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Comment by d883kd8 | Hacker News Reader

I am sorry to be so blunt but I must correct this dangerous misinformation. Feeding a cat a vegan diet will kill him. Period. They are carnivores and cannot live without animal-derived nutrition.

Any vet can tell you about cases of malnourished cats whose irresponsible owners failed to provide enough meat.

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> They are carnivores and cannot live without animal-derived nutrition.

I'm curious what nutrients can only be animal-derived. Some nutrients are probably cheaper to get from animals, but I am curious what nutrients can only come from animals.

I know several people that "make their own" vegan cat food, and their animals are not sick, sickly or dying. It is quite possible that their lifespan has been shortened by the vegan diet, but I would definitely not state boldly that they "cannot live without animal-derived nutrition" because they are clearly living without animal-derived nutrition.

Lots of carnivores don't have the ability to manufacture all of the amino acids their body requires. They need to get them from other animals, often because their digestive system isn't able to break down plant matter. The same is true of many vitamins. Each animal is different.

This doesn't mean that it necessarily has to come from animals though. Unlike many animals, humans don't manufacture their own vitamin C. We can get vitamin C by eating other animals, but we can also get it from sources rich in vitamin C like oranges, bananas or lemons[1]. If a human isn't able to digest citrus, it's also possible to obtain vitamin C supplements.

[1] I'll note that limes are lacking enough in vitamin C that when the Royal Navy switched from lemons to limes (they were cheaper) sailors started getting scurvy again, and the 'cure' for scurvy was lost until the actual reason that lemons cure scurvy (vitamin C) was discovered.

I'm curious what nutrients can only be animal-derived.

I came across the following list recently:

1. Vitamin B12

2. Creatine

3. Carnosine

4. Cholecalciferol (Vitamin D3)

5. Docosahexaenoic Acid (DHA)

6. Heme-iron

7. Taurine

Source: http://authoritynutrition.com/7-nutrients-you-cant-get-from-...

Your source doesn't even agree with the assertion that the nutrients can only be animal-derived (at least for some of them).

That's not a list of nutrients that can only be animal-derived. It's a list of nutrients that are rarely (or never) found in plant foods.

Vitamin B-12, for instance, is bacteria-derived. It's easy to obtain via supplements and fortified plant-based foods.

The longest living cat on record was vegetarian. It's true there are certain nutrients a cat needs from animals though.

Source? Both of the possible claimants to that title are said by their Wikipedia articles to have eaten a diet containing animal protein.

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