RDA represents the average daily dietary intake level sufficient to meet the nutrient requirements of nearly all (97–98%) healthy individuals in a specific age and gender group. RDAs serve as goals for individual daily nutrient intake and help prevent nutritional deficiencies.

Key Points About RDA

• RDAs are derived from Estimated Average Requirements (EARs)
• RDAs vary by age, sex, and physiological status (pregnancy, lactation)
• RDAs differ from Adequate Intakes (AIs), which are used when insufficient evidence exists for RDA
• Upper Tolerable Nutrient Intake Levels (ULs) indicate maximum intake without adverse health effects

A food composition table is a reference tool listing the amount of nutrients in 100g or 100mL of edible food portions. These tables include macronutrients (carbohydrates, proteins, fats) and micronutrients (vitamins, minerals).

Steps to Calculate Nutrient Intake

Step 1: Determine the weight of each food consumed in grams.

Step 2: Locate the nutrient values for each food from the composition table (values are per 100g).

Step 3: Calculate the nutrient content using the formula:

$\text{Nutrient consumed} = \frac{\text{Weight consumed (g)} \times \text{Nutrient value per 100g}}{100}$

Step 4: Sum all nutrients from each food item to get total intake.

A person consumed the following foods in one day:

• 2 boiled eggs (each 50g)
• 2 slices of white bread (each 50g)
• 20g sugar in tea
• 400g maize stiff porridge
• 200g chicken relish with coconut milk

Food Composition Table Provided

Solution

Step 1: Total weight of each food consumed

• Eggs: 50g × 2 = 100g
• Bread: 50g × 2 = 100g
• Sugar: 20g
• Maize stiff porridge: 400g
• Chicken relish: 200g

Step 2: Calculate nutrients for each food

Eggs (100g):

• Carbohydrate: (100 × 1.1) ÷ 100 = 1.1g
• Protein: (100 × 12.6) ÷ 100 = 12.6g
• Fat: (100 × 10.6) ÷ 100 = 10.6g

White bread (100g):

• Carbohydrate: (100 × 51.9) ÷ 100 = 51.9g
• Protein: (100 × 8.8) ÷ 100 = 8.8g
• Fat: (100 × 3.0) ÷ 100 = 3.0g

Sugar (20g):

• Carbohydrate: (20 × 100) ÷ 100 = 20.0g
• Protein: (20 × 0) ÷ 100 = 0g
• Fat: (20 × 0) ÷ 100 = 0g

Maize stiff porridge (400g):

• Carbohydrate: (400 × 25.6) ÷ 100 = 102.4g
• Protein: (400 × 2.7) ÷ 100 = 10.8g
• Fat: (400 × 1.2) ÷ 100 = 4.8g

Chicken relish (200g):

• Carbohydrate: (200 × 2.3) ÷ 100 = 4.6g
• Protein: (200 × 6.1) ÷ 100 = 12.2g
• Fat: (200 × 11.8) ÷ 100 = 23.6g

Step 3: Total nutrients consumed

• Total Carbohydrate: 1.1 + 51.9 + 20 + 102.4 + 4.6 = 180.0g
• Total Protein: 12.6 + 8.8 + 0 + 10.8 + 12.2 = 44.4g
• Total Fat: 10.6 + 3.0 + 0 + 4.8 + 23.6 = 42.0g

Step 4: Calculate energy (kcal)

Remember: 1g carbohydrate = 4kcal, 1g protein = 4kcal, 1g fat = 9kcal

• Energy from carbohydrate: 180g × 4 = 720 kcal
• Energy from protein: 44.4g × 4 = 177.6 kcal
• Energy from fat: 42g × 9 = 378 kcal

Total daily energy intake = 720 + 177.6 + 378 = 1,275.6 kcal

After calculating nutrient intake, compare the results against RDA values from standard tables to assess adequacy.

RDA Reference Values (Selected)

Interpretation

• Intake meets RDA: Nutrient needs are adequately met for most individuals
• Intake below RDA: Risk of nutrient deficiency; dietary improvement needed
• Intake significantly above RDA: May indicate excess; consider balance

When calculating micronutrients, follow the same procedure as for macronutrients.

Example: Iron Intake Calculation

Using the food composition table below:

Calculation:

• Kande: (300 × 1.5) ÷ 100 = 4.5mg
• Dried fried fish: (20 × 1.7) ÷ 100 = 0.34mg
• Cooked spinach: (100 × 3.6) ÷ 100 = 3.6mg
• Watermelon: (150 × 0.2) ÷ 100 = 0.3mg

Total Iron = 4.5 + 0.34 + 3.6 + 0.3 = 8.74mg

If RDA for iron is 8mg for adult males, this intake meets the requirement.

When computing nutrient intake for different population groups, consider:

• Age groups: Children, adolescents, adults, and elderly have different RDAs
• Sex: Males and females have different iron and energy requirements
• Physiological status: Pregnant and lactating women require increased nutrients
• Activity level: Physically active individuals need more energy

In Tanzania, a student or community health worker can use food composition tables and RDA values to plan meals for a family or in school feeding programs. For example, when budgeting for a student's lunch at a local market in Dar es Salaam, calculating the protein and iron content from a serving of beans (150g) and rice (200g) using the Tanzania Food Composition Table helps ensure the meal meets the student's RDA for iron (8mg/day) and protein (56g/day), enabling better nutritional planning with limited money.