Friday, January 30, 2009
Saturday, January 24, 2009
FIRST TOPICAL TEST WILL BE ON THE 2ND OF FEBRUARY FOR 5B, 5E, 5C AND 5H AND FOR 5A IT WILL BE ON THE 3RD OF FEBRUARY
TOPICS TESTED: TRANSPORT SYSTEM IN MAMMALS AND RESPIRATION (INCLUDING RESPIRATORY SYSTEM AND BREATHING MECHANISM)
Sunday, January 18, 2009
STRONG SOLUTION = HYPERTONIC SOLUTION = CONCENTRATED SOLUTION
CONTAINS LESS FREE WATER MOLECULES
THEREFORE : LOW WATER POTENTIAL
WEAK SOLUTION = HYPOTONIC SOLUTION = DILUTE SOLUTION
CONTAINS MORE FREE WATER MOLECULES
THEREFORE: HIGH WATER POTENTIAL
WATER ALWAYS HAS THE HIGHEST WATER POTENTIAL
OSMOSIS: MOVEMENT OF WATER MOLECULES FROM SOLUTION WITH HIGH WATER POTENTIAL (DILUTE SOLUTION) TO SOLUTION WITH LOW WATER POTENTIAL (CONCENTRATED SOLUTION) ACROSS A SEMI PERMEABLE MEMBRANE
Monday, January 12, 2009
Thursday, January 8, 2009
- Aerobic respiration occurs in the presence of oxygen whereas anaerobic respiration occurs in the absence of oxygen.
- Aerobic respiration releases a large amount of energy (efficient in terms of energy yield) whereas anaerobic respiration only releases a small amount of energy (less efficient in terms of energy yield)
- Aerobic respiration always produces carbon dioxide and water as the waste products whereas anaerobic respiration produces lactic acid (as in the case of anaerobic respiration in muscle cells) and ethanol and carbon dioxide (as in the case of anaerobic respiration in yeast)
HOW DOES THIS STORED CHEMICAL ENERGY RELEASED FROM THE FOOD?
since the energy is locked up in the organic food molecules, an organism will have to oxidise them. This process of oxidation which occurs within every living cells of animals (aw well as plants) is called respiration.
When students were asked about their pre-conceptions about respiration, the common misconception was that respiration is thought to be a scientific name for breathing.... NO... Totally WRONG!..... But breathing does help indirectly by bringing in oxygen into your body.....
DEFINITION OF RESPIRATION IN GENERAL:
Respiration is the oxidation of food substances (mainly glucose) with the release of energy in living cells.
Note: Do Not use BURNING or BREAK DOWN...... Stick to OXIDATION....... and it is very important for you to remember that respiration occurs within living cells and where in the cells? The MITOCHONDRIA.....
Respiration can be of two forms: AEROBIC RESPIRATION and ANAEROBIC RESPIRATION.
Aerobic respiration is defined as the oxidation of food substances in the presence of oxygen with the release of a large amount of energy and carbon dioxide and water as the waste products.
Aerobic respiration can be represented by the following equation.
C6H12O6 + 6O2 --> 6CO2 + 6H2O + Energy
How much energy? 17.1kJ/g of glucose.
The process shown by the above equation involves many enzyme-catalysed reactions. The enzymes for each of these enzyme-catalysed reactions are found in the mitochondria. Hence mitochondria are important in respiration. In fact it is the site where respiration occurs.
USES OF ENERGY PRODUCED AS A RESULT OF AEROBIC RESPIRATION
- Synthesis of proteins from amino acids
- Cell division and therefore growth
- Respiratory movements
- Muscular contractions
- Active transport (absorption of glucose and amino acids by the villi in the small intestine is by active tranport. So does absorption of mineral salts by the root hair cells)
- Transmission of nerve impulses
Anaerobic respiration is defined as the oxidation of food substances in the absence of oxygen with the release of a small amount of energy.
ANAEROBIC RESPIRATION IN YEAST (FERMENTATION)
Yeast is a kind of fungi which is used in bread making. Yeast cells oxidise glucose during frementation. The products is ethanol which is an alcohol. For this reason, anaerobic respiration is yeast is also called alcoholic fermentation. Anaerobic respiration is yeast can be represented by the following equation:
C6H12O6 --> 2C2H5OH + 2CO2 + Energy
How much energy is released? 1.17kJ/g glucose.
Less energy is released because the alcohol molecule is relatively large and still contains a conisderable amount of chemical energy. The small amount of energy released is only enough for the yeast to survive.
(Note: the carbon dioxide produced as the waste products actually helps in raising the bread dough thus making the bread fluffy)
(Note: wine is also made in a similar way. The glucose in grapes is oxidised in the same way)
ANAEROBIC RESPIRATION IN MUSLCES
Normally muscle cells respire aerobically (using oxygen gas). But in certain circumstances, where oxygen is not available for a very short period of time, these cells need to respire anaerobically (without oxygen gas). This usually occurs during a vigorous or strenous exercise such as sprinting in a 100m race.
What actually happens here?
