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a diet containing the essential nutrients with a reasonable ration of all the major food groups.
a diet containing adequate energy and all of the essential nutrients that cannot be synthesized in adequate quantities by the body, in amounts adequate for growth, energy needs, nitrogen equilibrium, repair, and maintenance of normal health.
balanced dietA diet containing proportionate amounts of those food groups which are considered to be optimal for good health. A properly balanced diet should: be highest in fruits and vegetables; have a moderate amount of refined carbohydrates (e.g., breads and cereals), fish and dairy products; lesser amounts of meat; and minimal amounts of fats (e.g., butter) and refined sugars.
balanced dietClinical nutrition A diet with proportionate amounts of foods which are optimal for good health. See Food groups, Food pyramid.
bal·anced di·et(bal'ănst dī'ĕt)
A diet containing the essential nutrients, with a reasonable ration of all major food groups.
balanced dietan intake of the various types of food, including vitamins, minerals and roughage, in such proportions as to promote good health.
balanced dieta diet which provides adequate intake of both macronutrients and micronutrients, proper regulation of metabolic processes, and maintenance of an optimal body mass. In general, dietary guidelines for the average population are also applicable to athletes, but there are differences for athletes in the recommended intake of macronutrients, in terms of grams per day, grams per day per kg body mass or percentage of energy intake from each of the main foodstuffs. See also dietary reference values (DRV); Table 1, Table 2, Table 3, Table 4.
|Energy value||Reference nutrient intake (RNI)||Sources||Functions||Deficiency||Excess||Notes|
|Carbohydrate 1 g yields 16 kJ (3.75 kcal)||Minimum of 47% of total daily energy intake; not >10% should be provided by added sugars. RNI for non-starch polysaccharide: 18 g/d||Sugar, potatoes, rice, pasta, noodles, bread, breakfast cereals||Provides energy for metabolism||Weight loss, ketosis||Obesity, elevated blood triglyceride||Diets high in carbohydrate tend to be low in fat|
|Protein 1 g yields 17 kJ (4 kcal)||Meat, fish, eggs, nuts, pulses, dairy products, tofu, Quorn||Component of all body tissues; energy source in some situations||Retarded growth; weight loss and muscle wasting; poor wound healing; impaired immune system; fat deposition in the liver||Possible link with loss of minerals from bone and age-related deterioration in renal function||Protein content of Western diets is usually higher than the RNI|
|Fat 1 g yields 37 kJ (9 kcal)||Should not exceed 35% of total daily energy intake. Of this no more than 10% should be saturated fatty acids||Butter and other full-fat dairy products, margarine; cooking oils and fried food; pastry, cakes, biscuits; meat, oily fish, seeds, nuts, chocolate, crisps||Provides energy for metabolism; energy stores and insulation in body fat; synthesis of steroid hormones; constituent of cell membranes, and of nerve fibres||Weight loss; deficiency of essential fatty acids can lead to neurological damage||Obesity, with increased risk e.g. of cardiovascular disease and some cancers||Normal development of the nervous system depends on the essential fatty acids, linoleic and alpha linolenic|
|Vitamin||RNI (DoH 1991)||Sources||Action/functions||Deficiency||Excess||Special points|
|Vitamin B group|
|B1 Thiamin(e)||0.4 mg/1000 kcal||Fortified breakfast cereals, yeast extract, vegetables, fruit, wholegrain cereals, milk, liver, eggs, pork||Coenzyme for carbohydrate metabolism||Encephalopathy can occur with alcohol excess and low food intake. Beri-beri where polished rice is staple||Headache, insomnia, irritability, contact dermatitis||Requirement related to carbohydrate intake|
|B2 Riboflavin||Milk, milk products, offal, yeast extract, fortified breakfast cereals||Coenzyme for the metabolism of carbohydrate, fat and protein||Fissures at corners of mouth; tongue inflammation; corneal vascularization||No toxic effects, since large quantities are not absorbed||Destroyed by sunlight|
|B3 Niacin (nicotinic acid and nicotinamide)||6.6 mg/1000 kcal as nicotinic acid equivalents||Meat, fish, yeast extract, pulses, wholegrains, fortified breakfast cereals||Energy metabolism, as part of coenzymes NAD and NADP involved in oxidation and reduction reactions||Pellagra: dermatitis, diarrhoea and dementia||Liver damage, skin irritation||Also synthesized from the amino acid tryptophan|
|B5 Pantothenic acid||None set||Widespread in food, e.g. liver, eggs, yeast, vegetables, pulses, cereals||Protein, fat, carbohydrate and alcohol metabolism||Vomiting, insomnia||Not reported|
|B6 Pyridoxine||Meat, fish, eggs, some vegetables, wholegrains||Production of haemoglobin and of coenzymes involved in many metabolic processes||Rare. Metabolic and nervous system disorders||Peripheral nerve damage||Requirement is related to protein intake|
