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VOLUME 9 NUMBER 3 • SEPTEMBER 2012
EDUCATOR’S FOCUS
SA JOURNAL OF DIABETES & VASCULAR DISEASE
Chromium is widely distributed in foods but most provide only small
amounts (< 2 mcg) per serving. Meat and wholegrain products as
well as some fruit, vegetables and spices are relatively good sources,
whereas foods high in simple sugars are low in chromium.
The absorption of chromium in the digestive tract is low, ranging from
0.4
to 2.5% of the amount consumed. Vitamin C and niacin enhance the
absorption of chromium from the diet.
The body’s chromium content may be reduced under several condi-
tions. Diets that are high in simple sugars (> 35% of calories) can in-
crease chromium excretion in the urine. Infection, acute exercise, preg-
nancy and lactation, and stress increase chromium losses and can lead
to deficiency, especially if chromium intakes are already low.
Chromium deficiency impairs the body’s ability to use glucose to meet
its energy needs and raises insulin requirements. It has therefore been
suggested that chromium supplements might help to control type 2 dia-
betes or the glucose and insulin responses in persons at high risk of
developing the disease.
Recent studies have shown that chromium reduces HbA
1
c
levels by
0.6%
in type 2 diabetes and reduces fasting glucose levels by 1 mmol/l.
There is less weight gain in patients who use chromium in combination
with diabetes treatment than with treatment alone. Chromium has more
consistent effects in those with poorer glycaemic control, patients who
are insulin resistant, and those who are chromium deficient.
Suggested dosages in type 2 diabetes can range from 200–1 000
mcg/day. Few serious adverse effects have been linked to high chromium
intake, so the Institute of Medicine has not established a tolerable upper
intake level. Chromium supplements are available as chromium chloride,
chromium nicotinate, chromium picolinate, high-chromium yeast and
chromium citrate, some of which have poor bioavailability.
My choice of supplement is chromium nicotinate. I often prescribe
chromium with meals due to its appetite-reducing effects, which would
therefore help weight-loss patients keep to their eating plans.
Magnesium
There is an increased interest in the role of magnesium in the prevention
and management of disorders such as hypertension, cardiovascular dis-
ease and diabetes. Magnesium plays an important role in carbohydrate
metabolism. It may influence the release and activity of insulin, the hor-
mone that helps control blood glucose levels.
Low blood levels of magnesium (hypomagnesaemia) are frequently
seen in individuals with type 2 diabetes. Hypomagnesaemia may worsen
insulin resistance, a condition that often precedes diabetes, or may be a
consequence of insulin resistance.
Individuals with insulin resistance do not use insulin efficiently and
require greater amounts of insulin to maintain blood sugar within normal
levels. The kidneys possibly lose their ability to retain magnesium during
periods of severe hyperglycaemia (significantly elevated blood glucose
levels). The increased loss of magnesium in the urine may then result in
lower blood levels of magnesium.
In older adults, correcting magnesium depletion may improve insulin
response and action. It is postulated that magnesium may improve the
action of insulin and decrease blood glucose levels, particularly in the
elderly, where there is a definite decline in magnesium intake and in-
crease in magnesium secretion.
The recommended amount of magnesium per day is 300–420 mcg. The
following foods have high amounts of magnesium: green leafy vegetables,
wholegrain, high-bran cereals, nuts and seeds, legumes, and bananas. The
indications for supplementation are:
uncontrolled diabetes as magnesium is lost in the urine when glu-
•
cose rises above 8 mmol/l
diabetics with uncontrolled hypertension
•
diabetics using certain medications such as diuretics (Lasix, thiaside
•
diuretics) or antibiotics (gentamicin, amphotericin)
older diabetics; with aging, magnesium intake decreases and mag-
•
nesium excretion increases.
Doctors can evaluate the magnesium status when these medical prob-
lems occur and determine the need for magnesium supplementation.
Oral magnesium supplements combine magnesium with another sub-
stance such as a salt. Examples of magnesium supplements include
magnesium oxide, magnesium sulfate and magnesium carbonate.
Elemental magnesium refers to the amount of magnesium in each
compound. The amount of elemental magnesium in a compound and its
bioavailability influence the effectiveness of the magnesium supplement.
Bioavailability refers to the amount of magnesium in food, medications
and supplements that is absorbed in the intestines and ultimately avail-
able for biological activity in the cells and tissues. Enteric coating (the
outer layer of a tablet or capsule that allows it to pass through the stom-
ach and be dissolved in the small intestine) of a magnesium compound
can decrease bioavailability.
In a study that compared four forms of magnesium preparations,
results suggested lower bioavailability of magnesium oxide, with sig-
nificantly higher and equal absorption and bioavailability of magnesium
chloride and magnesium lactate. This supports the belief that both the
magnesium content of a dietary supplement and its bioavailability con-
tribute to its ability to restore deficient levels of magnesium.
Thiamine
Thiamine is an essential micronutrient that acts as a co-factor for several
key enzymes in glucose and amino acid metabolism. Thiamine deficiency
leads to a relative reduction in the function of specific metabolic path-
ways and can lead to endothelial dysfunction and potentially worsen type
2
diabetes.
