As I’m learning nutrition and metabolism in my Anatomy and Physiology class, I realize that I have many misconceptions about nutrition. It’s quite easy to decide what to eat and what not to eat based on personal taste preference or popular opinions and trends. It’s another to know the science behind it.
What I realize is that all of the nutrients are essential for our physical and mental functions. Since our body doesn’t produce many nutrients directly, we need to obtain them from the foods we eat or from dietary supplements if necessary.
I think it’s helpful to have a basic idea about the various types of nutrients, what they do, where we can get them, and how much is required on a daily basis. With this knowledge, we can be smarter about our nutritional choice.
| Functions | Daily Requirement | Sources | |
| Carbohydrates | Power cellular processes; supply our daily energy requirement
| 200-300 grams (To avoid breaking down of proteins in body tissue) | Simple Carbohydrates: honey, fruits/vegetables, diary products, cane/beet sugar, molasses (by-product of processing sugar cane and beet into sugar) Complex Carbohydrates: starch from grains and vegetables; glycogen from meats and liver
|
| Lipids (fats, oils, and fat-like substance such as phospholipids and cholesterol)
| Supply energy for cellular process; building blocks for cell membranes, steroid hormones | Must be sufficient to supply and carry fat-soluble vitamins A, D, E, K Not to exceed 30% of total daily calories (American Heart Association)
| Saturated Fats: meats, eggs, milk, butter, palm and coconut oil Unsaturated Fats: seeds, nuts, olive oil Cholesterol: abundant in liver and egg yolk, in trace amount in whole milk, butter, cheese, and meats
|
| Proteins
| Regulate metabolism (enzymes); build and repair tissues; transport drugs, vitamins and minerals; provide energy
| 0.8 gram/kg of body weight or 10% of diet | Meats, fish, poultry, cheese, milk, eggs, cereals and legumes including beans and peas |
| Fiber
| Absorbs and holds water; regulates bowl function
| Under 50: 38 grams for men and 25 grams for women; Over 50: 30 grams for men and 21 grams for women
| Whole-grains, nuts, vegetables |
| Fat-soluble Vitamins
| |||
| Vitamin A
| An antioxidant necessary for vision; normal development of bones and teeth; and maintenance of epithelial cells
| 4,000-5,000 IU | Liver, fish, whole milk, butter, eggs, leafy green vegetables, yellow and orange vegetables |
| Vitamin D
| Promotes absorption of calcium and prosphorus; promotes development of teeth and bones
| 400 IU | Exposure to sunlight, milk, egg yolk, fish liver oils, fortified foods (e.g., fortified cereal) |
| Vitamin E
| An antioxidant; prevents oxidation of vitamin A and polyunsaturated fatty acids; may help maintain stability of cell membranes
| 30 IU | Oils from cereal seeds, salad oils, margarine, shortenings, fruits, nuts, and vegetables |
| Vitamin K
| Required for blood clotting | 55-70 ug | Leafy green vegetables, egg yolk, pork liver, soy oil, tomatoes, cauliflower
|
| Water-soluble Vitamins
| |||
| Thiamine (Vitamin B1)
| Required for oxidation of carbohydrates | 1.5 mg | Lean meats, liver, eggs, whole-grain cereals, leafy green vegetables, legumes |
| Riboflavin (Vitamin B2) | Required for oxidation of glucose and fatty acids, and for cellular growth
| 1.7 mg | Meats, diary products, leafy green vegetables, whole-grain cereals |
| Niacin (Nicotinic Acid, Vitamin B3) | Required for oxidation of glucose and synthesis of proteins, fats and nucleic acids
| 20 mg | Liver, lean meats, peanuts, legumes |
| Pantothenic Acid (Vitamin B5)
| Required for oxidation of carbohydrates and fats | 10 mg | Meats, whole-grain cereals, legumes, milk, fruits and vegetables
|
| Vitamin B6 | Required for synthesis of proteins and various amino acids, for conversion of tryptophan to niacin, for production of antibodies, and for nucleic acid synthesis | 2 mg
| Liver, meats, bananas, avocados, beans, peanuts, whole-grain cereals, and egg yolk
|
| Cyanoco-balamin (Vitamin B12) | Required for synthesis of nucleic acids and metabolism of carbohydrates; plays roles in myelin synthesis; required for normal red blood cell production
| 3-6 ug | Liver, meats, milk, cheese, eggs |
| Folacin (Folic Acid)
| Required for metabolism of certain amino acids and for DNA synthesis; promotes production of normal red blood cells
