Patients who choose to have bariatric surgery have an increased risk of developing certain vitamin and mineral deficiencies, including calcium. This article explains the role of calcium, the symptoms of calcium deficiency, how much calcium bariatric patients need, food sources, the importance of vitamin D, lab tests, types of calcium supplements and how to improve absorption.
Key takeaways
- The ASMBS recommends 1,200–1,500 mg/day of calcium citrate after a gastric band, sleeve gastrectomy or gastric bypass, and 1,800–2,400 mg/day after a duodenal switch.
- Take calcium in divided doses of 500–600 mg, at least two hours apart, and at least two hours away from iron.
- Calcium citrate with vitamin D3 is the preferred form for bariatric patients.
- Serum calcium is not a good indicator of calcium status; PTH combined with other lab values is.
- The risk of deficiency increases over time – keep taking your vitamins and minerals as recommended.
Calcium's role
Calcium is an essential element for human life. It is the most abundant mineral in the human body: 99% of your body's calcium is found in your teeth and bones, and the remaining 1% in blood, nerve cells and body tissue. In addition to its well-known role in healthy teeth and bones, calcium is essential for growth, maintenance and reproduction. It also plays a role in blood clotting, muscle contraction, hormone secretion and the expansion and contraction of your blood vessels. Not getting enough calcium can contribute to poor bone health and other long-term consequences.
The body tightly regulates serum calcium: serum levels do not change in response to dietary calcium intake. This means the body uses bone as a reservoir and source of calcium to maintain constant levels in the blood, muscle and intracellular fluids (1).
Bone is in a constant state of turnover, with regular withdrawals and deposits of calcium:
- Children and adolescents: bone formation (deposits of calcium; build-up of bone) exceeds resorption (withdrawals of calcium; breakdown of bone) during periods of growth (1).
- Early and middle adulthood: both processes are relatively equal (1).
- Around the age of 30: adults reach peak bone mass. Adequate calcium intake is important to ensure optimum bone mass and slow the loss of bone that naturally occurs with ageing.
Osteopenia, a condition of lower than normal bone density, can lead to osteoporosis, which increases the risk of bone fractures, especially in older individuals (1). Osteoporosis causes the bones to become fragile and porous (like a sponge) and is a leading contributor to fractures of the hip, wrist, pelvis, ribs and vertebrae. In the United States, osteoporosis affects 10 million adults, 80% of whom are women; an additional 34 million have osteopenia, a precursor to osteoporosis; and an estimated 1.5 million fractures occur annually due to osteoporosis (1). Regular physical activity and calcium intake (of the proper amount and type) along with vitamin D can help to reduce your risk of osteoporosis after bariatric surgery.
Symptoms of calcium deficiency
Not consuming enough calcium from food and/or supplements has no obvious symptoms in the short term. However, low calcium levels over time may result in (1):
- Numbness and tingling of the fingers
- Muscle cramps and convulsions
- Lethargy
- Poor appetite (this may be hard to recognise in bariatric surgery patients)
- Abnormal heart rhythms
If calcium deficiency is left untreated over time, it can lead to death (1).
When the body does not get the calcium it needs, it starts to take calcium from the bones. Over time, this "stealing" of calcium makes your bones sponge-like and much more fragile, which decreases your overall bone health. It has been suggested that individuals who choose to have bariatric surgery are at risk of long-term consequences related to bone health (2).
One study evaluated almost 100 patients who had bariatric surgery over 20 years and reported that 21 of these patients suffered a total of 31 fractures – more than twice the fracture risk of the general population. Most fractures occurred on average seven years after surgery, mainly in the hands and feet; other sites included the hip, spine and upper arm (3). Bone loss is a potential side effect after all types of bariatric surgery, and getting adequate calcium is one important piece of the puzzle in helping to prevent bone loss and fractures.
Additionally, deficits in calcium and vitamin D increase the risk of not only skeletal disorders, but also colon cancer, breast cancer, prostate gland cancer, chronic inflammation and autoimmune disease (e.g. type 1 diabetes mellitus, inflammatory bowel disease, multiple sclerosis, rheumatoid arthritis), metabolic disorders (e.g. metabolic syndrome and high blood pressure) and peripheral vascular disease (4,5).
How much calcium?
