GLYCEMIC INDEX AND DIABETES

Not all carbohydrate foods are created equal impact, in fact they behave quite differently in our bodies. The glycemic index or GI describes this difference by ranking carbohydrates according to their effect on our blood glucose levels. Choosing low GI carbohydrates that produce only small fluctuations in our blood glucose and insulin levels is the secret to long-term health reducing our risk of heart disease and diabetes and is the key to sustainable weight loss. 

The Glycaemic Index (GI) categorizes starchy foods according to their potential to raise the blood glucose levels. Blood glucose levels fluctuate following ingestion of foods containing carbohydrates. GI measures the effects of carbohydrates on blood glucose levels by serving either a 50 g or a 25 g available carbohydrate portion (which may or may not be the normal serving size).

GI of a test food is calculated with reference to a standard ,

        GI   =  IAUC of test food   x  100

                   IAUC of standard

(IAUC : incremental area under the blood glucose response curve )

Standard used is either white bread or glucose and is given the value 100. Glycaemic response is influenced by the amount of the food we eat, type of the food, meal accompaniments and the processing/preparation method.

According to the GI values obtained with glucose as the standard, foods are categorized as low, medium or high GI foods.

Low GI = 55 or less             Medium GI = 56-69             High GI = 70 or above

Glycaemic Load

As GI is estimated with a standard amount of carbohydrate load which may or may not be the normal serving size, glycaemic load (GL) was introduced to apply the GI concept to the normal serving sizes of foods (edible portions).

Glycaemic load is calculated as,

         GL  = [GI x amount of carbohydrate (grams) in the edible portion]

                               100

Thus, high GI/low carbohydrate diets or low GI/high carbohydrate diets can have the same GL.

According to the glycaemic load values foods can be categorized as given below (with reference to glucose):

Low GL = 10 or less                Medium GL = 11-19              High GL = 20 or more

High GI foods - Carbohydrates are digested fast. Thus, glucose is released into the blood rapidly.

Low GI foods – Glucose is released slowly into blood stream.

Foods with low GI are reported to reduce the risk of diabetes and coronary heart disease and maintain a healthy body weight. The high glycaemic responses resulting from high GI foods can be lowered by consuming high GI foods with low or medium GI foods. Ex. Bread or high GI rice with curries made with low GI foods.

Measuring the Glycemic Index of Foods 

To determine the glycemic index of a food, volunteers are typically given a test food that provides 50 grams of carbohydrate and a control food (white bread or pure glucose) that provides the same amount of carbohydrate on different days. Blood samples for the determination of glucose are taken prior to eating and at regular intervals after eating over the next several hours. 

The changes in blood glucose over time are plotted as a curve. The glycemic index is calculated as the area under the glucose curve after the test food is eaten, divided by the corresponding area after the control food is eaten. The value is multiplied by 100 to represent a percentage of the control food. 

For example, a baked potato has a glycemic index of 76 relative to glucose and 108 relative to white bread, which means that the blood glucose response to the carbohydrate in a baked potato is 76% of the blood glucose response to the same amount of carbohydrate in pure glucose and 108% of the blood glucose response to the same amount of carbohydrate in white bread. 

In contrast, cooked brown rice has a glycemic index of 55 relative to glucose and 79 relative to white bread. In the traditional system of classifying carbohydrates, both brown rice and potato would be classified as complex carbohydrates despite the difference in their effects on blood glucose levels.

Diabetes

Diabetes mellitus type 1 (Type 1 diabetes, IDDM, or, obsoletely, juvenile diabetes) is a form of diabetes mellitus that results from autoimmune destruction of insulin-producing beta cells of the pancreas. The subsequent lack of insulin leads to increased blood and urine glucose. The classical symptoms are polyuria (frequent urination), polydipsia (increased thirst), polyphagia (increased hunger), and weight loss.

Type 1 diabetes is fatal unless treated with insulin. Injection is the most common method of administering insulin; insulin pumps and inhaled insulin have been available at various times. Pancreas and islet transplants have been used to treat type 1 diabetes; however, islet transplants are currently still at the experimental trial stage. 

Diabetes mellitus type 2 – formerly non-insulin-dependent diabetes mellitus (NIDDM) or adult-onset diabetes – is a metabolic disorder that is characterized by high blood glucose in the context of insulin resistance and relative insulin deficiency. Diabetes is often initially managed by increasing exercise and dietary modification. If the condition progresses, medications may be needed.

