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May 20, 2014

Carbohydrates

by Helene van den Berg

MOLECULAR CLASSIFICATION of carbohydrates:

  • MONOSACCHARIDES: (single sugars)
  1. They are simple sugars, which cannot be broken down into smaller units by hydrolysis during gastrointestinal digestion e.g. glucose (blood sugar) , fructose (fruit sugar) and galactose (milk sugar). These three monosaccharides are the most important ones in nutrition and each contain 6 carbon atoms, 12 hydrogens and 6 oxygens (C6 H12 O6). The monosaccharides differ in their arrangements of the atoms. These chemical differences account for the differing sweetness of the monosaccharides e.g. glucose and galactose are hardly sweet at all, while fructose is very sweet, such as honey.

  • DISACCHARIDES: (pairs of monosaccharides)
  1. They are pairs of the three monosaccharides e.g. sucrose (= fructose + glucose) e.g. cane/ beet sugar , lactose (galactose + glucose) e.g. milk sugar and maltose (glucose + glucose) is produced when starch breaks down during carbohydrate digestion. Glucose occurs in all three of the pairs. Chemical reactions link these carbohydrates linked together (condensation) or take them apart (hydrolysis).
  • POLYSACCHARIDES: (chains of monosaccharides)
  1. Larger complex molecules formed by a chain of monosaccharides. Three types of polysaccharides are important in nutrition: starches (storage form of energy in plants) , fibers (structural parts of plants) and glycogen (storage form of energy in the body).

TYPE OF CARBOHYDRATES and it’s relevance to BLOOD SUGAR LEVELS and DISEASE:

  • REFINED – means processing foods in a way that removes the vitamins, minerals and fibre e.g. white flour/rice, unbleached white flour and enriched flour.
  • UNREFINED – means minimally processed and contain the vitamins, minerals and fibre e.g. wheat flour, brown rice, or any whole grain product.

Carbohydrates are classified as “simple” or “complex” depending on their molecular structure.

  • SIMPLE CARBOHYDRATES are monosaccharides and disaccharides or SUGARS – table sugar (sucrose), honey, maple syrup, fruit sugar (fructose) and corn syrup are SWEET. They are found in both refined and unrefined products.
  • COMPLEX CARBOHYDRATES are polysaccharides or STARCHES and FIBERS – wheat, rice, pasta, corn, potatoes, lentils are NOT sweet. The grains in this category may be refined (white flour) or unrefined (wheat flour).

Both simple and complex carbohydrates are converted into GLUCOSE or BLOOD SUGAR, in the body. Glucose provides the fuel for brain, muscles and other tissues. Glucose is stored in the liver and muscles as GLYCOGEN, which can be easily reconverted to glucose for energy.

THEREFORE one needs to determine whether a carbohydrate is simple or complex, refined or unrefined, BECAUSE these differences have HUGE health and disease implications!!.

The carbohydrate portion of our diet should be mostly COMPLEX AND UNREFINED.

A COMPLEX CARBOHYDRATE (rice, pasta) consist of very long strands of simple sugars (polysaccharides), which are too long to be absorbed across the small intestine lining into the blood stream. Digestion must occur, in order for these long strands to be broken into separate simple sugar molecules (monosaccharides) small enough to enter the bloodstream. Various enzymes perform this task. This process takes time and produces a slow, gradual increase in blood sugar levels as more and more simple sugar molecules are broken off from the long strands and absorbed into the bloodstream.

As the blood sugar level gradually rises, this signals the pancreas to release a corresponding amount of insulin into the blood stream. Insulin facilitate the sugar molecules to penetrate the cell walls (nourish the body’s cells) and prevents the accumulation of too much sugar in the blood. Diabetics who have no insulin or who’s body cells are unresponsive to the action of insulin, have a high blood glucose level as a result.

To summarize:

  • Slow release system of blood sugar:
  • Ingestion of complex carbohydrates→ gradual rise of blood sugar→ gradual release of insulin (pancreas)→ gradual return of blood sugar levels…to what it was before you ate.
  • This slow-release system of blood sugar ensures a consistent level of fuel to the body’s cells (especially the brain). Therefore unrefined, complex carbohydrates seem to be the ideal food for this slow-release system!. In a well-balanced diet, 50-60% of daily caloric intake, should come from complex carbohydrates.

Glycogen is the form in which the animal cell stores carbohydrate. (Glycogen is a polymer of glucose and yields glucose on hydrolysis). Cellulose is the structural component of plant tissues. The human digestive tract does not secrete an enzyme, which is capable of digesting cellulose. When ingested with fruits, vegetables or as the indigestible residue of whole grains, it provides the roughage, which is essential for optimal functioning of the colon (large intestines) and the formation of faeces.

Here is a GOOD QUESTION for you:

If complex carbohydrates break down into simple sugars, why are they different from the simple carbohydrates found in sugar?. Don’t they provide the same amount of energy?

The answer is yes and no: They do provide the same amount of energy/calories. BUT the body treats complex carbohydrates differently. They break down more slowly, consuming more metabolic energy in digestion and keeping glucose levels more stable; we eat less complex carbohydrates per gram of food. Complex carbohydrates are also rich in vitamins and nutrients and high in fibre. Forget the old diet myths that breads and pasta are fattening. Carbohydrates contain far fewer calories per gram (4 per gram) than fats (9 per gram). Eating a diet high in complex carbohydrates- fruits, vegetables and grains – will help shed excess kilograms and gain extra years of youth. Cereals, vegetables and fruits are the major natural sources of carbohydrates. Milk and it’s derivatives contribute lactose to the diet, the only major carbohydrates of animal origin.

Refined carbohydrates/sugars are very quickly digested and absorbed into our bloodstream and raise blood glucose levels too high (hyperglycemia) – one symptom of diabetes. Insulin very efficiently, removes the excess glucose from our bloodstream. Then our glucose levels may fall too rapidly or too low (hypoglycemia) – symptoms include dizziness, depression, insomnia, aggression, weakness and loss of consciousness. When our blood glucose falls too low, our adrenal glands, mobilize the body’s stores of glycogen and also stimulate the synthesis of glucose from proteins.

A diet of refined carbohydrates causes the pancreas and adrenal glands to be in a constant biochemical see-saw, overworking them. If our pancreas weakens, it secretes less insulin, our blood glucose remains high, resulting in hyperglycemia and glucose spill into our urine. Cardiovascular complications that develop from excess glucose and/or fats kill many diabetics. Additionally, hard fats interfere with insulin function, leading to “insulin insensitivity”.

With adrenal exhaustion, the adrenals are unable to respond biochemically to stress and stress-caused diseases occur. Overworked adrenal glands fail in their blood sugar-raising function, resulting in low blood sugar (hypoglycemia) from the action of insulin. Hypoglycemia causes a craving for sweets; the sugar of the sweets is rapidly absorbed and another vicious hyperglycemia-hypoglycemia-sugar craving cycle starts.

Insulin sensitivity could be improved by :

  • reducing excessive body weight,
  • engage in regular physical activity
  • correct a magnesium deficiency (if indicated)
  • vanadium (vanadyl sulfate supplementation)
  • zinc supplementation– helps with glucose control and insulin action.
  • Chromium supplementation – improves glucose tolerance. Chromium assist in the maintenance of normal lipid and carbohydrate metabolism and promote insulin sensitivity. Chromium deficiency causes symptoms associated with adult-onset diabetes and cardiovascular disease.
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