Food at Work
Given below are the types of food that are capable of specific functions. These have to be consumed in specified quantities and at specified intervals.
Proteins are the body building nutrients. In order that your body be able to use proteins for body building, these must always be eaten in conjunction with carbohydrates and fats, that is, with adequate energy giving foods and nutrients.
The body building food could be from two sources - plant and vegetable foods and animal foods. They are pulse, lentil, and legume; nut and oilseed; milk and milk products; meat, poultry and seafood (which contribute significantly to fats).
Dried pulses are rich in proteins (containing about 19 to 24 percent). Puffed pulses that are consumed as snacks are also very healthy.
Nuts and oilseeds (except
coconut) contain about 18 to 40 percent proteins. Soybean is high in protein about 40%. They are used as milk substitutes that can be fed to infants.
Milk is among the most wholesome of foods though it does not remedy deficiencies of iron and vitamins C and D. One litre of cow's milk provides about 35 gm of protein and 35 gm of fat (buffalo's milk has twice the amount of fat than does cow's milk).
Meat, poultry and seafood are high protein foods. Both Meat and Fish contain 18-22 percent proteins. Egg white contains 12 percent protein, egg yolk contains 15 percent protein. Liver contains 18-20 percent protein.
Carbohydrates and fats are energy giving nutrients. Proteins also give you energy. Other energy giving foods are cereals, sugars, roots and tubers, fats and oils, and alcohol. Cereals are the staple foods of a large majority of the population of the world and they provide 70 to 80 percent of the energy.
Sugars are simple and pure carbohydrates that serve mainly as a source of concentrated energy. In industrialised countries sugar has become an important source of energy.
Roots and tubers in general are good sources of carbohydrates alone and form the staple food in some countries. They can be used as partial substitutes for cereals. They do not provide the proteins that cereals do.
Fats and oils provide double the quantity of energy when compared to carbohydrates. Alcohol provides greater energy per gram than do carbohydrates, but it has to be used with caution and in limited quantities.
Protectors and Regulators
The protective and regulatory nutrients are vitamins and minerals.
Let us take a look at the minerals the body needs.
Most growing organisms need or have 'organic' chemicals such as carbon, oxygen, nitrogen and hydrogen. Apart from these the human body needs 28 inorganic chemical elements.
The most important minerals that the
body needs (and that comprise more than seven grams of adult body weight
and involve a daily consumption of 100 mg) are - calcium, phosphorus,
magnesium, sodium, potassium, chloride and sulphur.
The less important elements or Trace
Elements (that comprise less than seven grams of adult body weight and
involve a daily consumption of less than 100 mg) are - iron, zinc, copper,
iodine, manganese, chromium, cobalt, molybdenum, selenium and fluoride.
Other minor elements, essentially
nitrogen, can be subdivided into seven major and 10 minor or trace
elements. Some of these elements are silicon, vanadium, nickel, tin,
cadmium, aluminium, arsenic, strontium, barium, boron and lithium.
Calcium and phosphorus are important for the bones and teeth.
Sodium, potassium and chloride maintain the electrolyte/acid-base balance of the body.
Iron is essential for generation of blood.
Zinc is essential for growth as well as fast wound healing.
Iodine is essential for the thyroid
gland, and helps to prevent a deficiency disorder called goitre
(swelling of the thyroid).
Fluoride is essential for strong, sparkling teeth - which is why we find fluoride in toothpaste.
These are thirteen complex
organic compounds. Some, like the following,
are water soluble: ascorbic acid - vitamin C, B complex - thiamin (B1), riboflavin (B2), pathothenic acid, niacin, pyridoxine (B6), biotin, folic acid, and cyanocobalamin (B12). Some, like the
following, are fat soluble: such as vitamins A, D, E and K.
Vitamin A is essential for eyesight. Bitot's spots and Night Blindness are associated
with vitamin A deficiency. This also adversely affects
skin and organ linings. That is why you have ointments with Vitamin A for
Acne and Pimples.
Vitamin B complex - A
deficiency of this vitamin affects appetite, the skin, eyes, lips, blood
and the nervous system. For example, a deficiency of Thiamin (B1) causes a
disease called Beriberi. Deficiency of Niacin causes a disease called
Vitamin C is essential for the gums. A
deficiency of this vitamin causes a disease called Scurvy. Vegetables and
fruits, particularly citrus fruits are rich sources of vitamin C.
Vitamin D is essential for bones and the skeletal system. A deficiency of this
vitamin in a child causes rickets, bowlegs, pigeon chest and brittle bones
that are easily fractured. In adults, osteoporosis (melting of bones) and
osteomalacia are major problems.
Vegetables and fruits are hence the protective and regulatory foods that are rich in the numerous vitamins and minerals listed above.
