Morning Glory Muffin Add-Ins

[StacyA]

I want to make the Whole Foods 'Morning Glory' Muffins:

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I'm considering adding things like flaxseed, canned yams/frozen summer squash/canned pumpkin, crushed pineapple, or other stuff I find laying around.

The problem is I'm not good at substitutions. If I add fruit or yams, I assume I should decrease the sugar a little because of sweetness. Do I also decrease the oil because of the fluid and oil content of what I add (such as oils found in squashes and flaxseed) or is it not enough to matter? I don't want to throw off the balance too much so it's too wet or dry or falls apart...

Any input would help. I never studied baking enough to know what happens if you mess with oils, eggs, baking soda, etc in the balance of things.

[RiceGuy]

It has been my observation, that squashes, pumpkin, etc tend to retain moisture, so you'd probably need to reduce the water. If adding a fatty ingredient, then yes, reduce the amount of oil. Not sure if whole flax seeds would introduce much oil, unless you add a lot of them, but there is that gel which forms when they get wet. That'll change the texture, and could cause a slightly gooey texture depending on how much you add. The pineapple will add some liquid unless you drain it really well. It may interfere somewhat with the structure though, again depending on how much you add.

Additional flour may subsequently be necessary, and thus I think the recipe may require additional binders and leavening too. I think it might be worth waiting to see the consistency of the dough/batter before the additions. That way after adding them, you'll have a better idea how to compensate. The total amount will obviously be more than what the recipe normally yields.