|Biotin||None set||Widely distributed in many foods, e.g. offal, egg yolk, legumes, etc. Can be synthesized by intestinal bacteria||Essential in fat metabolism||Rare; dermatitis, hair loss, nausea, fatigue and anorexia||None known|
|B12 Cobalamins||15 μg/g of protein||Animal products, meat, eggs, fish, dairy products, yeast extract||Anaemia; irreversible spinal cord damage||Not reported|
|Folates (folic acid)||200 μg/d||Green leaf vegetables, bread, fortified breakfast cereals, yeast extract, liver||Red blood cell production; DNA synthesis||Can mask the effects of B12 deficiency||Supplements before and during pregnancy reduce the incidence of spinal cord defects|
|Vitamin C ascorbic acid||40 mg/d||Collagen synthesis, formation of bones, connective tissue, teeth. Iron absorption for red blood cell production. Acts as an antioxidant||Sore mouth and gums; capillary bleeding; scurvy; delayed wound healing, scar break down||Diarrhoea; oxalate stones in kidneys||Destroyed by cooking in the presence of air and by plant enzymes released when cutting and grating raw food|
|Vitamin A retinol||As retinol in liver, kidney, oily fish, egg yolk, full-fat dairy produce. As the provitamin carotenes in green, yellow, orange and red fruit and vegetables, e.g. broccoli, carrots, apricots, mangoes, sweet potatoes and tomatoes||Visual pigments in retina, aids night vision. Normal growth and development of tissues; essential for healthy skin and mucosae. Acts as an antioxidant||Poor growth; rough dry skin and mucosae; xerophthalmia and eventual blindness; increased risk of infection; poor night vision||In pregnancy, high doses can cause fetal malformations||Synthesized in the body from carotenes present in the diet|
|Vitamin D cholecalciferol ergosterol||10 μg/d if housebound||Oily fish, egg yolk, butter, fortified margarine; action of ultraviolet rays (sunlight)||Calcium and phosphorus homeostasis||Rickets (children); osteomalacia (adults)||Rare; weight loss and diarrhoea||Produced in the body by action of sunlight on a provitamin in the skin: deficiency develops in those who are not exposed to sun|
|Vitamin E tocopherols tocotrienes||None set||Wheat germ, vegetable oils, nuts, seeds, egg yolk, cereals, dark green vegetables||Neurological abnormalities; anaemia: rare, from malnutrition or malabsorption||Muscle weakness, gastrointestinal disorders||Requirement is increased with increased intake of polyunsaturated fatty acids|
|Vitamin K phylloquinones menaquinones||None set||Green leafy vegetables, fruit and dairy products||Needed for the production of prothrombin and other coagulation factors||Impaired clotting; liver damage||Not so far observed from naturally occurring vitamin||Synthesized by intestinal bacteria so deficiency unusual|
|Name and chemical symbol||Reference nutrient intake (adults, per day)||Sources||Functions||Deficiency||Excess|
|Calcium Ca||700 mg||Milk and milk products, green vegetables, soya beans, white bread, hard water||Calcium deposits in soft tissue can occur, but probably not related to high intake|
|Chlorine Cl||3.4 g (as chloride)||Salt-containing foods||Unlikely with normal diet||As NaCl, risk factor for high blood pressure|
|Chromium Cr||25 μg||Vegetables, cereals, meats, vegetable oils, whole grains||Co-factor for some enzymes involved in glucose and energy metabolism|
|Copper Cu||900 μg||Meat, drinking water||Co-factor for some enzymes; intermediate in electron transfer during oxidative phosphorylation||Low activity of antioxidant enzymes||Very high intake can cause liver damage|
|Iodine I||140 μg||Seafood, iodized salt, milk and milk products, meat and eggs||Synthesis of thyroid hormones||Thyroid swelling (goitre) with hypothyroidism: low BMR, lethargy||Rarely any effect; may exacerbate some skin diseases|
|Iron Fe||Liver, kidney, red meat, egg yolk, wholegrains, pulses, dark green vegetables, dried fruit, treacle, cocoa, molasses||Component of haemoglobin, myoglobin and many enzymes||Can be toxic if very excessive. (from blood transfusions rather than from diet); gastrointestinal upset; may promote vascular disease|
|Fluoride F||3-4 mg||Drinking water, mostly as calcium fluoride; tea, seafood||May be important in maintenance of bone structure||Increased risk of tooth decay||Unlikely from dietary sources|
|Magnesium Mg||Cereals, milk, nuts, seeds, and green vegetables||Co-factor for enzymes essential in metabolism; role in calcium homeostasis; skeletal development; neuromuscular function||Uncommon; can occur with malabsorption or in chronic renal failure, when it accompanies hypocalcaemia||Unlikely from dietary sources|
|Phosphorus-P||550 mg (as phosphate)||Milk, cheese, yogurt, meat, poultry, grains, fish||Adenosine phosphate compounds vital in energy metabolism. With Ca in bones and teeth||Only in severe malnutrition; muscle weakness, bone pain, rickets, anorexia, anaemia||In treatment of osteoporosis or bone cancer with biphosphonates|
|Potassium K||3.5 g||Fruit, vegetables, meat, wholegrains||High ECF [K+] (hyperkalaemia) causes cardiac arrest|
