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N U T R I T I O N. MBC 142  4 Lectures  Dr. Usman Ghani. O V E R V I E W. Basic concepts of human nutrition Recommended daily allowances (RDA) Energy requirement in humans Macronutrients (proteins, carbohydrates, lipids, dietary fibers) and micronutrients (vitamins, minerals)

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MBC 142  4 Lectures  Dr. Usman Ghani


  • Basic concepts of human nutrition

  • Recommended daily allowances (RDA)

  • Energy requirement in humans

  • Macronutrients (proteins, carbohydrates, lipids, dietary fibers) and micronutrients (vitamins, minerals)

  • Nutritional diseases

  • Diet and cancer

  • Dietetic treatment (treatment of disease by diet)

W h a t i s N u t r i t i o n ?

  • Utilization of foods by living organisms

  • The process of utilization is biochemical

  • Human nutrition has three types:

    • Undernutrition

    • Optimal nutrition

    • Overnutrition

N u t r i e n t s a n d D i e t

  • Nutrients are the ingredients of food needed for normal functioning of the body

  • Nutrients provide energy for various body functions

  • Quality (what food items) and quantity (how much nutrients) are important for maintaining good health

T y p e s o f N u t r i e n t s

  • Two types:

    • Macronutrients

    • Micronutrients

M a c r o n u t r i e n t s

  • Nutrients needed by the body in large amounts are called macronutrients

  • Three types of macronutrients

    • Proteins

    • Carbohydrates

    • Fats

  • Macronutrients provide energy and building blocks of proteins, carbohydrates and fats

M i c r o n u t r i e n t s

  • Nutrients needed by the body in small amounts are called micronutrients

  • Major types of micronutrients

    • Vitamins

    • Minerals / trace elements

  • Required for maintaining normal health and preventing various diseases

N u t r i e n t s f r o m D i e t

  • Proteins, carbohydrates, fats

  • Essential fatty acids

  • Essential amino acids

  • Vitamins

  • Minerals

  • Dietary fibers

  • Water

Recommended Daily Allowances (RDA)

  • RDA are the levels of intake of essential nutrients considered by the Food and Nutrition Board, USA, to be enough to meet the nutritional needs of all healthy persons

  • RDA varies according to age and sex

E n e r g y C o n t e n t o f F o o d

  • Much of the food we eat is converted to ATP and other high-energy compounds

  • This energy is used for biosynthetic pathways, muscle contraction, nerve impulse, etc.

  • Energy content of food is measured in calories (Kilocalories) of heat energy released by combustion (burning) of that food

  • One calorie is the heat required to raise the temperature of 1 gm. of water by 1oC

  • Proteins 4 kcal/gm

  • Carbohydrates  4 kcal/gm

  • Fat  9 kcal/gm

E n e r g y E x p e n d i t u re

  • Depends on four factors:

    • Surface area of the body (height and weight)

      • The greater the surface area the greater the heat loss

    • Age

      • Growth and lean muscle mass

      • Infants have higher basal metabolic rate (rate of energy utilization in resting state)

  • Sex

    • Women have lower BMR than men

  • Activity level

    • Exercise increases energy expenditure

Recommended Energy Intake

Some Definitions

  • Omnivorous: eat both meat and vegetables

  • Carnivorous: eat meat only

  • Herbivorous: eat vegetable, grass only

Vegetarianism - Definitions

  • Lacto-Ovo Vegetarian

  • Lacto Vegetarian

  • Vegan

Vegetarianism - Definitions

  • Lacto-ovo vegetarian: Avegetarian who consumes eggs (ovo) and milk (lacto)

  • Lacto vegetarian: Does not eat eggs, meat, poultry or fish/seafood of any kind, but does consume dairy (lacto) products

  • Vegan: A strict vegetarian who does not eat animal products, meat, fish, poultry, eggs or dairy

Vegetarian and nutrient intake

  • Lower intake of iron

  • Lower intake of calcium and vitamin D

  • May develop megaloblastic anemia because of vitamin B12 deficiency

  • Most consume enough protein

  • Lower in total dietary fat

Vegetarian diet and disease(Research results)

  • Lower Body Mass Index (BMI)

  • Ischemic heart disease lower than non-vegetarians

  • Lower blood pressure

  • Lower cancer rates compared to non-vegetarians

Dietary guidelines – more about RDA

  • Recommended Dietary Allowance (RDA)

    • Developed during the 1940’s

    • Prevention of vitamin and mineral deficiencies

    • Revised every 5 year

  • Dietary goals

    • Goals for healthy diet

    • Health promotion and disease prevention

Food PyramidUnited States Department of AgricultureCenter for Nutrition Policy and Promotion

  • Educational tool for public – established in 1992

  • Healthy eating guide

  • Size of each section reflects daily servings recommended

  • Pyramid shape

  • Fats, oils and sweets occupy only a tiny triangle at the top

The Food Pyramid

Dietary Goals


  • Major cause of many diseases: obesity, diabetes, hypertension, etc.

