Diagnosed in toddlers, X-linked hypophosphatemia (XLH) is the most common form of heritable rickets, in which soft bones bend and deform, and tooth abscesses develop because infections penetrate soft teeth that are not properly calcified. Researchers at McGill University and the Federal University of Sao Paulo have identified that osteopontin, a major bone and tooth substrate protein, plays a role in XLH. Their discovery may pave the way to effectively treating this rare disease.

The findings were made by the laboratories of Marc McKee, a professor in the faculty of dentistry and the Department of Anatomy and Cell Biology at McGill University, and of Nilana M.T. Barros, a professor at the Federal University of Sao Paulo. The team built upon previous research that had shown that mutations in the single gene PHEX are responsible for causing XLH. The results of this latest research by Drs. McKee and Barros will be published in the March issue of the Journal of Bone and Mineral Research.

“XLH is caused in part by renal phosphate wasting, which is the urinary loss from the body of phosphate, an important building block of bones and teeth, along with calcium.” says Prof. McKee. “In pursuing other factors that might contribute to XLH, we used a variety of research methods to show that PHEX enzymatic activity leads to an essentially complete degradation of osteopontin in bones.”

This loss of osteopontin, a known potent inhibitor of mineralization (or calcification) in the skeleton and dentition, normally allows bones and teeth to mineralize and thus harden to meet the biomechanical demands placed on them. In XLH patients lacking functional PHEX enzyme, osteopontin and some of its smaller potent inhibitory peptides are retained and accumulate within the bone. This prevents their hardening and leads to soft, deformed bones such as bowed legs (or knock-knees) seen in toddlers.

While not life-threatening, this decreased mineralization of the skeleton (osteomalacia), along with the soft teeth, soon leads to a waddling gait, short stature, bone and muscle pain, weakness, and spontaneous tooth abscesses.

The fact that these symptoms are only partially improved by the standard treatment with phosphate — which improves circulating phosphate levels — prompted the researchers to look for local factors within the bone that might be blocking mineralization in these patients.

“With this new identification of osteopontin as a substrate protein for PHEX,” says Professor Barros, “we can begin to develop an enzyme-replacement therapy to treat XLH patients who have nonfunctional PHEX, much as has been done using a different enzyme to treat another rare bone disease called hypophosphatasia.”

This research was jointly funded by the Canadian Institutes of Health Research (Canada) and Fundação de Amparo ȧ Pesquisa do Estado de São Paulo (Brasil).

In group 1, oatmeal prevented healing and encouraged new cavities, presumably due to its ability to prevent mineral absorption. In group 2, simply adding vitamin D to the diet caused most cavities to heal and fewer to form. The most striking effect was in group 3, the group eating a grain-free diet plus vitamin D, in which nearly all cavities healed and very few new cavities developed. Grains are the main source of phytic acid in the modern diet, although we can’t rule out the possibility that grains were promoting tooth decay through another mechanism as well.

Dr. Mellanby was quick to point out that diet 3 contained some carbohydrate (~45% reduction) and was not low in sugar: “Although [diet 3] contained no bread, porridge or other cereals, it included a moderate amount of carbohydrates, for plenty of milk, jam, sugar, potatoes and vegetables were eaten by this group of children.” This study was published in the British Medical Journal (1) and the British Dental journal. Here’s Dr. Edward Mellanby again:
The hardening of carious areas that takes place in the teeth of children fed on diets of high calcifying value indicates the arrest of the active process and may result in “healing” of the infected area. As might be surmised, this phenomenon is accompanied by a laying down of a thick barrier of well-formed secondary denture… Summing up these results it will be clear that the clinical deductions made on the basis of the animal experiments have been justified, and that it is now known how to diminish the spread of caries and even to stop the active carious process in many affected teeth.
Dr. Mellanby first began publishing studies showing the reversal of cavities in humans in 1924. Why has such a major medical finding, published in high-impact peer-reviewed journals, faded into obscurity?

Dr. Weston Price also had success curing tooth decay using a similar diet. He fed underprivileged children one very nutritious meal a day and monitored their dental health. From Nutrition and Physical Degeneration (p. 290):
About four ounces of tomato juice or orange juice and a teaspoonful of a mixture of equal parts of a very high vitamin natural cod liver oil and an especially high vitamin butter was given at the beginning of the meal. They then received a bowl containing approximately a pint of a very rich vegetable and meat stew, made largely from bone marrow and fine cuts of tender meat: the meat was usually broiled separately to retain its juice and then chopped very fine and added to the bone marrow meat soup which always contained finely chopped vegetables and plenty of very yellow carrots; for the next course they had cooked fruit, with very little sweetening, and rolls made from freshly ground whole wheat, which were spread with the high-vitamin butter. The wheat for the rolls was ground fresh every day in a motor driven coffee mill. Each child was also given two glasses of fresh whole milk. The menu was varied from day to day by substituting for the meat stew, fish chowder or organs of animals.
Dr. Price provides before and after X-rays showing re-calcification of cavity-ridden teeth on this program. His intervention was not exactly the same as Drs. Mellanby, but it was similar in many ways. Both diets were high in minerals, rich in fat-soluble vitamins (including D), and low in phytic acid.

Price’s diet was not grain-free, but used rolls made from freshly ground whole wheat. Freshly ground whole wheat has a high phytase (the enzyme that degrades phytic acid) activity, thus in conjunction with the long yeast rises common in Price’s time, it would have broken down nearly all of its own phytic acid. This would have made it a source of minerals rather than a sink for them. He also used high-vitamin pastured butter in conjunction with cod liver oil. We now know that the vitamin K2 in pastured butter is important for bone and tooth development and maintenance. This was something that Dr. Mellanby did not understand at the time, but modern science has corroborated Price’s finding that K2 is synergistic with vitamin D in promoting skeletal and dental health
to design the ultimate dietary program to heal cavities that incorporates the successes of both doctors, it would look something like this:
Rich in animal foods, particularly full-fat pastured dairy products (if tolerated). Also meat, organs, fish, bone broths and eggs.
Fermented grains only; no unfermented grains such as oatmeal, breakfast cereal, crackers, etc. No breads except true sourdough (ingredients should not list lactic acid). Or even better, no grains at all.
Limited nuts; beans in moderation, only if they’re soaked overnight or longer in warm water (due to the phytic acid).
Starchy vegetables such as potatoes and sweet potatoes.
A limited quantity of fruit (one piece per day or less), but no refined sweets.
Cooked and raw vegetables.
Sunlight, high-vitamin cod liver oil or vitamin D3 supplements.
A generous amount of pastured butter.
No industrially processed food.