PART 1: Calcium Supplements and Your Heart: Why a New Study Has Us Reading the Label Twice
A pill is easy. When work and family take most of the day, a supplement may be the one piece of self-care that actually happens (the bottle is simply easier to pack than lunch). Sometimes we do need one, especially when the body requires a larger amount of a nutrient to get back into balance. Food is still the best source, and many of us worry that overused farmland is making our food less nutritious, so it is tempting to let the pills take up the slack. A new study in the Journal of the American Heart Association suggests slowing down first.
What the Hong Kong study found
In a recent YouTube video, Dr. Mikhail Kogan reported on this study. It looked at people who had already had a major cardiovascular event, meaning a heart attack, a stroke or coronary heart disease, and asked what happened to those who were prescribed calcium supplements. After matching patients on age, health conditions and medications, the researchers compared 17,720 people who took calcium with 17,720 who did not, about 35,000 people in all. Most were followed for less than two years. Some were followed for as long as 15.
Overall, the people taking calcium had about a 10% higher risk of another cardiovascular event. The breakdown tells you more than that headline number does:
- Calcium alone: about a 21% higher risk of a repeat event.
- Calcium with vitamin D: no meaningful difference from people who took no calcium.
- Dose: among calcium-only users, risk was highest at 1,000 mg a day or more.
- Sex: the increase in risk was larger in men than in women.
Before you toss your bottle
This was an observational study, so it shows an association and cannot show that calcium caused the extra events. The people prescribed calcium were older and more likely to have kidney disease, fractures and osteoporosis. The researchers adjusted for those differences, but some things can’t be fully accounted for, and one of them is how much calcium people were eating. Everyone in the study lived in Hong Kong, where diets tend to be lower in calcium and vitamin D deficiency is common, so the results may not carry over to people here. The study also looked only at supplements. Food wasn’t part of it.
Not the first warning
Doctors and researchers have argued about calcium supplements and heart health for years, and the evidence is mixed. Some analyses of clinical trials found a higher risk of heart disease with calcium supplements. Other large studies, the Nurses’ Health Study among them, found no link. An expert panel that reviewed the evidence in 2016 concluded that calcium intake within the recommended upper limit appears safe from a cardiovascular standpoint in generally healthy adults. The Hong Kong study differs in who it looked at: people who already have heart disease and are at high risk for another event.
Why extra calcium might matter to the heart
Calcium is the body’s most abundant mineral, and both bones and the heart depend on it. But calcium that ends up where it doesn’t belong can stiffen blood vessels. The study authors point out that a calcium supplement can raise the calcium level in the blood for six hours or more, which may encourage buildup in the arteries, and they suggest that vitamin D may help protect the vessel walls. Those explanations are plausible. They are unproven.
I’m a nutritionist, and I lean toward food as the better delivery system. Calcium from food arrives in smaller amounts, along with the other nutrients the body uses to handle it. The body also copes with excess reasonably well: when there is more calcium than it needs, some leaves in the urine.
What to do about it
- If you take calcium, take it with vitamin D. That pairing looked much better than calcium alone.
- Keep each dose modest. The National Institutes of Health notes that the body absorbs calcium best from doses of 500 mg or less, and Dr. Kogan recommends 400 to 500 mg at a time, divided into portions through the day.
- Count your food first. Many people already get a good share of their calcium from what they eat, so don’t assume you need a pill to reach your number.
- Talk to your provider before you change anything. If you have heart disease or have been prescribed a calcium supplement, please do not stop it on your own.
How much calcium do we need?
Needs depend on age and health. According to the NIH Office of Dietary Supplements, adults from 19 to 50 need 1,000 mg a day. After 50, women need 1,200 mg a day. Men need 1,000 mg until age 70 and 1,200 mg after that. The upper limit for adults over 50 is 2,000 mg a day. Those numbers count calcium from food and supplements together, so a good day of eating may cover much of it.
Next post: calcium on the plate, and it isn’t only in the dairy aisle.
This article is for education and is not a substitute for medical advice. Please talk with your health care provider before starting, stopping or changing any supplement, especially if you have heart disease or kidney disease.
Sources:
Zhang X, et al. Association between calcium supplementation and recurrence of cardiovascular events in patients with cardiovascular disease: a population-based cohort study. J Am Heart Assoc. 2026;15(8):e047455 (PubMed PMID 41954050), https://doi.org/10.1161/JAHA.125.047455.
NIH Office of Dietary Supplements, Calcium Fact Sheet for Health Professionals, https://ods.od.nih.gov/factsheets/Calcium-HealthProfessional/.
© Ajowa Nzinga Ifateyo
