Transcript Nutrition 142.ppt
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) 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) food of heat energy released by combustion (burning) of that
One calorie is the heat required to raise the temperature of 1 gm. of water by 1 o C 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
Sex
Men Women Pregnant Lactating
Age
23–50 23–50 -
Weight (Kg)
70 55 -
Avg. Energy Needs (kcal)
2900 2200 +300 +500
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: A vegetarian 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 dairy : A strict vegetarian who does not eat animal products, meat, fish, poultry, eggs or
Vegetarian and nutrient intake
Lower intake of iron Lower intake of calcium and vitamin D May develop megaloblastic anemia because of vitamin B 12 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 Pyramid
United States Department of Agriculture Center 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
Overnutrition
Major cause of many diseases: obesity, diabetes, hypertension, etc.
High morbidity (disease) and mortality
Nutritional Screening/Assessment
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 PVT TIM HALL P henylalanine V aline T ryptophan I T M hreonine soleucine ethionine H A L istidine* rginine* ysine L eucine *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) – Diarrhea – Weak immune system – Dry, weak hair – Dermatitis – 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
Carbohydrates
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
Carbohydrates in Food
Simple Carbohydrates
Added – table sugar (sucrose) – – honey, high fructose corn syrup, fruit juice concentrate, etc.
Naturally occurring – fruit (fructose) milk (lactose)
Complex Carbohydrates
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
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
Carbohydrates
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 Fat
From 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
Recommendations for Omega-3 Fatty Acid Intake American Heart Association Guidelines Population
Patients without coronary heart disease (CHD) Patients with CHD Patients who need to lower triglycerides (fats)
Recommendation
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
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 Fiber Most 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 Fiber Most 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: fruits, strawberries, carrots Apples, citrus
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