Mealworms, MBD, and Calcium Deficiency - Mostly Myth or Serious Risk?

Answer: It depends on how much you're feeding!

Concerns about calcium deficiency and MBD (metabolic bone disease) related to feeding mealworms has skyrocketed in the last few years, particularly in response to legitimate concerns about feeding mealworms to wildlife. Leaving out large bowls and feeders of dried mealworms for wildlife can result in animals like wild hedgehogs eating only mealworms, which is a wildly unbalanced, calcium deficient diet - and will cause serious issues over time!

Let's look at some key factors.

Staple Diets

When considering a hedgehog's overall nutrition, most owners are feeding a staple diet which is balanced with both a percentage and proportion of Calcium and Phosphorus that meet their needs based on their life stage. This is normally a dry kibble of some kind, whether a food like our Standard Formula or a cat food, multiple foods mixed, a different hedgehog food, etc.

Mealworms

Mealworms are exceptionally low in calcium, especially compared to their phosphorus content - which understandably scares people! However, if you feed mealworms in moderation (as most things should be), their overall impact on the total Calcium:Phosphorus intake a hedgehog has in a given night is far less impressive than some online would have you believe.

Labeling Limitations

One of the struggles and limitations here is limited nutrient content reporting plus unhelpful minimums used in labeling here in the United States. It is really hard to find accurate info on how much calcium and phosphorus is in a given food item. For example, a label may report "1% min calcium" and "1% min phosphorus" which would seem to imply a 1:1 ratio, but the actual content could be 1% calcium and 3% phosphorus. Accuracy of these mins and maxes, when they are even provided, are very rarely 3rd party verified or are companies held accountable for being in the ballpark of the truth, even if technically correct. One reason for this is that companies know that their overall nutrient composition will vary a bit with each production run, and they don't want to be "tied down" too tightly by what their packaging guarantees. And when it comes to treats, things like mineral content are considered irrelevant because it won't be a big component of the animal's diet.

A Realistic Example

Let's say you want to look at the impact of feeding dried mealworms on one hedgehog's nightly food intake. This example hedgie is on our Standard Formula, and eats ~10 grams of kibble per night.

Our HP Standard label guarantees 0.8% calcium, and 0.7% phosphorus, minimum. However, we can cheat and use actual lab reports of what our food contains as-fed, which is 0.98% calcium, and 0.81% phosphorus.

Next, actual lab reports we've run on typical dried mealworms come back at 0.04% calcium, and 0.76% phosphorus. Yikes! Right? Except you shouldn't be feeding tons of worms. We recommend 5-10 mealworms/night if you are offering them. 10 dried mealworms weighs about 0.5g, so we will pretend our hedgie is eating 10 tonight.

To recap: Our example hedgie is eating a total of 10.5g of food, 10g of their staple diet, and 0.5g of dried mealworms. Now we can calculate out how much calcium and phosphorus we're getting, based on accurate percentages from the lab.

Total calcium: 0.098g from staple diet, 0.0002g from mealworms = 0.0982g
Total phosphorus: 0.081g from staple diet, 0.0038g from mealworms = 0.0848g

This calculates out to an overall intake of 0.93% calcium and 0.81% phosphorus, or a 1.15:1 Ca:P ratio.

In short, even if your hedgie eats 10 dried mealworms, they're still getting more calcium than phosphorus overall once you factor in their whole diet.

We wanted to provide this example to show how important it is to look at an animal's whole diet, and not just individual ingredients or treats.

Some people are scared of peas in dry food because they're high in phosphorus, but same scenario - the overall diet is still properly calcium and phosphorus balanced across all ingredients.

If your hedgehog ONLY will eat mealworms, that's a big issue that you'll need to address with your vet. But if you feed mealworms occasionally or even nightly, as long as it's in moderation, you are not going to cause deficiencies or metabolic disease so long as their staple diet is balanced. After all, that's what treats are for! Variety even if they aren't a perfect replica of all necessary nutrients in perfect proportion. (Fun fact... virtually all foods or ingredients are "deficient" in many ways. That's why staple diets have to be formulated with multiple ingredients to get just the right amount of each nutrient!)

Final Takeaway

Please don't be afraid of mealworms! Just because they suck at retaining calcium, doesn't mean they aren't wonderful, affordable, accessible treats to provide variety and enrichment to your hedgie. And if you are really worried, there are other dried bugs with "better" nutrient profiles you can try - like Black Soldier Fly Larvae or Dubia.