenzyme for coagulation factors• Acts as intracellular second messenger (signal)

Trace Elements in the human bodyTrace Elements in the human body• Trace elements are also essential for normal maintenance of

health and metabolism.

• They form the functional prosthetic groups in many proteins and enzymes.

• Trace elements in the body are by definition present in concentrations less than 100 ppm.

• The daily requirement is less than 100 mg• Chromium, cobalt, copper, fluorine, iodine, iron, manganese,

molybdenum, selenium, silicon and zinc are known trace elements in the body.

TRACE ELEMENTS FUNCTIONS

1.Chromium In glucose metabolism

2.Cobalt Component of Vit B12

3.Copper Cofactor for cytochrome oxidase

4.Fluorine Present in bone and teeth

5.Iodine component of thyroid hormones

6.Iron Present in haem pigments

7.Manganese Cofactors for many enzymes

TRACE ELEMENTS FUNCTIONS

8.Molybdenum Cofactor for xanthine oxidase

9.Selenium Cofactor for glutathione peroxidase

10.Silicon Present in cartilage

11.Zinc Cofactor for many enzyme