1. Dietary Reference Intakes (DRIs)

Dietary Reference Intakes are a set of recommended scientific reference values for nutrient intake to promote health and avoid either deficiency or excess. DRIs include four main types of reference values:

Estimated Average Requirements (EARs)

These are values that represent the average daily intake level of a nutrient estimated to meet the requirements of half (50%) of healthy individuals in a particular age and gender group. They are mainly used to assess the nutrient intakes of groups of people and to plan nutritionally adequate meals for them.

Recommended Dietary Allowance (RDA)

This is an average daily dietary intake level sufficient to meet the nutrient requirements of nearly all (97–98%) of healthy individuals in a group. It provides recommendations on the average daily intake of essential nutrients necessary to maintain good health and prevent nutritional deficiencies. The RDAs are developed from an Estimated Average Requirement (EAR). If sufficient scientific evidence is not available to establish EARs, an Adequate Intake (AI) is usually developed.

Adequate Intakes (AIs)

These are values that represent an estimate of nutrients intake that is assumed to be adequate for maintaining health in the absence of specific RDA values. They are used when there is insufficient scientific evidence to establish RDA.

Upper Tolerable Nutrient Intake Levels (ULs)

These are values that represent the maximum daily intake of a nutrient that is likely to pose no risk of adverse health effects to almost all individuals in the general population. Exceeding ULs on a regular basis may increase health risks such as hypervitaminosis (excess vitamins).

2. Nutrient Reference Values (NRVs)

Nutrient Reference Values are values commonly used and found in pre-packaged food labelling to help consumers make choices that contribute to an overall healthy dietary intake. They were established by the Food and Agriculture Organization (FAO) and World Health Organization (WHO).

There are two types of NRVs:

Nutrient Reference Values - Requirements (NRVs-R)

These are values based on the levels of nutrients associated with nutrient requirements. NRVs-R are established for vitamins, minerals, and proteins. They are used to convert the amount of a nutrient in metric units into percentages of daily requirement when indicated on food product labels.

Example of NRVs-R for individuals older than 36 months:

Nutrient Reference Values – Non-Communicable Diseases (NRVs-NCD)

These are NRVs based on the levels of nutrients associated with the reduction of the risk for diet-related non-communicable diseases. They emphasize nutrients that play significant roles in the prevention and management of these conditions. Currently, NRVs-NCD have been established for:

• Saturated fat: should not exceed 20g
• Sodium: should not exceed 2000 mg
• Potassium: should achieve 3500 mg

Nutrient values are used for various purposes:

1. Meal planning — They are used in formulating balanced diets for individuals, schools, and institutional catering such as prisons by providing dietary guidance.

2. Interpreting food consumption records — They are used to assess the adequacy of food in relation to respective nutritional needs.

3. Food labelling — They enable the declaration of proper dosage or usage indicated on product labels as recommended intake for intended consumers.

4. Agricultural planning policies — They guide food production in terms of quantity and quality by considering the nutritional needs of the population. They also guide policy for food export and import.

5. Food choice and portioning — They guide consumers in making food choices by considering nutrition information that declares the percentage of recommended nutrient values.

6. Food product development — They are used in developing new food products in food industries by considering the nutrient requirements of consumers.

7. Nutritional counselling — They are applied by nutritionists and health professionals in advising individuals who require special lifestyle considerations, such as vegetarians or those with health conditions.

8. Development of dietary guidelines — They contribute to developing dietary guidelines for individuals in particular countries or regions, for example, Tanzania Food-Based Dietary Guidelines.

The establishment of nutrient values considers three major factors:

1. Age

Nutritional requirements vary throughout life stages. Infants, children, adolescents, adults, and elders have different nutrient needs due to growth, development, and metabolic changes. For example, children need more calcium and protein for bone growth, while older adults may need less energy but more calcium to prevent bone loss.

2. Sex

Biological differences between males and females can have direct impact on nutrient requirements. For example, females may need more iron due to menstruation. Also, males and females may have differences in energy requirements due to differences in body composition and metabolism. Generally, males require higher energy intake than females due to larger muscle mass.

3. Physiological Status

Different physiological conditions can influence body nutrient requirements. Pregnant women and lactating mothers have increased nutritional needs to support growth and development of the fetus and the infant. Their bodies' requirements for certain nutrients increase significantly. For instance, pregnant women need additional iron, folic acid, and calcium to support fetal development.

Summary of factors affecting nutrient needs:

A food product contains 20 μg of Selenium per 100g. Using the NRVs-R table where Selenium = 60 μg, calculate the percentage of NRV contributed by consuming 100g of this product.

Solution:

• Amount of Selenium per 100g = 20 μg
• NRV for Selenium = 60 μg

Using the formula:

$\text{Percentage NRV} = \frac{\text{Amount of nutrient}}{\text{NRV}} \times 100$

$\text{Percentage NRV} = \frac{20}{60} \times 100 = 33.3\%$

Therefore, consuming 100g of this product provides approximately 33% of the daily Selenium requirement.

In Tanzania, nutrient values are essential when shopping at local markets or supermarkets. For example, when buying packaged cooking oil, a student can use the nutrient label to check the saturated fat content (NRVs-NCD recommends not exceeding 20g). If a 500ml bottle shows 15g of saturated fat per 100ml, the student can calculate whether the product meets healthy dietary guidelines. This helps families in Tanzania make informed food purchases that prevent non-communicable diseases like heart disease, which are increasingly common in urban areas like Dar es Salaam.