Nutrition calculation (recipe pages)

This document describes how aggregated recipe nutrition is computed and displayed on recipe pages via <RecipeFoods />, so editorial copy and the implementation stay aligned.

Data source

• Each food page stores nutrition_per_100g (typically from USDA FoodData Central via the site’s curation workflow).
• Recipe totals do not invent new chemistry; they combine those per-100 g panels using the rules below.

Two modes

Mode	When	What gets summed
Scaled to recipe	Front matter includes recipe_nutrition with ingredients[].food + grams	For each ingredient: (nutrient per 100 g × grams) ÷ 100, summed across foods.
100 g per linked food	No recipe_nutrition	For each tagged food linked to a food page: the site adds that food’s per-100 g panel once (as if 100 g of each tagged ingredient). Not scaled to real portions.

Servings: If recipe_nutrition.servings is greater than 1, displayed amounts in the table are per serving (totals are divided by servings).

Implementation references:

• src/theme/RecipeFoods/index.tsx — UI, legacy vs weighted branching, fibre/polyphenol rows.
• src/utils/recipeNutritionWeighted.ts — computeWeightedNutrients, trace thresholds.

Table columns (recipe nutrition block)

Column	Definition
Nutrient / class	Human-readable label (Energy, Protein, Iron, …).
Foods in recipe	Food pages that contribute to that row (hyperlinked). In weighted mode, only foods with a non-trace contribution for that nutrient; in legacy, foods whose panel includes that key.
Total	Header: “Total (scaled to recipe)” or “Total (100 g per linked food)” depending on mode. Numeric total for the row; trace when below reporting thresholds (weighted mode only).
% RDA aggregate	Only for core + micronutrient keys (see keys below). (amount ÷ adult RDA) × 100. Uses fixed adult reference values in RecipeFoods (must match NutritionTable where applicable). — for fibre and polyphenol proxy rows.

Nutrient keys included in the main table

• Core: kcal, protein_g, fat_g, sat_fat_g, carbs_g, sugar_g, fibre_g (see also dedicated fibre row below).
• Micronutrients: iron_mg, zinc_mg, magnesium_mg, selenium_ug, calcium_mg, potassium_mg, copper_mg, choline_mg, folate_ug, vitamin_b12_ug, vitamin_b6_mg, vitamin_e_mg, vitamin_k_ug.

Defined in src/data/nutritionTableMapping.ts (CORE_NUTRIENT_KEYS, MICRONUTRIENT_KEYS).

Fibre row

• Weighted: Sum of fibre_g contributions using the same (per 100 g × g) / 100 rule per recipe_nutrition ingredient.
• Legacy: Sum of each linked food’s fibre_g per-100 g value (unscaled).
• % RDA: Not shown (—).

Polyphenols (proxy) row

• Sums mg from food front matter supplementary / functional metric entries whose labels match an internal polyphenol-related pattern (not a full FDC polyphenol database).
• May show qualitative text when only amount_display is present.
• % RDA: Not shown (—).

Trace

Weighted totals below absolute or %RDA floors display as trace (see isTraceTotal / isTraceContribution in recipeNutritionWeighted.ts).

Editorial: recipe_nutrition (YAML)

recipe_nutrition:
  servings: 4
  ingredients:
    - food: Extra Virgin Olive Oil   # must match food page title or tag label
      grams: 62
    - food: Rosemary
      grams: 1

• grams = grams for the full recipe (all servings combined), unless the team standardises otherwise—must match RecipeFoods / computeWeightedNutrients behaviour.
• food must resolve to a food document via title or tag label.

See also: docs/recipes/.cursor/rules/Recipe-Pages.mdc.

User-facing copy

Introductory paragraphs under Recipe nutrition are maintained in RecipeFoods and should stay consistent with this document when behaviour changes.