- At the beginning of an exercise, the muscle cells first respire aerobically
- Soon the amount of oxygen available in the muscle cells becomes depleted
- Despite the increased breathing rate and heart beat, oxygen cannot be transpoted to the mucles fast enough to be used for respiration
- Under this circumstance, the muscle cells then respire anaerobically to continue producing energy (though only a small amount is produced)
- In the absence of oxygen in the muscle cells, the glucose is converted to lactic acid together with a comparativley small amount of energy
How much energy is released? 0.83kJ/g glucose
- During the exercise period the muslces is said to incur an oxygen debt (more oxygen is used up than can be supplied by the blood)
- This "debt" is "paid" by fast and deep breathing in the recovery period after the exercise
- During the recovery period, 1/6 of the lactic acid produced during the exercise is oxidised aerobically into carbon dioxide and water to produce enough energy to convert 5/6 of the lactic acid back into glucose
- The glucose formed this way is then used in the normal aerobic respiration to relaease a large amount of energy
- Note: Sometimes, individual experiences muscle cramp. This is due to an accumulation of lactic acid in their muslces. If the level of lactic acid exceeds the individual tolerance level (depending on how fit the individual is), muslces stop contracting and cramp occurs)
Sunday, July 20, 2008
What is the part of the alimentary canal that stores undigested food temporarily?
But here's some of the responses by some students but before that do you even know what UNDIGESTED FOOD means? Its FAECES OK.....
T A H I in Malay:
So here are some of the answers:
- In the mouth (Imagine that!....)
- Anus (If this is the case..... tumbir tumbir tu eh..... like macam inda bebasuh... euuu)
Movement of water molecules through semi-permeable membrane?
Jawapan nya OSMOSIS..... OSMOSIS BAH OSMOSIS..... BUKAN NYA DIFFUSION......
Just look at the WATER MOLECULES there.... that should give you a clue already that the process involved is OSMOSIS........ heesssshhhhhh!!!
Repeat after me M A L T O S E .... Got it? I hope so............ Now to get GLUCOSE out of starch, you must have another enzyme to digest this maltose..... The enzyme is MALTASE....
I hope I will not encounter this misconception ever again.....
Friday, July 18, 2008
This process is simply a process in which big fat globule is broken down into small fat droplets (without changing the fat chemically) So you starts with fats and ends with fats, get it?. Its just like shaking oil in water where you would observed tiny emulsions formed. The idea here is to increase the surface area to volume ratio of the fats so that chemical digestion by LIPASE could be facilitated.
In human digestive system, during the process of digestion, this process takes place in the duodenum. Whenever chyme containing fats enters the duodenum, your gall bladder will secrete bile into the duodenum (Remember: the gall bladder is an organ which stores bile temporarily and this bile will only be secreted if chyme enters the duodenum.... and and.... the organ that manufactures the bile is the LIVER..... please remember these facts). By the way after bile is secreted into the duodenum, it will emulsify the fats present in the chyme. Only after emulsification would fats be digested chemically by LIPASE into three fatty acids and one glycerol.................
Wednesday, July 16, 2008
The figure above shows the chemical formula of AMINO ACID. From the figure you can see that it consists of the amino group and the carboxylic acid group. During the process of DEAMINATION in the LIVER, an amino acid is broken down into two parts - the amino group and the part of the amino acid which contains the carboxylic acid group (which is now referred to as the carbohydrate group).
The carbohydrate group will eventually be converted into GLYCOGEN and stored in the liver itself as well as in your muscle tissues. This GLYCOGEN can be converted to glucose should your body need it as a fuel for cellular respiration. Otherwise, if the glycogen is not utilized within a duration of about 6 hours, it will eventually be converted into FATS and stored in the liver itself as well as in the adipose tissues under your skin.
The amino group on the other hand will be converted to UREA and this UREA will be send (via your blood circulatory system) to your kidneys. Your kidneys will then EXCRETE the UREA along with excess water and minerals (UREA + water + minerals = URINE).
SECRETION vs EXCRETION?
WHEN TO USE THESE TERMS?
SECRETION FOR USEFUL SUBSTANCES LIKE ENZYMES AND HORMONES
EXCRETION FOR WASTE PRODUCTS OF METABOLISM LIKE UREA AND CARBON DIOXIDE....
- Circular and longitudinal muscles contract or relax at the same time
- Some students used circular or longitudinal tissues instead of muscles
- Some students were not aware about the role of peristalsis in digestion
It is the ALTERNATE contraction and relaxation of the circular and longitudinal muscles causing bolus to be pushed down and also at the same time to be physically digested.
In the recent test, many students failed to include ALTERNATE. It is very important to do so because it shows that you understand that these muscles are actually working antagonistically (that is, when one set of muscles relaxes the other set contracts - for example when the circular muscles relax, the longitudinal muscles contract). Now, it should be understood that without ALTERNATE in your definition, the meaning could be misleading. It can be assumed that both set of muscles are actually contracting or relaxing at the same time.
Students should also be aware about the role of PERISTALSIS. One is to move bolus down along the alimentary canal and the second function is to break the bolus down into smaller pieces without changing them chemically (this is a kind of PHYSICAL digestion).
And lastly..... where is PERISTALSIS occurring?
Not only the oesophagus but actually along the alimentary canal......
Friday, May 9, 2008
Although most famines coincide with regional shortages of food, famine in some human populations has occurred amid plenty or on account of acts of economic or military policy that have deprived certain populations of sufficient food to ensure survival.
