Nutrition Flashcards
Basic Nutrition Concepts
Macronutrients and Micronutrients
Nutrition Strategies
Hydration
Macronutrients — nutrients that are required in large quantities, typically in the range of tens to hundreds of grams (g) per day, divided into carbohydrates, proteins, and fats.
1. Carbohydrates — composed of carbon, hydrogen, and oxygen, usually have a hydrogen to oxygen (H:O) ratio of 2 to 1 as is the case with water (H2O) - hence the term hydrate.
1.1. Sugars — sweet crystalline simple carbohydrates and comprise monosaccharides (單醣) (e.g. glucose, fructose, galactose) and disaccharides (二堂) (two simple sugars linked together - e.g. sucrose 蔗糖, lactose, maltose 麥芽糖)
1.2. Carbohydrates also occur as long chains that can be branched (e.g. starch, soluble and insoluble fiber).
1.3 Fiber — indigestible and provides no calories, have health benefits, cause a feeling of fullness and decreased appetite. All other Carbs provide 4 Kcal of energy per gram.
1.3.1. Soluble Fiber — binds dietary cholesterol and can help reduce blood LDL (low-density lipoproteins 低密度脂蛋白) cholesterol - the bad cholesterol, help slow the breakdown and absorption of carbs which can help control blood sugar.
1.3.2. Insoluble Fiber — help speed the passage of stools (糞便), can relieve constipation.
1.3.3. All fiber is found in plant foods (e.g. soluble fiber — oatmeal, beans, and fruits; insoluble fiber — whole wheat, brown rice, and seeds).
1.4. Glucose — the six-carbon sugar, the main substrate for energy metabolism although fructose is also used, the primary sugar circulating in the blood and its levels are controlled by hormones such as insulin, glucagon (一高血糖素), norepinephrine, epinephrine, and cortisol in response to diet, energy expenditure, and stress; can be derived from simple sugars (e.g. sucrose) and from starches.
1.5. Glucose is stored in the polymer glycogen (聚合物堂原) in muscle, liver, and other tissues for easy access when energy is needed. Skeletal muscle is the most significant site of glycogen storage in the body.
2. Proteins — long chains of amino acids, which have the general formula RCHCOOH and are bound together in proteins by peptide bonds (勝太監).
2.1. Amino Acids — there are 20 amino acids important in human metabolism, with 8 to 10 of them considered Essential because they are required in the diet. Arginine (精氨酸) and histidine (組胺酸) are not always included as they are only essential under certain conditions, such as periods of fast growth.
2.2. Animal products (e.g. meat/fish/eggs/dairy) contain complete protein because all of the essential amino acids are provided. Plant food contain incomplete protein, which is why vegetarians need to eat a wide variety of plant food in order to meet their protein needs.
2.3. PVT TIM HALL (Private Tim Hall) — a mnemonic for the 10 essential amino acids: phenylalanine (苯丙胺酸), valine (協胺酸), threonine (蘇胺酸), tryptophan (色胺酸), isoleucine (義輛胺酸), methionine (但胺酸), histidine (組胺酸), arginine (精氨酸), leucine (輛胺酸), lysine (賴氨酸) with the caveat that arginine and histidine be considered conditionally essential as they are only necessary during periods of rapid growth and some other conditions.
2.4. Protein can also serve as an energy source when other sources are depleted. In particular, the branched chain amino acids (之戀胺基酸) - leucine, isoleucine, and valine - are plentiful in muscle and can be used as fuel during intense exercise. As a fuel, protein provides 4 kcal of energy per gram.
3. (Dietary) Fat provides 9 kcal of energy per gram.
3.1. Lipids (之職), which includes fats and their derivatives as well as other water-insoluble compounds (e.g. sterol 固醇) supply fuel as well as play important structural and regulatory roles.
