Calcium is an essential element for human life. It is the most abundant mineral in the human body and 99% of your body’s calcium is found in your teeth and bones. The remaining 1% of calcium in the body is found in blood, nerve cells, and body tissue. In addition to the commonly known role calcium plays in healthy teeth and bones, it is also 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.
It is important to note that the body tightly regulates serum calcium. Serum levels of calcium do not change in regards to dietary intake of calcium. This means the body uses bone as a reservoir for and as a source of calcium in order to maintain constant levels of calcium in the blood, muscle, and intracellular fluids (1).
Bone is in a constant state of turnover with regular withdrawals and deposits of calcium over time. Bone formation (i.e., deposits of calcium; buildup of bone) exceeds resorption (i.e., withdrawals of calcium; breakdown of bone) during periods of growth in children and adolescents (1). During early and middle adulthood both processes are relatively equal (1). Adults reach peak bone mass around the age of 30 and adequate calcium intake is important to ensure optimum bone mass and slow the loss of bone that naturally occurs with aging. 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 is a condition that causes the bones to become fragile and porous (like a sponge) and is a serious concern and leading contributor to fractures of the hip, wrist, pelvis, rib, and vertebrae. Osteoporosis affects 10 million adults in the United States and 80% of these individuals are women (1). An additional 34 million have osteopenia, which is a precursor to osteoporosis (1). An estimated 1.5 million fractures occur annually in the United States 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 following 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 a period of time may result in numbness and tingling of the fingers, muscle cramps, convulsions, lethargy, poor appetite (this side effect may be hard to ascertain in bariatric surgery patients), and abnormal heart rhythms (1). If calcium deficiency is left untreated over time, it can lead to death (1).
When the body does not get the required calcium it needs, it starts to take calcium from the bones. Over time this “stealing” of calcium from your bones causes them to become 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 for long-term consequences related to bone health (2).
In fact 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. That is more than twice the fracture risk of the general population. Most fractures occurred on average seven years following bariatric surgery, with the primary locations being the hands and the feet. Other fracture sites included the hip, the spine, and the upper arm (3). Unfortunately, bone loss is a potential side effect after all types of bariatric surgery and getting adequate calcium is one important piece of the puzzle to helping to prevent bone loss and bone 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. The RDA is 1,000 milligrams (mg) of calcium per day for males aged 19-70 years of age and females aged 19-50 years of age require. Males aged 71 years of age and older and females aged 51 years of age and older require 1,200 mg of calcium per day to meet the RDA (1).
However, bariatric surgery patients have varied needs. The American Society for Metabolic and Bariatric Surgery (ASMBS) recommends 1,200-1,500 mg/day of calcium citrate in divided doses (explained in next paragraph) for the adjustable gastric band, sleeve gastrectomy, and roux-en-Y gastric bypass (6). Calcium recommendations for the biliopancreatic diversion with duodenal switch are 1,800-2,400 mg/day according to the ASMBS (7). According to the ASMBS, bariatric surgery patients should get calcium from dietary sources and supplements, with the proportion of each dependent upon the type of surgery (6,7). It is very important to get your personal calcium level 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.
It is important to note that the total daily dose of calcium should be divided into 500-600 mg doses (i.e., 1,500 mg would be taken three times per day at 500 mg per dose period). Absorption of calcium is highest in doses less than or equivalent to 500 mg (1). Also, calcium should never be taken at the same time as iron or a multivitamin containing iron. These products should be separated by at least two hours. Additionally, each dose of calcium should be separated by at least two hours.
Food Sources of Calcium
Eating foods rich in calcium is also important. Calcium containing foods include dairy products (preferably low-fat or non-fat), leafy greens (spinach, collard greens, and mustard greens), and calcium-fortified food products, such as soy, tofu, rice drinks, orange juice, cereals, etc. Other foods that contain calcium include celery, broccoli, sesame seeds, and cabbage (1,8).