Requirement and Absorption
Sources of Iron
Iron is an essential element for the formation of haemoglobin of red cells of blood.
It plays an important role in the transport of oxygen.
Tissues also require iron for various oxidation/reduction reactions.
Requirement and Absorption
Most of the iron in the body is reutilised. Some of the body iron is also stored in the liver and spleen.
The amount of iron to be absorbed from daily diet is quite small. It is in the neighbourhood of 1-3 mg depending upon the sex and the physiological status of a person. Since there is limited capacity to absorb dietary iron, diet should contain 10-25 fold in iron required daily.
Diets differ very widely in the bioavailability of their iron. Diets predominantly based on cereals permit only a low level of absorption in the range of 2-5% while diet containing low levels of cereals and high levels of meat and fish permit 10-20% absorption.
The types of diet consumed normally in India should contain 20-30 mg iron to meet the iron requirements, availability of iron from the composite diet is more important that from the individual foods because of profound interaction between foods in influencing iron absorption.
Although diet rich in iron may be able to meet our daily iron requirement and prevent iron deficiency, they may not be effective in correcting iron deficiency anaemia as indicated by lowered level of haemoglobin in the blood. Medicinal iron in the form of iron salts and other haematinics have to be provided to correct anaemia. Pregnant woman because of her high iron requirement often suffer from anaemia even on a diet containing normal levels of iron. In such cases supplementation with iron salts may be essential at least during later half of pregnancy.
In view of widespread prevalence of iron deficiency - anaemia in many parts of the world, fortification of foods with iron is advocated to prevent iron deficiency. In India fortification of common salt with iron has been successfully developed and demonstrated to be effective in preventing iron deficiency in the population if regularly used in place or ordinary salt.
Sources of Iron
Rich sources of iron are cereals, millets, pulses, and green leafy vegetables. Of the cereal grains and millets, bajra and ragi are very good sources of iron. Since these grains are contaminated with dust etc. the true contents of these grain are often lower than the values obtained by analysis of the market samples. Milk, a good source of several nutrients is a poor source of iron.
Inclusion in our daily diet about 50g green leafy vegetables, which are rich sources of iron, can meet a fair proportion of iron needs besides providing Calcium, beta-carotene and vitamin C.
Anaemia is another important nutritional problem affecting all segments of the population in general and children, women (especially pregnant women) in particular. In the latter groups anaemia may be as high as 60-70%.
Anaemia in India is essentially due to iron deficiency although in children and pregnant women, folate deficiency also plays a part. Although our diets contain fairly good amount of iron, its absorption is very poor (2-3%). Anaemia can be aggravated by environmental factors that lead to blood loss e.g hookworm infestation. All the available information indicates that anaemia can prevented by increasing iron intake in the population.
A therapeutic supplementation of iron and folate tablets and the other is fortification of a dietary iron should be tried to overcome anaemia. A public health programme of distribution of iron folate tables to pregnant women (during last trimester) and preschool children is in operation as a part of MCH services. This approach is designed to achieve results in a limited time, like pregnancy.
An alternate, preventive approach is to improve iron balance in the entire population through fortification of a commonly consumed dietary item with iron. Towards this end a technology for fortifying salt with iron has been developed in India by the National Instate of Nutrition its effectiveness in reducing anaemia was demonstrated in pilot trials.
Importance of Calcium
Calcium Rich Foods
Calcium Needs during Pregnancy
Calcium Needs– General
Importance of Calcium
Calcium is an essential element required for several life processes.
As the structural component, calcium is required for:
- Formation and maintenance of skeleton and teeth.
Processes that require Calcium are:
- Normal contraction of muscle
- Limb movement
- Contraction of heart for its normal function
- Neurological activity
- Blood clotting.
These later functions are carried out by ionized calcium present in the cells. The Calcium levels in cells and plasma are well maintained. Calcium present in bone helps to maintain the Calcium level in the plasma in the face of dietary Calcium deficiency.
Calcium Rich Foods:
Calcium is present in both animal and plant foods.
The richest source of Calcium among animal foods is milk and milk products
- Butter milk,
- Skim milk
The richest source among vegetables sources is green leafy vegetable group.
- Drumstick leaves
- Tapioca (among root vegetables)
Most cereals and millets contain some amount of this element
Rice is a poor source of calcium and therefore insufficiency of calcium is one of the main defects of diets largely based on rice.
Certain foods like leafy vegetables viz. amaranth are rich in oxalates which bind Calcium to form insoluble calcium oxalate and thus render Calcium unavailable to the body. Similarly, phytates present in whole cereals bind calcium. Other food which contain oxalates are horse gram, gingelly seeds, tea and coffee, but in the case of latter beverages only small amounts of oxalates pass into infusion.