  • High morbidity (disease)

    and mortality


  • It is a nutrition assessment process

  • Identifies persons who are malnourished

  • Done by a physician, nurse, dietitian or other qualified health-care professional

  • Identifies individuals who require aggressive nutrition support

  • Restores or maintains an individual’s nutrition status

  • Identifies appropriate medical nutrition therapies

  • Monitors the efficacy of these interventions

Nutritional Importance of Proteins

  • Proteins supply amino acids and amino nitrogen for the synthesis of important nitrogenous compounds such as purines, pyrimidines and heme

  • Types of amino acids:

    • Essential (body can’t synthesize)

    • Non-essential (body can synthesize)

Recommended Daily Protein Intake

  • RDA:0.8 gms/kg body weight

  • World Health Organization

    10 to 15 % of total calories

Recommended Daily Protein Intake(mg/Kg body wt.)

  • Infants (4–6 months)

    • 1100

  • Children(10–12 year)

    • 1000

  • Adult (Men and Women)

    • 800

  • Pregnancy

    • Additional 200

  • Lactation

    • Additional 300

Essential Amino Acids

  • Essential amino acids are not synthesized by the body and must be supplied in diet






    *Essential only in children

N i t r o g e n B a l a n c e

  • Normal Nitrogen Balance

    • In a healthy person, the nitrogen intake is equal to nitrogen loss

  • Negative nitrogen balance

    • When nitrogen loss is more than intake

  • Positive nitrogen balance

    • When nitrogen intake is more than loss

Protein-Energy Malnutrition

  • Malnutrition:

    • Condition/disease caused by not eating enough food or not eating a balanced diet

  • Malnutrition due to inadequate intake of proteins or energy

  • Two conditions:

    • Marasmus

    • Kwashiorkor

  • Marasmus:

    • Inadequate intake of both proteins and energy (calories)

    • Occurs in growing children under 5 year

    • Usually found in poor population suffering from food shortage

  • Clinical Features

    • Thin appearance

    • Weight loss

    • Small for his/her age

    • Poor physical/mental development

    • Weak immune system

    • Sensitive to developing infection

  • Kwashiorkor

    • Inadequate intake of proteins with adequate energy intake

  • Clinical features

    • Edema (swelling of body)– Dry, weak hair

    • Diarrhea– Dermatitis

    • Weak immune system – Retarded growth

    • Sensitive to developing infection

Excess Protein-Energy Intake

  • Can lead to obesity, diabetes, hypertension, coronary heart disease, etc.

C a r b o h y d r a t e s

  • Their major role in diet is energy production

  • Excess carbohydrates are converted to glycogen (in liver) and triacylglycerols (fat) for storage in adipose tissue

  • Carbohydrate intolerances

    • Diabetes mellitus

    • Lactase insufficiency


  • Provide 4 kcals/gram

  • Major energy supply to the cells

  • RDA: 130 grams/day for adults and children

  • World Health Organization

    • Lower limit:55% of total calories

    • Upper limit:75% of total calories


table sugar (sucrose)

honey, high fructose corn syrup, fruit juice concentrate, etc.

Naturally occurring

fruit (fructose)

milk (lactose)

Refined grains

white breads, rice, pasta

cereals, crackers

Whole grains

whole wheat breads and pasta; brown and wild rice

whole oats

cereals, crackers and baked goods made with “100% whole wheat flour”

Carbohydrates in Food

Simple Carbohydrates

Complex Carbohydrates


Protein-sparing effect

  • Dietary protein requirement and CHO diet are related to each other

  • If CHO intake is less than 130 g/day:

    • more protein is metabolized

    • more gluconeogenesis


  • CHO have protein-sparing effect:

    • inhibit gluconeogenesis from amino acids

    • amino acids are used for repair and maintenance of tissue protein

    • not for gluconeogenesis

  • Protein-sparing (protein-saving)