Famine is typically induced by a human population exceeding the regional carrying capacity to provide food resources. An alternate view of famine is a failure of the poor to command sufficient resources to acquire essential food, analyses of famine that focused on the political-economic processes, an understanding of the reasons for mortality in famines, an appreciation of the extent to which famine-vulnerable communities have strategies for coping with the threat of famine, and the role of warfare and terrorism in creating famine. Modern relief agencies categorize various gradations of famine according to a famine scale.
In biological terms, a population beyond its regional carrying capacity causes famine. While the operative cause of famine is an imbalance of population with respect to food supply, some famines are caused by a combination of political, economic, and biological factors.
Famines can be exacerbated by poor governance or inadequate logistics for food distribution. In some modern cases, it is political strife, poverty, and violence that disrupts the agricultural and food distribution processes.
Modern famines have often occurred in nations that, as a whole, were not initially suffering a shortage of food. One of the largest historical famines (proportional to the affected population) was the Great Irish Famine, 1845-1849, which began in 1845 and occurred as food was being shipped from Ireland to England because the English could afford to pay higher prices.
The largest famine ever (in absolute terms) was the Chinese famine of 1958–61 that occurred as a result of the Great Leap Forward. In a similar manner, the 1973 famine in Ethiopia was concentrated in the Wollo region, although food was being shipped out of Wollo to the capital city of Addis Ababa where it could command higher prices. In contrast, at the same time that the citizens of the dictatorships of Ethiopia and Sudan had massive famines in the late-1970s and early-1980s, the democracies of Botswana and Zimbabwe avoided them, despite having worse drops in national food production. This was possible through the simple step of creating short-term employment for the worst-affected groups, thus ensuring a minimal amount of income to buy food, for the duration of the localized food disruption and was taken under criticism from opposition political parties and intense media coverage.
The failure of a harvest or the change in conditions, such as drought, can create a situation whereby large numbers of people live where the carrying capacity of the land has dropped radically. Famine is often associated with subsistence agriculture, that is, where most farming is aimed at producing enough food energy to survive. The total absence of agriculture in an economically strong area does not cause famine; Arizona and other wealthy regions import the vast majority of their food, since such regions produce sufficient economic goods for trade.
Disasters, whether natural or man-made, have been associated with conditions of famine ever since humankind has been keeping written records. The Torah describes how "seven lean years" consumed the seven fat years, and "plagues of locusts" could eat all of the available food stuffs. War, in particular, was associated with famine, particularly in those times and places where warfare included attacks on land, by burning or salting fields, or on those who tilled the soil.
As observed by the economist Amartya Sen, famine is sometimes a problem of food distribution and poverty. In certain cases, such as the Great Leap Forward, North Korea in the mid-1990s, or Zimbabwe in the early-2000s, famine can be caused as an unintentional result of government policy. Famine is sometimes used as a tool of repressive governments as a means to eliminate opponents, as in the Ukrainian famine of the 1930s. In other cases, such as Somalia, famine is a consequence of civil disorder as food distribution systems break down. Most cases are not simply the result of the excedence of the Earth's carrying capacity.
Approximately 40% of the world's agricultural land is seriously degraded. In Africa, if current trends of soil degradation continue, the continent might be able to feed just 25% of its population by 2025, according to UNU's Ghana-based Institute for Natural Resources in Africa. As of late 2007, increased farming for use in biofuels, along with world oil prices at nearly $100 a barrel, has pushed up the price of grain used to feed poultry and dairy cows and other cattle, causing higher prices of wheat (up 58%), soybean (up 32%), and maize (up 11%) over the year. Food riots have recently taken place in many countries across the world.
There are a number of ongoing famines caused by overpopulation, loss of arable land, war or political intervention. Beginning in the 20th century, nitrogen fertilizers, new pesticides, desert farming, and other agricultural technologies began to be used as weapons against famine. Between 1950 and 1984, as the Green Revolution transformed agriculture around the globe, world grain production increased by 250%. These agricultural technologies temporarily increased crop yields, but there are signs as early as 1995 that not only are these technologies reaching their peak of assistance, but they may now be contributing to the decline of arable land (e.g. persistence of pesticides leading to soil contamination and decline of area available for farming. Developed nations have shared these technologies with developing nations with a famine problem, but there are ethical limits to pushing such technologies on lesser developed countries. This is often attributed to an association of inorganic fertilizers and pesticides with a lack of sustainability. In any case, these technological advances might not be influential in those famines which are the result of war. Similarly so, increased yield may not be helpful with certain distribution problems, especially those arising from political intervention.
David Pimentel, professor of ecology and agriculture at Cornell University, and Mario Giampietro, senior researcher at the National Research Institute on Food and Nutrition (INRAN), place in their study Food, Land, Population and the U.S. Economy the maximum U.S. population for a sustainable economy at 200 million. To achieve a sustainable economy and avert disaster, the United States must reduce its population by at least one-third, and world population will have to be reduced by two-thirds, says study.
The authors of this study believe that the mentioned agricultural crisis will only begin to impact us after 2020, and will not become critical until 2050. The oncoming peaking of global oil production (and subsequent decline of production), along with the peak of North American natural gas production will very likely precipitate this agricultural crisis much sooner than expected. Geologist Dale Allen Pfeiffer claims that coming decades could see spiraling food prices without relief and massive starvation on a global level such as never experienced before.