Calcium in Pregnancy
Calcium requirements are also increased during pregnancy to meet the needs of growing foetus and during lactation to compensate for Calcium secreted in breast milk. A healthy breast fed baby of three months receives a large amount of Calcium all of which has been drawn from mother's milk. If the mother's diet during this period is deficient in Calcium, the Calcium present in the mother’s bones will be depleted and she will become prone to fractures. The mother’s health and probably that of infant will suffer due to the poor Calcium content in the mother.
In the case of pregnant and lactating mothers, the Nutrition Expert group of the Indian Council of Medical Research has suggested a daily allowance of 1.0g. In recommending these dietary allowance of Calcium, the fact that part of Calcium in cereal based diets is unavailable due to the presence of phytate and oxalic acid, has been taken into account.
The habit of chewing betel leaves with slaked lime (Calcium hydroxide), a practice quite common in India, particularly among the poor can increase Calcium intake. Calcium ingested in this way can be utilized by the body. The habit of chewing betel leaves with slaked lime several times a day by expectant and nursing mothers in India has indeed a scientific basis. Since many cereal-based diets are not likely to provide enough Calcium unless plenty of milk is consumed, it may be useful to supplement the diet with Calcium during pregnancy and lactation.
Calcium Needs – General
Based on the available information on retention of Calcium by the human body in long-term balance studies, the suggested level of intake for an adult man and growing children is between 0.4 and 0.6 g/d.
Children need relatively more Calcium than adults to meet the requirements of growing bones.
Since there are no specific signs and symptoms attributable to Calcium deficiency, the Calcium requirement of man is not known with certainty. Moreover, man appears to adapt himself to low intakes of Calcium without any apparent deleterious effects. The currently recommended allowances for Calcium should be considered only as tentative.
Electrolytes and Trace Elements
Major elements like Sodium, Potassium and Magnesium are essential as electrolytes to maintain electrolyte balance. A wide range of trace elements are known to be required for cellular function, essentiality of only some of them like Zinc, Chromium, Copper, Manganese and Selenium have been established in humans.
Sodium and Potassium
- Trace Elements
- Other Trace Elements
Sodium and Potassium
Sodium and Potassium are important constituents of fluids present outside and within the cell. Proper concentration of these electrolytes inside and outside the cell is essential to maintain osmotic balance and keep cells in proper shape.
Plant foods are a rich source of Potassium. The exact requirement of Potassium is not known, but the amount present in a vegetarian diet is probably adequate to meet the daily requirement.
Sodium (Na) is lost in urine and particularly in sweat as sodium chloride. Sodium present in foods is not adequate to meet the requirement. Hence sodium chloride or common salt has to be included in the diet. Besides imparting taste to food, salt provides necessary amount of Na required by the body.
The daily intake of salt in our country may be as high as 20g the average being around 15 g per adult. A lower intake of 8-10g/day may be advisable, due to salt’s association with hypertension. Under conditions of excessive sweating as in summer and for those who work in a hot environment a slightly higher intake may be necessary.
Magnesium is present in small concentration in all cells and is required for cellular metabolism. It is also present in bone along with calcium. Magnesium shares many of the properties of calcium so far as absorption and metabolism and tissue distribution are concerned. Magnesium is also implicated to have a role in cardiovascular disease.
Dietary intake of magnesium to maintain balance is around 350 mg/day. Cereals pulses and nuts contain 40-200 mg magnesium per 100g. Magnesium content of foods is generally much higher than Calcium. Leafy vegetables are also a good source of magnesium.
It is known now that a large number of elements are required in trace amounts for a wide range of functions in the body. Some of the important trace elements of relevance in human nutrition are zinc, copper, selenium, cobalt, fluoride, manganese, chromium, iodine and molybdenum. Other trace elements are arsenic, nickel, vanadium and silicon.
Iodine deficiency diseases including goitre are widespread in many parts of the world and it forms a major public health problem in India. Over 120-150 million people in the world are estimated to suffer from iodine deficiency.
Iodine deficiency is characterized by swelling of thyroid gland in the neck. In the foetal stage it may lead to mental retardation and in later life retardation of the body growth.
The daily requirement of iodine is reported to be 100-150 Mg. In a non-endemic area 60-75% of the iodine needs are met by the iodine present in the diet and the rest through iodine content of water. In an endemic goitre area, there is iodine deficiency in the soil, water and locally grown foods. Besides, certain compounds present in foods, particularly vegetables of brassica species (vegetables such as Broccoli, Brussels Sprouts, Cabbage, Cauliflower, Collards, Kale, Kohlrabi, Mustard, Rape, Rutabaga and Turnip) interfere with iodine utilization and lead to goitre. They are known as goitrogens.
One of the well tested approaches to control iodine deficiency disease in the population is the distribution of iodised salt to the affected population. A programme of distribution of iodised salt in the endemic area is in operation in India.
