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Macronutrients 101

Several months ago I picked up a copy of "Perfect Health Diet" by Paul and Shou-Ching Jaminet. The book focuses on optimizing  nutrition and diet by teaching what and how much you should eat. The authors argue that the right diet can be a potent catalyst for good health.

Reading the book I've realized that I lack a fundamental understanding of nutrients. What really is a protein and carbohydrate? What is a nutrient? This post contains my notes collected from various articles and Wikipedia.

Even if you don't read the book, I believe having a basic understanding of macronutrients is valuable. Because without them, you wouldn't be alive.


Nutrients are substances needed for growth and maintaining body functions.

Macronutrients are nutrients that provide energy (aka calories):

  • Macronutrients have specific roles in maintaining our body
  • Macronutrients contribute to taste, texture, and appearance of foods

There are 3 broad classes of macronutrients:

  • Proteins
  • Carbohydrates
  • Fats

A molecule is two or more atoms held together by chemical bonds (they do not have an electrical charge)

A biomolecule (biological molecule), is a molecule that is present in living organisms (example of biomolecules: proteins, carbohydrates, fats)

Insulin is a hormone produced by body that regulates the metabolism of protein, carbohydrates, and fats

Proteins (4 calories/gram)

  1. Molecules consisting of smaller units called amino acids (building blocks of proteins)
  2. Present in every living cell
  3. Hold together, protect, and provide structure to our body
  4. Complex molecules, body needs time to break them down
  5. Provide:
    1. Slower and longer-lasting source of energy compared to carbohydrates
    2. Energy and growth
    3. Tissue repair, immune system function, hormone and enzyme production, muscle mass and tone
  6. To make the proteins that it needs (protein biosynthesis), the body needs proteins
  7. When eaten, proteins broken down into amino acids (dietary source of nitrogen)
  8. There are 20 amino acids
    1. Body can synthesize (production of chemical compounds by reaction from simpler materials) 11 amino acids from molecules within body
      1. This is done through de novo synthesis (from scratch): the synthesis of complex molecules from simple molecules
    2. 9 amino acids cannot be synthesized de novo by body and they must be provided by diet
      1. These 9 are called essential amino acids:
        1. histidine
        2. lysine
        3. isoleucine
        4. leucine
        5. methionine
        6. phenylalanine
        7. threonine
        8. tryptophan
        9. valine
  9. Proteins from animal sources are complete proteins because they contain all essential amino acids
  10. Proteins from plants, legumes, grains, nuts, seeds, and vegetables are called incomplete proteins because they lack one or more essential amino acids
  11. USDA (department agriculture) recommends adults eat 60 grams protein per day (0.8 per kg of weight)

Carbohydrates (4 calories/gram)

  1. Molecule consisting of carbon, hydrogen and oxygen atoms
    1. Carbohydrates are a synonym for saccharide, a group that includes 3 types:
      1. Sugars
        1. General name for short-chain, soluble carbohydrates
        2. Many types of sugars are used in food
        3. Table sugar = sucrose
      2. Starch
        1. Polymeric (large molecule composed of many repeated subunits) carbohydrate consisting of a large number of glucose units
        2. Polysaccharide produced by most green plants as an energy store
        3. Most common carbohydrate (common in foods such as: potatoes, wheat, corn, rice)
        4. Has two components:
          1. Amylose (20-30% of weight)
            1. Polymer (large molecule) made of d-glucose units, bound by glycosidic bonds
            2. More resistant to digestion than other starch molecules
            3. Preferred starch for energy storage in plants
          2. Amylopectin (70-80% of weight)
            1. Highly branched polymer of glucose found in plants
            2. Soluble molecule that can be quickly degraded as it has many endpoints that an enzyme can attach to
      3. Cellulose
        1. Polysaccharide consisting of a linear chain of many D-glucose units
    2. Saccharides are divided into four chemical groups
      1. Monosaccharide
      2. Disaccharides
      3. Oligosaccharides
      4. Polysaccharides
  2. Two major roles of carbohydrates:
    1. Primary energy source for body
    2. Source of calories to maintain body weight
  3. Involved in the construction of the body organs and nerve cells
  4. Body uses carbohydrates in the form of glucose and can quickly convert simple and complex carbohydrates into energy
    1. The body stores a small amount of excess carbohydrate as energy reserve
    2. The brain uses/needs glucose as an energy source, fat cannot be used for this purpose
  5. Glycogen, is a complex carbohydrate the body can easily and rapidly convert to energy
    1. Muscles store glycogen, which they use during periods of intense physical activity
  6. Two basic types of carbohydrates (depending on their size)
    1. Simple carbohydrates (aka monosaccharide)
      1. Cannot be broken down into simple sugars
      2. Absorbed directly into the bloodstream
      3. Include various forms of sugar such as:
        1. Glucose (aka dextrose)
          1. Simple sugar, circulates in animals as blood sugar (amount of sugar present in the blood)
          2. A primary source of energy for body's cells
          3. Transported from the intestines or liver to body cells via the bloodstream, and is absorbed by cells via the hormone insulin
        2. Fructose (aka fruit sugar)
          1. Found in many plants, often bonded to glucose to form the disaccharide sucrose
          2. Natural sources include: fruits, vegetables, and honey
        3. Galactose
          1. Monosaccharide sugar that is less sweet than glucose and fructose
          2. When combined with glucose, through a reaction the result is the disaccharide lactose
          3. Found in dairy products, sugar beets
      4. Fastest source of energy as they can be broken down by body quickly
      5. Absorbed by small intestine into the bloodstream, then transported to where they are required
      6. Sources in diet: fruits, berries, vegetables, honey
    2. Complex carbohydrates: larger and consist of long strings of simple carbohydrates, 3 groups: 
      1. Disaccharides (two monosaccharides joined by glycosidic linkage)
        1. Sucrose
          1. Naturally occurring carbohydrate found in many plants
          2. Combination of glucose and fructose
          3. Often extracted and refined from cane or beet sugar for human consumption
            1. Refined form of sucrose = table sugar
        2. Lactose
          1. Disaccharide sugar found in milk
          2. Composed of galactose and glucose
        3. Maltose
          1. Disaccharide formed from two units of glucose joined an alpha bond from a condensation reaction (chemical reaction where two molecules combine to form a larger molecule)
          2. Produced when amylase breaks down starch
            1. Amylase is an enzyme (molecular biological catalyst) that catalyses (starts/increases rate of chemical reaction) the hydrolis (unbinding) of starch into sugars
              1. Present in saliva of humans where it begins the chemical process of digestion
              2. Why a sweet potato is "sweet" when chewed - amylase degrades some of it's starch into sugar
      2. Oligosaccharides
          1. Simple polymer containing small number of simple sugars (monosaccharides)
            1. Fructooligosaccharide (FOS)
              1. Used as an alternative sweetener
              2. Extracted from blue Agave plant, bananas, onions, chicory root, garic, asparagus, wheat, and barley
      3. Polysaccharides
          1. Long chains of monosaccharide  units bound by glycosidic bonds (covalent bond that joins a  carbohydrate to another molecule)
            1. Starch
            2. Maltodextrin
              1. Polysaccharide that is used as a food additive
              2. Produced from starch by hydrolysis
                1. Enzymatically derived from any starch (typically corn or wheat)
              3. Commonly used in soft drinks and candy and other processed foods
            3. Amylose
            4. Amylopectin
          2. Broken down by enzymes into smaller sugars which are then absorbed into bloodstream