Fats in the Diet

  • Concentrated source of energy – 9 kcals/gram

  • Triacyglycerols (fats) are used as energy source

  • Supply essential fatty acids that cannot be synthesized by the body (linoleic and linolenic acids)

  • Phospholipids are essential for membrane function

  • Help in the absorption of fat-soluble vitamins

  • Source of fat-soluble vitamins (A, D, E and K)

Fats in the diet

  • Contribute to the satiety (satisfactions) of a meal

  • Contribute to taste and smell of foods

  • May stimulate appetite

  • Slow gastric emptying

  • Excessive fat intake can cause

    • atherosclerosis/heart disease

Dietary FatFrom animals and plants

  • Animal fats

    • Usually high melting point

    • Solid (hard) at room temperature

  • Plant fats (oils)

    • Usually low melting point

    • Liquid at room temperature

Recommendations for Total Fat

  • World Health Organization

    • Lower limit: 15% of total calories

    • Upper limit: 30% of total calories

  • National Cancer Institute

    • 30% or less of total calories

Recommendations for Saturated Fat

  • World Health Organization

    • Lower Limit: 0% of total calories

    • Upper Limit: 10% of total calories

Essential Fatty Acids

  • Two essential fatty acids:

    • α-linolenic acid (ω-3 fatty acid)

    • linoleic acid (ω-6 fatty acid)

  • Deficiency causes: scaly skin, dermatitis, reduced growth (most common in infants)

  • Deficiency very rare

  • ω-3 and ω-6 fatty acids used to make eicosanoids which appear to have cardioprotective effects

    • decreased blood clotting

    • decreased blood pressure

Essential Fatty Acids

Food Sources of α-Linolenic Acid

  • Vegetable Oils

    • Soybean oil

    • Flaxseed oil

  • Fish oils

    • Especially from fatty fish

    • Provide a mixture of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)

Omega-3 Fatty Acids

  • EPA and DHA primarily found in cold-water ocean fish such as: albacore, mackerel, salmon, sardines, tuna, whitefish

  • Play an important role as:

    • Structural membrane lipids

    • Modulator of ω-6 fatty acid metabolism


Patients without coronary heart disease (CHD)

Patients with CHD

Patients who need to lower triglycerides (fats)


Fatty fish twice a week

Include oils and foods rich in a-linolenic acid (flaxseed, canola and soybean oils; flaxseed and walnuts)


1 gm of EPA+DHA per day from fatty fish

EPA+DHA supplements


2 to 4 grams of EPA+DHA per day provided as capsules under a physician’s care

Recommendations for Omega-3 Fatty Acid IntakeAmerican Heart Association Guidelines

Mediterranean Diet

  • Seasonal food

  • More vegetables and fruits

  • Less red meats

  • Olive oil – a major fat source

  • Rich in:

    • monounsaturated fatty acids (olive oil)

    • Omega-3 fatty acids (fish, nuts)

  • Low in saturated fat

  • Reduces total serum cholesterol and LDL

Trans Fatty Acids

  • Unsaturated fatty acids, behaving more like saturated fatty acids in the body

    • increase serum LDL (but not HDL)

    • risk of CVD

  • Not found in plants (animals only)

  • Formed during the hydrogenation of liquid vegetable oils

  • Found in baked food: cookies, cakes, deep-fried foods

D i e t a r y F i b e r

  • The component of food that cannot be broken down by human digestive enzymes

  • Dietary fiber provides little energy

  • Functions

    • Reduces constipation

    • Increases bowel movement

    • Reduces exposure of gut to carcinogens

    • Decreases absorption of dietary fat and cholesterol

    • Delays gastric emptying

    • Generates sensation of fullness

Two Types of Dietary FiberMost high fiber foods are a combination of insoluble and soluble dietary fibers

  • Insoluble Fiber

    • tough, fibrous structures of fruits, vegetables and grains

    • indigestible food components that do not dissolve in water

    • usually passes though the body unchanged

Two Types of Dietary FiberMost high fiber foods are a combination of insoluble and soluble dietary fibers

  • Soluble Fiber

    • indigestible food components that readily dissolve in water

    • gel-like or gummy in nature

    • tend to be broken down by bacteria in the colon

Recommendation for Dietary Fiber

  • World Health Organization

    • More than 25 grams per day

  • Recommended Dietary Allowance (adults)

