Digestive Processes 2026 complete update
Concordia University
BIOL 203
Lesson 1:
Nutrition: How an organism acquired food and uses food to support all processes required for its
existence.
Plant Nutrition:
- Plants are anchored by roots to the ground
- They absorb nutrients from soil solution and directed upward toward leaves
- Developing leaf buds and flower buds pick up the bulk of the nutrients
- Together with photosynthesis, plant has all it needs to grow into tree towering more
than 30m high
Roundworm Nutrition:
- A biologist studying the nutrition of a roundworm for ex: Cetegans would be
interested in its locomotion during the time it is foraging for food
- Once food is located, worm biologist is interested in the type and rate of digestion in
each comportment of the worm’s elementary canal
- Next, biologist may question how the nutrients are absorbed, stored and metabolized
by the cells that make up the organism
- They also study the neurobiology of feeding in simpler animals like roundworms.
Roundworms are great model organisms because of their neurological simplicity
- Only 309 nerve cells make up the entire organism
Human Nutrition:
- The science of nutrition is the study of the nutrients and other substances in food and
the body’s handling of them
- It’s a young science
, - More recently, it has a sister discipline called Nutritional Genomics: the science for
how nutrients affect gene expression
What is food?
- There are drawbacks to the advances made in the field of nutrition
- The science of nutrition is partly to blame for anyone of these being considered as
food: milkshakes, tarts, granola bars etc.
- Nutritionists broke down food into an amalgam of nutrients and offer the advice that
we need X amount of these nutrients every day
- Pop-tarts and protein shakes = not food
- Food is more than just a collection of vitamins, minerals and macronutrients
- Food and eating is a satisfy activity we engage in at least 3x per day
- Organs of the digestive system communicate with the brain and vice versa to offer a
feeling of wellness and satisfaction
- Food provides us with essential nutrients that must be supplied by the diet because
the human body cannot synthesize them. It can, but not in sufficient quantities hence
we eat food to get an adequate amount of the essential nutrients to promote
optimal health
, - Absence of an essential nutrient would lead to a deficiency disease like scurvy and
eventual death
- It also matters the proportion of essential nutrients consumed
- Too much can lead to chronic diseases like cardio disease, type 2 diaebetes or
sudden death from overdosing on supplements
- Energy yielding nutrients = carbs, lipids, proteins
- Non-energy yield nutrients = vitamins, minerals, water
- Food also contains non-nutrients like fiber and phytochemicals, which starve off
chronic diseases
o Fiber promoted bowel health: food waste is quickly and effortlessly
eliminated, helping to reduce the risk of colon cancer
o Phytochemicals: function as antioxidants to help reduce the risks of chronic
diet-related diseases
- Many types of compounds found in plants are now studied for their curative power,
example: flavonoids found in tea and blueberries are thought to decrease risk of
some forms of cancer and even improve memory
The Challenge of Food:
- Why do we make poor choices when it comes to eating healthy?
- We can split our choices into a dichotomy of processed foods and whole foods
(unprocessed or minimally processed)
- Phytochemicals clearly promotes consuming whole foods for optimal health yet we
continuously make poor food choices
- Factors that drive food choices: convenience, advertising, economy, emotional
comfort, social network, beliefs
- It all comes down to cooking skills and hardware
- What does social psychology have to do with eating?
o Pro nutrition altitudes don’t always align themselves with behaviour. Example:
we know its vital to have a healthy diet yet we behave in a contradictory
manner. Because you cant cook, solution: learn about nutrition (cognitive fix)
= vital, learn how to cook (non-cognitive fix) = life-skill
Cooking:
- A skill that is disappearing from our society
- Cooking, being physically in the kitchen is incompatible with achieving professional
success
- Multi-billion $$ food industry is now cooking for us
- Many think that spinach on frozen pizza or V8 are what constitute a proper dinner
- Cooking can teach us: how to be organized, how to socialize, how to love, food
chemistry
- Food rules: food safety, discipline and stay away from kitchen gadgets
Lesson 2:
Dietary Reference Intakes (DRI):
, - Reference values that are quantitative estimates of nutrient intakes to be used for
planning and assessing diets for healthy people
- It’s an umbrella term/group name ◻ group includes a set of 6 nutrients intakes
standards aimed for healthy people
- Based on these standards, dieticians can plan or assess someone’s diet
- In the past, the sole purpose of DRIs was to reduce risk of deficiency diseases
- Today, in developed countries, defiency diseases are rare, chronic diet related
diseases have replaced them
- Majority of population over 40 beginning to worry about cardio disease and type 2
diabetes
- DRIs now have 3 objectives:
o Prevent deficiency diseases
o Reduce the risk of chronic diseases with recommendations
o Establish the upper safety for nutrient intake for supplement use and
fortification
- 6 Nutrient Intake Standards:
Most Nutrients: All essential nutrients have 1 or more of these DRIs
o Estimated Average Requirement (EAR) ◻ targets deficiency diseases
o Recommended Daily Allowance (RDA) ◻ targets deficiency diseases
o Adequate Intake (AI) ◻ targets deficiency diseases
o Tolerable Upper Intake Level (UL) ◻ targets supplement use
Energy and Macronutrients: These standards are different because they deal with caloric intake
o Estimated Energy Requirement (EER) ◻ targets carbs, lipids + protein intake
o Acceptable Macronutrient Distribution Ranges (AMDR) ◻ targets carbs, lipids
+ protein intake
- Nutrient standards differ by gender and life stage
- Men = 10 life stages, Women = 16 life stages (includes periods of pregnancy +
lactation)
- Pregnancy and lactation are so taxing on the female body that nutrient intakes must
increase during this period. Example: recommended intake of iron for women:
o 13 yrs old = 8mg, 14-50 yrs old = 15mg, 50+ yrs old = 8mg, pregnant = 27mg
- Average daily requirement for each nutrient – expressed as mg/day, g/day, or
ng/day
DRIS: Most Nutrients
Estimated Average Requirement (EAR)
- Defined as the average daily intake level of a nutrient to meet the needs of ½ the
healthy people in a life stage or gender group
- 2 key features
o Its based on a diagnostic test that can measure adequate amounts in the
body, some nutrients lack a diagnostic test, thus an EAR cannot be
established
o It’s a requirement, not a recommendation