3.2. Fat pads (脂肪墊), or adipose tissue, provide energy stores and protect the body and its organs.
3.3. Fatty Acid is the simplest type of lipid, may be Saturated (no double bonds), Monounsaturated (1 double bond), or Polyunsaturated (multiple double bonds). Unsaturation produces kinks (扭結) in fat molecules that improve fluidity and are protective against cardiovascular disease. Synthetic trans-unsaturated fats (反式脂肪) are not kinked and are thought to be detrimental to health.
3.4. Omega-3 and Omega-6 fatty acids have double bonds and are essential in the diet as human lack the enzymes required to do omega-3 and omega-6 desaturations (去飽和) (DHA is important for brain and vision).
3.5. Triglycerides (三酸甘油脂) — The body packages stored fat into triglycerides. Intramuscular triglycerides are an important fuel during exercise. High levels of triglycerides in the blood are a risk for cardiovascular disease.
3.6. Fat Acids are converted into energy through an aerobic process called betaoxidation, which occurs in mitochondria. Betaoxidation breaks down the fatty acid two carbons at a time. In order for these two carbon units to be completely oxidized, an intermediate (中間產物), oxaloacetate (草蜥蟻酸), from carb metabolism is required. With insufficient carb intake, these two carbon units form keto acids, which can be toxic.
3.7. Fat is the most significant store of energy in the body, with muscle glycogen being second.
The energy derived from food or expended as exercise may be measured in calories, kilocalories (kcal) or in Calories.
1. A calorie is the energy needed to raise the temperature of 1 gram of water 1 degree of Celsius.
2. Kcal and Calories with a large C are the equivalent of 1000 calories with a small c.
Alcohol is not a nutrient, although it’s a source of empty calories (e.g. has no nutritional value), providing 7 kcal/gram. It contributes to weight gain just as any other energy source does.
Micronutrients (微量營養素) — nutrients required in small quantities - typically micrograms (維克) to milligrams (毫克) - or in some cases, around a gram. Vitamins and minerals are micronutrients.
1. Vitamins — organic molecules that essential in small quantities for life because they cannot be synthesized by the body; divided into those which are water-soluble and fat-soluble; all are required in the diet; often act as cofactors in enzymatic reactions; often recycled in reactions rather than broken down, they tend to be required in small quantities.
1.1. Vitamin C — antioxidant, cofactor in collagen synthesis, fatty acids desaturation.
1.2. Thiamine (B-1 硫胺素), riboflavin (B-2 和黃素), niacin (B-3 菸鹼酸), Pyridoxine (B-6 必多唇), Biotin (B-7) and Pantothenic Acid (B-5 泛酸) are involved in energy metabolism. Pyridoxine (B-6) is also involved in amino acid metabolism.
1.2.1. Folate/Folic Acid (葉酸) — deficiency leading to impaired DNA synthesis; Cobalamin (B-12 估安素).
1.3. Fat-Soluble Vitamin A and D — function as hormones regulating the expression of a variety of genes, important in vision (Vitamin A) and bone (Vitamin D) formation respectively.
1.4. Beta-Carotene — a precursor to vitamin A, found in yellow and orange vegetables, also a weak antioxidant, less toxic consumed in excess than fully formed vitamin A.
1.5. Vitamin E — antioxidant, protects membrane lipids.
1.6. Vitamin K — involved in blood clotting and bone formation.
2. Minerals — help maintain the proper pH and fluid levels/pressure of the blood, divided into macrominerals and microminerals.
2.1 Macrominerals — required in greater quantities than microminerals, including: Calcium (Ca), Phosphorus (P 林), Potassium (K) — required for protein synthesis and insulin secretion, Magnesium (Mg), Sodium (Na), Chloride (CI 綠) and Sulfur (S).
2.2 Microminerals (aka trace minerals) — including: Iron (Fe) — anemia is one of the deficiency symptoms, Zinc (Zn), Copper (Cu), Iodine (I) — deficiency symptom: goiter (甲狀腺腫大), Selenium (Se), Manganese (Mn), and Chromium (Cr) — improves insulin sensitivity.
