Garlic for dogs?

Lots of confusion around this topic, we attempt to clear things up

oooo…garlic!

TLDR: In appropriate amounts for your dog (based on their size) garlic is not toxic. Should you feed your dog garlic? That’s up to you and your vet. The purpose of this article is to explain how garlic came to be so feared, what the actual benefits and risks are, and most importantly, to help dispel unwarranted fear around real foods. :)

There’s few greater touch points for very aggressive reactions in dog lovers than garlic or onions. We previously covered onions (which are actually not so good for dogs) and today we take a deep dive into garlic. We cover the potential benefits, flaws in previous research, levels of true toxicity and finally dosing in the studies. Before that here is how to make the garlic “bread”:

What makes something toxic?

Toxicity is a complex subject. The old adage “the dose makes the poison” has some serious foundation in science, but like anything else it’s highly dependent on the toxin. Many vitamins, especially in their synthetic forms are toxic in small amounts (vitamins D and A, for example, but also some minerals like iron, copper, and zinc can cause issues at high doses). We tend to think of synthetic chemicals as being the most poisonous, but many of the most toxic compounds on earth are completely natural.

Botulinum toxin (the same stuff that’s in botox) is considered to be the most deadly biological toxin known to science. According to the WHO, the median lethal dose is 2 nanograms per kilogram of body weight. To put this in perspective a single grain of salt is approximately 58,000 nanograms. Despite this incredible toxicity, over 10 million botox procedures occur every year. Market research firms estimate that usage is growing by about 15% per year. So not only are a lot of people routinely injecting the most toxic substance on earth into their faces, more and more people are doing it every year.

As we’ve repeated ad nauseam, even plain water can be toxic if you drink too much of it. Many people have succumbed to hyponatremia. This condition occurs when blood sodium levels get diluted from excess water, leading to brain swelling, seizures and in rare cases death. If even water can be toxic, then pretty much anything else can be too.

Garlic benefits

There are numerous health benefits to garlic consumption in people and in animals. Garlic has been used as a folk remedy in many cultures for thousands of years. In modern times research on garlic in people has shown benefits to immune function, reducing blood pressure, and reducing inflammation amongst many others.

In dogs, several double-blinded controlled studies have shown statistically significant benefits. In one study, garlic consumption showed reduction in blood glucose levels in diabetic dogs. Some studies showed an increase in anti-inflammatory enzymes. This last study also showed that anemia was non-existent at lower doses (the main concern with garlic and onion consumption). More on that below.

that’s a lot of garlic

Garlic toxicity in dogs vs humans

It is true that high doses of garlic can be toxic to dogs. Thiosulfates are formed when garlic is crushed and as part of metabolizing sulfur compounds in garlic. These compounds can damage the hemoglobin inside red blood cells. When lots of blood cells are damaged it triggers an immune response and macrophages are deployed to destroy these damaged cells, causing hemolytic anemia. Since red blood cells carry oxygen around the body, excessive damage to red blood cells can hurt organs and in rare instances cause death.

Humans are less susceptible to thiosulfates for two reasons. First, we have higher levels of enzymes that neutralize thiosulfates. Second, dogs’ red blood cell are more sensitive to oxidative stress from thiosulfates. In other words, dogs and humans both have mechanisms to digest the toxins from garlic, but people have a far higher capacity to do so than dogs.

Hormesis: when a little bad stuff is actually good

Between 1982-1984 a group of apartments in Taipei, Taiwan were constructed with steel that was accidentally contaminated with radioactive material. In total approximately 10,000 people were exposed to elevated levels of radiation for between 9-20 years. On average the residents were exposed to 0.4 sieverts of radiation per year or about 400-times the annual recommended limit. Based on these numbers the residents should have a far higher incident of cancer and birth defects.

Surprisingly, researchers that studied the population found the residents had a far lower incident of cancer and congenital birth defects. The initial research found a 96.4% reduction in cancer rates and a 93.5% reduction in birth defects compared to the broader population. (Because many of the residents were younger, later age-controlled studies revised the cancer figure to a 40% reduction of total cancer rates compared to the broader population, but found some rare cancers had a higher incident). With this much radiation exposure, this large of a group having a lower incident of cancer and birth defects than the general population is remarkable. Though the effect is still debated, this phenomenon is known as radiation hormesis.

There are many examples of hormesis including exercise (believe it or not, the benefits of exercise were also once heavily debated), where stressing muscles and joints leads to stronger tissue. Other examples include caloric restriction that increases lifespan in animals, and heat stress (the sauna for example) that boosts metabolism and increases stress resistance. Of course overdoing these things can cause significant damage, for example injury from too much exercise, starvation from severe caloric restriction, and heatstroke from excessive heat.

Plant compounds like polyphenols, tannins, and alkaloids likely work via hormesis. These compounds, like thiosulfates in garlic, are mildly toxic to insects, but beneficial to other animals in small doses. Large doses, however can cause issues. Like most things, a little goes a long way.

Garlic doses in studies

Toxicity of garlic is overblown. Many of the studies that conclude garlic is toxic for dogs fed large amounts of raw garlic. Cooking garlic drastically reduces the potency because organic sulfur compounds (thiosulfates) start to decompose above 50°C.

One small controlled study that fed garlic extract equivalent of 5 g of raw garlic per kg of body weight per day found dogs DID NOT develop hemolytic anemia, but did find evidence of red blood cell damage. They recommended not to feed garlic, but the dose of their test group would be equivalent to Cedric (14 lbs) eating 5-7 whole cloves of raw garlic daily. We don’t even eat that much cooked garlic daily.

Also 5 g / kg daily is about 50-100 more than the dose given in the study that showed increased anti-inflammatory activity (a very good thing). In that study both 45 mg and 90 mg of aged garlic per kg per day were effective. The higher dose is about what Cedric ate on the garlic bread in our most recent video, or, roughly about one to two cloves of garlic per week.

The studies that show hemolytic anemia in dogs after consuming garlic gave them very high doses. For example the equivalent of feeding a dry dog food with 11% whole garlic powder does indeed induce anemia. But who the heck would do that? Other anecdotal toxic reports involve small dogs, like a schnauzer, consuming large portions of baked garlic. (Schnauzers are notorious for metabolic issues.)

Conclusion

You definitely don’t have to feed garlic to your dog. The point is that there’s no need to be afraid of it! If you do want to feed garlic, in small amounts it is not only well tolerated, there is also a substantial body of evidence that it is beneficial. If you feed 1-2 cloves per week (for a small dog), the potential benefits include reducing blood sugar levels, lowering blood pressure, while increasing anti-inflammatory enzymes. Although some dogs may be particularly sensitive, the idea that garlic is toxic for dogs is greatly overblown. Trust the science, not the anecdotes, and ALWAYS question the fear tactics used to influence you.

That’s all for this week.

All the best,

Joelle and The Precious Creatures Team