Type 2 Diabetes Mellitus 

After a high-glycemic load meal, blood glucose levels rise more rapidly and insulin demand is greater than after a low-glycemic load meal. High blood glucose levels and excessive insulin secretion are thought to contribute to the loss of the insulin-secreting function of the pancreatic beta-cells that leads to irreversible diabetes. 

High dietary glycemic loads have been associated with an increased risk of developing type 2 diabetes mellitus (DM) in several large prospective studies. In the Nurses’ Health Study (NHS), women with the highest dietary glycemic loads were 37% more likely to develop type 2 DM over a 6-year period than women with the lowest dietary glycemic loads. Additionally, women with high-glycemic load diets that were low in cereal fiber were more than twice as likely to develop type 2 DM than women with low-glycemic load diets that were high in cereal fiber. 

The results of the Health Professionals Follow-up Study (HPFS), which followed male health professionals over six years were similar. In the NHS II study, a prospective study of younger and middle-aged women, those who consumed foods with the highest glycemic index values and the least cereal fiber were also at significantly higher risk of developing type 2 DM over the next eight years. 

The foods that were most consistently associated with increased risk of type 2 DM in the NHS and HPFS cohorts were potatoes (cooked or French-fried), white rice, white bread, and carbonated beverages.The Black Women's Health study, a prospective study in a cohort of 59,000 U.S. black women, found that women who consumed foods with the highest glycemic index values had a 23% greater risk of developing type 2 DM over eight years of follow-up compared to those who consumed foods with the lowest glycemic index values. 

In the American Cancer Society Cancer Prevention Study II, which followed 124,907 men and women for nine years, high glycemic load was associated with a 15% increased risk of type 2 DM. Further, in a cohort of over 64,000 Chinese women participating in the Shanghai Women's Health Study, high glycemic load was associated with a 34% increase in risk of type 2 DM; this positive association was much stronger among overweight women. 

A U.S. ecological study of national data from 1909 to 1997 found that increased consumption of refined carbohydrates in the form of corn syrup, coupled with declining intake of dietary fiber, has paralleled the increase in prevalence of type 2 DM. Today, high-fructose corn syrup (HFCS) is used as a sweetener and preservative in many commercial products sold in the United States, including soft drinks and other processed foods. 

To make HFCS, the fructose content of corn syrup (100% glucose) has been artificially increased; common formulations of HFCS now include 42%, 55%, or 90% fructose. When consumed in large quantities on a long-term basis, HFCS is unhealthful and may contribute to other chronic diseases besides type 2 DM, including obesity and cardiovascular disease.

References :

http://www.diabetesnet.com
http://www.whfoods.com 

http://lpi.oregonstate.edu

ARTIFICIAL (SYNTHETIC) GROWTH REGULATORS AND FRUIT RIPENING AGENTS

Growth regulators, also known as phytohormones, are substances that act as hormones in plants to regulate faster plant growth. Most plants naturally generate growth regulators for various development processes, like formation of stems, leaves, flowers, shedding of leaves and ripening of fruits. They also help to shape the plant appropriately, affect the seeding phase, the right time of flowering, the sex of flowers and aging of vegetables and fruits. However, growers with the help of artificial growth regulators can push the growth of plants to get desired results. Growth regulators are produced in low concentrations and sometimes plants also produce regulators that encourage growth in other plants.

With the help of growth regulators plant can easily respond to environmental pressures. For instance, during the draught conditions, growth of a plant is suppressed because of less water. And, during the year where there is enough rain, the growth of a plant is triggered as the tree takes full advantage of different weather conditions. It’s very important to give plants special attention while providing them water, growth regulators or fertilizers, as it damage plants.

When people trick plants with applications of water, fertilizers, or growth regulators, sometimes they become unhealthy unless they are closely monitored. With the help of artificial growth regulators, can accomplish different goals, such as productions of healthy roots, encourage faster fruiting, reduce the number of suckers etc. Growth regulators are very helpful to grow ornamentals because they can efficiently prolong the flowering phase to give bigger and colorful flowers, they are also used for faster growth of vines, new leaves and fruits etc.


ARTIFICIAL GROWTH REGULATORS

Biochemists studied the structural properties and applications of IAA and Kinetin and prepared similar compounds in their laboratories. They are the synthetic growth regulators. They are also called artificial growth regulators. Some examples of synthetic growth regulators are IAA (Indole Acetic Acid), IBA (Indole Butyric acid), NAA (Naphthalene Acetic Acid), 2-4 D, (2-4-Dichlorophenoxy Acetic Acid), BAP (Benzyl Amino Purine) and Ethephon (2-chloroethyl phosphoric acid). Among these IAA, IBA, NAA and 2-4-D are the synthetic auxins. BAP is the synthetic cytokinin and Ethephon is a synthetic ethylene - releasing compound.


