As of 2015 the only noted negative side effect of consuming blackstrap molasses is its sugar content. One tablespoon contains 5.88 grams of sucrose, 2.56 grams of fructose and 2.38 grams of glucose, with a glycemic index of 55, reports Superhuman Coach.
The sugar content of blackstrap molasses is a negative side effect only due to the known effects of over-consumption of sugar. Used judiciously there is nothing inherently bad about this substance. Blackstrap molasses is a good substitute for simpler sugars because it contains manganese, copper, iron and calcium. Safe amounts of sugar consumption are relative to the individual, states Superhuman Coach. Active people are able to use more sugar than those with sedentary lifestyles.