This document provides an overview of human nutrition. It discusses the biological values of proteins and how they are measured. It also summarizes the key aspects of carbohydrates, lipids, and proteins as nutrients - including their dietary sources, essential uses in the body, and dietary requirements. Pathways of lipid metabolism and hormonal controls of protein synthesis are also briefly covered. The document serves to introduce the topic of human nutrition and its various biochemical components.

1. Presented by :
Arvind Singh Heer
(M.Sc -Analytical Chemistry)
HUMAN NUTRITION

2. CONTENT
 Introduction
 Biological values of human nutrition
 Estimation of enzymes
 Carbohydrates
 Lipids
 Proteins

3. INTRODUCTION
What is Human Nutrition?
 Human nutrition refers to the provision of
essential nutrients necessary to
support humanlife and health. Generally, people
can survive up to 40 days without food, a period
largely depending on the amount of water
consumed, stored body fat, muscle mass and
genetic factors.

4. BIOLOGICAL VALUES
 Biological value (BV) is a measure of the
proportion of absorbed protein from a food which
becomes incorporated into the proteins of the
organism's body. It captures how readily the
digested protein can be used in protein
synthesis in the cells of the organism. Proteins
are the major source of nitrogen in food. BV
assumes protein is the only source of nitrogen
and measures the proportion of this nitrogen
absorbed by the body which is then excreted. The
remainder must have been incorporated into the
proteins of the organisms body. A ratio of nitrogen
incorporated into the body over nitrogen
absorbed gives a measure of protein 'usability' -
the BV.

5. ESTIMATION OF ENZYMES
 Enzyme assays are laboratory methods for
measuring enzymatic activity. They are vital for
the study of enzyme kinetics and enzyme
inhibition.

6. CARBOHYDRATES
 Carbohydrates are one of the main types of nutrients.
They are the most important source of energy for your
body. Your digestive system changes carbohydrates into
glucose (blood sugar). Your body uses this sugar for
energy for your cells, tissues and organs.
 Energy Metabolism
 Glucose is the fuel used by cells to make ATP
 Neurons and RBCs rely almost entirely upon glucose
 Excess glucose is converted to glycogen or fat and stored
 Dietary sources
 Starch (complex carbohydrates) in grains and vegetables
 Sugars in fruits, sugarcane, sugar beets, honey and milk
 Insoluble fiber: cellulose in vegetables; provides roughage
 Soluble fiber: pectin in apples and citrus fruits; reduces
blood cholesterol levels

7.  Dietary requirements
 Minimum 100 g/day to maintain adequate blood
glucose levels
 Recommended minimum 130 g/day
 Recommended intake: 45–65% of total calorie
intake; mostly complex carbohydrates
 Dietary Fiber
 water-insoluble fiber adds bulk to fecal matter
facilitating its passage through and elimination from
the digestive system
 water-soluble fiber may absorb dietary cholesterol,
reducing its absorption by the digestion tract

8. LIPIDS
Lipids are a group of naturally occurring molecules that
include fats, waxes, sterols, fat-soluble vitamins (such as
vitamins A, D, E, and K), monoglycerides, diglycerides,
triglycerides, phospholipids, and others.
Dietary sources
 Triglycerides
 Saturated fats in meat, dairy foods, and tropical oils
 Unsaturated fats in seeds, nuts, olive oil, and most
vegetable oils
 Cholesterol in egg yolk, meats, organ meats, shellfish,
and milk products

9. Essential uses of lipids in the body
 Help absorb fat-soluble vitamins
 Major fuel of hepatocytes and skeletal muscle
 Phospholipids are essential in myelin sheaths and
all cell membranes
Functions of fatty deposits (adipose tissue)
 Protective cushions around body organs
 Insulating layer beneath the skin
 Concentrated source of energy

10.  Essential fatty acids
 Linoleic and linolenic acid, found in most vegetable oils
 Must be ingested
 Regulatory functions of prostaglandins
 Smooth muscle contraction
 Control of blood pressure
 Inflammation
 Functions of cholesterol
 Stabilizes membranes
 Precursor of bile salts and steroid hormones
Dietary requirements suggested by the American Heart
Association
 Fats should represent 30% or less of total caloric intake
 Saturated fats should be limited to 10% or less of total fat
intake
 Daily cholesterol intake should be no more than 300 mg

11. Pathways of Lipid Metabolism

12. Proteins
• Any of a class of nitrogenous organic compounds
which have large molecules composed of one or
more long chains of amino acids and are an
essential part of all living organisms, especially as
structural components of body tissues such as
muscle, hair, etc., and as enzymes and antibodies.
• Enzymes
• Structural proteins (shape and form of cells and
tissues)
• Hormones
• Immunoglobulins (antibodies)

13. EssentialAmino Acids
• Tryptophan
• Methionine
• Valine
• Threonine
• Histidine(infants)
• Phenylalanine
• Leucine
• Isoleucine
• Lysine
• Arginine

14. Dietary sources
 Eggs, milk, fish, and most meats contain complete
proteins
 Legumes, nuts, and cereals contain incomplete proteins
(lack some essential amino acids)
 Legumes and cereals together contain all essential
amino acids
Uses:
 Structural materials: keratin, collagen, elastin,
muscle proteins
 Most functional molecules: enzymes, some
hormones

15. Use of amino acids in the body
1. All-or-none rule
 All amino acids needed must be present for
protein synthesis to occur
2. Adequacy of caloric intake
 Protein will be used as fuel if there is
insufficient carbohydrate or fat available
Nitrogen balance
 State where the rate of protein synthesis
equals the rate of breakdown and loss
 Positive if synthesis exceeds breakdown
(normal in children and tissue repair)
 Negative if breakdown exceeds synthesis (e.g.,
stress, burns, infection, or injury)

16. Hormonal controls
 Anabolic hormones (GH, sex hormones)
accelerate protein synthesis

17. REFERENCE
General, Organic and Biological
Chemistry
H. Stephen Stoker
-
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