Water deficits, which are already spurring heavy grain imports in numerous smaller countries, may soon do the same in larger countries, such as China or India. The water tables are falling in scores of countries (including Northern China, the US, and India) due to widespread overpumping using powerful diesel and electric pumps. Other countries affected include Pakistan, Iran, and Mexico. This will eventually lead to water scarcity and cutbacks in grain harvest. Even with the overpumping of its aquifers, China has developed a grain deficit, contributing to the upward pressure on grain prices. Most of the three billion people projected to be added worldwide by mid-century will be born in countries already experiencing water shortages. After China and India, there is a second tier of smaller countries with large water deficits — Algeria, Egypt, Iran, Mexico, and Pakistan. Four of these already import a large share of their grain. Only Pakistan remains marginally self-sufficient. But with a population expanding by 4 million a year, it will also soon turn to the world market for grain.
According to a UN climate report, the Himalayan glaciers that are the principal dry-season water sources of Asia's biggest rivers - Ganges, Indus, Brahmaputra, Yangtze, Mekong, Salween and Yellow - could disappear by 2035 as temperatures rise and human demand rises. Approximately 2.4 billion people live in the drainage basin of the Himalayan rivers. India, China, Pakistan, Afghanistan, Bangladesh, Nepal and Myanmar could experience floods followed by severe droughts in coming decades. In India alone, the Ganges provides water for drinking and farming for more than 500 million people.
The demographic impacts of famine are sharp. Mortality is concentrated among children and the elderly. A consistent demographic fact is that in all recorded famines, male mortality exceeds female, even in those populations (such as northern India and Pakistan) where there is a normal times male longevity advantage. Reasons for this may include greater female resilience under the pressure of malnutrition, and the fact that women are more skilled at gathering and processing wild foods and other fall-back famine foods. Famine is also accompanied by lower fertility. Famines therefore leave the reproductive core of a population—adult women—lesser affected compared to other population categories, and post-famine periods are often characterized a "rebound" with increased births. Even though the theories of Thomas Malthus would predict that famines reduce the size of the population commensurate with available food resources, in fact even the most severe famines have rarely dented population growth for more than a few years. The mortality in China in 1958–61, Bengal in 1943, and Ethiopia in 1983–85 was all made up by a growing population over just a few years. Of greater long-term demographic impact is emigration: Ireland was chiefly depopulated after the 1840s famines by waves of emigration.
Friday, May 2, 2008
Malnutrition is a condition in which a person's diet is inadequate to meet minimum daily requirements for nutrients such as proteins, fats, vitamins, and minerals.
It is caused by one of two factors. First, a person simply may not get enough food to eat and, thus, fails to take in the nutrients needed to remain healthy. Someone who is hungry all the time obviously is not eating enough food to remain healthy. Second, a person may eat a limited diet that fails to deliver vital nutrients to the body. Anyone who tries to survive on a diet consisting of potato chips, candy bars, and sodas will not be getting the complete range of nutrients his or her body needs.
Individuals at risk
The single most important factor that leads to malnourishment is poverty. Vast numbers of people who live in less-developed countries of the world either do not get enough to eat or do not eat the correct foods. Those who are most at risk of malnutrition where conditions of poverty exist are infants, children, pregnant women, and the elderly.
Nutritional deficiency diseases
The human body requires a wide range of nutrients in order to remain healthy, grow normally, and develop properly. These nutrients include carbohydrates, fats, proteins, vitamins, and minerals. Other substances, such as water and fiber, have no nutritional value but are needed to maintain normal body functions.
Nutrients serve a number of functions in the human body. Carbohydrates and fats, for example, are used by the body to produce the energy humans require to stay alive and healthy and to grow and develop normally. Proteins are used in the production of new body parts, to protect the body against disease and infection, in the regulation of bodily functions, and in a variety of other ways. Vitamins and minerals are used in the body for a number of different purposes, such as controlling the rate at which many chemical changes take place in the body. Overall, more than 50 different nutrients are needed to keep the human body healthy. The absence of any one of these nutrients can result in the development of a nutritional deficiency disease. Some common nutritional deficiency diseases are discussed below.
Kwashiorkor and Marasmus
Kwashiorkor (from the West African word for "displaced child") is a nutritional deficiency disease caused when infants and very young children are weaned from their mother's milk and placed on a diet consisting of maize flour, cassava, or low-protein cereals. That diet is generally high in calories and carbohydrates, but low in protein. The most striking symptom of kwashiorkor is edema, a bloating caused by the accumulation of liquids under the skin. Other symptoms may include loss of hair and skin pigmentation, scaliness of the skin, and diarrhea. As the disease progresses, a person may develop anemia (a disorder in which a person's red blood cell count is low and they lack energy), digestive disorders, brain damage, a loss of appetite, irritability, and apathy (lack of interest in things).
Most children do not die of kwashiorkor directly. Instead, they develop infections that, if left untreated, can be fatal. They die from measles, the flu, diarrhea, or other conditions that could be treated relatively easily in a healthy child.
Marasmus (from the Greek word for "to waste away") is a more severe condition than kwashiorkor. It results when a person's diet is low in both calories and protein. The disease is characterized by low body weight, wasting of muscle tissue, shriveled skin, and diarrhea. The most prominent feature of marasmus is a severely bloated belly. A child with marasmus has the appearance of an old person trapped in a young person's body.