The recommended dietary allowance (RDA) was developed for the general, healthy population, and these recommendations do not always apply to bariatric surgery patients.
| Group | Calcium per day |
|---|---|
| RDA: males aged 19–70 and females aged 19–50 | 1,000 mg (1) |
| RDA: males aged 71+ and females aged 51+ | 1,200 mg (1) |
| ASMBS: adjustable gastric band, sleeve gastrectomy and Roux-en-Y gastric bypass | 1,200–1,500 mg calcium citrate in divided doses (6) |
| ASMBS: biliopancreatic diversion with duodenal switch | 1,800–2,400 mg (7) |
According to the American Society for Metabolic and Bariatric Surgery (ASMBS), bariatric surgery patients should get calcium from dietary sources and supplements, with the proportion of each depending on the type of surgery (6,7). It is very important to have your calcium status checked via laboratory studies so your bariatric surgeon can determine your individual calcium recommendation based on your medical history, laboratory studies and personal calcium consumption from food.
Divide your total daily dose of calcium into 500–600 mg doses (e.g. 1,500 mg is taken three times per day at 500 mg per dose). Absorption is highest in doses of 500 mg or less (1). Never take calcium at the same time as iron or a multivitamin containing iron – separate them by at least two hours – and separate each dose of calcium by at least two hours.
Food sources of calcium
Eating foods rich in calcium is also important. Calcium-containing foods include (1,8):
- Dairy products (preferably low-fat or fat-free)
- Leafy greens (spinach, collard greens and mustard greens)
- Calcium-fortified products, such as soya, tofu, rice drinks, orange juice and cereals
- Celery, broccoli, sesame seeds and cabbage
Not all calcium from food is absorbed in the gut. Humans absorb about 30% of the calcium in foods, but this varies depending on the type of food consumed (1). In theory, this could be worsened by the type of bariatric surgery.
What groups of individuals are at risk for calcium inadequacy?
In addition to bariatric surgery, there are other reasons (or a combination of reasons) why someone might be at risk of calcium inadequacy:
- Postmenopausal women: at increased risk of bone loss due to the decrease in oestrogen production, which both increases bone resorption and decreases calcium absorption (1). Consuming adequate calcium from food might help to slow the rate of bone loss in all women; postmenopausal women should discuss all treatment options with their physician (1).
- Lactose intolerance: individuals who avoid dairy products are at increased risk of calcium inadequacy (1). Research suggests that most people with lactose intolerance can consume up to 12 grams of lactose – the amount in about 240 ml of milk – with minimal to no symptoms, especially when combined with other foods (1). Some bariatric patients develop varying degrees of lactose intolerance after surgery (9).
- Cow's milk allergy: also a risk factor, although this condition is quite rare (1). Lactose-intolerant individuals and those with a cow's milk allergy can choose alternative calcium-rich foods, such as kale, bok choy, Chinese cabbage, broccoli, collards and fortified foods (1).
- Vegetarians and vegans: some are at risk due to a potentially higher intake of oxalic and phytic acids from a plant-based eating plan, which decrease calcium absorption (1,8). Not all vegetarians follow the same eating plan, so each should be evaluated individually.
Importance of vitamin D
Vitamin D is necessary for the absorption of calcium and helps to maintain adequate serum (a component of the blood) levels of calcium. Several studies have linked low levels of vitamin D to various diseases, such as cancer, osteoporosis and cardiovascular (relating to the heart and blood vessels) disease (10).
Most over-the-counter vitamin D products contain vitamin D3 (cholecalciferol). In the United States, prescription vitamin D is generally vitamin D2 (ergocalciferol). Vitamin D3 is superior to vitamin D2 (11).
Most bariatric surgery patients require additional vitamin D after surgery, due to decreased absorption of vitamin D in the small intestine and/or to continue treating a pre-operative vitamin D deficiency. Some patients may reach their target vitamin D levels through careful selection of their multivitamin and calcium supplements, while others will require additional therapeutic vitamin D. Talk to your bariatric surgeon about your vitamin D levels and how much supplemental vitamin D you need to optimise your health and calcium absorption (remember to factor in the vitamin D in your bariatric multivitamin and calcium citrate supplements).
Calcium and related laboratory studies
Calcium deficiency, as indicated by low serum calcium, would not be expected until osteoporosis has severely depleted the skeleton's calcium stores (7). This means serum calcium is not the best indicator of calcium status.
Parathyroid hormone (PTH) is the best indicator of calcium status when combined with serum calcium, 25-hydroxyvitamin D (25(OH)D), phosphorus and alkaline phosphatase (7). Bone mineral density testing is also an excellent tool to get a better picture of total body bone health (7).
Why do bariatric patients require more calcium?
There are several reasons why bariatric surgery patients require additional calcium after surgery, above and beyond the RDA. Because of these, it is important to take your calcium regularly as directed by your bariatric surgeon to reduce the risk of deficiency and bone loss and to prevent long-term effects of calcium deficiency.
- Before surgery: up to 41% of patients may be at increased risk of elevated PTH levels (12), while up to 80% may present with vitamin D deficiency (13).