Not all calcium consumed from dietary sources is absorbed in the gut. Humans absorb about 30% of the calcium in foods, but this varies depending upon the type of food consumed (1). This lack of absorption could be worsened, in theory, 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 as to why someone might be at risk for calcium inadequacy. Postmenopausal women are at an increased risk for bone loss due to the decrease in estrogen production, which both increases bone resorption and decreases calcium absorption (1). Consuming adequate amounts of calcium from food sources might help to slow the rate of bone loss in all women, however, postmenopausal women should discuss all treatment options with their physician (1).
Individuals with lactose intolerance that avoid dairy products are at an increased risk of calcium inadequacy (1). Research suggests that most individuals with lactose intolerance can consume up to 12 grams of lactose, such as the amount present in 8 ounces of milk, with minimal to no symptoms, especially when combined with other foods (1). Some bariatric patients develop varying degrees of lactose intolerance following their bariatric surgery (9). Individuals who are allergic to cow’s milk are also at risk for calcium inadequacy, however this condition is quite rare (1). There are alternative forms of calcium-rich foods that both lactose-intolerant individuals and those with cow’s milk allergy can choose, such as kale, bok choy, Chinese cabbage, broccoli, collards, and fortified foods (1).
Some vegetarians and some vegans are also at risk for calcium inadequacy due to a potential higher intake of oxalic and phytic acids from a plant-based eating plan (1,8). Oxalic and phytic acid decrease calcium absorption. However, not all vegetarians follow the same eating plan and each one should be evaluated on an individual basis for calcium adequacy.
Importance of Vitamin D
Vitamin D is necessary for the absorption of calcium and helps to maintain adequate serum (i.e., 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 (i.e., of, relating to, or affecting the heart and blood vessels) disease (10).
Most over-the-counter vitamin D products are available in a form known as vitamin D3 or cholecalciferol. Generally, in the United States, prescription vitamin D is vitamin D2 or ergocalciferol. Vitamin D3 is superior to vitamin D2 (11).
Most bariatric surgery patients require additional vitamin D supplementation post-operatively due to decreased absorption of vitamin D in the small intestine post-operatively and/or to continue treating a pre-operative vitamin D deficiency. Some patients may achieve targeted vitamin D levels through careful selection of their multivitamin and calcium supplements, while other patients 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 take in order to optimize your health and calcium absorption (remember to factor in the vitamin D found in your bariatric multivitamin and calcium citrate supplements).
Calcium and Related Laboratory Studies
Calcium deficiency as notated by low serum calcium would not be expected until osteoporosis has severely depleted the skeleton of calcium stores (7). This means that serum calcium levels are not the best indicator for calcium levels.
Parathyroid hormone, commonly referred to as PTH, is the best indicator for calcium status when combined with serum calcium, 25-hydroxyvitamin-D (25(OH)D), phosphorus, and alkaline phosphatase (7). Additionally, bone mineral density testing is a wonderful assessment tool to get a better picture of total body bone health (7).
Why do Bariatric Patients Require More Calcium?
There are several reasons as to why bariatric surgery patients require additional calcium following bariatric surgery above and beyond the RDA. Due to the reasons listed below, it is important that bariatric surgery patients regularly take their calcium as directed by their bariatric surgeon to reduce the risk of deficiency, bone loss, and prevent any long-term challenges from the effects of calcium deficiency.
- - Prior to surgery, up to 41% of patients may be at an increased risk for elevated PTH levels (12), while up to 80% of patients may present with vitamin D deficiency (13).
- - According to the National Health and Nutrition Examination Survey (NHANES) from 2003-2006, mean calcium intake from food for males aged one and older ranged from 871-1,266 mg/day depending on life stage group and females ranged from 748-968 mg/day. Groups that fell below their respective estimated average requirement (ERA) and therefore had a prevalence of inadequacy greater than 50% included boys and girls aged 9-13 years, girls aged 14-18 years, and women aged 51-70 years, and both men and women greater than 70 years (1). We know that bariatric surgery patients consume less calories than non-bariatric surgery patients and therefore, one can deduce how most, if not all, bariatric surgery patients will require some supplemental calcium in order to reach their recommended intake.
