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View Full Version : CAUTION: Vitamin Overdose


Melody
Apr 28th 2007, 11:50 AM
I was reading some posts on another forum which included recipes for fish food. When I read the vitamin supplements suggested for some of them, I was alarmed at how much was recommended.

Many times it is suggested that we use crushed multivitamins intended for human adults. Some of these recipes are calling for more than a dozen! Most of the fish we keep are smaller than our hand, many are much smaller. Not only do they not require high doses of vitamins, it can actually hurt or kill them. Depending on the recipe size, one or two adult multivitamins is plenty unless the batch is huge.

Fish, and humans for that matter, can only utilize so much of their vitamin intake. After that it is either expelled or stored, depending on whether it is a water or fat soluable vitamin. That is one of the reasons that I recommend frequent feeding, with very little food in each portion. The fish are then able to utilize the maximum amount of nutrition and put it to good use. Remember that most fish kept in captivity are grazers - they pick at food all day in the wild.

When it comes to water soluable supplements, such as Vitamins A & C, any amount not used by the fish is simply passed through. They would benefit much more from being fed small amounts several times per day, but otherwise the dose would have to be screaming high to be detrimental to their health.

Fat soluable vitamins, on the other hand, are stored in the body if they are not used. They can build up to toxic levels and begin to cause serious problems. These vitamins include A, D, E & K. Minerals such as calcium & iron can also be overdosed. All of these vitamins & minerals are in multivitamin supplements and even humans shouldn't take more than one/day, since they often supply a high percentage of the daily recommended amount. You can imagine what kind of damage using a lot of them in our homemade fish foods could do!

Unfortunately, there are too many fish species & sizes to ever compile a list of recommended doses so please, use common sense - more is not better and can be very dangerous. I strongly suggest using either a vitamin supplement specifically designed for fish, or baby vitamins for your homemade foods, and don't overdose on those either.

I believe that fish benefit from supplementation if it is used within reason and I recommend the use of supplements in homemade food. Keep in mind that you are dealing with fish, however, which have different requirements and definitly require less than humans.

Just like humans, it is best to provide a varied diet so the fish obtain their vitamins and minerals from food sources. Commercial foods are largely a multivitamin, with questionable amounts of nutrition coming directly from food sources due to processing. If you can, feed fresh or frozen foods along with freeze-dried & dehydrated products to provide natural sources of nutrition, combined with high quality flakes or pellets.

Edit: Just a note that Garlic can also be overdosed. Too much can irritate mucus membranes and too much is simply wasted.

CACAdmin
Apr 28th 2007, 12:25 PM
Excellent points, Melody. People often forget (or don't know) that many vitamins are fat-soluble and simply think that excess is excreted from the body unused. Multi-vitamins are recommended to be taken with a meal for that reason (to ensure benefit from the fat-soluble ones). I hadn't really considered the fact that because the excess of these are stored in fat that they can build up to toxic levels. And in fish because of their small size, this could happen very quickly.:wideeyed: It's definitely something to be aware of and thus exercise caution with when preparing food for consumption by your aquatic creatures (or even non-aquatic) pets.:yes:

Melody
Apr 28th 2007, 12:49 PM
Exactly. What's more, most of the vitamins and minerals in a multivitamin probably aren't required by fish at all.:no:

Melody
Apr 28th 2007, 01:14 PM
Here's a little tidbit for breeders: In humans, overdoses of vitamin E can cause reproduction issues. :wideeyed: Whether that's the case for fish or not is anyone's guess, but I'm not gonna chance it!

Osprey
Apr 28th 2007, 06:35 PM
Too much vitamin E has been known to cause liver failure, as well. :nah: One reason not to feed spirulina exclusively is because of it's high vitamin E content.
BTW... I believe vitamin B is the other water-soluble vitamin that will be flushed out if too much is taken.
Be careful of hyper-doses of vitamin C! In spite of the fact that it will be flushed out in the urine before it can cause severe damage, it can interfere with the uptake of Ca and Mg, leading to weak bones...in humans. I have no idea what it does in fish or snails.
There are a number of heavier elements that are required by humans that are lethal to fish, plants, and inverts in higher concentrations... Zn and Cu come specifically to mind.

Melody
Apr 28th 2007, 08:11 PM
Very interesting stuff! One thing that makes me hesitate about specific warnings is that they are normally for humans. However, most of the information came from testing on animals, so I'm betting its closer than we know.

Thanks so much for expanding on the topic! As I mentioned to someone earlier, we have enough problems with our fish without killing them with kindness.