Oxalic Acid and Guinea Pigs

Usually, when we talk about a food on this blog, it's something that guinea pigs can eat, even if only occasionally. In this post, we're going to start off by talking about something you should never feed a guinea pig.

The other day, the humans brought home a new food from the grocery store, and we got excited.

What is it? Can we eat it?

Why is it just sitting in a jar? Shouldn't someone be eating it?

Wow, it comes with instructions?

So it turns out that this is a type of fruit known as monstera deliciosa, or Delicious Monster. Humans have to let it sit in a jar and let the green scales fall off before it's edible for them. Before that, it has too much oxalic acid to be safely consumed. Even after the scales fall off, "Sensitive individuals (may) suffer throat irritation, urticaria and anaphylaxis," according to the Encyclopedia of Fruit and Nuts. The humans reported some tingling in their mouths after eating it. We'll have to take their word for it.

Unfortunately, keeping your guinea pig safe from oxalic acid isn't as easy as just avoiding the delicious monster. Oxalic acid is found in many different types of food. It's also found in many household plants, which is why the humans freaked out that one time I ate a lily.

So what exactly is oxalic acid? It's a chemical substance that occurs naturally in plants, and can be toxic at high dosages. When eaten, it combines with metals in your body like magnesium and calcium to form a type of salt called oxalates. The body has no use for oxalates, and so it expels them through urine. At low dosages, this is generally not a problem. However, at higher dosages, important nutrients are trapped in oxalates, preventing your body from absorbing them. Also, oxalates crystals can be sharp, which can irritate the body and cause problems, such as kidney stones. In guinea pigs, too much oxalic acid can be fatal.

As we mentioned in our post on Guinea Pig Nutrition, guinea pigs should generally eat no more than 50 mg per day of oxalic acid. Some foods that are high in oxalic acid include:

• Beet Greens (leaves) = 610 mg per 100 grams
• Parsley = 425 mg per 25 grams
• Radishes, mild = 480 mg per 100 grams
• Spinach = 970 mg per 100 grams
• Sweet Potato = 240 mg per 100 grams

Guinea pigs can still eat these foods, but in moderation--for example, maybe only 5 grams of spinach per day or less to avoid exceeding 50 mg limit.