- - Many gastric bypass patients (and some other bariatric surgery patients) develop lactose intolerance following their bariatric surgery making it more difficult to eat foods high in calcium (9).
- - In gastric bypass patients, true calcium absorption has been shown to be lessened following bariatric surgery (14).
- - One study reported 48% of patients had low calcium blood levels two years after their malabsorptive bariatric surgery (15).
- - A daily multivitamin may not prevent a calcium deficiency since so many patients require above and beyond what is included in their daily multivitamin, if any. In fact most multivitamins do not contain calcium and if they do, it is generally a very small amount (100-200 mg per daily serving).
- - Keep in mind the risk of calcium deficiency increases over time as the body eventually runs out of calcium stores.
- - If you chose gastric bypass, then the primary area of absorption for calcium was bypassed and this further increases your need for calcium supplementation. This same area is also bypassed in the biliopancreatic diversion with duodenal switch.
- - Following biliopancreatic diversion with duodenal switch, 63% of patients experienced vitamin D deficiency, 48% experienced low calcium levels, and 69% of patients experienced 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 when it comes to supplementation. One of the common calcium supplements recommended to the general public is calcium carbonate. However, calcium carbonate is not the preferred source of calcium supplementation for bariatric surgery patients according to the ASMBS. The ASMBS recommends that bariatric surgery patients take calcium citrate supplements (6,7). Calcium citrate is the preferred source of calcium supplementation for bariatric surgery patients because 1) it does not require stomach acid to aid in its absorption (21), 2) there is less risk of kidney stones when supplementing with calcium citrate versus calcium carbonate (22), 3) calcium citrate is less constipating compared to calcium carbonate (23), and 4) calcium citrate can be taken with or without a meal, whereas calcium carbonate must be taken with a meal (21), which can often be difficult for the immediate post-operative bariatric surgery patient.
However, calcium citrate has less elemental calcium (20-21%) compared to 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.
It is recommended to avoid calcium supplements made of dolomite, oyster shell, and bone meal as these may contain metals and lead (23). Other calcium salts include calcium phosphate, calcium lactate, and calcium gluconate, however these are not the preferred source of calcium for bariatric surgery patients.
It is recommended that your calcium citrate supplement also contain vitamin D. It is ideal to look for options that are low in sugar or sugar-free. Keep in mind some calcium supplements are akin to candy and the calorie count can add up quite quickly, especially if you have to take three or four calcium supplements daily.
Most bariatric surgeons recommend that their patients start with a chewable or liquid calcium citrate supplement that contains vitamin D. Some surgeons allow patients to progress to a tablet product, but be sure to check with your bariatric surgeon before making that switch.
Please be sure to check the serving size of your calcium supplement; one pill, chewable, tablet, etc. is not always equivalent to one dose (i.e., 500 mg) of calcium citrate. If you notice stomach upset or nausea, try taking your calcium supplement with food to decrease gastrointestinal distress.
Lastly, consider the form of vitamin D. Not only should you look for vitamin D3 or cholecalciferol. You should also look for a water-miscible form of this nutrient. Sometimes this is also referred to as dry vitamin D. Typically, fat-soluble vitamins (i.e., vitamins A, D, E, and K) require fat for optimal absorption. A dry or water-miscible form of these nutrients does not require fat for absorption and this is ideal for the bariatric patient since meals may not contain enough fat to optimize absorption and/or patients may take the product separate from meals.
How to Increase Calcium Absorption/What Decreases Calcium Absorption
There are ways to ensure you are getting the most bang for your buck when taking calcium supplements. Be sure to speak to your bariatric surgeon and/or dietitian before making any changes to your supplement regimen.
- - Ensure your calcium supplement also contains vitamin D3 to enhance calcium absorption (24).
- - Ensure you are getting adequate amounts of vitamin D as this nutrient improves calcium absorption (1).
- - Be cautious with the amount of calcium consumed per dose period. The efficiency of absorption decreases as calcium 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 (general intake) (24). This is especially important for those trying to increase their calcium levels.
