Option A: Nutrition and Health Flashcards
Define nutrient.
A nutrient is a chemical substance found in foods that is used in the human body.
What are essential nutrients?
Essential nutrients are those that cannot be synthesised by the body.
Carbohydrates are not considered essential nutrients because in certain human diets, energy is obtained from other sources.
What are some examples of essential nutrients?
Amino Acids Fatty Acids Minerals Vitamins Water
How does the body get non-essential nutrients.
Non-essential nutrients can be synthesised in the body from other nutrients.
Outline the cause of protein deficiency malnutrition.
Proteins in the diet supply the amino acids required to to build our own proteins. There are 20 amino acids to build proteins: 8 of these are essential in adults and an additional 2 are essential in children. All the others are non-essential.
Lack of the essential amino acids leads to a deficiency of plasma proteins which leads to a water imbalance between the blood and the tissue fluid causing fluid to be retained in the tissue.
Outline the consequences of protein deficiancy malnutrition.
lack of blood plasma proteins;
leading to tissue fluid retention/swollen abdomen;
lethargic/little interest in surroundings;
thin muscles/flaky appearance of skin/sparse hair with lack of pigmentation;
physical and mental development retarded;
What are the causes of phenylketonuria (PKU)?
Phenylalanine is an essential amino acid and Tyrosine is a non-essential amino acid. Phenylalanine is normally converted to tyrosine by an enzyme but a mutation for this enzyme means Phenhylalanine is instead converted into phenylpyruvic acid, resulting in a high level of ketones in the blood and urine.
What are the consequences of Phenylketonuria?
High levels of ketones in the blood may result in brain damage and mental retardation. This is especially during pregnancy, when the excess phenlalanine in the fetal blood diffuses across the placenta from the fetus and is removed by the mother. After birth, accumulation of phenylalanine in the baby’s blood causes severe mental retardation.
How can the consequences of Phenylketonuria be reduced?
Diagnosis can be made by a simple blood test that tests for high levels of phenylalanine. As PKU results in the build up of phenylalanine in the bloodstream, it is treated by following a special diet that is low in protein.
a. PKU caused by deficiency/ lack of enzyme (tyrosine hydroxylase);
b. phenylalanine cannot be converted/metabolized (to tyrosine) so builds up in
blood and tissues/remains high;
c. so extra sources of phenylalanine in the diet must be controlled/reduced;
d. diet should include fruit/grain/vegetables/special formula milk;
e. diet must be undertaken very early in life;
f. to reduce brain damage/mental retardation;
g. symptoms occur from three/four months;
What is the difference in the molecular structure of saturated fatty acids and unsaturated fatty acids?
Saturated fatty acids have no double bonds between carbon atoms. Unsaturated fatty acids have one or more double bonds between carbon atoms.
What is the difference in molecular structure between mono-unsaturated fatty acids and polyunsaturated fatty acids?
Mono-unsaturated fatty acids only have one double bond between two carbon atoms.
Polyunsaturated fatty acids have two or more double bonds between carbon atoms.
What is the difference in molecular structure between cis and trans unsaturated fatty acids?
Cis unsaturated fatty acids have hydrogen atoms attached to the double-bonded carbon atoms on the same side.
Trans unsaturated fatty acids have hydrogen bonds attached to the double-bonded carbon atoms on different sides of the bond.
What are the sources consequences of diets rich in saturated fatty acids?
Sources: meat and whole-milk dairy products, coconut and palm oil and cocoa butter.
Consequence: raises levels of Low -density lipoproteins (LDL) cholesterol. This can lead to atherosclerosis and coronary heart disease.
What are the sources and consequences of diets rich in trans unsaturated fatty acids?
Sources: Margarine, peanut butter, dairy products, beef, lamb, fried food etc.
Consequences: significantly increases LDL and decreases HDL. Strong links to atherosclerosis and coronary heart disease.
What are the sources and consequences of diets rich in cis unsaturated fatty acids?
Sources: Vegetabke oils, fish oils
Consequences: promotes beneficial HDL cholesterol, inhibits harmful LDL cholesterol and contains omega-3 which is linked to brain development.
What are the sources and consequences of diets rich in mono-unsaturated fatty acids?
Sources: canola, olive and peanut oils, avocados
Consequences: Decreases LDL and therefore decreases risk of coronary heart disease.
What are the sources and consequences of diets rich in polyunsaturated fatty acids?
Sources: sesame, sunflower, corn, walnut and soybean oils.
Consequences: Decreases LDL and therefore decreases risk of coronary heart disease.
What are the key facts about cholesterol?
Cholesterol is a type of lipid and is in the blood in two forms (HDL and LDL - high-density and low-density lipoprotein) LDL contains mostly lipid in the form of cholesterol and HDL contains mostly protein and removes cholesterol from the body by transporting it to the liver. A high LDL:HDL ratio increases the risk of coronary heart disease.
Distinguish between minerals and vitamins in terms of their chemical nature.
Minerals are usually inorganic elements in their ionic form. Examples: Sodium (Na+), Potassium (K+), Calcium (Ca 2+), Iodide (I–)
Vitamins are organic compounds made by plants and animals. Some, e.g. vitamin D, can be synthesised by the body but most cannot and required in the diet. (e.g vitamins A, B, C, D, E)
What is RDI?
RDI is the recommended daily intake of Vitamin C
Outline a process for determining the RDI using Guinea Pigs.
Guinea pigs are unable to synthesise vitamin C. Guinea pigs were given a diet of grain, which does not contain vitamin C, and they quickly showed symptoms of scurvy. Further groups were given the same diet of grain but supplemented by different amounts of lemon juice or cabbage, both of which contain vitamin C.
Blood plasma and urine were analysed for vitamin C content and skin and bone samples were tested for strength (as vitamin C is required for collagen synthesis and collagen is a protein used to strengthen tissues such as skin and bone). The results were used to find the RDI for a guinea pig and by scaling up, the RDI for a human could be estimated.
Outline a process for determining the RDI using humans.
Using guinea pigs as a model for humans is not fully satisfactory as guinea pigs may absorb more or less from the gut and scaling up may not be proportionately correct.
20 human volunteers were used in trials. Throughout the initial period of 6 weeks, and the following trial period of 8 moths, all the volunteers were given a diet lacking in vitamin C but with daily supplements. During the initial 6 months, all volunteers were given 70mg of vitamin C daily. In the 8 month trial period, they were divided into three groups. The first group were given no vitamin C supplement and developed signs of scurvy within 6-8 months and wound healing was slow. The other two groups were given 10mg and 70mg respectively and neither group showed symptoms of scurvy and their healing was normal. This would indicate that 10mg a day is sufficient to prevent scurvy. The RDI from this work was set at 30mg a day to allow for differences in body mass and efficiency of absorption.
Discuss the amount of vitamin C that an adult should consume per day.
RDI varies from country to country and will also vary between individuals according to age and gender. Investigations indicated 10mg a day was sufficient and there was no further benefit from taking up to 70mg a day. An unsupported claim was made by a famous scientist (Linus Pauling) that 1000mg per day gave protection against upper respiratory tract infections. However, excessive dietary vitamin C is excreted and excessively high levels of dietary intake, such as 1000mg a day, leads to mechanisms developing to excrete this excess. if the person returns to a normal RDI, these mechanisms continue to excrete high levels. This leads to a deficiency of vitamin C in the body resulting in the development of scurvy. This is called rebound malnutrition.