DRI (Dietary Reference Intake 膳食參考攝入量) — includes:
1. RDA (Recommended Daily Allowance 建議每日攝入量) — the amount estimated to meet the needs of virtually all healthy people.
2. AI (Adequate Intake 足夠攝入量) — used when there is not enough data to determine an RDA.
3. UL (Upper Limit) — the limit above which toxic effects may occur.
4. EAR (Estimated Average Requirement 估計平均需求量) — the amount meeting the needs of half the individuals in a group.
Carbohydrates and Fats are the main fuels for exercise and physical activity.
1. Fat predominates during low-intensity activity.
2. Both carbs and fats play a role in fueling moderate-intensity exercise.
3. Carb dominate at high-intensity exercise.
Endurance training increases fat oxidation capability, sparing (保留) glycogen; Weight training increases glycogen reserves and carb oxidation capacity.
The sources of carbs during exercise are:
1. blood glucose
2. muscle and liver glycogen
3. glucose from gluconeogenesis in the liver
4. carbs consumed during exercise.
Fat is available from Triglycerides in the muscle and those stored in adipose tissue. Fatty acid release and transport from adipose tissue occurs quickly upon initiation of exercise and is generally more than sufficient to meet the needs of the muscle. Blood lipoproteins are also a source of fat.
Protein can also provide energy for exercise through the oxidation of amino acids, especially when carb and fat stores are low. Endurance training stimulates the oxidation of amino acids at higher rates as intensity increases. Protein is not used as much as a fuel in strength training. However, both types of exercise can damage muscle fibers, leading to an increase in the need for dietary protein for repair.
Per USDA Food Guide Pyramid published in 1992, nutrient-rich foods include whole grains, vegetables, fruits, lean meats, fish, and low-fat dairy products.
The Food Guide Pyramid divides food into 5 food groups: grain, vegetable, fruit, protein, and dairy. The consumption of simple sugars as well as fats and oils should be minimized.
In contrast to the Food Pyramid Guide, the MyPlate program recommends a greater emphasis on fruits and vegetables, which are often more nutrient dense and rank lower in the glycemic index (升糖指數) than grains.
Glycemic Index — a measure of the rise in blood glucose caused by a standard amount of food - usually 50 grams. The blood glucose rise is plotted for two hours. The glycemic index is calculated as the area under the glucose curve (AUC) divided by the AUC of a standard food (white bread) times 100. Eating an excess of food with a high glycemic index increases the risk for obesity and type 2 diabetes.
Eating several small meals throughout the day helps even out blood glucose and insulin levels and helps the individual avoid hunger. Whether one eats several small meals throughout the day or 3 meals per day, it’s important that attention is paid to portion sizes and the amount of calories consumed.
* The volume of oxygen consumed (VO2) can be used to determine how many calories have been expended. Resting VO2 is about 3.5 mL of oxygen per kg of body weight per min. For every liter of oxygen consumed during exercise, about 5 kcal are burned.
*Metabolic Equivalents (METs 代謝當量) — another measure of exertion and can be related to caloric expenditure. It’s the ratio of the working metabolic rate to the resting metabolic rate. One MET = 1 kcal/kg/hour in caloric expenditure. One MET is also = an oxygen usage of VO2 of 3.5 mL/kg/min.
* One of two formulas can be used to convert METs to caloric expenditure (these two formulas give close results):
1. MET (for given exercise) * 3.5 mL oxygen/kg/min * body weight (kg) * mins exercised * 1 liter (L)/1000 mL * 5 kcal/L oxygen
2. MET (for given exercise) * 1 kcal/kg/hour * body weight (kg) * hours exercised
Carb consumption is particularly important before, during, and after endurance events.
