Becca's Digestion Tip Number Eight: Protect against free radicals through food.
If an apple is cut and left uneaten, it will start to turn brown. Why? Well, it was exposed to the air and oxygen, and it underwent oxidation. Free radicals in the air also bind to the apple and begin breaking its cells down (which turns them brown). Moreover, some fruits and veggies contain an enzyme called polyphenol oxidase. This enzyme changes the chemical structure of the food (and thus their color) when it comes in contact with air.
Therefore, when we want to prevent the freshness of our fruit salad and our guacamole, we need to stop both the air and this enzyme from turning our food brown before consumption. For instance, it appears that avocado pits prevent oxidation (not sure of the mechanism of this, maybe Myth Busters know?). Another way to keep air away is to wrap the food very tightly with plastic wrap (e.g. press the wrap right on the guacamole so that no air is lies between the plastic and the guac). As for the enzyme, refrigeration can slow its activity or you could add an acidic food (like lemon or lime juice) as the enzyme does not function well in an acidic environment.
Also, if keeping air away from the food is not easy an option, then you can always add some antioxidants to the food to combat the free radicals. Citrus foods contain antioxidants (their name is derived from their ability to prevent (or be "anti") oxidation), so lemon or lime juice would work here too.
But why is this a digestion tip? The point of all of this is that oxidized food is not good for the body. You can see the effect of free radicals on something as simple as a sliced apple; image what they can do to your insides! If you are ever faced with something that may have gone a little bad, make sure to eat with lots of antioxidants to protect you body from any free radicals present. This is why lots of fish and flax oils contain rosemary extract; rosemary is an antioxidant and thus it will protect the body from any free radicals that may have accumulated in these fragile oils. Lastly, it is important to eat lots of antioxidant-rich foods on a daily basis because every time we breath we intake some free radicals. These foods include: berries, purple fruits and veggies, citrus fruits, red wine, green vegetables, and some beans (pinto, kidney) and nuts (pecans, peanuts). Final thought: In order to keep the body healthy on the inside, chow down on protective foods!