Only ingested carbohydrates, proteins and lipids will count towards total caloric intake and will be digested into monomers like glucose for absorption and assimilation. National Health Service (2012) recommends daily caloric intake of 2500Kcal and 2000Kcal which will be derived from the proteins, lipids and carbohydrate sources in a diet for average adult males and females respectively.
Age, sex, health condition and physical activities influence dietary needs. This essay will discuss a balanced diet for an adult including the structure, sources, functions, recommended daily allowance (RDAs), deficiency and excessive effects of the macronutrients. Also the micronutrients and water which are not considered as nutrients will be discussed.
THE FOOD PYRAMID
Carbohydrates contain carbon, hydrogen and oxygen. British Nutrition Foundation (2013), recommends that 47.7% (203g) and 48.5% (275g) of daily energy should come from carbohydrates for females and males respectively with 29g being roughages. Carbohydrates exist naturally or refined as monosaccharides that are reducing sugars. Monosaccharides build the complex carbohydrates, disaccharides and polysaccharides through dehydration synthesis. Monosaccharides have general formula (CH2O)n where n determines whether pentose(5Carbons) or hexose (6Carbons). Glucose found in maple syrup, fructose in corn syrup and galactose in honey are hexose-isomers; having the same formula, C6H12O6 but different structures.
The disaccharides with the general formula C12H22O11 are sucrose made from fructose and glucose, maltose from two glucose molecules and lactose from galactose and glucose. Sucrose is derived from beet sugar, lactose from milk and maltose from vinegar. The polysaccharides with general formula (C6H10O5)n where 40â‰¤nâ‰¤3000, exist as starch or non-starch polysaccharides (NSPs) which can be soluble or insoluble. Starch consists of glucose molecules joined by glycosidic bonds.
The NSPs include oligosaccharide (raffinose) and cellulose (dietary fibre). Potatoes, yams and cassava are rich in starch and are very digestible. Whole grain cereals, legumes (appendix2), fruits and storage vegetables like asparagus and cabbage are rich in the NSPs. Raffinose is an indigestible trisaccharide of fructose,glucose and galactose with formula C18H32O16. Animal sources of carbohydrates are liver and scallops.
Carbohydrates provide sweetness and are the primary source of energy especially for brain and blood cells. Cellular respiration converts glucose monomers into ATP. Fats cannot be oxidised without glucose. Most NSPs are partially digestible or indigestible due to lack of Î±-galactosidae (enzyme) in GI Tract. They reduce glycaemia index and plasma cholesterol levels, increase bile acid excretion, promote normal laxation and prevent breast cancer, gallstones, haemorrhoids, and irritable bowel syndrome (Kumar et all 2012).
Furthermore, Kumar (2012) concluded that excessive carbohydrates will cause dental decay, kidney damage, stroke, diabetes due to obesity and short term conditions like hyperglycaemia. Carbohydrate deficiency will cause constipation, fatigue, weak immunity, muscle cramps and ketosis; this is very rare as 50g/day of carbohydrate is needed to prevent ketosis.
THE DEHYDRATION SYNTHESIS TO FORM MALTOSE
EQUATION: (C6H12O6 + C6H12O6 = C12H22O11 + H2O)
(Marshall University 2012)
Proteins or polypeptides consist of three to 100000 or more long chains of the organic molecules called amino acids joined together by covalent peptide bonds. A protein of two amino acids is called a dipeptide. There are 20 common forms of amino acids either termed non-essential (synthesised by the liver) and essential that needs to be ingested. Proteins consist of a central carbon atom, a hydrogen atom, amino group (-NH2), Carboxylic group (-COOH) and the variable R group (figure3).
The term amino acid is derived from the amino and carboxylic groups that all amino acids have in common. According Kuil (2012), principal sources of proteins are lean meat, seafood, poultry, eggs, cereals, legumes (refer to appendix3), cereals and processed food like low-fat milk.
Proteins form about 45% of human body and perform the following seven essential functions: structural (hair, ligaments), contractile (muscles), transport (haemoglobin), metabolic regulation (enzymes), buffering, defence (antibodies) and coordination and control (hormones) (Martini 2006). Haemoglobin transports oxygen and a lack of protein (haemoglobin) can deny vital organs the needed oxygen for metabolism.
Protein deficiency can also cause fatigue, anaemia, weak immunity, skin problems, impairment of cognition and mental health problems. Whereas excessive proteins can cause obesity, osteoporosis and kidney stones (Georgetown University 2012). About 15% of an adults caloric intake should come from protein equivalent to 56g and 46g for male and female respectively (Centre for Diseases Control and Prevention, 2012).
DEHYDRATION OF AMINO ACIDS TO FORM DIPEPTIDE PROTEINS
(Marshall University 2012)
Lipids are made up of an even number of carbon from 12 to 20, oxygen, hydrogen and sometimes traces of phosphorus, sulphur or nitrogen. Lipids are grouped into 4: steroids, phospholipids, waxes and glycerides. Most of the 70 identified lipids are synthesised by the body whereas linoleic (omega6) and alpha-linolenic (omega3) acids are two essential lipids to be ingested.
