1. Unhealthy gut flora or some other intestinal problem which is preventing the absorption of nutrients (which could be as simple as a lack of fat eaten with the food and lack of fat or low fat in the diet, specifically saturated fat*)
2. Lack of oil eaten with the dark leafy greens (which if you don't eat oil with your greens and other food, you can't get the ideal amount of nutrients from them)
3. Too little fat, and saturated fat, in the diet (Yes, I know I've repeated myself.)
4. Not converting K1 to K2
5. Not getting enough of D and calcium, or getting enough, but no K2 which would not do the teeth and bones (or the entire body) any good.
*If you see the healthy vegans and babies a few posts back, did you notice the coconut? I did.
You'll have to read most of the posts on this blog to follow along with the background on these points, I don't want to reiterate all the stuff I've covered over again.
Fat-soluble vitamins are responsible for mineral transport and delivery so intake of vitamin A, D and K as well as saturated fat are necessary. You see you can eat all the calcium you want and it will never get into your blood without A and D. And it will never get out of your blood and into your bones and teeth without vitamin K2. (Activator X turns out to be K2)
Vitamin K2 in particular can significantly lower bacterial count in your mouth, but it can also change your saliva from phosphorous taking to phosphorous bearing. See source at VegSoc Australia
Dr. William Davis, MD wrote about K2 and some of the research: Food sources of vitamin K2. When you read this, and I suggest you read it several times, you'll see how K2 plays a VITAL role in our health and why lack of it (when all other components are there as far as vitamins and minerals from veggies) will make you one unhealthy vegan.
Another interesting fact: Since mammals synthesize a small quantity of Vit K2 forms from vitamin K1, then eating lots of green vegetables should provide substrate for some quantity of K2 conversion. However, work by Schurgers et al have shown that K1 absorption is poor, no more than 10%, but increases significantly when vegetables are eaten in the presence of oils. (Thus arguing that oils are meant to be part of the human diet. Does your olive oil or oil-based salad dressing represent fulfillment of some subconscious biologic imperative?)
--The MK-4 form of vitamin K2 [animal derived] is short-lived, lasting only 3-4 hours in the body. The MK-7 form, in contrast, the form in natto, lasts several days. MK-7 and MK-8-10 [natto derived] are extremely well absorbed, virtually complete.
You can get K2 from a supplement or from yucky natto. Yes, there is natto supplements but there's no mention of whether or not K2 is in those supplements, they just talk about enzymes on the bottle (I just went to the health food store). As you can see from the study at that link, you can increase your absorption of K1 and turn it into K2 by adding fat/oil in your kale salad and I would suggest probiotics because your intestines, to put it frankly, might suck. But to be safe, if you are experiencing any teeth issues, please consider taking a supplement or learning to love natto. You can get the supplement it at Pangea, a very popular vegan shop!
Whatever diet you're on, be sure that you get K2: Vegan K2
Now, I would not get all up in arms and start downing K2. There's got to be a way of checking your levels. If you are a heart patient, go to your doctor.