Scurvy is one of the oldest deficiency diseases recorded and the first one to be cured by adding a vitamin to the diet. The main symptom of scurvy is hemorrhaging, the heavy discharge of blood that results when a blood vessel is broken. The gums swell and usually become infected. Wounds heal slowly and the bleeding that occurs in or around vital organs can be fatal. The disease is slow to develop and its early stages are characterized by fatigue (tiredness), irritability, and depression. In the advanced stages of the disease, laboratory tests will show an absence of the vitamin needed to protect against the disease.
Beriberi (not in syllabus)
Beriberi is a disease that occurs widely in China, Indonesia, Malaysia, Burma, India, the Philippines, and other parts of Asia and the South Pacific Ocean. It is characterized by edema (accumulation of water in body tissues), fatigue, loss of appetite, numbness or tingling in the legs, and general weakness of the body.
Beriberi is caused by an absence of vitamin B1 (thiamine) in the diet. The disease can be prevented by eating foods that are rich in this vitamin, foods such as meats, wheat germ, whole grain and enriched bread, legumes (beans), peanuts, peanut butter, and nuts.
Pellagra (not in syllabus)
The symptoms of pellagra are sometimes referred to as the "three Ds": diarrhea, dermatitis, and dementia. Dermatitis refers to skin infections while dementia means deterioration of the mind. If the disease is not treated, it may lead to death.
Pellagra is caused by an insufficient amount of niacin (vitamin B3). Niacin occurs naturally in foods such as liver, meat, fish, legumes, and dried yeast. Today it is added to many processed foods such as bread, flour, cornmeal, macaroni, and white rice. This practice has essentially eliminated pellagra as a medical problem in developed countries, although it remains a serious health problem in some less-developed countries of the world.
Rickets is a bone disorder caused by a lack of vitamin D. Vitamin D is often called the "sunshine" vitamin because it can be produced in the human body by the effects of sunlight on the skin. Rickets was once a common disease of infants and children. However, all milk and infant formulas now have vitamin D added to them. Thus, the disorder is rarely seen today in countries where "fortified" milk is available. Symptoms of rickets include legs that have become bowed by the weight of the body and wrists and ankles that are thickened. Teeth may be badly affected and take a longer time to mature.
Mineral deficiency diseases
About 25 mineral elements are required in the human body for the maintenance of good health. Calcium and phosphorus, for example, are needed to produce teeth and bones.
One of the exceptions is the disorder known as goiter. Goiter is a condition caused by an insufficient amount of iodine in the diet. Iodine is used by the thyroid to produce hormones that control the body's normal functioning as well as its normal growth. If sufficient iodine is not available in a person's diet, the thyroid gland begins to enlarge its cells in an effort to produce the needed hormones. This enlargement produces the characteristic swelling in the neck characteristic of goiter. Today, goiter has virtually disappeared from most developed nations because of the practice of adding small amounts of iodine (in the form of sodium iodide) to ordinary table salt.
Perhaps the most common of all mineral deficiency disorders is anemia. The term anemia literally means "a lack of blood." The condition is caused when the number of red blood cells is reduced to a level lower than that necessary for normal body functioning. The human body gets the energy it needs to stay alive and function normally by oxidizing nutrients in cells. The oxygen needed for this process is carried from the lungs to cells on red blood cells. The "working part" of a red blood cell is a complex molecule called hemoglobin. Each hemoglobin molecule contains a single atom of iron at its center. The iron atom combines with oxygen from the lungs to form a compound known as oxyhemoglobin.
It is in this form that oxygen is transferred from the lungs to cells. If the body fails to receive sufficient amounts of iron, an adequate number of hemoglobin molecules will not be formed. In that case, there are not enough functioning red blood cells to carry all the oxygen that cells need to produce energy. A person becomes weak and listless and may suffer headaches, soreness of the mouth, drowsiness, slight fever, gastrointestinal disturbances, and other discomforts.
The treatment for malnutrition and for nutrient deficiency diseases is obvious: a person who lacks adequate amounts of food or fails to eat the right kinds of food must change his or her diet. That instruction is easy to give but in many parts of the world it is impossible to follow.
Marasmus, kwashiorkor, beriberi, scurvy, rickets, and other deficiency disorders are common in less-developed countries of the world because sufficient food is either not available or, if it is, it is not sufficiently nutritious.
In more-developed countries of the world, people often have ready access to nutritious foods in sufficient quantities so that malnutrition is less of a problem than it is in less-developed countries. In addition, a very large variety of supplements are available, such as vitamin and mineral pills.
Anyone who fears that he or she may not be receiving enough of any given vitamin or mineral can easily supplement his or her diet with products available at the corner grocery store.
Friday, March 28, 2008
Scurvy is a condition caused by a lack of vitamin C (ascorbic acid) in the diet. Signs of scurvy include tiredness, muscle weakness, joint and muscle aches, a rash on the legs, and bleeding gums. In the past, scurvy was common among sailors and other people deprived of fresh fruits and vegetables for long periods of time.
Scurvy is very rare in countries where fresh fruits and vegetables are readily available and where processed foods have vitamin C added. Vitamin C is an important antioxidant vitamin involved in the development of connective tissues, lipid and vitamin metabolism, biosynthesis of neurotransmitters, immune function, and wound healing. It is found in fruits, especially citrus fruits like oranges, lemons, and grapefruit, and in green leafy vegetables like broccoli and spinach. In adults, it may take several months of vitamin C deficiency before symptoms of scurvy develop.