APPLICATION OF SYNTHETIC GROWTH REGULATORS

Synthetic growth regulators are commonly used in agriculture and horticulture for crop improvement. They are also used in tissue culture laboratories. Important applications are,

· Induction of rooting

Gardeners in nurseries dip the cut ends of branches and leaves in a dilute solution of NAA or IBA to induce adventitious roots. In practice, these synthetic growth regulators are more efficient than IAA.

· Prevention of Abscission layer

The premature fall of leaves, flowers and fruits is common in plants like apple, pear, mangoes etc. It is due to the development of abscission layer in the petiole and pedicel. The abscission layer development is due to the deficiency of natural auxins in the plants and that can be prevented by spraying synthetic growth regulators. This action of synthetic growth regulators has been used in agriculture and horticulture to prevent premature fall of leaves and fruits. Premature fall of fruits in apple and pear can be prevented by spraying proper concentrated solution of IBA or NAA. A spray of 2-4-D in dilute concentration over cabbage heads prevents defoliation. 

· Production of parthenocarpic fruits

Synthetic auxins are used to produce seedless or parthenocarpic fruits. A spray of NAA or IBA induced parthenocarpic fruits in tomato, brinjal, watermelon, certain varieties of grapes and oranges.

· Eradication of weeds

2-4-D is a selective weed killer. By spraying concentrated solutions of 2-4-D weeds can be eradicated from the crop fields, forests and along the railway lines. 2-4-D shows greater toxicity to dicotyledonous (broad leaved) plants than monocotyledonous (narrow leaved) plants. A spray of 2-4-D to corn field irradicated broad leaved weeds in the field leaving the corn plant intact.

· Flower initiation

Auxins generally inhibit the flowering but in pineapple spraying of low concentration of NAA initiate uniform flowering in the whole crop, so that harvesting becomes easy. Lettuce is a leafy vegetable grown for its vegetative parts, but when the plant develops flower it looses the market value. But a spray of NAA is proper concentration over the plant lettuce delayed the flowering and induced the plant to grow vegetatively.

· Apical dominance and dormancy

Potato tubers can be stored maximum for one year and later the axillary buds in the "eyes" develop into small thick branches. But that can be prevented by spraying proper concentrated solution of NAA over the surface of tubers.

· Induction of callus and regeneration of microshoots

Synthetic auxins like IAA, IBA, NAA and 2-4-D are used to induce callus formation. When the non meristematic tissues in the stem, root vegetative buds etc are cultured on a nutrient medium with the synthetic auxins they develop callus at the injured regions. Subculture of callus on a nutrient medium with cytokinin like BAP promote the development of stem buds and later the microshoots. BAP is a strong and effective cytokinin used extensively for the regeneration of microshoots in a variety of medicinal, ornamental, forest and crop plants.

· Ethephon is a commercial fruit ripener

Ethephon is known by its trade name, Ethrel. It has several valuable commercial applications. Ethephon is used to ripen bananas, pineapple, melons and tomatoes, and when applied as a pre-harvest spray it promotes uniform ripening of apples, cherries and pineapple. It is used to increase the production of female flowers in cucumbers, which develop fruits and increase yields.

RIPENING AGENTS

Ripening agents speed up the ripening process.

They allow many fruits to be picked prior to full ripening, which is useful, since ripened fruits do not ship well. For example, bananas are picked when green and artificially ripened after shipment by being gassed with ethylene. A similar method used in parts of Asia is to put a plastic cover over a bed of slightly green-harvested mangos and a few small open containers of clumps of calcium carbide. The moisture in the air reacts with the calcium carbide to release the gas acetylene, which has the same effect as ethylene. Ethylene is not emitted by the plant naturally, and cannot activate the ripening of nearby fruits, rather, it is used as a hormone within the plant.

Calcium carbide is used for ripening fruit artificially in some countries. Since industrial-grade calcium carbide may contain traces of arsenic and phosphorus, the use of this chemical for this purpose is illegal in most countries. Calcium carbide, once dissolved in water, produces acetylene, which acts as an artificial ripening agent. Acetylene is believed to affect the nervous system by reducing the oxygen supply to the brain; however, it has been shown that, in practice, acetylene is not sufficiently reactive to affect consumers.

Catalytic generators are used to produce ethylene gas simply and safely. Ethylene sensors can be used to precisely control the amount of gas.