| 0.4 mg | Liver, leaf green vegetables, whole-grain cereals, legumes |
| Biotin | Required for metabolism of amino acids and fatty acids, and for nucleic acid synthesis
| 0.3 mg | Liver, egg yolk, nuts, legumes, mushrooms |
| Ascorbic Acid (Vitamin C) | Required for collagen production, conversion of folacin to folinic acid and metabolism of certain amino acids; promotes absorption of iron and synthesis of hormones from cholesterol
| 60 mg | Citrus fruits, tomatoes, potatoes, leafy green vegetables |
| Major Minerals | |||
| Calcium (Ca) | Structure of bones and teeth; essential for neurotransmitter release, muscle fiber contraction, and blood coagulation; increases permeability of cell membranes; activates certain enzymes
| 800 mg | Milk, diary products, leafy green vegetables |
| Phosphorus (P)
| Structure of bones and teeth; in nearly all metabolic reactions; in nucleic acids, many proteins, some enzymes, and some vitamins; in cell membrane, ATP, and phosphates of body fluids
| 800 mg | Meats, cheese, nuts, whole-grain cereals, milk, legumes |
| Potassium (K)
| Help maintain intracellular osmotic pressure and regulate pH; required for nerve impulse conduction
| 2,500 mg | Avocados, dried apricots, meats, nuts, potatoes, bananas |
| Sulfur (S)
| Essential part of certain amino acids, thiamine, insulin, biotin, and mucopolysacharides
| No RDA * established | Meats, milk, eggs, legumes |
| Sodium (Na)
| Help maintain osmotic pressure of extracellular fluids; regulates water movement; plays a role in nerve impulse conduction; regulates pH and transport of substances across cell membranes
| 2,500 mg | Table salt, cured ham, sauerkraut, cheese |
| Chlorine (Cl)
| Help maintain osmotic pressure of extracellular fluids, regulates pH; maintains electrolyte balance; forms hydrochloric acid; aids transport of carbon dioxide by red blood cells
| No RDA * established | Table salt, cured ham, sauerkraut, cheese |
| Magnesium (Mg) | Required in metabolic reactions in mitochondria that produces ATP; plays a role in the breakdown of ATP to ADP
| 300-350 mg | Milk, diary products, legumes, nuts, leafy green vegetables |
| Trace Minerals | |||
| Iron (Fe)
| Part of hemoglobin molecules; catalyzes formation of vitamin A; incorporated into a number of enzymes
| 10-18 mg | Liver, lean meats, dried apricots, raisons, enriched whole-grain cereals, legumes, molasses |
| Manganese (Mn)
| Activates enzymes required for fatty acids and cholesterol synthesis; formation of urea, and normal functioning of the nervous system
| 2.5-5 mg | Nuts, legumes, whole-grain cereals, leafy green vegetables, fruits |
| Copper (Cu)
| Essential for hemoglobin synthesis; bone development, melanin production, and myelin formation
| 2-3 mg | Liver, oysters, crabmeat, nuts, whole-grain cereals, legumes |
| Iodine (I) | Essential component for synthesis of thyroid hormones
| 0.15 mg | Food content varies with soil content in different geographic regions; iodized table salt |
| Cobalt (Co) | Component of cyanocobalamin; required for synthesis of several enzymes
| No RDA * established | Liver, lean meats, milk |
| Zinc (Zn) | Component of enzymes involved in digestion, respiration, bone metabolism, liver metabolism; necessary for normal wound healing and maintaining the integrity of the skin
| 15 mg | Meats, cereals, legumes, nuts, vegetables
|
| Fluorine (F) | Component of tooth structure
| 1.5-4 mg | Fluoridated water |
| Selenium (Se) | Components of certain enzymes
| 0.05-2 mg | Lean meats, fish, cereals |
| Chromium (Cr) | Essential for use of carbohydrates
| 0.05-2 mg | Liver, lean meats, wine |
* RDA = recommended daily allowance
* IU = international unit
Source: Hole’s Human Anatomy & Physiology, Twelfth Edition, by Shier.Butler.Lewis
So what do you think? Does your typical diet contain all of the essential nutrients you need?
For me, I realize that many of the foods that I have not been eating very much – for no good reasons other than personal preference or vague ideas I get from popular media – such as liver, egg yolk and milk are actually excellent sources of many essential nutrients, especially the organic versions which are free of hormones and antibiotics.
Our diet is so important for our health and wellbeing. I’m going to broaden my food choices to ensure that they’re well balanced and contain all of the essential nutrients if possible. I hope you’ll too!
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