B-complex vitamins are important in energy metabolism. Likewise, exercise may increase the need for the antioxidants beta-carotene, vitamin C, and vitamin E as increased energy metabolism and mitochondrial activity can produce greater amounts of free radicals.
Athletes - esp. endurance athletes - may have a higher requirement for iron. Aerobic exercise caused an increase loss of iron through the breakdown of hemoglobin in blood, an increased loss of iron in sweat and urine, and also increase the need for iron-containing myoglobin (肌紅蛋白) and respiratory enzymes. A simple hematocrit test (血球容積比測試) can detect iron-deficiency anemia. Since iron can be toxic in excess, iron supplementation should only be done under the supervision of a physician.
Water — comprises roughly 45 - 70% of body weight. Lean muscle mass contains significantly more water than adipose tissue does. Water lubricates tissues and transports nutrients and other chemicals into, throughout, and out of the body. Water volume maintains blood pressure, and the evaporation of water cools the body.
Hydration — fluid intake sufficient to maintain optimal body water content, is critical to health and performance.
Electrolytes — minerals that circulate in the blood as positively and negatively charged ions, include sodium, potassium, magnesium, calcium, chloride, phosphate. The main electrolytes lost in sweat are sodium and potassium. These ions are responsible for the transmission of electrical signals across nerve and muscle cell membranes, and sodium is critical to maintaining blood volume.
Dehydration — a decrease in total body water, can lead to GI distress, increased heart rate, greater muscle glycogen use, and most importantly, an inability to properly cool the body.
A drink or food containing carbs will help supply blood glucose and maximize glycogen stores. Fruit juice or sprot drinks are suitable for pre-exercise hydration. During exercise lasting more than 1 hour, fluids containing carbs and electrolytes are recommended.
Not only does hydration with sport drinks prevent overheating, it also improves performance and reduces glycogen use by supply blood glucose.
Heat and humidity increase hydration needs but so can the cold, esp. at high elevations. Cold increases the water vapor lost through respiration and may increase urinary losses. Heavy clothing may increase sweating and make cooling difficult as well.
Application of Nutrition Concepts
Body Composition
Weight Management
Eating Disorders
Maximizing Performance
BMI (Body Mass index) = Weight (kg) / Height Squared (m) — the simplest indicator of a healthy vs. an unhealthy weight, but it does not directly correlate with body fat.
1. < 18.5 — underweight.
2. 18.5 - 24.9 — healthy weight.
3. 25.0 - 29.9 — overweight.
3. >= 30.0 — obese.
While there is a correlation between BMI and the risk of diseases (e.g. diabetes, cardiovascular disease), BMI is not an accurate measure of a healthy weight for all individuals. For example, people with heavier bones or with a large muscle mass from strength training may appear to be overweight according to BMI but actually be at a healthy weight.
Body Composition — another way of assessing health, can be divided into FM (fat mass) and FFM (fat-free mass).
1. FM — the weight of body fat, can be measure in lab settings through densitometry (underwater weighing 密度測定法) and dual-energy X-ray absorptiometry (吸收測定法).
2. FFM — the weight of everything else: muscle, soft tissues, skeleton.
LBM (Lean Body Mass) = BW (Body Weight) - BF (Body Fat) — composed of organs, tissues, bones, and muscle; similar to FFM but includes fatty tissues (e.g. brain, spinal cord); typically 40-90% of body weight, which would result in BF comprising about 10-60% of body weight.
High body fat - esp. abdominal fat - is a risk factor for diabetes, cardiovascular and heart diseases, metabolic syndrome, insulin resistance, HBP, some cancers, and arthritis. Low body fat reduces the risk for these disease, but taken to an extreme, it can increase the risk for reproductive problems, osteoporosis, and a range of nutrient deficiencies.
In general, a body fat range of 10-22% for men and 20-32% for women is considered healthy.