Covered fruit ripening bowls are commercially available. The manufacturers claim the bowls increase the amount of ethylene and carbon dioxide gasses around the fruit, which promotes ripening.

Climacteric fruits are able to continue ripening after being picked, a process accelerated by ethylene gas. Non-climacteric fruits can ripen only on the plant and thus have a short shelf life if harvested when they are ripe.

Health consultants highly recommend fruits and salads in their prescriptions and we take the best advantage of the availability of the range of variety in the markets. But how close we are to nature, when we are consuming these fruits is a very big question mark. Fruits and vegetables are known to be possessing antioxidant and anti-aging factors. If they are a source of harmful chemicals as well, then are we heading towards fitness or otherwise some harmful effects.....

In recent times, there is much concern about artificial ripening of fruits. Though fruits like mango naturally ripen in trees, some chemicals are used to ripen them artificially which hasten the ripening process. Ripe fruits are not suitable to carry and distribute as they get rotten. So traders pick unripe fruits and use certain methods to increase their shelf life.

For many years, ethylene had been used as a fruit ripening agent, but nowadays ethane, calcium carbide and ethephon are commonly used for faster ripening. But inappropriate use of these chemicals to ripen fruits is associated with many health hazards.

Ripening is a process in fruits that causes them to become edible. Globally, the ripening is done through gas emission systems or ethylene generator systems, depending on quality and shelf life desired.
Effects of Artificial Ripening

· Ethylene is known to cause damage to the neurological system, affects the eyes, skin, lungs, memory and leads to prolonged hypoxia (lack of oxygen supply).

· Ethephon is a plant growth regulator. It promotes pre-harvest ripening in apples, currants, blackberries, blueberries, cranberries, morello cherries, citrus fruit, figs, tomatoes, sugar beet and fodder beet seed crops, coffee, capsicum. Ethephon is easily converted into ethylene and has the same harmful effects.

· State Food and Drugs Control Administration (FDCA) has banned the use of ethephon , but fruit traders have now resorted to bethylene.

· Bethylene is not known to have any harmful effects but it alters the taste and the nutritional value of fruits and also reduces the shelf life of the fruits, if used beyond the recommended limits. And most of the traders do use quantities of bethylene which are much higher than the prescribed limits.

· Besides ripening agents, farmers also use many pesticides to grow fruits and vegetables which are detrimental to our health.

· Calcium carbide is used for ripening the fruit artificially in some countries. Industrial-grade calcium carbide may contain traces of arsenic and phosphorus, and, thus, use of this chemical for this purpose is illegal in most countries. Calcium carbide, once dissolved in water, produces acetylene, which acts as an artificial ripening agent. Acetylene is believed to affect the nervous system by reducing oxygen supply to brain, however, it has been shown that, in practice, acetylene is not sufficiently reactive to affect consumers.

Ethylene and calcium carbide

Ethylene is a natural plant hormone.It affects the growth, development, ripening, and senescence (aging) of all plants. It is normally produced in small quantities by most fruits and vegetables. Many fruits produce larger quantities of ethylene and respond with uniform ripening when exposed to an external source of ethylene.

Ethylene is Generally Recognized as Safe (GRAS) by the United States Food and Drug Administration (FDA). Given the numerous amounts of food substances, the FDA does not categorize every one. Salt, pepper and vinegar are examples. These, along with ethylene, all are within the category of food substances that, when used for the purposes indicated, in accordance with good manufacturing practice, are regarded by the FDA as generally recognized as safe (GRAS) for such uses.

Ethylene has been found not harmful or toxic to humans in the concentrations found in ripening rooms. In fact, ethylene was used medically as a anesthetic in concentrations significantly greater than that found in a ripening room. However, ethylene is often targeted as the reason for difficulty in breathing in ripening rooms; what can affect some people is usually either:

a) Carbon Dioxide (CO2,) levels: CO2, is produced by the ripening fruit in the room and levels increase over time, or

b) Oxygen levels: The oxygen in the room when loaded is taken in by the ripening fruit. This sometimes will make breathing in a ripening room difficult. The increased CO2, and decreased oxygen levels are the main reasons for venting the ripening room.

Calcium Carbide is NOT safe for ripening. Calcium Carbide is used in some countries as source of acetylene gas, which is an artificial ripening agent. However, acetylene is not nearly as effective for ripening as is ethylene, and acetylene is not a natural plant hormone like ethylene. Also, calcium carbide may contain traces of arsenic and phosphorus, both highly toxic to humans, and the use of this chemical for ripening is illegal in most countries.

References :

www.tutornext.com

books.google.lk

www.catalyticgenerators.com