WORK SESSION 2: Diets

AIMS

This session aims to raise awareness of the importance of diet in good health, and to consider some of the issues surrounding the assessment of dietary intake, through analysis of your own diet, and comparison to nutritional guidelines.

OBJECTIVES

By the end of this Work Session you will:

• Be able to record and analyse dietary intake and energy expenditure
• Be able to assess the nutritional quality of a diet
• Be able to calculate a Body Mass Index (BMI)
• Be aware of the dietary guidance offered by the Department of Health
• Have an awareness of the biochemistry of micro-nutrient dietary components

PREPARATION FOR THIS SESSION

Before this Practical you should:

1. Record and analyse your own diet over a 24 hour period.
2. Keep an activity diary for the same period, and calculate your energy expenditure.
3. Ensure that you know your own height (in metres) and weight (in kilograms).

1.You need to record as accurately as possible everything you eat or drink during your chosen 24 hour period. Try to choose a day (Saturday or Sunday may be best) when you have time to do this properly. Keep a diary of food and drink consumed, and note down the nutritional data from all the packaging of the food you eat. Remember to include "hidden" foods, e.g. milk in coffee, Be careful - constituents are usually given both per serving and per 100g. If you cook for yourself, or have meals in Hall, you will need to estimate the weight of food consumed, and look up the nutritional content using Food Tables. These are available on counter collection in the library, (McCance & Widdowson's The Composition of Foods). For comparison purposes, it is necessary that everyone uses the same sources of information, so for this exercise, use only the resources shown above.

When you have recorded your complete intake for the day, you need to calculate the fat, protein, carbohydrate (CHO) and energy content of your diet. This is most easily performed using an Excel spreadsheet. The final record should show food and drink consumed in menu form, analysed under the following headings:

2.On the same day, record your physical activity, noting what you did, and the approximate length of time for each activity. Then use the following tables to calculate your energy expenditure for 24 hours.

	kcal/hr	kJ/hr
Resting (sleeping, studying, watching TV)	70	294
Light exercise (walking, shopping)	150	630
Moderate exercise (swimming, cycling)	300	1260
Strenuous exercise ( sports, e.g. squash, football)	500	2100

Bring both your diet analysis spreadsheet and energy diary to the work session. During the work session use the data you have collected to answer the following questions. Discuss your results in groups, and compare your diet with that of others.

What we eat, and the effects of our diet on our overall health, are major socio-medical issues. We are constantly bombarded with advice on what we should or should not eat, and the success of the many books on "diet" demonstrate the interest and concern generated. Obesity is an increasing problem in the UK; a recent article in the British Medical Journal reported that nearly 10% of boys, and 15% of girls aged 4-11 are classified as overweight. There are also groups who will suffer as a result of under-nutrition, with respect to particular components of the diet. For example, anaemia resulting from iron deficiency is a common complaint amongst pre-menopausal women. Health professionals have a substantial role in advising their patients on their diet, both to help patients maintain good health, to prevent development of diseases such as hypertension, non insulin-dependent diabetes and coronary heart disease and to help those with clinical conditions who require dietary control.

Nutrition is the study of the qualitative and quantitative requirements of the diet necessary to maintain good health. While there is great variation in what people eat, and hence no "ideal diet", governments in most countries, including the UK, provide dietary guidelines, based on scientific research and epidemiological studies. The Food Standards Agency uses a "Food Plate Guide" which divides foods into five groups:

• Fruit and vegetables
• Bread, cereal and potatoes
• Meat, fish and alternatives
• Milk and dairy foods
• Fatty and sugary food

The proportion of the plate covered by each food group is intended to provide guidance as to the relative proportions of each type of food group in a balanced diet. Additional guidelines are also offered; for example, it is recommended that everyone should eat:

• 5 portions of fruit and vegetables each day
• at least two portions of fish (including one portion of oily fish, e.g. salmon, trout)
• no more than 6 g of salt/day (2.3 g sodium)

Daily intake of alcohol should not exceed 3-4 units for men and 2-3 units for women.

Note that this approach avoids any "calorie counting" and is based purely on the portions of food eaten.

It is possible to assess food intake in a more detailed manner using food tables that allow a quantitative analysis of both macro- and micro- nutrients. This is of particular value in assessing vitamin and mineral intake, or where particular clinical conditions require nutritional intervention.

The following table, adapted from the DEFRA(Manual Of Nutrition, 10^th ed.) shows reference values (RNI, Reference Nutrient Intake) which have been calculated to supply almost every individual with sufficient nutrient for their needs.

* Note, however, that absorption of dietary iron from vegetable foods is lower than from animal sources. When a vegetarian diet is consumed, the iron requirement is significantly increased.

1. Compare your energy intake with the RNI values given on the previous page . Was your energy intake similar to the RNI for your gender and age? Why might these values be different from yours?
2. Compare your energy intake with your energy expenditure. Are you approximately in energy balance? Why is it important that these values should balance?
3. Calculate your Body Mass Index (BMI), using the formula:

BMI = weight/ height² (where height is measured in metres and weight in kg).

Using the table below, comment on whether your BMI falls within the "desirable" range.

BMI
<20	Underweight
20-24	Desirable
25-30	Overweight
> 30	Obese

4. What are the maximum and minimum weight limits for an individual of your height to fall into the desirable range for BMI?
5. Look at the Health Education "Food Plate Guide". Think about your diet in terms of portions (not calories). To what extent does your diet meet these guidelines (i.e. approximately 35% of your food from cereal/bread/potatoes, 35% from fruit and vegetables, 12% each from meat and dairy products and 6% from sugary/fatty foods)?
6. Using the following conversion factors, calculate the proportion of your energy intake derived from:

1. protein
2. carbohydrate
3. total fat
4. alcohol

1g CHO yields 4.1 kcal (17 kJ)1g fat yields 9.2 kcal (39 kJ)

1g protein yields 4.1 kcal (17 kJ)1 unit of alcohol (8g) yields 56 kcal ( 232kJ)

7.Compare your values, and those of the rest of your group with the values in the table below, which shows the percentage of energy derived from different metabolic fuels for the average British diet, compared with the national dietary guidelines.

How many of you have diets which approximate to the national average or guidelines?

8.What proportion of your energy intake was provided by saturated fat? How does this compare with recommended value of < 10%?

9.How far did your diet supply your body's daily requirements for: (See Table on p 3)

1. protein
2. ascorbic acid (vitamin C)
3. iron

10. How much sodium (salt) did you consume? How does this compare with current government advice? Why is it considered important to control salt intake?

11. How many portions of fruit and vegetables did you eat (one portion = 80 g, i.e. one piece of fruit, 3 tabblesspoons of vegetables)?

13. What might you add you your diet to include:
(a) more iron
(b) more calcium
(c) more folic acid

14.How much fluid did you take in during the 24 hour period? What did it consist of?

15. It is recommended that everyone drinks at least 1 litre of fluid per day excluding alcohol. How does your fluid intake compare with the recommendations? Why is alcohol excluded from the total?

16. How easy did you find it to record your diet over a 24 hour period? How accurate do you believe your record is? What were the main problems you encountered?

17. How useful might such a record be for a GP who was asked to give advice on a patient's diet?

(You might consider how typical of your overall diet your 24 hour sample was. Is your record complete....and entirely truthful?! Is it important for an advisor to know what the individual normally eats?)

THIS MAY BE COMPLETED AFTER THE CLASS

18.Complete the following table relating to the biochemical and clinical importance of vitamins and minerals. Kumar and Clark provides a suitable level of detail.

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