Fats (9 calories/gram)

  1. A lipid (naturally occurring molecule that includes fats and fat soluble vitamins such as A, D, E)
    1. Store energy
    2. Structural components of cell membranes
  2. Also know as triglyceride, an ester of three fatty acid chains and the alcohol glycerol
    1. Fatty acid: Carboxylic acid with a long aliphatic chain (saturated or unsaturated)
      1. Important source of fuel, when metabolized yield large quantities of ATP
        1. Adenosine triphosphate (ATP)
          1. small molecule in cells used as a coenzyme
          2. molecule that carries energy to the place where energy is needed
    2. Esters: chemical compounds derived from an acid (organic or inorganic)
      1. Usually derived from a caroxylic acid an an alcohol
    3. Glycerol: Simple polyol (alcohol containing multiple hydroxyl groups) compound
      1. Colorless, odorless, liquid that is sweet-tasting and non-toxic
      2. Hydroxyl: chemical group containing one oxygen atom connected by covalent bond to a hydrogen atom
      3. Alcohol: organic compound where the hydroxyl group (-OH) is bound to saturated carbon atoms
  3. Fats are a source of energy (slowest but most energy-efficient form of food) and protect internal organs
  4. Four main types:
    1. Saturated fats
      1. Fatty acids all have a single bond
      2. Called saturated because they are fully saturated with hydrogen atoms and cannot incorporate more
      3. Solid at room temperature
      4. Examples: butter, cheese, whole milk dairy products and fatty meats
      5. Provide source of energy, building blocks for cell membranes and hormones
    2. Unsaturated fats (molecules contain less than the maximum amount of hydrogen)
      1. Monounsaturated fats
        1. Composed of monounsaturated fatty acids
        2. Liquid at room temperature
        3. Examples: olive, peanut, and canola oil, olives, nuts, peanuts, avocados
      2. Polyunsaturated fats
        1. Found in nuts, seeds, fish, leafy greens
        2. Position of the carbon-carbon double bonds in carboxylic acid chains in fats is designated by Greet letters
          1. Carbon atom at the end of a hydrocarbon chain is called the omega carbon (last letter of Greek alphabet)
          2. Omega-3 fatty acids
            1. Final carbon-carbon double bond in the n-3 (n minus 3) position
            2. Three types:
              1. a-linolenic acid (ALA)
                1. found in plant oils
                2. walnut, edible seeds, flaxseed oil
              2. eicosapentaenoic acid (EPA)
                1. commonly found in marine oils
                2. fish oils, egg oils, krill oil
              3. docosahexaenoic acid (DHA)
                1. commonly found in marine oils
                2. fish oils, egg oils, krill oil
          3. Omega-6 fatty acids
            1. Final carbon-carbon double bond in the n-6 (n minus 6) position
            2. Found in sunflower seeds, sesame, walnuts, soybean, corn
          4. Essential fatty acid (EFA)
            1. Fatty acids humans must ingest because body requires them and cannot synthesize them
              1. Alpha-linolenic acid (omega-3)
              2. Linoleic acid (omega-6)
      3. Trans fatty acids (trans fats)
        1. Type of unsaturated fats, occur in small amounts in nature
          1. Widely produced artificially from vegetable fats for use in snack foods, margarine, baked goods
          2. Easy to use, inexpensive to produce, last a long time = fast foods restaurants use to deep fry
        2. Frying and baking fats (hydrogenated vegetable oils)
        3. Hydrogenation: forced chemical addition of hydrogen into omega-6 polyunsaturated oils to make them hard at room temperatures, primarily as a cheaper and less perishable substitute for butter in crispy bread products