1. A process for the preparation of an orally administrable calcium composition, said process comprising the steps of: (i) obtaining a physiologically tolerable particulate calcium compound having a mean particle size in the range 3 to 40 mkm, having a crystalline structure and having a surface area of 0.1 to 1.2 m<2>/g; (ii) mixing said calcium compound with a water-soluble diluent and an aqueous solution of a water soluble binder in a fluid bed granulation apparatus and drying the resulting mixture to produce a first granulate; (iii) optionally mixing said first granulate with one or more further components to produce a second granulate; and (iv) optionally compressing said first or second granulate to form tablets. 2. A process as claimed in claim 1 wherein said calcium compound is selected from calcium carbonate, calcium lactate, calcium gluconate, calcium citrate, calcium glycerophosphate, calcium phosphate, calcium hydrogen phosphate, calcium glucuronate, calcium aspartate, calcium glucoheptonate and mixtures of two or more thereof. 3. A process as claimed in claim 1 wherein said calcium compound is calcium carbonate. 4. A process as claimed in any one of claims 1 to 3 wherein said calcium compound makes up 68 to 80% wt. of said first granulate. 5. A process as claimed in any one of claims 1 to 4 wherein said calcium compound makes up 60 to 95% wt. of said second granulate. 6. A process as claimed in any one of claims 1 to 5 wherein in step (i) the same material is used as said diluent and as said binder. 7. A process as claimed in any one of claims 1 to 6 wherein said water-soluble diluent comprises at least one sweetener. 8. A process as claimed in claim 7 wherein said sweetener is selected from sorbitol, xylitol, isomalt, mannitol, sucrose, fructose, maltodextrin, inulin and oligofructose. 9. A process as claimed in any one of claims 1 to 8 wherein said water-soluble diluent makes up 70 to 96% wt. of the total weight of said water-soluble diluent and said water-soluble binder in said first granulate. 10. A process as claimed in any one of claims 1 to 9 wherein said water-soluble binder is selected from celluloses, polysaccharides, maltodextrin, inulin and polyvinylpyrrolidone. 11. A process as claimed in any one of claims 1 to 10 wherein said water-soluble binder is a polyvinylpyrrolidone. 12. A process as claimed in any of claims 1 to 11 wherein said first granulate has a particle size distribution of D (V, 0.1) = 15-21 mkm, D (V, 0.5) = 70-120 mkm and D (V, 0.9) = 190-330 mkm. 13. A process as claimed in any one of claims 1 to 12 wherein a said further component is mixed with said first granulate, said further component being selected from: vitamin B6, vitamin K, vitamin C, vitamin D, isoflavones, inulin, and oligofructose and mixtures of two or more thereof. 14. A process as claimed in any one of claims 1 to 13 wherein in step (ii) said calcium compound is also mixed with isoflavones. 15. A granulate comprising a fluid bed granulation granulate product of a physiologically tolerable calcium compound, a water-soluble binder and a water-soluble diluent, said calcium compound having a mean particle size in the range 3 to 40ym, having a crystalline structure and having a surface area of 0.1 to 1.2 m2/g. 16. A granulate as claimed in claim 15 further comprising a lubricant. 17. A granulate as claimed in either of claims 15 and 16 wherein said calcium compound is selected from calcium carbonate, calcium lactate, calcium gluconate, calcium citrate, calcium glycerophosphate, calcium phosphate, calcium hydrogen phosphate, calcium glucuronate, calcium aspartate, calcium glucoheptonate and mixtures of two or more thereof. 18. A granulate as claimed in any one of claims 15 to 17 said diluent is a sweetener selected from sorbitol, xylitol, mannitol, sucrose, fructose, maltodextrin, inulin and oligofructose. 19. A granulate as claimed in any one of claims 15 to 18 wherein said water-soluble binder is selected from celluloses, polysaccharides, maltodextrin, inulin and polyvinylpyrrolidone. 20. A granulate as claimed in any one of claims 15 to 19 comprising a further component selected from: vitamin B6, vitamin K, vitamin C, vitamin D, isoflavones, inulin, and oligofructose and mixtures of two or more thereof. 21. A tablet comprising a compressed granulate as claimed in any one of claims 15 to 20 containing: calcium carbonate; vitamin D3; a lubricant; citric acid; and an oligosaccharide.