|Fishing Cat (Photo by Cheryl Morris)|
I find choline so intriguing because it is extremely complicated. Not only do mammals synthesize it, but it interacts with several other nutrients such as B12, folate and methionine. In other words, their status will impact the status of choline and vice versa. Choline is synthesized from the two amino acids serine and methionine through a reaction dependent on S-adenosylmethionine (SAMe). The later may be a compound you have seen on supplements, particularly for joint health.
A deficiency of choline will result in fatty liver and renal hemorrhage, along with potential cognitive loss or deficiencies in learning. Additionally, choline deficiency also has been documented to promote spontaneous development of cancer of the liver. In other words, a deficiency of choline is an ugly thing but it's a difficult one to asses because folate, B12, and methionine status also should be considered. Another compound called betaine and dietary methionine can actually replace some dietary choline in the diet. That said, a combination of high dietary methionine along with deficient choline likely results in elevated concentrations of plasma homocysteine, that in humans is a risk factor for vascular diseases. To say the least, choline is a complicated and fascinating nutrient.
Unprocessed and whole foods contain some choline. This is certainly one of those compounds that makes me happy I feed raw and makes me appreciate differences among species. When it comes to total choline concentrations, the best sources include beef liver (418 mg/100 g), lecithin (300 mg/100 g), chicken liver (290 mg/100 g) and eggs (251 mg/100 g). When it comes to muscle meats only, pork is the protein with the highest concentrations (>100 mg/100 g) compared with other proteins (Zeisel et al., Journal of Nutrition, 2003). The requirements for dogs and cats are set at approximately 1,700 and 2,500 mg per Kg of diet on a dry matter basis, or more simply...approximately 15 - 20 mg per pound of body weight for dogs and 20 - 30 mg per pound of body weight for cats. A typical egg is going to contain about 174 mg of choline (assuming it is 60 grams). Since my 35 Lb border collie eats 2 eggs daily, well over half of his choline requirement is coming from eggs. It is unlikely that raw diets including eggs and liver in the formulation will be deficient in choline.
There is indication in literature that perhaps choline requirements increase during exercise. Of course this hasn't been studied as it relates to agility dogs. Additionally, choline concentrations aren't documented in relation to raw meats typically fed to pets and carnivores. I've been on the fence about studying concentrations of choline in various meats and ingredients we typically use for carnivores, but it looks like we may head down that road. Somehow I always find questions that need answered regarding our sport dogs and raw diets...not to mention the exotic carnivores I continue to work with.