|Selenium Se||Seafood, meat, grains, wheat flour||Key component in the endogenous antioxidant, glutathione peroxidase||Health implications of low intake in UK currently under DoH review. May cause abnormality of heart muscle||Excessive supplements: hair loss, skin rash, neurological disorder|
|Sodium Na||1.6 g||Mainly as salt: table salt, and in milk, meat, vegetables, sauces, pickles, processed foods, snacks, cheese||Major extracellular cation; linked to ECF volume, hence to blood volume and blood pressure. Component of bone mineral||Loss in sweat and diarrhoea; dilution in body fluids due to excess water intake. Weakness, cramp; faintness, confusion||Oedema, hypertension|
|Zinc Zn||Red meat, dairy products, eggs, wholegrains, peas, beans, nuts, lentils|
|Substance||Description||Claimed ergogenic effect||Supporting evidence|
|With clear scientific evidence|
|Caffeine||Stimulant in coffee and tea||Improves performance in most events, except very short high-intensity exercise; increases cognitive functioning during exercise.|
|Creatine||Carrier of high-energy phosphates in muscle||Increases the energy reserve, improves strength, reduces fatigue, and increases protein synthesis||Increases intramuscular Cr and PCr; improves performance in repeated sprint bouts (and reported to do so after even a single bout); improves recovery between bouts (but response varies between individuals). Anabolic properties unclear.|
|Buffers||Improves high-intensity exercise performance by limiting decrease in pH in ECF as a whole and indirectly in muscle ICF||Large doses can improve performance|
|With mixed scientific evidence|
|Antioxidant nutrients||Vitamins, especially C and E||Provides protection against muscle damage by reducing oxidative stress||Benefits established at cellular level; no detectable aid to performance|
|Arginine||Amino acid in normal diet||Stimulates release of growth hormone, promoting gain in muscle mass and strength||Some evidence of GH promotion when combined with other amino acids (ornithine, lysine, BCAA); no conclusive evidence of effect when taken alone|
|Branched-chain amino acids (BCAA)||Leucine, isoleucine and valine||No good evidence of improved endurance performance. Evidence of accelerated recovery from muscle fatigue when given with other amino acids during eccentric exercise training|
|Glutamine||Amide of amino acid glutamate||Maintains a healthy immune system during training and improves muscle glycogen resynthesis||Does not affect immune function; possibly affects muscle glycogen resynthesis|
|Glycerol||Component of triacylglycerol molecule||Induces hyperhydration, decreases heat stress, and improves performance||Does have the first two actions, but effects on performance are unclear|
|Lacking scientific support|
|Androstenedione||Synthetic product||Increases testosterone and thus muscle mass and strength, and improves recovery||Does not increase testosterone secretion; has no effect on strength|
|Hydroxy-methyl butyrate (HMB)||Metabolite of the amino acid leucine||Enhances gain in body mass and strength associated with resistance training, and improves recovery||Possible small effects only on lean body mass and strength|
|Boron||Micronutrient present in vegetables and non-citrus fruits||Increases testosterone levels, to improve bone density, muscle mass, and strength||Improves bone mineral density in postmenopausal women; no effect on bone density, muscle mass or strength in men|
|Carnitine||Substance important for fatty acid transport into mitochondria||Improves fat oxidation, helps weight loss||No supporting evidence|
|Choline||Precursor of acetylcholine||Improves performance, decreases fatigue and enhances fat metabolism||No supporting evidence|
|Chromium (chromium picolinate)||Micronutrient that potentiates insulin action||Promotes fat oxidation and muscle building||No supporting evidence|
|Coenzyme Q10||Part of the electron transport chain in the mitochondria||Improves aerobic capacity and cardiovascular dynamics||No supporting evidence|
|Ginseng||Root of the Araliaceous plant||Improves strength, performance, stamina, and cognitive functioning; reduces fatigue||No supporting evidence|
|Inosine||Nucleoside found naturally in brewer's yeast and organ meats||Increases ATP stores, improve strength, training quality, and performance||No supporting evidence|
|Medium-chain triacylglycerols (MCT)||Triglycerides containing fatty acids with a carbon chain length of 6-10||Improves energy supply, reduces rate of muscle glycogen breakdown, and improves performance||No supporting evidence|
|Pyruvate||End-product of aerobic glycolysis||Improves endurance capacity and recovery; increases glycogen storage||Limited supporting evidence|
|Polylactate||Polymer of lactate||Provides energy||No effects on performance|
|Wheat germ oil||Wheat embryo extract||Improves endurance||No supporting evidence|
bal·anced di·et(bal'ănst dī'ĕt)
Diet containing essential nutrients with a reasonable ration of all major food groups.