Nutrition & Nutrients and The Digestive System

Nutrition: The study of nutrients and how the body utilizes them.
Nutrients: Chemicals supplied from the environment that an organism requires for survival.
- Includes: carbohydrates, lipids, proteins, vitamins, minerals, water.
Macronutrients: Nutrients required in large amounts (carbs, lipids, proteins).
Micronutrients: Nutrients required in small amounts (vitamins & minerals).
- Do not provide direct energy.
Essential Nutrients: Nutrients that human cells cannot synthesize (like amino acids); must obtain from food.

Excess energy intake is stored as fat; insufficient energy intake results in the body using stored fat.
Calorie: A measure of energy.
- Technical definition: The amount of heat required to raise the temperature of a gram of water by 1 °C.
Calorie number on food labels = 1000x (kilocalorie).
- For foods, calorie count is a measure of how much energy that food stores in chemical bonds.

Due to cellular oxidation:
- 1 g of carbohydrates = 4 Calories
- 1 g of fats = 9 Calories
- 1 g of proteins = 4 Calories
Total Calories = Carb Calories + Protein Calories + Fat Calories
- Using the “4-9-4” rule above.
- Food labels round for conciseness and consistency.

Dark chocolate macadamia nuts:
- Carbs: 14 g x 4 Cal = 56 Cal
- Fats: 11 g x 9 Cal = 99 Cal
- Protein: 2 g x 4 Cal = 8 Cal
- Total: 56 + 99 + 8 = 163 Calories

USDA introduced tools to show people how many servings of different food groups should be eaten.
1st guide introduced in 1992
- Shaped like a pyramid suggesting more foods from the bottom and fewer from the top → carb heavy diet
- Criticized for being impractical and inaccurate.
USDA introduced a 2nd, updated version in 2005 called MyPyramid
- Food groups depicted as ascending vertical bands emphasizing the right proportions of food groups (with a person walking up a flight of stairs to emphasize physical activity).
- Focused more on cups and ounces rather than servings.
- Still too complex and did not give people an easy way to compare their meals to the ideal balance recommended.
USDA changed MyPyramid to MyPlate in 2011
- Reflects an accurate nutritional balance of a healthy diet.
- Simpler concept: half of the plate should be vegetables and fruit, while the other half should be split between meats and grains.
- Still has some disadvantages: doesn’t explain plate size and doesn’t emphasize physical activity.

Regardless, obesity in the US has continued to increase.
Malnutrition – symptoms resulting from lack of specific nutrients
- May result from undernutrition or due to overnutrition
- Variety of factors: lack of availability, poor food quality, overeating, taking too many vitamin supplements, etc.
Nutritional assessment is a detailed investigation by a physician or dietician to identify and quantify clinically relevant malnutrition.
- Nutritional management effectively reduces the risk of morbidity and mortality.
ABCD’s of nutritional assessment
- Anthropometry – physical measurements of the body (ex: height, weight, skin folds, etc.)
- Biochemical assessment – measures for specific nutrients in body fluids (ex: sugar in urine indicates diabetes)
- Clinical observations – observation of hair, nails, skin, eyes, lips, etc.
- Dietary intake – diet history, food record, food frequency

Health claims can be misleading to how healthy a product actually is
- “sugar free” → may have higher fat content
- “fruit-flavored” → artificial sweeteners
- “low in sugar and fat” → may have higher salt content
- “natural” → high fat, sugar, etc.
- “made with whole grains” → pinch of whole grains mixed with refined grains
- etc.
Many food companies utilize vague phrases and beautiful packaging to make a product seem healthy and appealing
It is important to read nutrition labels on the back of the package to track how many nutrients are actually being consumed
According to the FDA, nutrition labels can be inaccurate by up to 20% when it comes to listing calories!
Therefore, everything should be consumed in moderation!

Free radicals are deficient in energy and attack other cells to snatch energy.
Antioxidants neutralize free radicals by giving them an extra electron, stopping the chain reaction and reducing the risk of sickness, disease, and aging.

Fat types:
- Essential fat: found in brain, bone marrow, nerves, and membranes
- Subcutaneous fat: stored under the skin (the fat that you can squeeze or pinch in your arms, belly, thighs, etc.)
- Visceral fat: stored in the abdomen and around major organs (most dangerous!)
Some fat is beneficial, necessary for health, while some is negative and contributes to disease.
ACE Body Fat Chart:
- Description, Men, Women
- Essential fat, 2-5%, 10-13%
- Athletes, 6-13%, 14-20%
- Fitness, 14-17%, 21-24%
- Average, 18-24%, 25-31%
- Obese, 25%+, 32%+

Body mass index (BMI) – a measure of body fat based on your weight in relation to your height
Scale:
- under 19: underweight
- 19–24: healthy weight
- 25–29: overweight
- 30-34: obese
- 35-39: severely obese
- over 40: morbidly obese
Used to define obesity for the general population
Inaccurate measurement
- doesn’t directly measure body fat, take into account muscle mass, bone density, racial and sex differences, etc.
High BMI and/or excess body fat is linked with increased risk of heart disease, hypertension, cancer, diabetes, etc.

Ideal weight ranges based on height and body frame (small, medium, large) are provided in a detailed chart for both women and men.

Energy is expended in three ways:
1. Resting energy expenditure – energy required for the body to accomplish its most basic life-sustaining functions (heart beat, body temperature regulation, blood pH, nerve tissue conduction, etc.)
  - can be calculated as a basal metabolic rate (BMR)
2. Diet-induced energy expenditure – energy expended as heat after eating a meal
  - commonly referred to as metabolism
3. Activity-induced energy expenditure – energy expended after physical activity
  - determined by body movement and size
People of different sizes burn calories at different rates depending on muscle density, current weight, and other lifestyle factors
- men typically have higher BMR than women
- BMR decreases with age
- physical activity increases amount of calories burned