- Low intake in general: according to the US National Health and Nutrition Examination Survey (NHANES) 2017–2018, mean calcium intake from food was 1,084 mg/day for males aged 20 and older and 857 mg/day for females (28). Groups below their estimated average requirement (EAR), with a prevalence of inadequacy above 50%, included boys and girls aged 9–13, girls aged 14–18, women aged 51–70, and men and women over 70 (1). Bariatric surgery patients consume fewer calories than non-bariatric patients, so most, if not all, will need supplemental calcium to reach their recommended intake.
- Lactose intolerance: many gastric bypass patients (and some other bariatric surgery patients) develop lactose intolerance after surgery, making it more difficult to eat foods high in calcium (9).
- Lower absorption: in gastric bypass patients, true calcium absorption has been shown to be lower after surgery (14).
- Low blood levels: one study reported that 48% of patients had low calcium blood levels two years after malabsorptive bariatric surgery (15).
- A multivitamin is not enough: a daily multivitamin may not prevent a calcium deficiency, since many patients need far more than their multivitamin contains, if any. Most multivitamins do not contain calcium, and those that do generally contain a very small amount (100–200 mg per daily serving).
- Stores run out: the risk of calcium deficiency increases over time as the body eventually runs out of calcium stores.
- Bypassed absorption site: with a gastric bypass, the primary area of calcium absorption is bypassed, which further increases your need for supplementation. The same area is bypassed in the biliopancreatic diversion with duodenal switch.
- Duodenal switch data: after biliopancreatic diversion with duodenal switch, 63% of patients experienced vitamin D deficiency, 48% low calcium levels and 69% an increase in PTH, which indicates bone loss (16). Bone loss has also been observed in gastric bypass (17), adjustable gastric band (18,19) and sleeve gastrectomy patients (20).
Types of calcium supplements
There are several types of calcium supplements. Calcium carbonate is commonly recommended to the general public, but it is not the preferred source for bariatric surgery patients according to the ASMBS, which recommends calcium citrate (6,7). Calcium citrate is preferred because:
- it does not require stomach acid for absorption (21);
- there is less risk of kidney stones with calcium citrate than with calcium carbonate (22);
- calcium citrate is less constipating than calcium carbonate (23);
- calcium citrate can be taken with or without a meal, whereas calcium carbonate must be taken with a meal (21), which can be difficult for patients in the immediate post-operative period.
| Type | Elemental calcium | Notes |
|---|---|---|
| Calcium citrate | 20–21% | Preferred for bariatric patients (ASMBS) |
| Calcium carbonate | 40% | Needs stomach acid; must be taken with a meal |
| Calcium phosphate, lactate, gluconate | – | Not the preferred source for bariatric patients |
| Dolomite, oyster shell, bone meal | – | Avoid: may contain metals and lead (23) |
Calcium citrate has less elemental calcium (20–21%) than calcium carbonate (40%) (1,23). What does elemental calcium mean? This means that typically the dosage listed on the label would then need to be multiplied by the percentage of elemental calcium associated with that type of calcium supplement to determine how much calcium is actually absorbed (i.e., the amount of calcium the body can actually use). Please keep in mind all Celebrate® products list the dosage as the elemental amount and you do not have to do this math (YAY!), so ultimately this difference does not matter when it comes to Celebrate’s® products.
What to look for in a calcium supplement
- Vitamin D: your calcium citrate supplement should also contain vitamin D.
- Sugar: look for options that are low in sugar or sugar-free. Some calcium supplements are akin to sweets, and the calories add up quickly if you take three or four a day.
- Form: most bariatric surgeons recommend starting with a chewable or liquid calcium citrate supplement containing vitamin D. Some allow patients to progress to tablets later – check with your bariatric surgeon before making that switch.
- Serving size: one pill, chewable or tablet is not always equal to one dose (500 mg) of calcium citrate.
- Stomach upset: if you notice stomach upset or nausea, try taking your calcium supplement with food.
- Form of vitamin D: look for vitamin D3 (cholecalciferol) in a water-miscible form, sometimes called dry vitamin D. Fat-soluble vitamins (A, D, E and K) usually need fat for optimal absorption; a dry or water-miscible form does not, which is ideal for bariatric patients, as meals may not contain enough fat and the product may be taken separately from meals.
How to increase calcium absorption / what decreases calcium absorption
There are ways to make sure you get the most out of your calcium supplements. Speak to your bariatric surgeon and/or dietitian before making any changes to your supplement regimen.
- Make sure your calcium supplement also contains vitamin D3 to enhance calcium absorption (24).