Zinc is an important element performing a range of functions in the body as it is a cofactor for a number of enzymes. Zinc deficiency leads to growth failure and poor development of gonadal function. Dwarfism and hypogonadism seen in Egypt and Iran are attributed to dietary zinc deficiency. Zinc intake and zinc absorption is low in diets of poor income groups in India suggesting a possible dietary zinc deficiency.
Copper is an essential element for man. It plays an important role in iron absorption. It is also involved in cross-linking of connective tissues, neurotransmission and lipid metabolism. Part of body copper circulates in plasma as ceruloplasmin. Copper is also present in oxidative enzymes like cytochromes.
Copper metabolism in the body is under homeostatic regulation. In case of inadequate intake excretion is reduced. The estimated dietary intake of copper from a typical Indian diet is around 2 mg/day. Absorption of copper from poor diet is lower than from well balanced diets, absorption varying from 5 to 33%.
Clinical symptoms due to copper deficiency either nutritional or genetic lead to pathological symptoms in organs rich in connective tissue. Central nervous system disorders may also result from copper deficiency with impaired myelination and catecholamine metabolism.
Chromium deficiency has been shown to lead to impaired glucose tolerance. The factor responsible for this property has not yet been isolated.
Chromium content of cereal based Indian diet ranges between 70-150 mg/day. Low-income group diets have generally a lower (25%) content. Although absorption of inorganic chromium is quite low i.e. 1-2% chromium present in our diets is absorbed to an extent of 70-80% or more. This is presumably due to the fact that chromium in foods is present in organically bound form, which facilitates greatly its absorption.
Chromium requirement has been estimated to be around 70 mg /day and most of our diets consumed by rich or poor are able to provide this amount of chromium.
Manganese is established as an essential element as it participates in a number of reactions as a component of metal enzyme or as enzyme cofactor. Its function is glycosyltransferase is well recognised and its deficiency leads to abnormality in skeletal bone mineralisation.
It also participates in lipid and carbohydrate metabolism. A large number of foods consumed in India have been analyzed for manganese. Manganese content of diets consumed in India varies from 4-10 mg/day. Absorption of manganese from these diets varies from 5-20 %.
Surprisingly, diets of poor income groups have a better absorption of manganese than diets of high-income groups. The estimated manganese requirement of these diets based on human balance studies is 5 mg/day. Most of our diets can provide this amount. Hence manganese deficiency is not likely to occur in the Indian population. Excess of manganese is toxic, a situation that may be encountered in manganese mines and other industries.
Molybdenum (Mo) is an essential constituent of xanthine and aldehyde oxidases and is involved in uric acid metabolism.
This daily requirement for an adult may range from 0.15 to 0.5 mg. Molybdenum content of several Indian foods has been estimated. Dietary deficiency of Mo is unlikely in the Indian population. However, excess Mo intake may increase the risk of gout. High Molybdenum and low copper intakes have been implicated in the etiology of endemic genuvalgum and bone disorders which occur in certain endemic fluorosis areas.
Fluoride (F) is also an important element in human health, a minimum amount being required for prevention of dental caries. However, its presence in high concentration in environment, particularly in water (>2-3ppm) leads to fluorosis resulting in hardening of bones. Fluorosis occurs as an endemic disease in India in parts of Andhra Pradesh (Nalgonda district) and Punjab (Patiala district). In the endemic area of Andhra Pradesh, another clinical manifestation of fluoride toxicity called genu valgum has been identified in recent years. Other environmental factors appear to have contributed to its emergence, viz high levels of Mo, and low levels of Cu.
It is estimated that by food alone 0.3-0.8 mg F may be supplied. Daily intake of F upto 2 mg through foods has been reported from some areas.
Fifty to 80% of food fluoride is absorbable. It is suggested that in assessing the benefits and risks of fluoride ingestion, that apart from water, F derived from foods also needs to be considered.
Other Trace Metals
Other trace metals of significance in human nutritional are selenium, cobalt, silicon, arsenic, nickel and vanadium. Selenium (Se) is an essential element and along with vitamin E, it is required for maintaining liver integrity.
Selenium deficiency leads to liver necrosis. An endemic disease of cardiomyopathy in children (Keshan syndrome) is attributed to low Se in the environment. Selenium deficiency is also implicated as a risk factor in cancer.
Cobalt (Co) is an important trace element as it forms part of the vitamin B12. It is also reported that cobalt is required for optimum utilisation of low doses of iodide. The possible role of low Co in iodine deficiency disorders (goitre) is however not known.
The above material was excerpted with permission from Nutritive Value of Indian Foods by G Gopalan, BV Rama Sastri and SC Balasubramanian, Published by National Institute of Nutrition, ICMR, Hyderabad - 500007