Currently, the recommended dietary allowance (RDA) for vitamin C is 50-60 mg/day for adults; 35 mg/day for infants; 40-45 mg/day for children 1-14; 70 mg/day during pregnancy; and 90-95 mg/day during lactation. The body's need for vitamin C increases when a person is under stress, smoking, or taking certain medications.
Causes and symptoms
A lack of vitamin C in the diet is the primary cause of scurvy. This can occur in people on very restricted diets, who are under extreme physiological stress (for example, during an infection or after an injury), and in chronic alcoholics. Infants can develop scurvy if they are weaned from breast milk and switched to cow's milk without an additional supplement of vitamin C. Babies of mothers who took extremely high doses of vitamin C during pregnancy can develop infantile scurvy. In children, the deficiency can cause painful swelling of the legs along with fever, diarrhea, and vomiting. In adults, early signs of scurvy include feeling weak, tired, and achy. The appearance of tiny red blood-blisters to larger purplish blotches on the skin of the legs is a common symptom. Wound healing may be delayed and scars that had healed may start to break down. The gums swell and bleed easily, eventually leading to loosened teeth. Muscle and joint pain may also occur.
Scurvy is often diagnosed based on the symptoms present. A dietary history showing little or no fresh fruits or vegetables are eaten may help to diagnose vitamin C deficiency. A blood test can also be used to check the level of ascorbic acid in the body.
Adult treatment is usually 300-1,000 mg of ascorbic acid per day. Infants should be treated with 50 mg of ascorbic acid up to four times per day.
Treatment with vitamin C is usually successful, if the deficiency is recognized early enough. Left untreated, the condition can cause death.
Eating foods rich in vitamin C every day prevents scurvy. A supplement containing the RDA of vitamin C will also prevent a deficiency. Infants who are being weaned from breast milk to cow's milk need a supplement containing vitamin C.
Calcium and Vitamin D are nutrients that have received much attention in recent years because they work together to prevent several chronic diseases. One of the best sources of calcium and Vitamin D is milk, but there are other sources. This post can help you understand why adequate amounts of these nutrients are needed for overall health and prevention of disease. You will also learn ways to meet the recommended intakes of each nutrient.
Where Is Calcium Found In The Body?
Calcium is a very important mineral because it...
- Combines with phosphorus to form bones and teeth, making them hard and resistant to breaks and decay. Children need to get enough calcium for their bones and teeth to develop normally. Getting enough calcium early in life helps bones remain strong later in life.
- Helps muscles to contract normally. A deficiency can cause muscle spasms and cramps.
- Helps blood to clot normally, when you get a cut or wound.
- Is essential for nerve messages to be passed along the nervous system from the brain to other parts of the body and vice versa.
- Helps regulate blood pressure. Low calcium intake has been associated with high blood pressure. People with high blood pressure should make sure they consume the recommended amount of calcium (1000 to 1500 mg per day). African-Americans have a higher rate of high blood pressure than other groups and tend to have low calcium intakes.
- Calcium may help prevent colon cancer, one of the most common forms of cancer. Calcium may reduce cancer risk in two ways: (a) by binding fat and bile acids in the large intestine, keeping them from causing harm and (b) by preventing the excessive growth of cells in the intestines, which could otherwise lead to cancer.
Vitamin D is a fat soluble vitamin that ...
- Must be present for calcium to be absorbed and used. For this reason, milk that is rich in calcium and fortified with Vitamin D is a good choice.
- Is essential for calcium to be used for building bones and teeth and for other roles in the body.
- May help prevent colon cancer by working with calcium to slow the growth of intestinal cells that could otherwise lead to cancer.
Other Important Facts About Vitamin D:
- Vitamin D is called the "sunshine vitamin" because it is formed in the skin by the action of ultraviolet rays from the sun. For fair skinned individuals, 15 minutes of sunlight will produce enough Vitamin D to last for several days, even when wearing light clothing. However, it takes 3 hours or more for this to happen with dark-skinned people.
- Clouds, smoke, and window glass also prevent penetration of ultraviolet rays
- Use of a sunscreen lotion of 8 SPF or higher will prevent the formation of Vitamin D in the skin. When sunbathing, just wait 15 minutes before applying sunscreen lotion (i.e. if you are fair skinned).
- Vitamin D is also present in fish oil and some types of saltwater fish and shellfish (salmon, halibut, herring, tuna, oysters, and shrimp).
- Other Vitamin D sources are fortified milk (400 IU per quart) and some cereals. Check nutrition labels of cereals to see which ones contain Vitamin D.
What Is Good Bone Health?
- Throughout life, calcium continuously moves in and out of the bones. During childhood and the teen years, bones grow in size and density. Calcium goes into the bones faster than it comes out.
- Between ages 20 and 30 years, the bones do not grow anymore in size, but they become more dense and hard if you are taking in enough calcium and Vitamin D. Therefore, the first 30 years (first third of life) is called the "bone building stage."
- After age 40, calcium begins to move out of the bones faster than it goes back in. This is called the "bone losing stage." It is very important to reach this age with the strongest, most dense bones possible to minimize the effects of calcium loss.