They are mostly insoluble due to the long chain of hydrophobic carbon-carbon end bonded to a short hydrophilic carboxyl group. The double covalent bond, (C=C) determines whether saturated (no C=C) or monounsaturated (1 C=C) or polyunsaturated (2 or more C=C). Glycerides are made up of glycerol bonded to 1 or more fatty acids by dehydration synthesis, triglyceride with 3 fatty acids is the predominant of the lipids (refer figure4). Unsaturated sources of lipids are olive oil, peanut, salmon, halibut and avocados. Saturated sources are butter, sausage and hydrogenated oil.
According to British Dietetic Association (2013), adults should consume not more than 20-30g of saturated-fat with 5g or less being trans-fat since saturated lipids are high in cholesterol. The structural lipids form cell membranes. Also fat cushions and protects organs including liver, heart, and kidney, energy source; twice as much as carbohydrates and proteins, thermoregulation (insulation), sex hormones, transport vitamins and monounsaturated fat can decrease cholesterol levels (USA Department of Agriculture, 2010). Excessive consumption of lipids will lead to obesity which is characterised by high BMI as shown in appendix 2, cardiovascular diseases, hypertension, colorectal cancer and diabetes, whereas deficiency will result in the body lacking the vital vitamins A,D,E and K (Schenker, 2012).
DEHYDRATION SYNTHESIS TO FORM TRIGLYCERIDE
(Marshall University 2012)
The micronutrients, vitamins and minerals are needed in minute quantities. Minerals can be classified as major or trace of which a few are essential including sodium, potassium, magnesium, zinc, iron, calcium, iodine, etc. (refer to appendix4 for RDAs). According to Higdon and Drake (2011), sources of minerals are plants that derive them from the soil and move on the food chain to the herbivores like cattle that eat them. Spinach, legumes, whole grains, dairy products, red meat, soybeans, salmon, cod, iodised table salt (iodine, sodium, chlorine) and eggs are excellent sources of minerals.
According to Whitley and Rolfes (2011), minerals perform the following functions: the electrolytes, sodium, potassium and chlorine transmit nerve impulses, control fluid balance (providing optimum pH for enzyme activities), control blood pressure and relax and contract muscles. Zinc, copper and selenium are antioxidants; they reduce the risk of heart diseases. Iron forms haemoglobin. Sodium and potassium coregulate ATP production. Calcium and phosphorus control blood clotting and together with magnesium build bones, teeth, maintain muscle and nerve cells. Iodine is needed for the production of thyroxin; deficiency will cause goitre.
Since some minerals are coenzymes, deficiency will cause malfunctioning cellular activities (digestion, metabolism). Iron deficiency causes anaemia whereas calcium, phosphorus and magnesium (hypocalcaemia) deficiency will cause osteoporosis. Calcium, magnesium and the electrolytes deficiencies will cause weakness, muscle cramps and impaired alertness. Zinc deficiency causes diarrhoea, skin and prostate cancers. Their intake should be balanced with use and excretion as excess may cause Hyperkalaemia (potassium), kidney-stones (calcium) and hypernatremia (sodium).
Vitamins are grouped into water soluble (WSV) including C and B complex vitamins; they cannot be stored and therefore, it is imperative to be part of a balanced diet, and fat soluble (FS) including vitamins K,E,D, and A; they can be stored (refer appendix 5 for RDA). Green leafy vegetables (lettuce), oranges, kiwi fruit, avocados, whole grains and cereals, banana, dairy products, liver, poultry, pork, oily fish, eggs, soybeans, chickpeas and nuts are excellent sources of the vitamins (Firth 2011). Vitamin K can be synthesised in the intestine which helps the blood clot whereas Vitamin D can be synthesised by the body using sunlight to help the absorption of calcium and phosphorus (Cranney et al (2010). Vitamins A and C build immunity. Vitamins B1,B2,B3, and biotin help release energy.
Vitamin A, niacin and pantothenic acid aid the absorption and use of macronutrients monomers. Vitamin C makes collagen and enhances folate absorption. Vitamin deficiency generally causes weak immunity and osteoporosis (Vitamin D), scurvy (Vitamin C), beriberi (B1), anaemia (B12 and folate) and night blindness (Vitamin A). Excessive amounts of vitamins E and K are usually not harmful but excess A,D and the WSV which can be excreted cause kidney problems and hypercalcaemia (excess D). Excessive vitamin C causes diarrhoea (NHS 2012).
In conclusion, spending excessively on supplements and creams as well as engaging in dangerous diets like the Atkins Diet are not necessary. The secret to healthy living is carefully selecting the right proportions of food from the Eatwell plate, drinking enough water in combination with regular exercises. Figure 5 and appendix 6 show functions of water. Consider the positives and negatives when selecting food products such as red meat; rich in protein but high in cholesterol whereas fatty fish enhances calcium absorption.
