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Increasing calcium intake at breakfast and lowering it at dinner was linked to a reduction in cardiovascular risk. Image credit: Martí Sans/Stocksy.
  • A new study of more than 36,000 American adults suggests that too much dietary calcium intake in evening meals could lead to a higher risk of cardiovascular disease.
  • Experts say that circadian rhythms help regulate the absorption of calcium, and daylight hours are generally the best for that process.
  • But too much calcium in general, especially from supplements, can lead to issues that contribute to cardiovascular problems.

Reducing the intake of dietary calcium at dinner and instead increasing it at breakfast could lead to a reduced risk of cardiovascular disease, a new study suggests.

The study, published in BMC Public Health, examined the dietary calcium intake of more than 36,000 American adults from the National Health and Nutrition Examination Surveys between 2003 and 2018.

The study participants were 17,456 males, 18,708 females, and 4,040 cardiovascular disease patients; their calcium intake from morning and evening meals was divided into five different quadrants.

Excluded from the study were people under 20 years old, pregnant women, anyone using calcium supplements, people who consumed more than 4,500 kilocalories (kcal) a day, and those with incomplete data.

Ultimately, researchers found, spreading the intake of calcium over the two meals was the best for reducing the risk of cardiovascular disease. But substituting a 5% calcium intake from dinner with that at breakfast pulled that risk down 6% overall.

Still, the authors write, there are other factors that are either unobserved or unknown that could affect the ultimate results, and that cohorts of other races and countries need to be examined for any discrepancies or similarities.

“Currently, the evidence for the relationship between dietary calcium intake and [cardiovascular disease] risk is insufficient and controversial,” the study authors wrote, while noting that this was the first such study to examine the links between calcium consumption at breakfast/dinner and cardiovascular disease.

“Studies have shown that too much or too little calcium intake has adverse effects on [cardiovascular disease],” they noted in their paper.

Calcium’s role in the body is most notably in the formation and maintenance of bones and teeth, but it also regulates muscle contraction, helps with blood clotting, and maintains the muscle processes of the heart.

Cardiovascular disease is known to be the most common cause of death globally, with at least 17.9 million people dying from it in 2019.

Where calcium and cardiovascular disease intersect may have to do with circadian rhythms, which can also affect the way that nutrients are absorbed in the body.

As the current study authors noted in their paper, recently: “[S]ome studies have demonstrated that the circadian clock system can interact with nutrients to influence bodily function. In mammals, circadian oscillations in physiology and behavior are controlled by a master clock located in the suprachiasmatic nucleus of the hypothalamus.”

Some researchers also believe that these internal rhythms can regulate the absorption of calcium and metabolism.

Melanie Murphy Richter, a registered dietitian nutritionist and the director of communications for the nutrition company Prolon, who was not involved in the study, told Medical News Today that circadian rhythms make a big difference:

“From a circadian pattern perspective, research suggests that calcium absorption might be slightly higher during the day because certain hormones that are required for calcium metabolism like the parathyroid hormone, for instance, tend to also be higher during daylight hours.”

Richter added that overuse of calcium supplements in general can also be problematic, given that dietary calcium can be difficult to consume too much of by itself.

“Most of the issues relating to calcium intake and cardiovascular health are related to supplementation, where toxic overloads are more easily achieved. Taking too much calcium can result in a condition called hypercalcemia,” she said.

“Hypercalcemia can contribute to heart arrhythmias, heart palpitations, fainting, and sometimes even more severe heart issues. Additionally, high calcium intake can contribute to the formation of calcium deposits in our arteries which can decrease blood flow and therefore increase incidents of stroke, hypertension or heart attack,“ explained Richter.

“Not to mention, excessive calcium supplementation can increase vascular inflammation and oxidative stress which can impact the development of more problematic cardiovascular diseases,” she added.

Kristin Kirkpatrick, a registered dietitian at the Cleveland Clinic Department of Wellness & Preventive Medicine in Cleveland, OH, and a senior fellow at the Meadows Behavioral Healthcare in Wickenburg, Arizona, who was also not involved in the study, told MNT that the decision to take a supplement — and which one to take — all depends on a person’s specific needs.

“Since calcium has other risk factors seen previously in studies, and since the different types of calcium — for example, citrate vs. carbonate — act differently in the body and have varying amounts of calcium the body can absorb, and absorption itself may vary based on type as well, the decision to take calcium must be carefully weighed against current health concerns and risks,” Kirkpatrick said.

“I encourage all my patients to discuss the pros and cons of calcium with their physician first. Not all calcium supplements are equal – I encourage my patients to check the latest data and independent lab analyses of certain calcium supplements,” she told us.

Richter said that supplementation depends on a lot of factors — age, genetics, overall health — but that a balanced, healthy diet may eliminate the need to do so.

“Older individuals, especially peri-menopausal women, for instance, are at higher need of calcium due to the reduction of estrogen production in the body which can decrease calcium absorption. To prevent bone loss and diseases like osteoporosis, it is wise to supplement with calcium and increase calcium-rich foods in the diet,” she noted.

“Anyone who eats a high processed foods diet low in leafy greens, nuts, and seeds are also going to be at higher risk for calcium deficiency, in which case, supplementation might be beneficial. Anyone who is lactose intolerant and needs to avoid dairy (a high calcium food) but isn’t also mindful of replacing their foods with vegetables and seeds may be at higher risk for low calcium levels. Overall, however, if you are eating a balanced diet rich in plants, nuts, seeds, and occasional dairy or fortified dairy alternatives, you likely do not need to supplement.”

– Melanie Murphy Richter

Kirkpatrick said that the way the body responds to calcium warrants smaller portions.

“Given that vitamin D enhances calcium absorption, there is a case for taking calcium in the morning. This allows for exposure to vitamin D throughout the day, primarily through sunlight,” Kirkpatrick noted.

“However, another approach is to divide the calcium dose into smaller portions taken with meals. This is beneficial because the body can only absorb a limited amount of calcium at a time,” she explained.

Richter added that certain supplements also have combinations of other elements that can be beneficial.

“Calcium supplements can be combined with magnesium, vitamin D, and zinc. In fact, all three of these additional nutrients can enhance bone support by increasing calcium absorption,” Richter said.