Nutrition Data

Future<bool> writeMeal({
  required DateTime startTime,
  DateTime? endTime,
  DateTime? recordingTime,
  MealType? mealType,
  double? calories,
  double? protein,
  double? carbs,
  double? fat,
  double? caffeine,
  String? name,
  // ... many more micronutrient parameters
})

Core Parameters

Parameter	Type	Description
`startTime`	`DateTime`	When meal was consumed
`endTime`	`DateTime?`	End time (optional)
`mealType`	`MealType?`	Breakfast, lunch, dinner, snack
`name`	`String?`	Meal name/description

Macronutrients

Parameter	Type	Unit	Description
`calories`	`double?`	kcal	Total energy
`protein`	`double?`	grams	Protein content
`carbs`	`double?`	grams	Carbohydrates
`fat`	`double?`	grams	Total fat
`fiber`	`double?`	grams	Dietary fiber
`sugar`	`double?`	grams	Sugars

Basic Usage

// Simple meal with macros
await health.writeMeal(
  startTime: DateTime.now(),
  mealType: MealType.BREAKFAST,
  name: 'Oatmeal with berries',
  calories: 350.0,
  protein: 12.0,
  carbs: 58.0,
  fat: 8.0,
);

// Lunch with detailed macros
await health.writeMeal(
  startTime: DateTime.now(),
  mealType: MealType.LUNCH,
  name: 'Grilled chicken salad',
  calories: 450.0,
  protein: 35.0,
  carbs: 25.0,
  fat: 20.0,
  fiber: 8.0,
  sugar: 5.0,
);

Meal Types

enum MealType {
  BREAKFAST,
  LUNCH,
  DINNER,
  SNACK,
  UNKNOWN,
}

// Usage
await health.writeMeal(
  startTime: DateTime.now(),
  mealType: MealType.SNACK,
  name: 'Apple with peanut butter',
  calories: 180.0,
);

Complete Nutrition Tracking

class MealLogger {
  final Health health;

  MealLogger(this.health);

  Future<bool> logMeal({
    required String name,
    required MealType type,
    DateTime? consumedAt,
    double? calories,
    double? protein,
    double? carbs,
    double? fat,
    double? fiber,
    double? sugar,
  }) async {
    return await health.writeMeal(
      startTime: consumedAt ?? DateTime.now(),
      mealType: type,
      name: name,
      calories: calories,
      protein: protein,
      carbs: carbs,
      fat: fat,
      fiber: fiber,
      sugar: sugar,
    );
  }

  Future<void> logDailyMeals() async {
    final today = DateTime.now();

    // Breakfast
    await logMeal(
      name: 'Scrambled eggs with toast',
      type: MealType.BREAKFAST,
      consumedAt: DateTime(today.year, today.month, today.day, 8, 0),
      calories: 400,
      protein: 24,
      carbs: 35,
      fat: 18,
    );

    // Lunch
    await logMeal(
      name: 'Chicken wrap',
      type: MealType.LUNCH,
      consumedAt: DateTime(today.year, today.month, today.day, 12, 30),
      calories: 500,
      protein: 32,
      carbs: 48,
      fat: 18,
    );

    // Dinner
    await logMeal(
      name: 'Salmon with vegetables',
      type: MealType.DINNER,
      consumedAt: DateTime(today.year, today.month, today.day, 19, 0),
      calories: 550,
      protein: 38,
      carbs: 42,
      fat: 22,
    );
  }
}

Micronutrients

The writeMeal method supports many micronutrients:

await health.writeMeal(
  startTime: DateTime.now(),
  name: 'Fortified cereal',
  calories: 250.0,

  // Vitamins
  vitaminA: 500.0,      // mcg
  vitaminC: 60.0,       // mg
  vitaminD: 10.0,       // mcg
  vitaminE: 15.0,       // mg
  vitaminK: 80.0,       // mcg
  vitaminB1: 1.2,       // mg (Thiamin)
  vitaminB2: 1.3,       // mg (Riboflavin)
  vitaminB3: 16.0,      // mg (Niacin)
  vitaminB6: 1.4,       // mg
  vitaminB12: 2.4,      // mcg
  folate: 400.0,        // mcg

  // Minerals
  calcium: 300.0,       // mg
  iron: 8.0,            // mg
  magnesium: 100.0,     // mg
  phosphorus: 250.0,    // mg
  potassium: 400.0,     // mg
  sodium: 200.0,        // mg
  zinc: 11.0,           // mg
);

Specialized Nutrients

// Caffeine tracking
await health.writeMeal(
  startTime: DateTime.now(),
  name: 'Coffee',
  mealType: MealType.BREAKFAST,
  calories: 5.0,
  caffeine: 95.0, // mg
);