    • Men: 38 grams per day

    • Women: 25 grams per day

Sources of Insoluble Fiber

  • Cellulose: Whole-wheat flour, bran, vegetables

  • Hemicellulose: Bran, whole grains

  • Lignin: Mature vegetables, wheat, fruits and edible seeds, such as flaxseeds and strawberries

Sources of Soluble Fibers

  • Gums: Oats, legumes, guar, barley

  • Pectin: Apples, citrus fruits, strawberries, carrots

Benefits of Fiber

  • Lowers serum LDL levels

  • Promotes feelings of fullness

  • Slows gastric emptying, long-term glucose control in patients with diabetes mellitus

  • Reduces energy consumption by displacing calorie-dense fats

  • Protects against colon cancer

Nutrition and cancer

Nutritional problems in cancer

  • Cachexia

    • Weakness, loss of appetite, metabolic/hormonal abnormalities, weight loss

  • Change in taste, lack of energy, feeling of fullness, nausea, vomiting

  • Tumors produce substances that cause loss of appetite

Nutritional problems due to cancer treatment

  • Radiation therapy:

    • Causes dry mouth, gum destruction, change in taste, difficulty in swallowing, malabsorption of nutrients, GIT damage

  • Chemotherapy:

    • Severe side effects

  • Surgery:

    • Limited swallowing/digestion of food

    • Limited absorption of nutrients

Nutritional needs of cancer patients

  • The diet must supply all nutrients

  • Energy and protein needs are increased by 20%

  • 3000 to 4000 calories

  • 100 to 200 g of proteins in the diet:

    • To prevent tissue breakdown/weight loss

Dietetic Treatment (Diet Therapy)

  • Treatment or control of diseases by therapeutic diet (modified diet)

  • Purpose:

    • Maintain/improve nutritional status

    • Maintain, increase or decrease body weight

    • Rest certain organs or whole body

    • Adjust the diet so that the body can handle it in a disease

How diet is modified?

  • Basic diet becomes therapeutic when:

    • Calories, fiber, some nutrients, food types are increased or decreased

    • Diet is modified to become soft or liquid

    • Certain foods are eliminated

Some examples of therapeutic diets

  • Consistency

    • Mechanical, tube feeding, high fiber, liquid

  • Carbohydrates

    • Diabetic diet, Low-calorie diet

    • Ketogenic diet

    • Lactose-free diet

Some examples of therapeutic diets

  • Fat

    • Restricted fat diet

    • Low cholesterol diet

  • Proteins

    • Restricted protein diet

    • Gluten-free diet

    • Restricted phenylalanine diet (for PKU)

    • Restricted purine diet (for gout)

    • High protein diet

Diet therapy of diabetes mellitus

  • Calories

    • Calorie intake should be the same for diabetics compared to non-diabetics

    • Adjustment in calories by modifying food contents

  • Proteins

    • 15 to 20% calories from proteins

    • RDA: 1 to 1.5 gm/kg

  • Carbohydrates

    • CHO content is the same as for normal diet

    • More complex CHOs + high fiber

    • Use of nutritive / non-nutritive sweeteners

  • Fats

    • 20 to 30% calories from fat

    • Low fat, lean meats, polyunsaturated fats, low cholesterol

  • Complex CHOs and fiber:

    • Improve glycemic control in diabetics

    • Lower serum cholesterol, triglycerides

    • Promote weight loss

  • 50 g or more fiber

  • Upto 60% complex CHO intake

Diet therapy of renal diseases

  • Calories

    • Protein restricted diet

    • Adequate calories are provided in the diet from other sources (fats, CHO) to avoid protein degradation in muscle

  • Proteins

    • RDA for renal patients: 0.5 to 1.5 gm/kg

    • Normal amount of proteins is provided if kidney function is normal

    • Restricted protein diet for patients with reduced kidney function to avoid retention of protein met. products

    • Protein content is increased to compensate for high albumin loss in urine

  • Electrolytes

    • Restricted sodium (500 mg/day) to avoid edema in hypertensive patients

    • Restricted potassium (1.5 gm/day)

      • Retained in kidney failure patients

  • Fluids

    • Restricted in patients with kidney failure

    • A balance of urinary input and output is maintained

Diet therapy of hyperlipidemia and cardiovascular disease

  • Saturated fat, cholesterol restricted diet

  • More polyunsaturated fats

  • Diet should meet RDA for proteins, CHOs

  • Sodium restricted diet to prevent:

    • Hypertension

    • Congestive heart failure

  • Sodium intake: 250 to 2000 mg/day

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