Bariatric surgery alters the anatomy and digestive tract, playing a significant role in vitamin and nutrient levels postoperatively. There is a great impact bariatric surgery has on bone density due to malabsorption, alteration of the intestinal tract, weight loss, and reduction of adipose tissue. 

The gastric bypass and the duodenal switch are both malabsorptive procedures, which results in a reduction in the amount of nutrients able to be absorbed. Coupled with the effects of intaking fewer calories due to the restrictive nature of all bariatric procedures, including the gastric sleeve, patients are at a higher risk of developing vitamin deficiencies after bariatric surgery. 

To avoid malnutrition, we require our patients to take multivitamins for life after their bariatric surgery procedure. Yet some nutrients pose a greater risk of deficiency in patients after bariatric surgery, including vitamins B12, C, A, D, and minerals such as iron and calcium. In this blog, we will talk specifically about the impact bariatric surgery has on bone density, including calcium and vitamin D levels. 

impact bariatric surgery has on bone density and calcium levelsThe Role of Calcium and Vitamin D in the Body

Calcium is the most abundant mineral in the body and supports your bones, blood vessels, muscle function, hormone secretion, and nerve transmission. When you are deficient in calcium, you may experience muscle aches, fatigue, dental problems, and bone breakage. Therefore, it is important to get the recommended calcium dosage each day to decrease your chances of having thin and brittle bones later in life.  

Vitamin D is essential for promoting calcium absorption and balance, immunity, and cellular function. Vitamin D is found in very few foods but instead is absorbed through the skin from the sun. Patients who are vitamin D deficient may experience bone or muscle pain and chronic cramping or body aches.

Calcium and vitamin D work together to support your bones and, therefore, should be taken together to improve absorption rates. 

The Impact Bariatric Surgery Has on Bone Density

After bariatric surgery, your digestive tract is altered and can lead to “impaired intestinal absorption,” especially for calcium and vitamin D. Additionally, there are hormonal changes that take place after bariatric surgery that likely also contribute to bone loss. 

From an anatomical standpoint, the duodenum (the first part of the small intestine) enhances calcium levels when dietary calcium intake is low. Yet after the gastric bypass and the duodenal switch, the duodenum is bypassed, resulting in lower calcium absorption when dietary intake is inadequate. Although the gastric sleeve does not result in the duodenum being bypassed, there is still evidence that the sleeve can decrease bone density due to a reduction in calories and nutrients absorbed.

Studies have also been conducted to review extreme weight loss’s impact on bone density. In theory, lower body weight and load on the bones can lead to less bone formation and thus increase the chances of experiencing thin and brittle bones. However, these findings are theoretical and may not directly impact fracture rate and bone density. 

Finally, there is believed to be a link between adipose tissue and bone formation that could result in a lower bone density after bariatric surgery. Leptin, the appetite suppressor, is a hormone released from fat cells within adipose tissue. As you lose weight, you reduce the amount of adipose tissue in the body, which lowers your leptin levels. The reduction in leptin (and ghrelin) results in bariatric surgery being considered a metabolic procedure that ultimately helps you lose a significant amount of weight. However, this reduction is associated with vitamin D deficiencies as leptin levels are reduced. 

impact bariatric surgery has on bone density and vitamin D levelsHow to Avoid Calcium and Vitamin D Deficiencies after Bariatric Surgery

Having a complete understanding of the impact bariatric surgery has on bone density emphasizes the importance of taking calcium and vitamin D supplements. In order to decrease your risk of bone fractures, we recommend all post-bariatric patients take supplements to enhance their recovery and improve their muscle mass.  


Bariatric patients who had the gastric bypass or the gastric sleeve must take 1500 mg per day of calcium citrate. If you had the duodenal switch, you would be required to take 2000 mg per day. To meet these recommendations, you need to take three doses a day. 

As a bariatric patient, it is essential to remember to take calcium citrate, NOT the calcium carbonate supplements found at your local convenience store. Calcium carbonate is not absorbed as quickly as calcium citrate is. 

Vitamin D

We recommend patients take 3000 international units (IU) a day. You may purchase your Vitamin D from a specialized retailer or you may pick up any Vitamin D3 supplement at your local convenience store. 

This article was originally published on the Bariatric Centers of America Blog.