diff --git a/app/controllers/foods_controller.rb b/app/controllers/foods_controller.rb
index 1185ef9..c6e3cde 100644
--- a/app/controllers/foods_controller.rb
+++ b/app/controllers/foods_controller.rb
@@ -49,7 +49,7 @@ class FoodsController < ApplicationController
 
   def destroy
     if @food.destroy
-      flash[:notice] = 'Deleted food'
+      flash.now[:notice] = 'Deleted food'
     end
   end
 
diff --git a/app/controllers/meals_controller.rb b/app/controllers/meals_controller.rb
index 5a9003f..0681168 100644
--- a/app/controllers/meals_controller.rb
+++ b/app/controllers/meals_controller.rb
@@ -93,6 +93,11 @@ class MealsController < ApplicationController
   end
 
   def prepare_meals
+    @meals_by_date = @project.meals.reject(&:new_record?)
+      .sort_by { |m| m.eaten_at || m.created_at }.group_by(&:display_date)
+
+    return if @meals_by_date.empty?
+
     @quantities = @project.meal_quantities.includes(:formula)
     @ingredients = @project.meal_ingredients.compute_quantities(@quantities) do |q, items|
       Hash.new { |h,k| k.composition } if q == Meal
@@ -100,7 +105,7 @@ class MealsController < ApplicationController
 
     @amount_mfu_unit = @ingredients
       .each_with_object(Hash.new(0)) { |(i, qv), h| h[i.food.ref_unit] += 1 }
-      .max_by(&:last).try(&:first)
+      .max_by(&:last).first
 
     @ingredient_summary = Hash.new { |h,k| h[k] = Hash.new(BigDecimal(0)) }
     @quantities.each do |q|
@@ -108,8 +113,7 @@ class MealsController < ApplicationController
         .each_with_object(Hash.new(0)) { |(i, qv), h| h[qv[q].last] += 1 if qv[q] }
         .max_by(&:last).try(&:first)
 
-      max_value = @ingredients.max_by { |i, qv| qv[q].try(&:first) || 0 }.last[q].try(&:first)
-      max_value ||= BigDecimal(0)
+      max_value = @ingredients.map { |i, qv| qv[q].try(&:first) || BigDecimal(0) }.max
       @ingredient_summary[:precision][q] = [3 - max_value.exponent, 0].max
     end
 
@@ -121,8 +125,5 @@ class MealsController < ApplicationController
         @ingredient_summary[meal.display_date][q] += a
       end
     end
-
-    @meals_by_date = @project.meals.reject(&:new_record?)
-      .sort_by { |m| m.eaten_at || m.created_at }.group_by(&:display_date)
   end
 end
diff --git a/app/models/food.rb b/app/models/food.rb
index 696857e..50d41f0 100644
--- a/app/models/food.rb
+++ b/app/models/food.rb
@@ -16,12 +16,11 @@ class Food < ActiveRecord::Base
   belongs_to :ref_unit, class_name: 'Unit', required: true
   belongs_to :source, required: false
   has_many :ingredients, dependent: :restrict_with_error
-  has_many :nutrients, foreign_key: 'registry_id', inverse_of: :food, dependent: :destroy,
-    validate: true
+  has_many :nutrients, as: :registry, inverse_of: :food, dependent: :destroy, validate: true
 
   DOMAIN = :diet
   alias_attribute :subitems, :nutrients
-  scope :subitems, -> { includes(nutrients: [:quantity, :unit]) }
+  scope :with_subitems, -> { includes(nutrients: [:quantity, :unit]) }
 
   validates :nutrients, presence: true
   accepts_nested_attributes_for :nutrients, allow_destroy: true,
diff --git a/app/models/formula.rb b/app/models/formula.rb
index eee0891..a0fbc3c 100644
--- a/app/models/formula.rb
+++ b/app/models/formula.rb
@@ -50,6 +50,8 @@ class Formula < ActiveRecord::Base
 
     def lastBefore(timepoints)
       self.map{ BigDecimal(2000) }
+      last_timepoint = timepoints.max
+      @quantity.quantity_values.includes(:registry)
     end
   end
 
diff --git a/app/models/ingredient.rb b/app/models/ingredient.rb
index d2c5215..81c78ea 100644
--- a/app/models/ingredient.rb
+++ b/app/models/ingredient.rb
@@ -6,7 +6,7 @@ class Ingredient < ActiveRecord::Base
 
   DOMAIN = :diet
   alias_attribute :subitems, :nutrients
-  scope :subitems, -> { includes(nutrients: [:quantity, :unit]) }
+  scope :with_subitems, -> { includes(nutrients: [:quantity, :unit]) }
 
   validates :ready_ratio, numericality: {greater_than_or_equal_to: 0.0}
   validates :amount, numericality: {greater_than_or_equal_to: 0.0}
diff --git a/app/models/measurement.rb b/app/models/measurement.rb
index 48e87d9..ff1588c 100644
--- a/app/models/measurement.rb
+++ b/app/models/measurement.rb
@@ -3,12 +3,12 @@ class Measurement < ActiveRecord::Base
     class_name: 'MeasurementRoutine'
   belongs_to :source, required: false
   has_one :project, through: :routine
-  has_many :readouts, foreign_key: 'registry_id', inverse_of: :measurement,
-    dependent: :destroy, validate: true
+  has_many :readouts, as: :registry, inverse_of: :measurement, dependent: :destroy,
+    validate: true
 
