What effects can diet have on my mood while pregnant?

Calcium is mood food. Calcium, 500-600 mg in the morning and the same dose in the evening might be a mood stabilizer. You need to divide it up and not take it all at once. Any calcium is fine, though you will see debates on which is 'best.' i think that if it fits your taste test, your convenience test and your finance test then it has past the test for you!
Depends on purpose. Difficult question, there are all kinds of diets, pregnancy is not a time for a weigh loss diet, its normal to gain weight, just not too much if you are overweight, save the diet for after pregnancy, eat healthy for your baby. There is lots of time to lose weight. If its another kind of diet like diabetic diet, low carb diet, ask you OB doctor.