- Make sure you get adequate vitamin D, as it improves calcium absorption (1).
- Be cautious with the amount of calcium per dose: absorption efficiency decreases as intake increases (above 500 mg over a 2-hour period) (1).
- Do not take calcium at the same time as your iron or a multivitamin containing iron. Separate calcium and iron by at least two hours.
- Do not consume a high amount of tannin-rich products (tea, wine, chocolate, coffee) throughout the day (24). This is especially important if you are trying to increase your calcium levels.
- Dietary fibre can reduce intestinal absorption of calcium, so avoid taking calcium-rich foods or supplements at the same time as foods containing wheat and oat bran or other sources rich in insoluble fibre (24).
- Nuts, legumes, fibre-containing wholegrain products, wheat bran, beans, seeds and soya isolates contain phytic acid, which binds calcium and decreases the amount the body can absorb – including calcium from other foods eaten at the same time (24).
- Oxalic acid, found naturally in plants such as spinach, collard greens, sweet potatoes, rhubarb and beans, binds calcium and decreases the amount the body can absorb. Unlike phytic acid, it does not bind calcium from other foods eaten at the same time (24).
- Diarrhoea moves substances through the intestines quickly, not allowing enough time for calcium to be absorbed (24).
Drug–nutrient interactions
These may not be avoidable if you are told to take these medications, but they further increase the need to have your calcium levels checked as recommended by your bariatric surgeon.
- Proton pump inhibitors (PPIs) and H2 receptor antagonists decrease calcium absorption. These are commonly used to treat heartburn or oesophageal reflux (GERD).
- Thyroid medication (such as Synthroid or levothyroxine): talk to your bariatric surgeon and/or pharmacist about the timing of your bariatric vitamins, as you may need to change the dosing schedule.
- Increased calcium loss: people taking anti-inflammatory corticosteroids for obesity-related arthritis, aluminium-containing antacids or thyroid hormones are at increased risk of urinary and stool calcium loss (1,8).
- Reduced medication absorption: taking calcium at the same time as bisphosphonates (used to treat osteoporosis), fluoroquinolone and tetracycline antibiotics, levothyroxine or phenytoin (an anticonvulsant) reduces absorption of the medication (1,8). Separate these medications from calcium supplements by two hours.
- Laxatives: mineral oil and stimulant laxatives decrease calcium absorption (8).
- Glucocorticoids such as prednisone can cause calcium depletion and eventually osteoporosis when used for months (25,26).
Taking too much vitamin A can also increase bone resorption, so it is important to take the appropriate amount (27). Your bariatric surgeon can help you determine the right amount of vitamin A based on your medical history and laboratory studies.
Too much of a good thing?
Taking too much calcium can cause side effects, so do not take more or start calcium without talking to your bariatric surgeon and/or dietitian and getting blood work done. The upper limit is set at 2,500 mg/day for adults aged 19–50 and 2,000 mg/day for adults aged 51 and older, but keep in mind this is for the general population (8). Excessive calcium intake may contribute to certain types of kidney stones, although more recent research suggests that taking the appropriate amount of calcium (not too much, not too little) is the best strategy to prevent kidney stones (24). Excessive calcium intake may also lead to constipation and may inhibit the absorption of iron and zinc from food (24).
Of note: if you do not take your vitamins, you cannot prevent deficiencies. While it is important to care about which brand you take and what is in your vitamins and minerals, it is just as important to take them daily. Your bariatric vitamin and mineral regimen is just as important in the first year after surgery as it is ten or more years later (your risk of nutritional deficiencies actually goes up over time), so do not stop taking them as recommended by your bariatric surgeon.* Keep following up with your bariatric surgeon and get your lab work done on time to track your nutritional status. Most nutritional deficiencies are easier to prevent than to treat. Tell your doctor, pharmacist and other healthcare providers about any medications and/or supplements you take.
Calcium deficiency is one of the more common deficiencies seen in post-operative bariatric patients, but it is also one of the most preventable, since we have good lab parameters to evaluate an individual's bone health. Follow the instructions of your bariatric programme regarding calcium supplementation and get follow-up blood work done in a timely manner. This will help you keep your calcium, PTH and vitamin D levels within normal limits, which ultimately leads to optimum bone health for life – so you can keep CELEBRATING your successes!
* Proper supplementation should be viewed as an individualised regimen based on each patient's medical history, laboratory studies and current medication use. Patients should follow the instructions of their bariatric surgery team, follow up at the recommended intervals and stay up to date with requested lab work.
Sources
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This article is for general information only and does not replace personal medical advice. Always discuss your situation, blood test results and supplementation with your bariatric team or healthcare provider.