Measurements of body composition that can be done in a fitness setting are (it’s important the client is well hydrated and has not eaten for about 3 or 4 hours prior to these assessment):
1. BOD POD (生化需氧量) — use air displacement (排氣量) to compare weight and volume.
2. Bioelectric Impedance (生物店抗阻) — based on the fact that fat contains less water than lean tissue and therefore is more resistant to the passage of an electrical current.
3. Skinfold (皮哲) — there are detailed procedures and formulas for measuring skinfold thickness with caliper (卡尺) and correlating the measurements to body fat percentage.
Other measurements that do not translate directly to body fat percentage but are indicators of the risk of disease are:
1. WHR (waist-to-hip ratio) — greater than 0.95 for men and 0.86 for women is considered unhealthy.
2. Waist Circumference — greater than 40” for men or 35” for women increase the risk of disease.
The most effective method to improve body composition is a combination of dietary change and increased exercise.
Resistance training - although it doesn’t expend many calories - can help build lean muscle mass, increasing resting metabolic rate (RMR 靜止代謝率) and possibly contributing to weight loss.
On average, it’s necessary for an individual to expend or reduce intake by 3500 kcal to lose 1 pound of body fat.
The average woman needs an intake of 2,000 kcal per day to maintain weight while the average man needs an intake of 2,500 kcal to do the same. However, these are only averages; the actual values will vary based on height, weight, age, and activity level.
The Harris-Benedict equation may be used to estimate caloric intakes for weight maintenance:
1. For males: RMR = 66 + 13.8 * body weight (kg) + 5 * height (cm) - 6.8 * age
2. For females: RMR = 655 + 9.6 * body weight (kg) + 1.8 * height (cm) - 4.7 * age
Multipliers for RMR for various activity levels will vary.
Body builders and some athletes may wish to increase their lean body mass, and as a result, their overall weight. In this case, a surplus of 400-500 kcal/day is recommended. This surplus will not exceed the body’s capability to add muscle mass so that fat gain is minimized.
* Caloric Intake = RMR + thermic effect of food + exercise expenditure + energy storage. Thermic effect of food is the energy expended in the digestion, absorption, and processing of nutrients.
* When caloric intake exceeds the first 3 terms in the equation, the excess energy is stored as fat and glycogen. When caloric intake is less than the first 3 terms, fat or other energy sources are burned. For individuals with a low RMR, weight loss can be more challenging.
Sleep deprivation (睡眠不足) is associated with insulin resistance and obesity. Sleep-deprived individuals tend to eat in greater quantity and choose high-calorie food.
Endocrine Abnormalities (e.g. diabetes) can also make weight management difficult. The insulin resistance typical of type 2 diabetes means muscles is less responsive and less able to absorb glucose from the blood and use it to build glycogen stores. Insulin is often used to lower blood glucose in diabetics and can lead to the storage of that excess glucose as fat. Exercise can help burn blood glucose, which will lower the level of insulin necessary and help to prevent weight gain.
Glucose from carbs is necessary to fuel the prolonged exercise necessary to achieve weight loss and build lean muscle mass. It’s also necessary to completely burn fats and avoid the buildup of toxic keto acids in the blood.
Excess protein consumption may strain the kidneys and increase the risk for osteoporosis, kidney stones, and some cancers.
It’s not possible to target specific body areas for weight loss as energy deficits will be met by fat loss throughout the body.
Anorexia Nervosa (神經性厭食症) — characterized by an extreme desire for thinness and fear of gaining weight. Anorexic individuals do not maintain healthy levels of body fat and consume too little essential nutrients.
Female Athlete Triad has been coined for disordered eating, amenorrhea, and osteoporosis. Calcium, magnesium, and vitamin D supplements may be helpful in ameliorating bone loss caused by the female athlete triad.
Bulimia Nervosa (神經性暴食症) — characterized by an uncontrollable urge to binge followed by compensatory actions (e.g. purging, fasting, excessive exercise, and the use of laxatives, enemas (灌腸), and diuretics (利尿劑)) to try to lose the calories consumed during the binge.
