Topic 1 week 3 - The elusive healthy diet Flashcards
Across the world what does the type of food people eat depend on?
Across the world, the foods people choose to eat not only depend on availability and affordability, but also on cultural and societal norms
How does the range and quality of food vary from low income and high income countries?
In many low-income countries, the range and quality of foods available to most of the population are inadequate, leading many to malnutrition and even starvation. In high-income countries, there is a huge diversity of foods available and the relative affordability of different foods drives nutritional behaviours that have different but significant impacts on long-term health. Furthermore, countries in transition from low income to middle income face both problems at the same time from different sectors of their society.
To stay healthy, the body needs a diet that provides the right balance of six categories of nutrients.
List the six categories of nutrients required in the diet.
The six nutrient categories are:
proteins fats carbohydrates (e.g. sugars, and starch in foods like flour and potatoes) vitamins minerals (e.g. iron and calcium) water.
What is a macronutrient and what do they consist of?
Dietary carbohydrates, fats and proteins are collectively termed macronutrients because the body requires them in relatively large amounts.
What in the diet provides the building blocks needed to construct cells?
Proteins also provide energy, but more importantly they are required to provide the building blocks needed to construct the cells that form most of the body’s structures.
What provides the body with the majority of energy?
Dietary carbohydrates and fats typically provide the body with most of its energy.
What are vitamins and minerals essential for in the body?
Vitamins and minerals are essential for regulating chemical reactions and some of them are required for building and maintaining structures in the body. Minerals like calcium are incorporated into the teeth and bones to make them dense and hard.
You met vitamin A in Week 2 of this topic. What body systems is this vitamin essential for?
Vitamin A is essential for the immune system which is responsible for fighting infectious disease and also for maintaining the health of the retina in the eye.
What are micronutrients and what do they consist of?
Dietary vitamins and minerals are collectively referred to as micronutrients because they are required by the body in very small amounts. But even these very small daily amounts can be very hard to come by for many people. You have seen evidence of the effect of vitamin A deficiency in South-East Asia and Africa; it is the leading world cause of preventable blindness in children. Deficiencies in the minerals iron and iodine can be as debilitating and cause, respectively, anaemia (a deficiency of red blood cells) and poor mental development.
How can macronutrients affect health?
On the other end of the scale, macronutrients are required in significant quantities in our daily diets and insufficient supplies can have just as catastrophic effects on human health, leading to stunting (insufficient growth in children) and wasting (severe loss of muscles and tissues leading to very low body weight). However, in terms of our macronutrient nutritional status there is an additional issue. It is not just the case that insufficient macronutrients cause ill health: an excess of these nutrients can also be damaging. Diets that contain more macronutrients than the body needs, or inappropriate proportions of the various macronutrients, are also at risk of causing poor health, and it seems that diets commonly consumed by people in middle- and high-income countries fall squarely into this category.
What is the eatwell plate and what does it represent?
The ‘eatwell plate’ represents a pie chart, where each ‘slice’ of the pie indicates the proportion of total food intake that should consist of a particular class of food. It visually summarises several current recommendations for a healthy diet, including:
plenty of starchy foods such as rice, bread, pasta and potatoes (choosing wholegrain varieties when possible)
plenty of fruit and vegetables; at least five portions of a variety of fruit and vegetables a day
some protein-rich foods such as meat, fish, eggs, beans and non-dairy sources of protein, such as nuts and pulses
some milk and dairy produce, choosing reduced-fat versions or eating smaller amounts of full-fat versions or eating them less often
just a little saturated fat, salt and sugar.
What are the Dietary Reference Values (DRVs) for selected nutrients (per day) for adults (age 19–50) in the UK. (Department of Health, 1991)? protein fibre salt iron zinc vitamin A folate vitamin C
Nutrient Dietary reference value (DRV) protein 53 g fibre 18 g salt 6 g iron 9 mg zinc 9.5 mg vitamin A 0.7 mg folate 0.2 mg vitamin C 40 mg
What is the percentage of Food energy (as a percentage of total food energy) for adults (age 19–50) in the UK. (Department of Health, 1991)?
Energy source Percentage of total food energy*
Total fats not more than 35%
of which saturated fats not more than 11%
Total carbohydrate 50%
of which intrinsic sugars, milk sugars and starch 39%
of which non-milk extrinsic sugars not more than 11%
Average total food energy for women is 8400 kJ per day (2000 kcal per day), and for men, 10 500 kJ per day (2500 kcal per day).
** Intrinsic sugars are those present naturally within the structure of food such as fruits and vegetables. Extrinsic sugars are generally those that are added to food.
What is coronary heart disease?
Coronary heart disease (CHD) is a disease in which a substance called plaque builds up inside the coronary arteries leading to a condition called atherosclerosis . These arteries supply oxygen-rich blood to the heart muscle. Over time, plaque can harden or rupture (break open). Hardened plaque narrows the coronary arteries and reduces the flow of oxygen-rich blood to the heart leading to heart attack.
Which nutrient is said to be responsible for coronary heart disease?