- "Good bone health" means reaching adulthood with the most dense, strong bones possible, and then keeping the bones strong by doing the things discussed in this pamphlet.
- On the other hand, if too little calcium is stored in the bones before age 30, or calcium is drawn out too fast in later life, you will be at risk for getting a disease called osteoporosis.
What Is Osteoporosis?
- Osteoporosis (OSS-tee-oh-pore-OH-sis) is a disease, occurring mostly in older adults, due to a loss of bone density and a break down of bone structure. The bones become porous, thin, and brittle. Osteoporosis is a major health problem in the U.S.
- One cause of this disease is getting too little calcium in early life and reaching age 30 with too little calcium in the bones. It can also result from calcium being drawn out of the bones too fast due to several conditions (risk factors) discussed below.
- As the bones in the spine lose calcium, they become more thin and soft and can no longer support the body, causing the person to stoop forward. Eventually, this becomes very serious because the lungs and organs may not have enough room to work properly.
- Bones also break easily, especially those in the hips, legs, and arms. Falls may cause a bone to break, or a bone might give way causing the person to fall.
Risk Factors for Osteoporosis
- Being female: 80% of people with osteoporosis are women. Females have smaller bones and tend to take in less calcium than males. On average, U.S. adult females consume only 450 - 550 mg of calcium per day, which is only half the recommended amount of 1,000 mg.
- Race: Whites and Asians are at greatest risk for osteoporosis, but African-Americans and Hispanics also have some risk.
- Having thin bones and a small frame: If you start out with smaller bones, then lose calcium and bone due to other risk factors, the effect will be more serious.
- Family history of osteoporosis: There is a tendency for osteoporosis to run in families.
- Being underweight or constantly dieting to lose weight: Heavier people tend to have more dense bones. This is one advantage of being overweight. People who constantly stay on a diet to lose weight often do not take in enough calcium.
- Post-menopause: After menopause (i.e. menstrual periods have stopped) women have much lower levels of estrogen, which causes a loss of calcium from the bones.
- Inadequate physical activity: Getting too little physical activity leads to a loss of calcium from the bones.
- Low calcium/Vitamin D intakes: If you do not get enough calcium and Vitamin D early in life, your bones will be less dense and smaller. When you start losing calcium after age 40, the bones will rapidly show the effects of calcium loss.
- Excessive intakes of sodium and protein: Eating excessive amounts of sodium (in salt) and protein (in meat), while not taking in enough calcium, causes the kidneys to excrete more calcium from the body.
- Smoking: Smokers tend to have a lower bone density, partly because smoking decreases calcium absorption.
- Alcohol intake: Excessive intake of alcohol causes a loss of calcium from the body.
- Certain medications: Long-term use of corticosteroids, anticonvulsants, and antacids, as well as excessive levels of thyroid hormones, may either reduce calcium absorption or cause increased loss of calcium from the bones. If you take any of these medications, talk with your doctor about your possible need of a calcium supplement.
A major health concern is that many children and teenagers are not taking in enough calcium. One culprit may be the increased drinking of soft drinks. Health experts fear that many children will develop osteoporosis later in life, due to low calcium intakes during childhood and the teen years.
Ways to Prevent Osteoporosis
- Avoid fad or very restrictive diets to lose weight. If you are trying to lose weight, follow a balanced eating plan with at least a minimum of two cups of low-fat milk or other low-fat milk products. It is best not to go below 1500 calories. If you cannot lose weight at this level, you may need to increase your physical activity.
- If you have gone through menopause or think you are near menopause, talk with your doctor about hormone replacement therapy (HRT) or estrogen replacement therapy (ERT).
- Participate in regular physical activity, including at least 30 minutes of activity on most days of the week. Stretching and weight-bearing activities, such as walking, can increase bone density and help bones remain strong throughout life. Weight lifting exercises are also beneficial to bones, balance, and overall health. Be sure to check with your doctor before starting any new physical activity or greatly increasing your level.
- Don't smoke. If you already smoke, try to stop, or at least cut down.
- Eat a wide range of foods by selecting a variety from each group of the Food Guide Pyramid. Several nutrients are needed to build strong bones and teeth. Eat a variety of foods to get all of them.
- Eat more calcium-rich foods. Milk and foods made with milk are the best sources of calcium. Fluid milk also contains Vitamin D. Cheese and other foods made from milk may not contain the same level of Vitamin D as fluid milk.
- Limit salt and meat intake to moderate levels. Recommended intakes are 2400 mg sodium (1 teaspoon or less of salt) and 2 servings (total of 6 ounces) of meat per day.
- Eat low-fat milk products. When trying to lose weight, or to reduce blood cholesterol, don't cut out milk. Instead, drink skim milk, 1% milk, or buttermilk, or eat low-fat cottage cheese (with added calcium) and yogurt.
- If you drink alcoholic beverages, limit the amount to no more than one per day for women and two per day for men (one drink = 12 ounces beer, or 5 ounces wine, or 1 1/2 ounces liquor).