As muscle glycogen is depleted, it’s increasingly important that blood glucose be maintained for aerobic exercise.
A moderately sized pre-exercise meal is useful to maximize glycogen storage and provide blood glucose for fuel. This meal can be consumed 1 to 6 hours before the event. It should be high in carbs, with some protein, and low in fat and fiber for ease of digestion.
The consumption of carbs during lengthy exercise can avoid depletion of blood glucose and glycogen stores and improve performance. Glucose, sucrose, and maltodextrin are superior to fructose in maintaining and replacing muscle glycogen.
Post-exercise combined carb/protein meals are more effective at replenishing muscle glycogen than protein or carbs alone, and protein also provides amino acids for muscle repair. Some fat is beneficial as well to replenish triglycerides.
Performance-Enhancing Substance
Supplements may be beneficial when diet is poor or restricted for weight loss purposes, but megadoses (大劑量) may be toxic and should never be taken.
Ergogenic aids (增強劑) are substances that are used to improve exercise or athletic performance by improving energy or strength.
Anabolic steroids (合成代謝類固醇) — synthetic compounds that mimic the action of testosterone (male sex hormones), can stimulate muscle growth, resulting in improved athletic performance. However, they are illegal in competition and have serious risks associated with them.
Diuretics (利尿劑) — drugs that increase urine excretion, sometimes used by athletes to flush out anabolic steroids or other banned drugs in an effort to avoid detection, may also be used by athletes who need to meet a maximum weight limit. Dehydration is a risk.
Beta Blockers (beta受體組惦記) — slow the heart and calm the symptoms of anxiety, sometimes used by athletes (e.g. archers/shooters/golfers) to improve focus, steady the hands , and relieve competition anxiety; illegal in competition and carry serious risks.
Blood Doping (血液激增/興奮劑) — illegal method of improving performance, an artificial increase of the oxygen-carrying capacity of the blood in order to improve aerobic performance, include transfusions (書血) and EPO (erythropoietin 促紅血球生成素). Since EPO thickens the blood, it can lead to stroke and heart attack.
Peptide Hormones (勝泰激素) — banned in competition, e.g. EPO, insulin, HGH taken by body builders to increase lean body mass and decrease fat, HCG (human chorionic gonadotropin), LH (luteinizing hormone). HGH can cause heart and nerve problems as well as glucose intolerance.
Some signs and symptoms of ergogenic aids abuse that the personal trainer should be on the lookout for: mood swings (情緒波動), depression, irritability, acne, male pattern baldness, enlarged male breasts, intramuscular abscesses, increased fatty acids in the blood, HBP, heart problems, and - in women - a deepening of the voice and an increase in facial/body hair.
Creatine — legal supplement used by athletes and fitness enthusiasts,. Phosphocreatine (PCr) is plentiful in muscle and recycles ADP to produce ATP while simultaneously buffering hydrogen ions built up during muscular contraction. PCr + ADP + H+ <—> ATP + creatine
* There is some evidence that creatine supplementation may improve performance in intense, short-duration events (e.g. sprinting, weight lifting). There is a limit as to how much creatine can be stored by muscles. Short-term use of 20g/day up to 5 days appear to be effective and safe. The safety of long-term use is unknow, but there have been anecdotal reports of kidney damage and muscle cramps.
Carbohydrate loading (碳水補充) — known as glycogen loading or muscle glycogen supercompensation, a technique used by endurance athletes to maximize muscle glycogen stores.
* Carbohydrate Loading involves eating relatively low carb diet (50% of total energy) for 3 days, with an exercise regimen designed to deplete muscle glycogen. This is followed by 3 days with little exercise and a high carb diet (70% of total energy) to fuel muscle glycogen repletion to the maximum possible level. The maximization of muscle glycogen can improve performance and endurance.
