[Calcium&Magnesium Episode 2] Do you get stones in your kidneys if you take calcium? | Dr. Esther Lyuh

misconceptions about calcium

Calcium supports colon health

Calcium supports colon health. In a randomized clinical study, calcium reduced the incidence of colon polyps, an effect observed up to 5 years after calcium discontinuation.  There is also a report that an intake of 700-800 mg of calcium reduced the incidence of colon cancer by 40-50%. However, in a randomized clinical study of 36,000 postmenopausal women in the United States, no colorectal cancer prevention effect was found. A Cochrane Review in 2008 acknowledged the potential of calcium supplements to reduce the occurrence of polyps but found that they were not sufficient to prevent colorectal cancer. Even if it's not until colon cancer if you have a lot of colon polyps, it's better to take calcium supplements.

Speaking of calcium and heart disease...

The most difficult part regarding calcium function is the effect of preventing cardiovascular diseases such as heart disease and stroke. Originally, calcium is known to be good for preventing heart disease by interfering with the absorption of fat in the intestines and lowering cholesterol. In a study of postmenopausal women in Iowa, USA, calcium supplements were also found to reduce the risk of coronary artery disease.

Contrary to the results...

However, many follow-up studies have shown the exact opposite effect of calcium in preventing heart disease. In a Swedish study of postmenopausal women, high intakes of calcium of 1,400 mg or more per day were associated with higher rates of heart disease and stroke than those who consumed 600 to 1,000 mg per day. Men who ate 1,000 mg of calcium per day had a 20% higher stroke mortality rate than men who did not. Even when large-scale clinical studies were conducted in the United States and Europe in 2011 and 2012, respectively, calcium supplements were found to increase the incidence of heart disease.

back to being neutral

A lot of people are confused. This is because it was lightning-fast news to those who had been taking calcium supplements because they were said to be helpful for bones as well as heart disease. However, in 2013, researchers at WHI in the United States reanalyzed 93,000 postmenopausal women for 8 years in addition to the existing data, and announced the results of a study that found no evidence that calcium increases the incidence of heart disease and stroke. WHI is a large-scale randomized clinical study that began in 1993 and has so far involved 160,000 American women. To summarize, at first it was said that calcium was good for heart disease, but it was changed to be bad in the middle, and now the conclusion is being gathered with a neutral position that it is neither good nor bad.

So, let's sort it out...

The controversy surrounding calcium's ability to prevent heart disease explains why we shouldn't be happy with the results of studies on the efficacy of nutritional supplements.  Again, calcium and other nutrients are foods, not drugs. Unlike drugs, foods are more likely to produce jagged results. It is necessary to wait until consistent results are obtained through several papers over a long period of time on the efficacy of nutritional supplements in treating diseases. Looking at the conclusions so far, calcium is necessary to prevent bone diseases such as osteoporosis, but it is not necessary to eat it to prevent heart disease, and excessive intake of calcium supplements should be avoided.

calcium and stone

What if stones form in the kidneys?  This is a question that many calcium supplement users wonder about. Theoretically, if you eat calcium, you'll be better off with stones. The most common form of kidney stone is calcium oxalate. A study of postmenopausal women who took 1,000 mg of calcium daily along with 400 IU of vitamin D for 7 years showed a 17% increase in kidney stones compared to placebo.

However, the opposite result when eating...

However, the strange thing is that there was no relationship between kidney stones when a lot of calcium was consumed in food. On the contrary, the less calcium they ate, the more stones they formed.  A recent study of 78,000 American women over an average of 8 years found that the 20% of the highest calcium intake group had a 28% lower incidence of kidney stones compared to the 20% of the lowest intake group. These findings can be explained by the fact that when calcium intake is low, the concentration of oxalic acid in the body increases, and stones are formed more easily.


So why do you get bad results when taking calcium as a nutrient? Experts focus on speed over quantity.  Calcium is a very safe mineral. Even if you look at the most conservatively established American National Medical Association's upper limit of calcium intake, it is 3,000mg for 9 to 18 years old, 2,500mg for 19 to 50 years old, and 2,000mg for 51 years of age or older. Even when the calcium level in the blood is quite high, it does not cause heart disease or kidney stones.

The problem is when an excess of calcium suddenly comes in.