The low-fat era began in the 1940s with a range of studies suggesting that low-fat diets were healthier. One very famous protagonist, Ancel Keys (Figure 1.2), a physiologist at the University of Minnesota, concluded there was a correlation between the amount of fat consumed and the incidence of coronary heart disease (CHD). Keys postulated that CHD was less common amongst populations where people traditionally ate a diet lower in fat. Keys was convincing enough to persuade the American Heart Association to publish guidelines in 1961 calling for Americans to cut back on saturated fat as the best way to reduce their risk of CHD.
What are fats? are they insoluble to water and what are they referred to as?
Fats are a group of chemicals that are insoluble in water and are also referred to as lipids. The term lipids also includes oils.
What is an important distinction between fats and oils?
The main difference between fats and oils relates to their state at room temperature; oils are liquid while fats are solid, but this is a very loose and unscientific definition that doesn’t tell us much about their individual properties. It is, however, an important distinction for the food industry, since liquid oils and solid fats have different functions in the manufacture and processing of foods
What function do lipids have within the body?
All diets must include some lipid and these important molecules have a range of functions in the body. Lipids:
provide energy, with 1 g of fat releasing 37 kJ of energy when oxidised within cells
are stored in adipose tissue for times of energy need
transport and store fat-soluble vitamins
provide a source of precursors (starting materials) for a number of cellular structures most notably cell membranes.
What is the most important steroid in the body?`
The term lipid also applies to a subclass of molecules known as steroids. The most common steroid in the human body is cholesterol; this molecule is an important component of cell membranes and is used to synthesise some hormones.
What is a glycerol?
An alcohol which condenses with three fatty acid molecules to give a triacylglycerol.
What is a fatty acid?
An organic molecule consisting of two distinct parts: a long hydrocarbon chain and a carboxylic acid group.
What molecules does fat contain?
Fats contain the elements carbon (C), hydrogen (H) and oxygen (O). Each molecule of fat is a combination of one molecule of glycerol and three molecules of substances called fatty acids.
What is the chemical composition of glycerol? what can glycerol also be termed as?
Glycerol is a liquid and is also known as glycerine. A molecule of glycerol has three carbon atoms attached together in a row, an OH group (one oxygen atom with one hydrogen atom) attached to each carbon atom, and the rest of the bonds of the carbon atoms are taken up with single hydrogen atoms.
What is the name of the COOH group?
COOH is the carboxylic acid group.
How many CH2 groups does the palmitic acid molecule have in its long tail?
There are 14 of them.
What information does the word ‘triacylglycerol’ convey to you about the chemical make-up of a fat molecule?
You should recognise ‘tri-’ as meaning that the molecule contains three of something – in this case, three fatty acids; that’s the ‘-acyl-’ part, which is similar to the word acid. Then ‘glycerol’ is the name of the component that makes up the rest of the molecule.
Do all fatty acids have a similar structure? what are fatty acids also called?
There are many different types of fatty acids, but they all have a similar basic structure, with the long tail of carbon atoms, and a COOH group at one end. Fats are often called triacylglycerols (pronounced ‘try-ay-sile-gliss-er-rols’), sometimes abbreviated to TAGs. You may also see them referred to by the older term triglycerides (pronounced ‘try- gliss-er-ides’).
what is the chemical reaction called that links fatty acid a glycerol together?
In order to make a molecule of fat it is necessary to link the three fatty acids and the glycerol together.
A type of chemical reaction called condensation is needed to link each fatty acid to glycerol via an ester bond. Figure 2.3a shows the reaction whereby one molecule of water is synthesised for every ester bond that forms. Three fatty acids need to be added to make a complete triacylglycerol molecule
How many water molecules are produced when a complete triacylglycerol (fat) molecule is made?
Since each time a fatty acid is linked to glycerol, one water molecule is produced, a total of three water molecules are produced when a complete triacylglycerol molecule is synthesised from glycerol and three fatty acids.
What two groups can fatty acids be classified according to their certain characteristics?
Fatty acids are classified according to certain specific characteristics, including:
the number of carbon atoms in their tails,
whether they are saturated or unsaturated.
How many carbon atoms are there in short chain, medium chain and long chain fatty acids?
Fatty acids with six or fewer carbon atoms are classed as ‘short-chain’ fatty acids; those with between eight and 12 carbon atoms are ‘medium-chain’ fatty acids. From 14 carbon atoms onwards, the fatty acids are called ‘long-chain’ and about 95% of the fats we eat contain long-chain fatty acids.
What does the term saturated mean with reference to organic compounds?
Saturated organic compounds contain no carbon-to-carbon double bonds (C=C).
Where is palmatic acid found?
Palmitic acid, shown in Figure 2.3a and b and reproduced below, is found in the seeds of the oil palm and coconut palm and is the most common fatty acid found in living organisms. It is a saturated fat as it does not contain any carbon-to-carbon double bonds.
What is this the structural formula of?
CH3–CH2–CH2–CH2–CH2–CH2–CH2–CH2–CH2–CH2–CH2–CH2–CH2–CH2–CH2–COOH
This is the full structural formula of palmitic acid but it can be abbreviated to this representation, which omits the carbon atoms and their associated hydrogen atoms along the carbon chain
