Diet and Gestational Diabetes

Gestational diabetes mellitus (GDM)

For gestational diabetes mellitus we mean any form of glucose intolerance (and of any degree) that arises In the period of the pregnancy (hence the synonym "gravidic diabetes"); gestational diabetes occurs more frequently between the 10th and 14th week of pregnancy and is very often attributable to a type 2 diabetes mellitus triggered by metabolic changes typical of gestation itself.

Gestational diabetes is therefore a silent diabetes mellitus which begins during pregnancy and which, in addition to impaired glucose tolerance, is characterized in 75% of cases by reduced insulin secretion.
NB. Gestational diabetes is very frequently correlated with a family history of type 2 diabetes mellitus.
Gestational diabetes is a fairly common morbid condition that should not be underestimated; in addition to "becoming chronic", worsening the state of health of the mother even after delivery, gestational diabetes can compromise fetal development to the point of causing neonatal death. AND" so deductible that the control of risk factors, monitoring of pregnancy values and early diagnosis of gestational diabetes are precautions necessary to reduce its morbidity.

Risk factors for gestational diabetes: obesity, family history of diabetes mellitus, glycosuria, previous gestational diabetes and age> 25 years.
In pregnancy it is normal for a certain reduction in glucose tolerance to occur starting from the 3rd month; to verify that the change is physiological and not pathological, it is necessary for the pregnant woman to start a process of screening glycemic through the "50g glucose test" which, if successful, requires further investigation with the "100g glucose test".

NB. Gestational diabetes (which arises in the period of pregnancy) MUST be well differentiated from that BEFORE conception (therefore already present from before pregnancy), better defined as "diabetes mellitus in pregnancy".

Diet

It is not easy to summarize in a few lines the guidelines for a good and healthy diet during pregnancy (even more important in the case of gestational diabetes); We will therefore try to be exhaustive but at the same time specific, mainly dealing with the energy aspects and the distribution of macronutrients.
Let's start by specifying that, if we recognize the first place among the risk factors obesity, to minimize the onset and worsening of gestational diabetes, it is first of all necessary normalize body weight BEFORE early pregnancy. This can be applied in a "planned" situation by remembering that: to lose weight while remaining healthy it is necessary to lose NO more than 3kg per month (ergo, maximum 36kg per year). It follows that, in an obese object, normalizing the weight in order to reduce the risk of gestational diabetes could require a conspicuous postponement of the pregnancy itself.
Even during pregnancy it is FUNDAMENTAL to monitor (better if weekly) the weight gain; the weight gain for an obese pregnant (overweight (7-11.5kg), normal weight (11.4-16kg) or underweight 12, 5-18kg) ... but this does not mean that generalized weight loss should occur during gestation, as this would prevent the correct development of the unborn child!
The caloric requirement of a subject with diabetes gravidarum (on average) should NOT exceed 30-32 kcal for each kg of desirable physiological body weight; therefore, FROM the 2nd MONTH onwards, the pregnant woman must take an energy-daily quantity proportional to her state of nutrition: for an obese or overweight subject it is + 200kcal / day, for a subject in normal weight it is + 300kcal / day and for an underweight subject is + 365kcal / day.

NB. In the event that the pregnant woman must remain at complete rest (semi-bed rest), for obese or overweight subjects the caloric surplus must be around 100kcal / day.
In the case of gestational diabetes, the protein share of the diet remains unchanged: about 13% of the total kcal + 6g, or 1.3-1.7g per kg of physiological body weight desirable. The lipid portion is even proportionally equal to the normal one, that is 25% of the total kcal, even if, more in the diabetic than in the healthy one, it would be advisable to keep the saturated fat levels at 7-10% and favor the intake more. of monounsaturated and essential fatty acids (ω ‰ 3 = 0.5% of the kcal tot and ω ‰‰ 6 = 2% of the kcal tot).
Before addressing the estimate of carbohydrates in the diet, we recall that diabetes mellitus is a metabolic disease that induces a reduced glucose tolerance and often a reduced secretion of insulin, therefore in food therapy it is extremely important to evaluate:

The glycemic load of the 6 daily meals
The glycemic index of foods.

Unfortunately It is NOT possible to excessively break down the portion of total carbohydrates, as they are necessary for the energy processes of the fetus, but it is Anyway it is desirable to reduce them to the bare minimum to help restore a satisfactory metabolic condition.
If in a healthy and sedentary subject, the nutritional breakdown is approximately: 13% proteins, 25-30% lipids and 62-57% carbohydrates ... in the pregnant woman becomes 13% + 6g protein, 25-30% lipids and what remains carbohydrates. In my opinion, in addition to preferring foods with the lowest glycemic index, in gestational diabetes it is essential to reduce the portion of simple carbohydrates "to the bone" (no more than 8-10%, against 12% of the healthy subject) and to increase the intake of fats and proteins up to the upper limit of the recommended. Let's take an example:

Pregnant with gestational diabetes, 6th month, BMI 29.4 for a weight of 78kg (physiological weight 55kg)

Energy requirement 32kcal * 55kg (desirable weight) = 1760kcal (which correspond to the normal energy + 200kcal of pregnancy in the presence of overweight).
Proteins, two methods of calculation:
- (13% of 1760) + 6g = 63.2g
- 1.3g * kg of physiological weight / protein energy coefficient = 71.5g

In this case, in order to keep the overall carbohydrate quota to a minimum, we choose the 2nd method!

NB. A coefficient of 1.3 was chosen, but as already specified above, it is possible to reach even 1.7g / kg of desirable physiological body weight.

Lipids: between 25% and 30%, we choose 30% to keep the total amount of carbohydrates to a minimum, with the simple precaution of keeping saturated fats at 7-10% and drastically increasing the amount of essential and monounsaturated fats ( duty of the dietician):
30% of 1760kcal / lipid energy coefficient = 58.7g
TOTAL carbohydrates: calculated on the remaining energy, excluding lipids and proteins from the total intake:
1760kcal - protein energy (286kcal) - fat energy (528kcal) / carbohydrate energy coefficient = 252g

NB. The share of simple carbohydrates must remain around 8-10% (the dietician's task).

Obviously it is not the intention of this "article" to simplify or provide the tools necessary to compose the diet of a gestational diabetic, the concepts to be taken into account are many more and this represents a complex job even for a professional. subjects at risk, I believe it may be helpful to have a general overview of the real needs referred to a disorder as widespread and as serious as gestational diabetes.

Bibliography:

DIABETES MELLITUS: Diagnostic and Therapeutic Criteria: an update - C. M. Rotella, E. Mannucci, B. Cresci - SEE Florence - page 43:45
Clinical Nutrition Manual - R. Mattei - Medi Care - Franco Angeli - page 407: 409.