1. Nutritional Requirements
Gastrointestinal & Nutrition Block (GINT-223)
Department of Biochemistry
College of Medicine
2018/2019

2. Objectives of the lecture:
Understand the basic terms of nutritional requirements.
Interpret the food pyramid that recommends daily serving size from each food group for vegetarians and non-vegetarians.
Identify dietary guidelines and goals that are necessary for good health.
Discuss energy requirement in humans including basic energy expenditure and the factors that affect it.
Understand total parenteral nutrition (TPN) and its applications.

3. Nutrition: Basic Terms
The science of foods and the nutrients, and of their actions within the body (including: ingestion, digestion, absorption, transport, metabolism, and excretion) that are necessary for the functioning of an individual at all stages of life.
Nutrient:
Are the chemical constituents of food necessary to sustain the normal functions of the body include the provision of energy, growth, renewal of tissues, reproduction, lactation, and reduce the risks of some diseases.
Calorie:
Is a measure of energy—technically, the amount of energy needed to raise the temperature of one gram of water one degree Celsius. Food energy is normally measured in kilocalories (1,000 calories =1 kilocalorie), kcal or C.
Calories provided by fats, carbs, proteins, alcohol

4. Optimal Requirements of Nutrients
Individual nutritional requirements are determined by age , gender, environment and genetic and isoenzyme constitution.
Optimal dietary requirements:
Are those dietary intakes of nutrients that are most likely to ensure that the individual will attain optimum potential nutritional status for:
Successful development in utero
Growth
Learning potential
Quality of life
Body function
Successful pregnancies
Adequate milk production for a baby’s needs
Expectation of a long and healthy life
Freedom from infection
Resistance to disease and response to diseases

5. Dietary Reference Intake
Dietary Reference Intakes (DRIs): Estimates of the amounts of nutrients required to prevent deficiencies and maintain optimal health and growth.
The DRIs consist of four dietary reference standards for the intake of nutrients designated for specific life stage (age) groups, physiologic states, and gender.

6. Dietary Reference Intake
1. Estimated Average Requirement (EAR): The average daily nutrient intake level estimated to meet the nutritional requirement of half of the healthy individuals (50%) in an age and gender group. 2. Recommended Dietary Allowance (RDA): The amount of nutrient intake that is sufficient to meet the nutritional requirement and would prevent deficiency disorders of 97% healthy individuals in a group. 3. Adequate Intake (AI): It is used instead of EAR and RDA if a nutrient is considered essential but the experimental data are inadequate for determining EAR and RDA. Al is obtained from the best available information. 4. Tolerable Upper Intake Level (UL): The highest level of daily nutrient intake that has no adverse health effects or toxicity in almost all individuals.

7. Comparison of the components of the Dietary Reference Intakes
Comparison of the components of the Dietary Reference Intakes. EAR = Estimated Average Requirement; RDA = Recommended Dietary Allowance; AI = Adequate Intake; UL = Tolerable Upper Intake Level.

8. Life Time Variation in Nutritional Requirements
Different groups have different nutritional needs are:
Infants
Children (1-3) years
Children (4-10) years
Children (11-18) years
Adults (19-50) years
Pregnant women
Lactating women
Adults (50+) years

9. Energy Requirement In Humans
Energy requirement in healthy individual is the food energy needed to maintain BMI and physical activity.
The Estimated Energy Requirement (EER): is the average dietary energy intake predicted to maintain an energy balance (the calories consumed are equal to the energy expended) in a healthy adult.
Total Energy Expenditure (TEE): is the number of calories the body uses in a 24 hour period.
Body mass index (BMI)

10. Energy Requirement In Humans Cont.
Involuntary total energy expenditure (TEE) includes:
1) Resting metabolism rate (RMR): the energy required to carry out the normal body functions, such as respiration, blood flow, and ion transport (1,800 kcal for men and 1,300 kcal for women).
2) Physical activity: a sedentary person requires 30%–50% above RMR, whereas a highly active individual requires 100% above RMR.
3) Thermic effect of food: is heat produced by the body due to food digestion and absorption, 5-10% of total energy expenditure.