Soybean, liver, green leafy vegetables, whole grains and legumes will provide almost all the nutrients; combine them in your diet in right proportions for optimal hormonal, metabolic, mental and physical functions of the body. It is important to consult a doctor before starting any diet as nutritional needs are affected by health and some medications affect absorption of nutrients.
FUNCTIONS OF WATER IN THE BODY
Mayo Foundation for Medical Education and Research, 2013
LIST OF APPENDIXES
|SERVINGS PER DAY | |Carbohydrates including bread, pasta, rice, potatoes and other starchy foods |6-10 servings | |Fruits and vegetables |3-5 servings | |Meat, fish, eggs, beans and nuts |2-3 servings | |Milk and dairy foods |2-3 servings | |Food and drinks high in fat and/or in sugar |Use sparingly |
University of Michigan Integrative Medicine, 2010
APPENDIX 2: OBESITY AND BODY MASS INDEX (BMI)
|BMI |LEVEL OF OBESITY | |Below 18.5 |Underweight | |From 18.5-24.9 |Healthy Range | |From 25-30 |Pre Obese | |Above 30 |Obese |
APPENDIX 3: FOOD GROUPS AND EXAMPLES
|FOOD GROUP |EXAMPLES | |Legumes |Beans, Lentils, Peas, Chickpeas, French beans, Kidney , soybeans, Coco beans etc. | |Whole grains |Barley, Corn, Millet, Oats, Rice, Milo, Wheat
| |Green leafy vegetables |Spinach, Broccoli, Lettuce, Cabbage, Mustard green, Kale examples |
APPENDIX 4: MINERALS AND THEIR RDA
|SYMBLE |SOURCES |RDA | |Na (Sodium) |Table Salt, Sea vegetables, spinach, milk |6g | |Ca (Calcium) |Salmon, Sardine, eggs, dairy products, nuts, oregano |700mg | |K (Potassium) |Spinach, legumes, tomatoes, banana, avocado, whole grains and |3500mg | | |yams | | |P (Phosphate) |Fish, poultry, oats, rice, red meat, |700mg | |Fe (Iron) |Eggs, spinach, shrimps, soybeans, lentils, tomatoes, olives, |M=8.7mg / F=4.8mg | | |tomatoes | | |Mg (Magnesium) |Spinach, soybean, sea vegetables, tomatoes, beans, brazil nuts|M=300mg / F=270mg | |I (Iodine) |Eggs, milk, fish, shellfish, yoghurt, strawberries, iodised |0.14mg | | |salt | | |Se (Selenium) |Cod, salmon, garlic, lamb, cheese, calf liver, barley, brazil |75mcg | | |nuts | | |Zn (Zinc) |Calf liver, spinach, eggs, oats, oyster, lean pork and beef, |M=5.5-9.5mg / F=4-7mg | | |asparagus | |
USA Department of Agriculture / Department of Health, 2010
APPENDIX 5: VITAMINS AND THEIR RDAS
|VITAMIN |SOURCES |RDA | |Retinol (A) |Liver, fish oil, carotenoids, milk fortified |M=0.7mg / F=0.6mg | |Ascorbic acid (C) |Citrus (oranges), kiwi fruit, broccoli |40mg | |Thiamin (B1) |Liver, pork, whole grains and products |M=1mg / F=0.8mg | |Riboflavin (B2) |Liver, eggs, milk, rice, mushrooms |M=1.3mg / F=1.1mg | |Niacin (B3) |Poultry, fish, beef, peanut butter, legumes |M=17mg / F=13mg | |Pyridoxine (B6) |Liver, pork, legumes, fish, whole grains |M=1.4mg / F=1.2mg | |Cobalamin (B12) |Beef, poultry, cod, salmon, cheese, eggs |0.0015mg | |Vitamin E |Vegetable oil, green vegetables, nuts |12mg | |Folate |Broccoli, peas, asparagus, brown rice |0.2mg | |Pantothenic acid |Milk, fruits, veggies, meat, fish, grains |10mg | |Biotin |Cottage cheese, liver, eggs, peanut, grain |300mcg | |Vitamin K |Green vegetables, fruits, nuts |75mg | |Note that Vitamin K can be synthesised in the intestine whereas Vitamin D can be derived salmon, fortified cereals and juices, milk and | |sunlight (No RDA but 15minutes in the sun thrice a week is enough) |
USA Department of Agriculture / Department of Health, 2010
APPENDIX 6: RECOMMENDED DAILY ALLOWANCE FOR WATER
|SEX |RDA FOR WATER | |MALE |3.7L with no upper limit increase with exercise to rehydrate | |FEMALE |2.7L with no upper limit increase with exercise to rehydrate and increase intake when | | |breast feeding. |
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