It can definitely be difficult to chip out knowledge from scientific articles, especially since the average layperson doesn't have access to most of them without paying for them. It's a set of terminologies that we don't fully understand as well. It's not like we learn all about free radicals, oxidization and cell damage in grade school or something. The amount of understanding needed for that is beyond basic education.
Combined with the general anti-intellectualism culture of the US it can make it very easy for snake oil salesmen to make the average person believe something that's patently false. And it's not that person's fault. But we should all strive to educate ourselves as to what the reality of the situation is.
In this case, I think it's easy to break down into layperson terms.
Alliums all share certain chemicals that are particularly concentrated in onions. These chemicals are easily absorbed by the gut and oxidize cells. Oxidizing agents are the OPPOSITE of Antioxidants. Antioxidants prevent oxidization, which is a form of cell damage, which is why they are good. Oxidizing agents are bad. Chemotherapy is an oxidizing agent, for example. It kills off all your cells slowly and makes you very sick. The reason it works as a cancer treatment is the cancer cells die faster than healthy cells. But the side effects are terrible. Radiation is another form of cell oxidation.
Dogs and cats have a particular sensitivity to these particular reactive agents. They are absorbed by the gut, and then these highly reactive agents enter the bloodstream where they damage blood cells. This means that the blood cells literally stop working properly (anemia). This can cause a cascade of problems across the body which manifests as dizziness, nausea, weakness, shortness of breath and other problems.
Additionally, the reason antioxidants are considered healthy cancer prevention agents is because when a body is damaged from oxidization (say, from radiation), there's a chance of the new cells developing incorrectly and becoming cancerous. This does not mean onions in dogs causes cancer, this has never been studied, but oxidative stress has been linked to advancing and potentially causing cancer. (citation! https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2990475/)
So TL,DR; don't feed your dogs onions.
Even if you don't see any problems it could cause long-term damage.
Combined with the general anti-intellectualism culture of the US it can make it very easy for snake oil salesmen to make the average person believe something that's patently false. And it's not that person's fault. But we should all strive to educate ourselves as to what the reality of the situation is.
In this case, I think it's easy to break down into layperson terms.
Alliums all share certain chemicals that are particularly concentrated in onions. These chemicals are easily absorbed by the gut and oxidize cells. Oxidizing agents are the OPPOSITE of Antioxidants. Antioxidants prevent oxidization, which is a form of cell damage, which is why they are good. Oxidizing agents are bad. Chemotherapy is an oxidizing agent, for example. It kills off all your cells slowly and makes you very sick. The reason it works as a cancer treatment is the cancer cells die faster than healthy cells. But the side effects are terrible. Radiation is another form of cell oxidation.
Dogs and cats have a particular sensitivity to these particular reactive agents. They are absorbed by the gut, and then these highly reactive agents enter the bloodstream where they damage blood cells. This means that the blood cells literally stop working properly (anemia). This can cause a cascade of problems across the body which manifests as dizziness, nausea, weakness, shortness of breath and other problems.
Additionally, the reason antioxidants are considered healthy cancer prevention agents is because when a body is damaged from oxidization (say, from radiation), there's a chance of the new cells developing incorrectly and becoming cancerous. This does not mean onions in dogs causes cancer, this has never been studied, but oxidative stress has been linked to advancing and potentially causing cancer. (citation! https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2990475/)
So TL,DR; don't feed your dogs onions.
Even if you don't see any problems it could cause long-term damage.
