Risk factors of osteoporosis in IBD include early age onset, corticosteroid (CS) therapy, malnutrition, low body mass, hormonal disorders, including a decreased oestrogen level and malabsorption causing a nutritional deficiency, particularly in terms of vitamin D and calcium. 

Numerous studies have shown that patients on prolonged CS therapy are at high risk of osteoporosis. Studies have also shown that 30%-50% of patients treated with CS may develop osteoporosis, because it increases apoptosis and decrease the formation of osteoblasts and promote osteoclastogenesis.  

Furthermore, CS influences calcium balance (decreasing calcium absorption in the intestine and renal resorption) and the neuroendocrine system. Data indicate that following the first year of CS therapy, bone mass may decrease by about 12%, and 2%–3% per year in the following year. In addition, CS use decreases muscle mass, which leads to an elevated risk of fractures. 

Importance of calcium and vitamin intake in patients with IBD  

Inadequate intake of nutrients increases the risk of bone loss. Dietary intake of essential nutrients (vitamins, minerals, protein, fats, water, and carbohydrates) is considered an important modifiable factor to promote bone health. 

Calcium is responsible for maintaining BMD, blood coagulation, and the proper functioning of the cardiovascular system. In the human body, more than 99% of calcium is stored in bones. Therefore, a decrease in serum calcium level results in the release of the mineral from bones and causes bone tissue resorption.  

Furthermore, an insufficient calcium intake causes hormonal disorders, leading to a higher risk of fractures. Calcium can be found in such sources as milk, dairy products, and green leafy vegetables.  

Between 80%-86% of patients with IBD who avoid mile and dairy products as a result of lactose intolerance, present with low calcium levels compared to those without IBD. Intake of calcium by every 300mg decreased the risk of fractures. The highest risk was found in the intake below 751mg of calcium. Supplementation of calcium in a 1000mg/day–1500mg/day dose is recommended for most patients with IBD.  

Furthermore, patients treated with steroids require vitamin D supplementation. Vitamin D comprises a group of chemical compounds such as ergocalciferol (vitamin D2) and cholecalciferol (vitamin D3). The active forms of vitamin D are 1.25(OH)2D and 24.25(OH)2D.  

Vitamin D acts directly and indirectly on the bone, regulates calcium absorption in the gastrointestinal (GI) tract, determines the proper serum calcium level, influences osteoblasts mineralisation and differentiation, and decreases the synthesis of parathormone and the reabsorption of phosphates from bones. Vitamin D can be found in fatty sea fish, cod liver oil, and yolk. 

IBD patients have a high risk of vitamin deficiency. Therefore, control their 25(OH)D serum level is required. The recommended vitamin D supplementation for healthy adults is 800–2000IU.  

Studies show that vitamin D serum levels are lower than 30ng/mL in patients with IBD compared to healthy controls. This may be because of a lower rate of exposure to sunlight as well as malabsorption caused by inflammation in the GI tract, one of the hallmarks of IBD. A vitamin D dose of 1820IU is sufficient to maintain the normal 25(OH)D serum level in patients with IBD. 

Several studies have shown that vitamin K not only increases BMD in patients with osteoporosis but can also actually reduce fracture rates. Evidence also shows that vitamin K and D works synergistically on bone density and play a central role in calcium metabolism. 

Two forms of vitamin K can be distinguished, namely K1 (phylloquinone, mainly found in green leafy vegetables) and vitamin K2 (menaquinone, mainly found in fermented dairy and produced by lactic acid bacteria in the intestine). 

Vitamin K1 is principally transported to the liver, regulating the production of coagulation factors, while vitamin K2 is transported to extrahepatic tissues, such as bone and the vascular wall, regulating the activity of matrix Gla protein (MGP) and osteocalcin (bone Gla protein) - the main vitamin K-dependent proteins.  

They require vitamin K for carboxylation in order to function properly. When circulating concentrations of vitamin K are insufficient, a greater proportion of MGP and osteocalcin remain uncarboxylated, which is associated with unfavourable outcomes such as cardiovascular disease, lower BMD, and osteoporosis.  

The current recommendation for vitamin K1 intake is 70μg/day for all adults defined by an adequate intake. This amount is solely based on maintaining coagulation function and might not be enough for optimal carboxylation of other vitamin K-dependent proteins, which require higher amounts of vitamin K. Vitamin D promotes the production of vitamin K-dependent proteins. 

Tips to optimise bone health 

• Consider supplementation in at risk patients: Calcium has been singled out as a major public health concern today because it is critically important to bone health and the average. Studies have shown that the majority of people globally have insufficient calcium levels. Vitamin D and K is important for good bone health because it aids in the absorption and utilisation of calcium. 
• Encourage physical activity: It helps to increase or preserve bone mass and to reduce the risk of falling. All types of physical activity can contribute to bone health, albeit in different ways. 
• Advice patients to maintain a healthy body weight: Being underweight raises the risk of fracture and bone loss. Weight loss is associated with bone loss as well, although adequate diet and physical activity may reduce this loss. 
• Incorporate fall prevention studies in your older patients: Fractures are commonly caused by falls, and thus fall prevention offers another opportunity to protect bones, particularly in those over age 60. Several specific approaches have demonstrated benefits, including muscle strengthening and balance retraining, professional home hazard assessment and modification, and stopping or reducing psychotropic medications. 
• Pay attention to women’s health issues, which may affect bone health: Pregnancy and lactation generally do not harm the skeleton of healthy adult women. Amenorrhea (cessation of menstrual periods) after the onset of puberty and before menopause is a very serious threat to bone health and needs to be attended to by individuals and their health care providers. 
• Evaluate the impact of certain medications on bone health: Several medical conditions and prescription medications can affect bone health through various mechanisms, and health care professionals should treat the presence of such conditions and the use of such medications as a potential red flag that signals the need for further assessment of bone health and other risk factors for bone disease. 
• Recommend smoking cessation: Smoking can reduce bone mass and increase fracture risk and should be avoided for a variety of health reasons. Heavy alcohol use has been associated with reduced bone mass and increased fracture risk. 

REFERENCES:  

1. Ilich JZ and Kerstetter JE. Nutrition in Bone Health Revisited: A Story Beyond Calcium. Journal of the American College of Nutrition, 2000.  
2. Office of the Surgeon General (US). Bone Health and Osteoporosis: A Report of the Surgeon General. Rockville (MD): Office of the Surgeon General (US); 2004. Available from: https://www.ncbi.nlm.nih.gov/books/NBK45513/  
3. Palacios C. The role of nutrients in bone health, from A to Z. Crit Rev Food Sci Nutr, 2006. 
4. Ratajczak AE, Rychter AM, Zawada A, et al. Nutrients in the Prevention of Osteoporosis in Patients with Inflammatory Bowel Diseases. Nutrients, 2020. 
5. Van Ballegooijen AJ, Pilz S, Tomaschitz A, et al. The Synergistic Interplay between Vitamins D and K for Bone and Cardiovascular Health: A Narrative Review. International Journal of Endocrinology, 2017. 
6. Weber P. Vitamin K and bone health. Nutrition, 2001.