Medical problems developing as a result of consuming refined or complex carbohydrates are generally of a digestive nature, such as longer transit time (refined carbs), or abdominal bloating (complex carbs), or they adversely affect mineral uptake and balance (Fe, Ca).  With the exception of dental caries that can be linked to the consumption of various types of carbs, medical problems resulting from ingesting simple carbs (sugar, honey, candy, pop, cakes, sweet/overripe fruit...) are much more significant:

•  In contrast to complex carbs, simple carbs require more resources of specific nutrients such as biotin,    Vit C, manganese and chromium.

•  Manganese is unaffected by complex carb intake, but simple carbs lower manganese levels in those  with hypoglycemic (low blood sugar) tendencies, and they raise manganese levels in individuals with an inclination for hyperglycemia (high blood sugar).

•  Simple carbs (including fructose from fruit) promote the formation of VLDL triglycerides, while refined or complex carbs don't, so in contrast to complex carbs, simple carbs raise the risk for cardiovascular disease.

•  Simple carbs decrease w3 EFAs and germanium levels (which have blood thinning properties), and complex carbs support or enhance both. 

•  Unlike simple carbs, complex carbs are fiber-rich, which:
   - improves digestive health and transit time,
   - may result in lower absorption/bioavailability of specific minerals, particularly calcium and iron,
   - slows glycogen conversion, which better stabilizes blood sugar.

•  Unlike complex carbs, simple carbs (sweets) can cause pain when in contact with exposed dental roots.

•  Simple carbs can promote osteoporosis in trabecular bone through the chromium / parathyroid mechanism, while complex carbs can promote osteoporosis in cortical bone through a calcium-lowering effect, which they have in common with high protein / phosphate sources.

•  Simple carbs - unlike complex carbs - trigger more medical symptoms such as headaches, fatigue, depression, drowsiness, mucus / throat discomfort, or sugar withdrawal symptoms.

•  According to some research, simple carbs - unlike complex carbs - promote free radicals.

•  Simple carbs - unlike complex carbs - effect an opposing change in hyper/hypoglycemics, resulting in a higher Na/K ratio with hyperglycemics, and a higher K/Na ratio with hypoglycemics, which can subsequently lead to an increase in blood pressure with the former, and a decrease in blood pressure  with the latter.

•  In contrast to complex carbs, ingesting simple carbs reduces the WBC's ability to destroy bacteria (phagocytosis).  In sugar-intolerant types, this can lead to increased pus formation, and in patients with leukemia to an increased WBC count.  There is also an inhibiting effect on the immune system by the formation of AGE's (advanced glycosylation end product).

In a comparison I did a few years ago of patients who had actual episodes of ischemic heart disease or strokes, the incidence of elevated VLDL triglycerides versus elevated LDL cholesterol was 2.2:1. Some reports I have come across by other researchers ranged from 2:1 to as high as 4:1 according to their statistics or observations, so simple sugar can be considered to be a much bigger culprit with cardiovascular disease or ischemic stroke than fats.

On the other hand, sodium counteracts the effects of saturated fats and/or transfatty acids, so people who retain a lot of sodium enjoy a moderate amount of protection from ischemic heart disease or stroke, but suffer from a greater risk of hemorrhaging stroke or (congestive) heart failure, while low aldosterone (low sodium) types are at a much higher risk from LDL cholesterol and subsequent effects and problems.

The Glycemic Index  (GI) has over the last years become the focus of heated debates among various health advocates, particularly with respect to weight and blood sugar management.  Proponents for the utilization of the glycemic index in clinical settings argue that consumption of low-GI meals results in greater weight loss and greater satiety compared to the consumption of high GI meals, while opponents of the GI question these findings and argue against high-GI foods promoting obesity.

One of the biggest predicaments surrounding the GI is the inconsistency with specific foods -- where the preparation of a particular food, or the ripening process can change the GI as much as 30%.  There is also the total rise versus acceleration in blood glucose, which lacks actual measurements/units per food item, and the question remains why some people are clearly affected by the GI, and why others show little, or no response at all.

From a personal clinical perspective, I can understand why some individuals have such an abnormal response to high glycemic index food sources, and that following the GI can be very helpful for them.

When you analyze these people's chemistry, their body is simply unable to compensate because of chemical/nutritional shortcomings.  The list of players affecting insulin/glucose balance is quite lengthy, and includes manganese, chromium, sodium, vanadium, biotin, potassium, Vit C, Vit B6, Vit B3/4, and to a lesser degree most common nutrients such as magnesium, calcium, germanium, zinc, Vit E, folate, PABA, essential fatty acids (EFAs), as well as other considerations, including hormones.

Sodium greatly affects insulin response, and it is along with Vit C and biotin one of the most important factors to prevent/reduce erratic glucose level changes on an in-between meal basis.  Manganese, and to some extent chromium and Vit B3/4 control glucose response and liver glycogen storage (Mn), while potassium and Vit B6 either help stabilize, or interfere with that process, depending on a patient's hypo or hyperglycemic disposition.

Once these factors are corrected and balanced, the GI becomes meaningless and can be largely ignored.  Instead - and as much as they have become a dinosaur in the eyes of some proponents of low-carb dieting - discriminating between simple, refined, and complex carbs (fibre-rich carbs) is as important and relevant as ever, particularly as far as long-term health effects are concerned.