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Dietary Reference Values (DRVs), current dietary goals, recommendations, guidelines and the evidence for them

Health and Social Behaviour: Dietary Reference Values (DRVs), current dietary goals, recommendations, guidelines and the evidence for them

Three main types of dietary recommendations may be produced by public health agencies: dietary allowances (DRVs), dietary goals, and dietary guidelines.

Dietary allowances are quantitative guidelines for different population subgroups for the essential macro- and micro-nutrients to prevent nutritional deficiencies.

Dietary goals are quantitative national targets for selected macronutrients and micronutrients aimed at preventing long-term chronic disease e.g. coronary heart disease, stroke and cancer. They are usually aimed at the national population level
rather than the individual level.

Dietary guidelines are broad targets aimed at the individual to promote nutritional well-being. They were initially introduced for macronutrients but are now being used for micronutrients. Dietary guidelines can be expressed as quantitative
targets (e.g. five servings of fruit and vegetables/day) or as qualitative guidelines (e.g. eat more fruit and vegetables).

Dietary Reference Values (DRVs)

  • The human body needs a variety of nutrients and the amount of each nutrient needed is called the nutrient requirement.
  • In the UK, estimated requirements for various groups within the UK population were examined and published by the Committee on Medical Aspects of Food and Nutrition Policy (COMA) in the 1991 report Dietary Reference Values for Food Energy and
    Nutrients for the United Kingdom. COMA has now been replaced by the Scientific Advisory Committee on Nutrition (SACN) who are likely to review the UK nutritional requirements in the near future.
  • DRVs are a series of estimates of the amount of energy and nutrients needed by different groups of healthy people in the UK population; they are not recommendations or goals for individuals.
  • DRVs have been set for following groups:

    Boys and girls aged 0-3 months; 4-6 months; 7-9 months; 10-12 months; 1-3 years; 4-6 years; 7-10 years
    Males aged 11-14 years; 15-18 years; 19-50 years; 50+ years
    Females aged 11-14 years; 15-18 years; 19-50 years; 50+ years; pregnancy and breastfeeding

     

  • In order to take account of the distribution of nutritional requirements within the population, COMA used four Dietary Reference Values (DRVs):
    • Estimated Average Requirements (EARs)
    • Reference Nutrient Intakes (RNIs)
    • Lower Reference Nutrient Intakes (LRNIs)
    • Safe Intake

      Source: Food and Agriculture Organization of the United Nations

      www.fao.org/tc/Tca/pubs/tmap40/40chap2.htm

    • EAR is an estimate of the average requirement of energy or a nutrient needed by a group of people i.e. approximately 50% of people will require less, and 50% will require more.
    • RNI is the amount of a nutrient that is enough to ensure that the needs of nearly all a group (97.5%) are being met i.e. the majority will need less.
    • LRNI is the amount of a nutrient that is enough for only a small number of people in a group who have low requirements (2.5%) i.e. the majority need more.
    • Safe intake is used where there is insufficient evidence to set an EAR, RNI or LRNI. The safe intake is the amount judged to be enough for almost everyone, but below a level that could have undesirable effects.
  • The amount of each nutrient needed differs between individuals and at different life stages. Individual requirements of each nutrient are related to a person’s age, gender, level of physical activity and health status.
  • The changes in estimated nutritional requirements at different life-stages are outlined in table 1 below:

    Table 1: Nutritional Requirements at Different Life-Stages

    Infants

    First 4-6 months of life (period of rapid growth and development) breast milk (or infant formula) contains all the nutrients required.

    Between 6-12 months - requirements for iron, protein, thiamin, niacin, vitamin B6, vitamin B12, magnesium, zinc, sodium and chloride increase.

    Department of Health advice recommends exclusive breastfeeding until 6 months of age with weaning introduced at 6 months.

    1-3 years

    Energy requirements increase (children are active and growing rapidly). Protein requirements increase slightly. Vitamins requirements increase (except vitamin D). Mineral requirements decrease for calcium, phosphorus and iron and
    increase for the remaining minerals (except for Zinc).

    4-6 years

    Requirements for energy, protein, all the vitamins and minerals increase except C and D and iron.

    7-10 years

    Requirements for energy, protein, all vitamins and minerals increase except thiamin, vitamin C and A.

    11-14 years 

    Requirements for energy continue to increase and protein requirements increase by approximately 50%.

    By the age of 11, the vitamin and mineral requirements for boys and girls start to differ.

    Boys: increased requirement for all the vitamins and minerals.

    Girls: no change in the requirement for thiamin, niacin, vitamin B6, but there is an increased requirement for all the minerals. Girls have a much higher iron requirement than boys (once menstruation starts).

    15-18 years 

    Boys: requirements for energy and protein continue to increase as do the requirements for a number of vitamins and minerals (thiamin, riboflavin, niacin, vitamins B6, B12, C and A, magnesium,
    potassium, zinc, copper, selenium and iodine). Calcium requirements remain high as skeletal development is rapid.

    Girls: requirements for energy, protein, thiamin, niacin, vitamins B6, B12 and C, phosphorus, magnesium, potassium, copper, selenium and iodine all increase.