- Have a bone density test, especially at age 65 and every 2 years thereafter. If you have 2 or more risk factors for osteoporosis, ask your doctor about having a bone density test at a younger age. The machine that measures bones in the entire body is referred to as a DEXA (dex-za) machine
Meeting Your Calcium Needs
DRIs for Calcium At Different Ages and Amount of Milk Needed
|Age Group||Calcium Needs||Milk to Provide Most of Calcium*|
|1 - 8 years||500 - 800 mg||2 to 3 cups|
|9 - 18 years||1300 mg||4 cups|
|19 - 50 years||1000 mg||3 cups or more|
|Women, 51+ (with **HRT) and Men, 51+||1200 mg||3 to 4 cups|
|Women, 51+ (without **HRT)||1500 mg||4 cups or more|
|Pregnant or Breastfeeding||1200 mg||3 to 4 cups|
|*1 cup (8 ounces) of Milk contains about 300 mg of Calcium. The above amounts of milk will not provide all the calcium needed, but there are other foods that can help meet calcium needs. |
**HRT = Hormone Replacement Therapy
What Are the Best Sources of Calcium and Vitamin D?
- The Milk, Yogurt, & Cheese Group of the Food Guide Pyramid is the best source of calcium and Vitamin D. It is very difficult to get enough calcium without drinking milk. One cup (8 ounces) of milk equals one serving and gives about 300 milligrams (mg) of calcium.
- Foods made with milk, such as cheese, yogurt, pudding, custard, ice milk, ice cream, and cream soups, are included in this group.
- Foods that are the lowest in calories, but contain the highest amount of calcium, are skimmed and low-fat fluid milk, buttermilk, and low-fat yogurt. Low-fat cottage cheese with added calcium is also an excellent choice. Plain, low-fat yogurt is especially high in calcium with 415 mg per cup.
- Cheeses contain varying amounts of calcium. The more firm the cheese, the more calcium it contains. For example, Swiss and Parmesan cheese are excellent sources of calcium, whereas softer cheeses (American, Farmers, Mozzarella, and Provolone) have lower amounts of calcium. Cream cheese is not a good source of calcium.
- Some cheeses are made with low-fat or skim milk and are lower in fat, cholesterol, and calories than regular cheese. Check "Nutrition Facts" labels to see how much fat and calcium you are getting in a serving. On the label, calcium is shown as a percent of the daily need of 1000 mg. To determine the milligrams of calcium in a serving, remove the % sign and add one 0. A food that provides 20% of calcium need in one serving will contain 200 mg of calcium.
- Canned fish, such as sardines and salmon, are good sources of calcium, if the bones are eaten.
- Tofu and soymilk are good sources of calcium if made with calcium.
- Almonds, dried beans and peas, and dark green leafy vegetables are fair sources of calcium.
- Due to their acid and Vitamin C content, some fruit juices increase the absorption of calcium.
Drinking orange or grapefruit juice with added calcium is a good way to meet calcium needs.
When substituting other calcium sources in place of milk, care must be taken to eat enough of these foods to equal the calcium in the milk that is replaced. The following foods provide about the same amount of calcium as 1 cup of milk (300 mg).
- Very Firm Cheeses (Swiss, Parmesan) - 1 ounce
- Less Firm Cheeses (cheddar, American, mozzarella and provolone) -1 1/2 ounces
- Regular Cottage Cheese - 2 cups
- Calcium-enriched Cottage Cheese - 3/4 cup
- Plain Ice Milk or Frozen Yogurt - 1 cup
- Plain Yogurt - 3/4 cup
- Pizza (2 slices) - 1/4 of a 12" pizza
- Tofu (cubes) - 1 cup
- Soybeans (cooked) - 2 1/3 cups
- Navy Beans (cooked) - 1 1/4 cups
- Pork N¹ Beans - 1 3/4 cups
- Salmon (canned with bones) - 5 1/3 ounces
- Turnip Greens - 1 1/2 cups
Contrary to previous belief, calcium from plant sources is well absorbed. One exception is the calcium in spinach, which is not well absorbed due to compounds called oxalates.
Cheese, yogurt, and buttermilk may not cause this problem since much of the "lactose" has already been broken down. Also, you may be able to drink smaller amounts of milk at one time (1 cup or less) without symptoms. Lactaid tablets (from a drug store) can be added to milk to reduce the lactose.
Do you need to take a calcium supplement?
Here are some things to consider, if you take a calcium supplement:
- Not all calcium supplements are equally well absorbed in the body. Calcium Carbonate and Calcium Citrate are fairly well absorbed. These are available in most drug stores without a prescription.
- Calcium Citrate is well absorbed under most conditions, but is best taken on an empty stomach. Calcium Carbonate needs acid to be absorbed, so it is best taken with a meal or soon thereafter when stomach acid is highest. Stomach acid may be low in older adults (called achlorhydria), causing reduced calcium absorption. Thus, Calcium Citrate might be the best choice for older adults.
- How much calcium should you take at one time? No matter what type of calcium supplement you take, limit the amount to no more than 500 mg at a time (calcium in food + supplement). This is all that the body can absorb at once. Some cereals provide 1000 mg calcium in a serving, which overloads the body's ability to absorb all of it.
- Do you also need a Vitamin D supplement? If you have dark skin, or are in the sun very little, you may need a calcium supplement that contains Vitamin D. Only 5 to 10 micrograms (200 to 400 IU) of Vitamin D are needed each day, but be sure to keep your intake below 50 micrograms (2,000 IU) per day. A daily intake higher than this can be very harmful.