The problem is when an excess of calcium comes in suddenly and at a rapid rate. Calcium, which comes from foods such as milk and spinach, is difficult to consume at once. Nutrients, on the other hand, are concentrated, so although the total amount is safe, they can put a strain on the body in terms of speed.  Calcium can only be processed in the gastrointestinal tract up to 600 mg at one time. The rest of the calcium floats in the blood and can be excreted by the kidneys, forming stones.

But most people have nothing to worry about

Calcium currently marketed as a nutritional supplement is usually about 500 to 1000 mg per tablet. Of these, the content of pure calcium is 40% in the case of calcium carbonate formulations and 21% in the case of calcium citrate formulations, so the calcium per tablet is about 100 to 400mg. If you are not a person who drinks a lot of milk, there is no reason to be afraid of taking calcium supplements because of kidney stones.  However, 8% of the population suffers from idiopathic hypercalciuria. These are constitutionally made a lot of stones in the kidneys for no reason. These people will usually have been diagnosed with stones once or twice due to severe pain. In this case, it is safer to consume calcium in food form rather than supplement form.

Calcium and Caffeine

The story that it is good not to eat caffeine in coffee or protein in meat when taking calcium supplements is a bit exaggerated.  This is because a cup of coffee can only remove 2 to 3 mg of calcium from the caffeine. It is true that protein excretes a lot of calcium from the kidneys, but the intestines, on the contrary, increase calcium absorption, so there is little calcium loss overall. This means that you don't have to be too afraid to eat coffee or meat even if you take calcium supplements.

How to take calcium supplements to avoid side effects

The most common side effects of calcium supplements are constipation, gas production, and gastrointestinal upset, including bloating. People with sensitive stomachs often feel uncomfortable when taking calcium supplements. In this case, it is better to divide it into two meals a day rather than eating all at once. The Food and Nutrition Board (FNB) of the American Medical Association recommends not taking more than 500 mg of calcium supplements at a time.

Among calcium supplements, we recommend calcium citrate. why

Calcium preparations are largely divided into calcium carbonate preparations and calcium citrate preparations. When possible, a calcium citrate preparation is recommended.  Although calcium citrate preparations are expensive, they have several advantages. Calcium carbonate preparations are affected by gastric acidity when absorbed. Therefore, it is absorbed most effectively when taken with food rather than on an empty stomach. On the other hand, calcium citrate preparations are well absorbed regardless of food, whether on an empty stomach or after a meal.  Calcium citrate preparations are better than calcium carbonate preparations when there is a low acidity environment where gastric acid is not secreted well, such as atrophic gastritis common in the elderly, inflammatory bowel disease such as Crohn's disease, or malabsorption. Gastrointestinal disorders such as gas, bloating, and constipation, which are the biggest side effects of calcium preparations, are also more common in calcium carbonate. Taking calcium supplements in small portions is a way to increase absorption and reduce side effects rather than taking large amounts at once.

How Much Calcium Am I Eating A Day?

In a typical Korean diet, the amount of calcium consumed by an adult with three meals and side dishes is approximately 400 to 500 mg. Most people who are on a diet or eat less often consume less than 400 mg of calcium per day. Since the daily recommended amount of calcium for Korean adults is 700-800mg, it means that at least 300mg of calcium needs to be supplemented separately.
The best sources of calcium are dairy products such as milk. 1 ml of milk contains approximately 1 mg of calcium. It's easy to understand if you think that a glass of milk (200ml() contains about 200mg of calcium. Drinking two glasses of low-fat milk a day is the simplest, because milk replenishes 400mg of calcium. If you don't like milk, try yogurt or You need to supplement with calcium-rich foods such as anchovies, whitebait fish, tofu, seaweed, etc. If these are not available, you must take calcium supplements every day.
Multivitamins also contain calcium, but in small amounts, so a multivitamin alone is not enough. This is why you need a separate calcium supplement. Even calcium supplements do not contain as much calcium as you might think. For calcium carbonate, the calcium content is usually 40%, so one 500mg tablet contains 200mg of calcium. Calcium citrate contains 21% calcium, so one 1,000mg tablet provides 210mg of calcium. If you do not drink milk and do not eat high-calcium foods such as anchovies or seaweed, it is recommended to take one or two calcium tablets a day.
Esther Lyuh, Doctor of Preventive Medicine, Seoul National University