// Water tracking
await health.writeMeal(
  startTime: DateTime.now(),
  name: 'Water',
  water: 500.0, // ml
);

// Fat breakdown
await health.writeMeal(
  startTime: DateTime.now(),
  name: 'Avocado toast',
  calories: 320.0,
  fat: 18.0,
  fatSaturated: 2.5,        // Saturated fat (g)
  fatMonounsaturated: 12.0,  // Monounsaturated fat (g)
  fatPolyunsaturated: 2.0,   // Polyunsaturated fat (g)
  cholesterol: 0.0,          // mg
);

Recipe-Based Logging

class Recipe {
  final String name;
  final double servings;
  final Map<String, double> nutrition;

  Recipe({
    required this.name,
    required this.servings,
    required this.nutrition,
  });

  Future<bool> logServing(Health health, double servingSize) async {
    final multiplier = servingSize / servings;

    return await health.writeMeal(
      startTime: DateTime.now(),
      name: name,
      calories: (nutrition['calories'] ?? 0) * multiplier,
      protein: (nutrition['protein'] ?? 0) * multiplier,
      carbs: (nutrition['carbs'] ?? 0) * multiplier,
      fat: (nutrition['fat'] ?? 0) * multiplier,
    );
  }
}

// Usage
final grilledChicken = Recipe(
  name: 'Grilled Chicken Breast',
  servings: 4.0,
  nutrition: {
    'calories': 660.0,
    'protein': 120.0,
    'carbs': 0.0,
    'fat': 18.0,
  },
);

await grilledChicken.logServing(health, 1.0); // Log 1 serving

Macro Calculation Helpers

class MacroCalculator {
  // Standard calorie values per gram
  static const double caloriesPerGramProtein = 4.0;
  static const double caloriesPerGramCarbs = 4.0;
  static const double caloriesPerGramFat = 9.0;

  static double calculateTotalCalories({
    double? protein,
    double? carbs,
    double? fat,
  }) {
    return (protein ?? 0) * caloriesPerGramProtein +
           (carbs ?? 0) * caloriesPerGramCarbs +
           (fat ?? 0) * caloriesPerGramFat;
  }

  static Map<String, double> calculateMacroPercentages({
    required double protein,
    required double carbs,
    required double fat,
  }) {
    final totalCalories = calculateTotalCalories(
      protein: protein,
      carbs: carbs,
      fat: fat,
    );

    if (totalCalories == 0) {
      return {'protein': 0, 'carbs': 0, 'fat': 0};
    }

    return {
      'protein': (protein * caloriesPerGramProtein / totalCalories * 100),
      'carbs': (carbs * caloriesPerGramCarbs / totalCalories * 100),
      'fat': (fat * caloriesPerGramFat / totalCalories * 100),
    };
  }
}

// Usage
final macros = MacroCalculator.calculateMacroPercentages(
  protein: 30,
  carbs: 40,
  fat: 15,
);

print('Protein: ${macros['protein']?.toStringAsFixed(1)}%');
print('Carbs: ${macros['carbs']?.toStringAsFixed(1)}%');
print('Fat: ${macros['fat']?.toStringAsFixed(1)}%');

Meal Timing Patterns

class MealTiming {
  static DateTime breakfast([DateTime? date]) {
    final d = date ?? DateTime.now();
    return DateTime(d.year, d.month, d.day, 8, 0);
  }

  static DateTime morningSnack([DateTime? date]) {
    final d = date ?? DateTime.now();
    return DateTime(d.year, d.month, d.day, 10, 30);
  }

  static DateTime lunch([DateTime? date]) {
    final d = date ?? DateTime.now();
    return DateTime(d.year, d.month, d.day, 12, 30);
  }

  static DateTime afternoonSnack([DateTime? date]) {
    final d = date ?? DateTime.now();
    return DateTime(d.year, d.month, d.day, 15, 30);
  }

  static DateTime dinner([DateTime? date]) {
    final d = date ?? DateTime.now();
    return DateTime(d.year, d.month, d.day, 19, 0);
  }
}

// Usage
await health.writeMeal(
  startTime: MealTiming.breakfast(),
  mealType: MealType.BREAKFAST,
  name: 'Morning oatmeal',
  calories: 350,
);

Platform Differences

iOS (HealthKit)
Android (Health Connect)

Stores as complete nutrition record
All micronutrients supported
Data appears in Apple Health app
Can link with Apple’s Nutrition app

See Also

Basic Writing - General health data
Data Types - Nutrition-related types
Basic Reading - Reading nutrition data