    Boys and girls have the same requirement for vitamin B12, folate, vitamin C, magnesium, sodium, potassium, chloride and copper. Girls have a higher requirement than boys for iron (due to menstrual losses) but a lower requirement
    for zinc and calcium.

    19-50 years

    Requirements for energy, calcium and phosphorus are lower for both men and women than adolescents and a reduced requirement in women for magnesium, and in men for iron. The requirements for protein and most of the vitamins and minerals
    remain virtually unchanged in comparison to adolescents (except for selenium in men which increases slightly).

    Pregnancy

    Increased requirements for some nutrients. Women intending to become pregnant and for the first 12 weeks of pregnancy are advised to take supplements of folic acid. Additional energy and thiamin are required only during the last three
    months of pregnancy. Mineral requirements do not increase.

    Lactation

    Increased requirement for energy, protein, all the vitamins (except B6), calcium, phosphorus, magnesium, zinc, copper and selenium.

    50+ years

    Energy requirements decrease gradually after the age of 50 in women and age 60 in men as people typically become less active and the basal metabolic rate is reduced. Protein requirements decrease for men but continue to increase
    slightly in women. The requirements for vitamins and minerals remain virtually unchanged for both men and women.

    After the menopause, women’s requirement for iron is reduced to the same level as that for men.

    After the age of 65 there is a reduction in energy needs but vitamins and minerals requirements remain unchanged. This means that the nutrient density of the diet is even more important.

     

    DRVs are estimates of energy and nutrient intakes and should therefore be used as guidance but should not be considered as exact recommendations. They show the amount of energy/nutrient that a group of people of a certain age range (and sometimes
    sex) needs for good health and they only apply for healthy people.

Current dietary goals, recommendations, guidelines and the evidence for them

The UK Food Standards Agency issues guidance on dietary recommendations on behalf of the Department of Health for the general public.  The current government recommendations are outlined in table 2 below.

Table 2: Government Dietary Recommendations

Dietary Recommendations
Total Fat Reduce to no more than 35% of food energy (currently at 35.3%)
Saturated Fat Reduce to no more than 11% of food energy (currently at 13.3%)
Total Carbohydrate Increase to more than 50% of food energy (currently at 48.1%)
Sugars (added) No more than 11% of food energy (currently at 12.7%)
Dietary Fibre (NSP) Increase the average intake of dietary fibre to 18g per day (currently 13.8g per day). Children’s intakes should be less
Fruit & Vegetables Increase to at least 5 portions (400g) of a variety of fruit and vegetables per day (currently 2.8 portions per day)
Alcohol Should not provide more than 5% of energy in the diet.

Women – should not regularly drink more than 2-3 units of alcohol/day

Men – should not regularly drink more than 3-4 units of alcohol/day

Salt Adults – no more than 6g salt a day (2.4g sodium)

1 to 3 years - 2 g salt a day (0.8g sodium)

4 to 6 years - 3g salt a day (1.2g sodium)

7 to 10 years - 5g salt a day (2g sodium)

11 and over - 6g salt a day (2.4g sodium)

The evidence for nutritional recommendations comes from a range of sources but particular emphasis is placed on COMA reports:

  • 1991, COMA report on energy and nutrients provided evidence for the dietary recommendations for total fat, saturated fat, total carbohydrate, sugars, and dietary fibre.
  • 1994, COMA recommended reducing the average salt intake of the population to 6g a day based on evidence of a link between high salt intake and high blood pressure. In 2003, the SACN reviewed the evidence (e.g. Intersalt study and Dietary
    Approaches to Stop Hypertension (DASH) sodium trial) since 1994 and concluded the strength for the association between high salt intake and hypertension had increased. High blood pressure increases the risk of stroke and cardiovascular disease.
    SACN confirmed that reducing salt intake to 6g per day would benefit the whole population.

Evidence for increasing the consumption of fruit and vegetables to 5 a day is provided by a number of sources.  The Department of Health estimated that eating at least 5 portions of a variety of fruit and vegetables can reduce the risk of
deaths from chronic diseases (heart disease, stroke and cancer) by up to 20%, delay the development of cataracts, reduce the symptoms of asthma, improve bowel function and help to manage diabetes.

References

  • British Nutrition Foundation http://www.nutrition.org.uk [accessed 01.08.08]
  • Department of Health. ‘Dietary Reference Values for Food and Energy and Nutrients for the United Kingdom.’ 1991. Report of the Panel on Dietary Reference Values of the Committee on Medical Aspects of Food Policy.
  • Department of Health http://www.dh.gov.uk/en/Publichealth [accessed 01.08.08]
  • Food Standards Agency http://www.food.gov.uk [accessed 01.08.08]
  • Gibney M., Margetts B., Kearney J., Arab L. Public Health Nutrition. The Nutrition Society. Blackwell Publishing.
  • Lewis, G. Sheringham, J. Kalim, K. Crayford, T. Mastering Public Health: A postgraduate guide to examinations and revalidation. The Royal Society of Medicine Press Limited.

© Hannah Pheasant 2008