- - Dietary fiber can reduce intestinal absorption of calcium, so avoid eating calcium-rich foods or taking your calcium supplements at the same time as foods containing wheat and oat bran or other sources rich in insoluble fiber for example (24).
- - Nuts, legumes, fiber-containing whole grain products, wheat bran, beans, seeds, and soy isolates contain phytic acid that can bind to calcium decreasing the amount of calcium that the body can absorb (24). Eating foods rich in phytates will bind calcium from other foods consumed at the same time (24).
- - Oxalic acid, which is found naturally in some plants, such as spinach, collard greens, sweet potatoes, rhubarb, and beans, binds to calcium decreasing the amount of calcium that the body can absorb (24). Unlike phytic acid, oxalic acid does not bind the calcium from other foods that are consumed at the same time (24).
- - Diarrhea moves substances through the intestines quite rapidly, not allowing enough time for calcium to be absorbed (24).
There are also a couple drug-nutrient interactions when it comes to calcium. These may not be preventable if you are told to take these medications (just something to keep in mind and further increases the need for getting calcium levels checked as recommended by your bariatric surgeon). If you take proton pump inhibitors (PPIs) or H2 receptor antagonists, then it decreases the absorption of calcium. PPIs or H2 receptor antagonists are medications commonly used to treat heartburn or esophageal reflux (GERD). If you take thyroid medications, such as synthroid, levothyroxin, etc., then it is important to talk to your bariatric surgeon and/or pharmacist about the timing of your bariatric vitamins, as you may need to change the dosing schedule due to taking this type of medication. Individuals taking anti-inflammatory corticosteroids for obesity-related arthritis, aluminum-containing antacids, or thyroid hormones are at an increased risk for urinary and stool calcium loss (1,8). Taking calcium at the same time as the following medications will reduce the absorption of the medication(s): bisphosphonates (used to treat osteoporosis), the fluoroquinolone and tetracycline classes of antibiotics, levothyroxine, and phenytoin (an anticonvulsant) (1,8). Therefore, it is recommended to separate the aforementioned medications with calcium supplements by two hours. Mineral oil and stimulant laxatives decrease calcium absorption (8). Glucocorticoids, such as prednisone, can cause calcium depletion and eventually osteoporosis when they are used for months (25,26).
Also, taking too much vitamin A can increase bone resorption so it is important to take the appropriate amount of vitamin A (27). Your bariatric surgeon can help you determine the appropriate amount of vitamin A for you 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 years and 2,000 mg/d for adults aged 51 and older, but keep in mind this is for general population (8). Excessive calcium intake may contribute to certain types of kidney stones, however 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, then you cannot prevent deficiencies. While it is important to be concerned about what brand you take and what is in your vitamins and minerals, it is just as important to remember to take them daily. It is also important to mention that your bariatric vitamin and mineral regimen is just as important the first year after bariatric surgery as it is ten or more years after your bariatric surgery (in fact, your risk of nutritional deficiencies actually goes up over time), so do not stop taking your bariatric vitamins and minerals as recommended by your bariatric surgeon.* Also, be sure to follow-up with your bariatric surgeon to and continue to get your lab work done in a timely manner in order to track your nutritional status. Most nutritional deficiencies are easier to prevent than to treat, so remember to take your bariatric vitamins and minerals daily. Be sure to tell your doctor, pharmacist, and other healthcare providers about any medications and/or supplements you are taking.
Calcium is one of the more common deficiencies seen in the post-operative bariatric patient, but is also one of the most preventable since we have great lab parameters to evaluate an individual’s bone health. Be sure to follow the instructions of your bariatric program in regards to calcium supplementation. Be sure to get follow-up blood work completed in a timely manner. This will help you to keep your calcium, PTH, and vitamin D levels within normal limits, which ultimately leads to optimum bone health for life in order to continuing CELEBRATING your successes!* Proper supplementation should be viewed as an individualized regimen based upon each patient’s individual medical history, laboratory studies, and current medication use. Patients should follow the instructions of their bariatric surgery team. Patients should also be sure to follow-up with their bariatric surgery team at frequent intervals as recommended and stay up-to-date with requested lab work.