Deserializing the nutrient list

FoodItem.cs

public void DeserializeNutrients(string tag = null)
{
  var elements = this.NutrientDoc["nutrients"].AsBsonDocument;
  var list = new List<Nutrient>();
  foreach (var element in elements.Elements)
  {
    if (!string.IsNullOrWhiteSpace(tag)) {
      if (element.Name != tag) {
        continue;
      }
    }
    var nutrient = new Nutrient 
    {
      FoodId = this.FoodId,
      NutrientId = element.Value.AsBsonDocument["id"].AsString,
      AmountInHundredGrams = element.Value.AsBsonDocument["amount"].ToDouble(),
      Definition = new NutrientDefinition
      {
        NutrientId = element.Value.AsBsonDocument["id"].AsString,
        UnitOfMeasure = element.Value.AsBsonDocument["uom"].AsString,
        Description = element.Value.AsBsonDocument["description"].AsString,
        TagName = element.Name,
        SortOrder = element.Value.AsBsonDocument["sortOrder"].AsInt32
      }
    };
    list.Add(nutrient);
  }
  this.Nutrients = list.ToArray();
}