   DOMAIN = :measurement
   alias_attribute :subitems, :readouts
-  scope :subitems, -> { includes(readouts: [:quantity, :unit]) }
+  scope :with_subitems, -> { includes(readouts: [:quantity, :unit]) }
 
   accepts_nested_attributes_for :routine, allow_destroy: true,
     reject_if: proc { |attrs| attrs['name'].blank? }
diff --git a/app/models/nutrient.rb b/app/models/nutrient.rb
index c7f6e46..1d75aed 100644
--- a/app/models/nutrient.rb
+++ b/app/models/nutrient.rb
@@ -1,5 +1,6 @@
 class Nutrient < QuantityValue
-  belongs_to :food, foreign_key: 'registry_id', inverse_of: :nutrients, required: true
+  belongs_to :food, foreign_key: 'registry_id', foreign_type: 'registry_type',
+    inverse_of: :nutrients, polymorphic: true, required: true
 
   # Uniqueness NOT validated here, see Value for explanation
   #validates :quantity, uniqueness: {scope: :food_id}
diff --git a/app/models/quantity.rb b/app/models/quantity.rb
index 11840d7..ef5dcd1 100644
--- a/app/models/quantity.rb
+++ b/app/models/quantity.rb
@@ -9,6 +9,7 @@ class Quantity < ActiveRecord::Base
   belongs_to :project, required: false
   has_many :nutrients, dependent: :restrict_with_error
   has_many :readouts, dependent: :restrict_with_error
+  has_many :quantity_values, dependent: :restrict_with_error
   has_many :exposures, dependent: :destroy
 
   has_one :formula, inverse_of: :quantity, dependent: :destroy, validate: true
diff --git a/app/models/quantity_value.rb b/app/models/quantity_value.rb
index 7851f30..9dd04b1 100644
--- a/app/models/quantity_value.rb
+++ b/app/models/quantity_value.rb
@@ -1,4 +1,6 @@
 class QuantityValue < ActiveRecord::Base
+  # Requirement validation for :registry left to subclasses
+  belongs_to :registry, polymorphic: true
   belongs_to :quantity, required: true
   belongs_to :unit, required: true
 
diff --git a/app/models/readout.rb b/app/models/readout.rb
index 52de298..d6efd38 100644
--- a/app/models/readout.rb
+++ b/app/models/readout.rb
@@ -1,7 +1,10 @@
 class Readout < QuantityValue
-  belongs_to :measurement, foreign_key: 'registry_id', inverse_of: :readouts, required: true
+  belongs_to :measurement, foreign_key: 'registry_id', inverse_of: :readouts,
+    polymorphic: true, required: true
 
   # Uniqueness NOT validated here, see Value for explanation
   #validates :quantity, uniqueness: {scope: [:measurement_id, :unit_id]}
   validates :value, numericality: true
+
+  delegate :completed_at, to: :measurement
 end
diff --git a/app/views/foods/destroy.js.erb b/app/views/foods/destroy.js.erb
index d1513c5..c2209b4 100644
--- a/app/views/foods/destroy.js.erb
+++ b/app/views/foods/destroy.js.erb
@@ -1,3 +1,5 @@
 <% if @food.destroyed? %>
   $('tr[id=food-<%= @food.id %>]').nextUntil('tr.primary').addBack().remove();
+<% else %>
+  $('#content').prepend('<%= j error_messages_for @food %>');
 <% end %>
diff --git a/app/views/layouts/body_tracking.js.erb b/app/views/layouts/body_tracking.js.erb
index 3c22679..3fd074c 100644
--- a/app/views/layouts/body_tracking.js.erb
+++ b/app/views/layouts/body_tracking.js.erb
@@ -1,3 +1,4 @@
 $('div[id^=flash_]').remove();
+$('div[id=errorExplanation]').remove();
 $('#content').prepend('<%= j render_flash_messages %>');
 <%= yield %>
diff --git a/lib/body_tracking/items_with_quantities.rb b/lib/body_tracking/items_with_quantities.rb
index 8d52dad..9c5b4a6 100644
--- a/lib/body_tracking/items_with_quantities.rb
+++ b/lib/body_tracking/items_with_quantities.rb
@@ -38,7 +38,7 @@ module BodyTracking
       items = all
 
       subitems = Hash.new { |h,k| h[k] = {} }
-      all.subitems.order('quantities.lft').each do |i|
+      all.with_subitems.order('quantities.lft').each do |i|
         i.subitems.each do |s|
           subitem_value = i.respond_to?(:amount) ? i.amount*s.amount/s.ref_amount : s.value
           subitems[s.quantity][i] = [subitem_value, s.unit]