11. Nutritional Requirements for Energy
Basal Energy Expenditure (BEE): energy needed to maintain essential physiological functions including growth, pregnancy, lactation…etc.
The Harris–Benedict equation is used to measure basal energy expenditure (BEE).
For men:
BEE = (13.75 × weight in kg) + (5.003 × height in cm) – (6.775 × age in years)
For women:
BEE = (9.563 × weight in kg) + (1.85 × height in cm) – (4.676× age in years)

12. Dietary Planning and Guidelines
Guidelines set by national and international agencies (WHO, FAO) aiming at defining nutrient recommendation for populations.
These recommendations vary from country to country, but the general theme is as follow:
1. Enjoy your food.
2. Eat a nutritionally adequate diet drawn from a variety of foods.
3. Reduce the consumption of fat, especially saturated fat (total fat should supply 30-35% of daily calories):
8–10% of total calories from saturated fatty acids
up to 10% of total calories from polyunsaturated fatty acids
up 15% of total calories from monounsaturated fatty acids

13. Dietary Planning and Guidelines Cont.
4. Achieve and maintain an appropriate body weight.
5. Increase the consumption of complex carbohydrates and dietary fiber.
6. Reduce the intake of sodium (< 6 g/day).
7. Carbohydrates should provide 55–60% of the daily energy intake, a high proportion of which should be fruit, vegetables and whole-wheat products.

14. Balancing Nutritional Requirements
Food Pyramid:
Illustrates the principles of good nutrition with fruits and vegetables on the bottom representing the bulk of a healthy diet and fats and oils at the top.
An improved Food Pyramid, as suggested by Walter Willet of the Harvard School of Public Health, emphasizes keeping one’s weight under control through daily exercising and avoiding an excessive total intake of kilocalories.
It recommends that the majority of one’s daily diet should be the consumption of the healthy monounsaturated and polyunsaturated fats and healthy carbohydrates, whole grain and unrefined.
A variety of fruits and nonstarchy vegetables with protective phytochemicals should be eaten in abundance. Dairy products should be limited to one or two servings daily. A daily multiple vitamin and mineral supplement should be taken.

16. Meatless Alternatives (Vegetarian)
Vegetarian Lifestyle:
There are different forms of vegetarianism:
Lacto vegetarians and Lacto-ovo vegetarians: consume dairy products or dairy products and eggs but do not consume animal flesh.
Vegan: pure vegetarians, consume no animal products at all.
Vegetarians have a lower incidence of heart diseases.
Cancers linked to red meat and dairy consumptions (Colon and prostate) are less common in vegetarians.
High fiber in a vegetarian diets plays a role in reducing risks of type 2 Diabetes and lowering cholesterol levels.
Vegetarians must ensure that iron, B vitamins (especially B12), Calcium, Vitamin D and essential amino acids are supplied.

17. Total Parenteral Nutrition (TPN)
A type of exogenous nutrition in which terminally-ill patients are provided with all essential nutrients intravenously or through tube feeding.
TPN is particularly indicated in severe inflammatory bowel disease, coma, cachexia, prolonged ileus and extensive burns.
Nutrients are pumped into a large central vein to allow rapid dilution of the solution (3 L / 24 hr).
Tube feeding is only provided to patients whose GI tract is intact and supports this type of nutrition.

18. Total Parenteral Nutrition (TPN)
Standard composition of TPN feed (24 hr requirement):
Energy content: 2000 kcal
Nitrogen: 12–14 g
Fat: 900 kcal
Glucose: 1000 kcal
Electrolytes, trace elements, vitamins: present
Volume: 3 liters
Individual nutritional requirements of patients may vary.
Continuous biochemical, hematological and immunological monitoring of patient on TPN is require.

19. Take home messages:
Understanding the basic terminology of human nutrition is essential for grasping the concept of assessing malnutrition and establishing nutritional requirement in a population.
The primary purpose of setting these standards is to curb nutritional deficiencies in a population and hence the diseases associated with them.
Establishing these requirements considers important factors including energy requirements and expenditure.
There are four standards based on which these requirements are defined: Estimated Average Requirement (EAR), Recommended Daily Allowance (RDA), Adequate Intake (AI) and Tolerable Upper Intake Level (UL).
Once these standards are set, recommendations are disseminated to public in the form of tools such as the food pyramid and dietary guidelines and goals, etc.
The standards also cater to nutritional requirements of patients who are otherwise unable to feed normally.

20. Reference:
Lippincott’s Biochemistry. 5th Edition, pp Lippincott Williams & Wilkins, New York, USA.
Understanding Nutrition. 10th Edition, pp Ellie Whitney & Sharon Rolfes, New York, USA.