Thought I would post this list of "feed and don't feed to the horse".
It was mostly created for the horses with I-R and EMS, but if you note the foods to avoid, it does mention "may cause gas" if some of them are eaten.
I got this from my local message board and don't have a clue where the OP found it, but I hope it helps
##############################################################################################
Some horses are insulin-resistant (diabetic). That means their bodies have a hard time processing sugar. Sugar comes not just from treats, but from grasses and hays as well. Recent studies indicate that certain types of non-structural carbohydrates and sugars can be a leading cause of laminitis.
If a horse is sugar intolerant, do not feed hard candies, sugar cubes or molasses treats at all. Instead, go with fibrous treats or the natural sugar in fruits (fructose) for a safe sweet treat. There are also low sugar prepared treats on the market that you can purchase if you feel unsure about regulating the sugar in your horse's diet on your own.
Even if your horse is not sugar intolerant, they would benefit from avoiding sugary treats in their entirety. It seems that many people associate giving a horse a treat with giving them a sweet one. However, horses are not humans! Although we bipedals may seek out Ben & Jerry's for a snack, a horse seeks out fiber-rich foods for a satisfying graze.
Therefore, consider a broader array of treats for your horse that are fibrous rather than sweet. In the wild, horses munch leaves, herbs, flowers, nuts and seeds. The following is a partial listing of safe fibrous foods for your horse (high sugar snacks are so noted and should be fed with caution, if at all, to the laminitic or insulin resistant horse):
Fruits, Vegetables and Seeds:
• Beets, cut up (high in sugar)
• Celery
• Sweet potato, cut up
• Squashes (pumpkins, butternut, acorn), cut up
• Leafy lettuces (small quantity)
• Carrots, cut into pieces (high in sugar)
• Apples, cut into pieces; red delicious and not the sour, granny smith types are preferable (somewhat high in sugar, feed rind only to the diabetic horse)
• Dates, pitted (high in sugar)
• Raisins (high in sugar)
• Grapes
• Blueberries
• Cranberries
• Fresh cherries, pitted
• Orange and lemon rinds
• Watermelon, rind and pulp
• Sunflower seeds, unshelled or shelled
• Pumpkin seeds, raw
• Flax seeds
• Peanuts (feed sparingly)
AVOID: Vegetables and fruits of the deadly nightshade family – potatoes, tomatoes, peppers, etc. Also avoid cruciferous vegetables – broccoli, cabbage, cauliflower, brussels sprouts - as they can cause rapid increase of gas in the stomach.
Herbs, Flowers and Leaves
Do not overlook the feeding of leaves, herbs and flowers, even teas, to your horse. Many have calming and antiseptic properties.
• Rosehips
• Chamomile
• Mint (your horse will love mint the way nature intended rather than in hard candy form)
• Rose petals, fresh
• Brewed tea (herbal, non-caffeinated), allowed to cool and poured right over feed
• Parsley
• Dried peach leaves
• Strawberry leaves
• Kudzu root
• Marigold flowers
Now that you see the wide variety of treats available to your horse, you can put down the peppermint candies! If you must feed them, remember they are hard and not easily digested and should consequentially be fed in very small quantities.
Horses do not need treats, and treats should not take the place of a high quality, low sugar hay diet. However, if you like to pamper your horse from time to time, hopefully you will consider the large array of high fiber snacks available that will improve your horse's digestion, as well as potentially calm and soothe him.