Dietary Fibers and Added Sugars Quiz

Lipids

• Lipids are not easily digested or absorbed due to their insolubility in water, with most digestion occurring in the small intestine.
• The process of lipid digestion involves:
  • Mouth and salivary glands: melting hard fats, and lingual lipase secreted from sublingual salivary gland (slight hydrolysis for most fats).
  • Stomach: churning action mixes fat with water and acid, and gastric lipase breaks down a small amount of fat.
  • Small intestine: bile emulsifies fat, and pancreatic and intestinal lipase break down emulsified fat further (e.g., triglycerides à 3 fatty acids and glycerol).
• Absorption of lipids involves:
  • Enterocyte (intestinal cell) absorbs digestive products, including cholesterol, free fatty acids, monoacylglyceride, or monoglyceride.
  • Assistance of micelle (combination of proteins, monoglycerides, and fatty acids) helps transport lipids into the intestinal cells or enterocytes.
• Once absorbed, micelle is disassembled, and absorbed products are treated differently:
  • Medium and short-chain fatty acids are absorbed directly into the blood, with solubility increased by albumin (protein).
  • Phospholipids, cholesterol, and resynthesized triglycerides are repackaged with protein into chylomicrons (lipoprotein) in the endoplasmic reticulum (ER) of enterocyte.
• Transportation of lipid products differs:
  • Short and medium-chain fatty acids move through the enterocyte and enter circulation via capillaries, riding on albumin, then carried to the liver.
  • Chylomicrons are too large to fit through the pores of the capillaries, so they are transported through the lymphatic system.

Lipoproteins

• There are four types of lipoproteins, which differ in size and density, depending on the proportion of lipids and proteins they carry:
  • Chylomicrons: transport dietary lipids from the intestine to other parts of the body.
  • Very Low-Density Lipoproteins (VLDL): transport endogenous (produced by the body) triglycerides from the liver to peripheral (adipose and muscle) tissues.
  • Low-Density Lipoproteins (LDL) or "bad cholesterol": transport cholesterol from the liver to peripheral tissues.
  • High-Density Lipoproteins (HDL) or "good cholesterol": remove excess cholesterol from the bloodstream and transport it to the liver for excretion.

Storage and Health Recommendations

• Adipose tissue is an efficient storage site for triglycerides, with virtually unlimited storage capacity.
• Health Canada recommends:
  • 20-35% of daily caloric intake from lipids.
  • Limiting Saturated Fatty Acids (SFA), Trans Fatty Acids (TFA), and dietary cholesterol.

Proteins

• Proteins are large complex molecules found in the cells of all living things, composed of strands of amino acids.
• Amino acids are the building blocks of proteins, with 20 different types, including:
  • 9 essential amino acids (indispensable) that cannot be synthesized by the body.
  • 11 non-essential amino acids that can be synthesized by the body.
• Protein synthesis involves:
  • Condensation (removal of water) to form a peptide bond.
  • Formation of a dipeptide or polypeptide chain.

Protein Quality and Digestibility

• Protein quality is determined by its ability to provide all essential amino acids.
• Digestibility depends on the protein source and other foods consumed together.
• Amino acid composition is critical to prevent protein breakdown.
• Mutual supplementation involves obtaining complete amino acid requirements from two or more incomplete protein sources.
• Complementary proteins are two or more proteins whose amino acids complement each other.

Fibers and Added Sugars

• Dietary fiber recommendations are about 14 grams per 1000 kcal/day.
• Added sugars are defined as sugars and syrups added to foods during processing or preparation.
• The World Health Organization recommends limiting added sugars to 10% or less of total daily energy intake.