Although adequate calcium is essential for cardiovascular and bone health, a steady stream of research has questioned the safety of high-dose calcium supplements for the cardiovascular system, in addition to questioning their value for preventing osteoporosis. About 50% of American women and 48% of adults over 60 consume less than the recommended amount of calcium each day, even with supplements.1 However, the research suggests that taking a large dose of supplemental calcium all at once is not the best way to meet your calcium needs.
A 2020 meta-analysis found no association between higher calcium intake from food (up to 1500 mg/day) and coronary heart disease or stroke in data from 26 prospective cohort (observational) studies. However, in 16 randomized controlled trials, calcium supplementation (1000-1400 mg/day) was associated with an 8% increase in risk of coronary heart disease and a 14% increase in heart attack risk. Notably, supplements containing calcium alone (without vitamin D) were associated with greater increases in risk, 20% for coronary heart disease and 21% for heart attack.2
Why are the results for food calcium different from those for calcium supplements?
The primary difference seems to be the size of the dose taken at one time. Many calcium supplements contain 1000 mg or more, which is much more than would be found in a typical meal.
Blood calcium is very tightly regulated, always kept in a narrow range. However, large doses of supplemental calcium have been shown to overwhelm the body’s natural regulatory mechanisms and increase blood calcium levels.3,4 The extra calcium in the bloodstream could contribute to vascular calcification, which is a risk factor for cardiovascular disease, or calcification of atherosclerotic plaque. Another possibility is an increase in blood coagulation due to increased circulating calcium.5 Calcification stiffens the arteries, increases the vulnerability of atherosclerotic plaques, and increases cardiovascular risk.6,7 Observational studies suggest that elevations in blood calcium contribute to atherosclerotic plaque thickness, coronary artery calcification, and cardiovascular events.6-10 Only high dose supplemental calcium can raise blood calcium significantly.
In a large study published in 2016, participants answered questions on their diet, medications, and supplements, and their coronary artery calcium (CAC) was measured. Ten years later, CAC was measured again. Among the participants who had a CAC score of zero at baseline, those with the highest total calcium intake had a lower risk of coronary artery calcium greater than zero at 10 years, whereas the use of calcium supplements was associated with an increase in risk.
Splitting participants into users and non-users of calcium supplements, the greatest risk of coronary artery calcification at 10 years was in supplement users in the lowest fifth of total calcium intake – the group that had the lowest food calcium intake but took calcium supplements.11 These findings, like those of the meta-analysis above, suggest that dietary calcium is protective, but conventional, high-dose calcium supplements may have negative effects.
Not every study has detected a harmful effect of calcium supplementation. Since 2020, of four meta-analyses that have pooled and analyzed many calcium supplementation trials, two reported an increase in the risk of heart disease-related outcomes, and two reported no difference in the risk between supplementation and control groups.2,12-14
Even within individual studies, there are seemingly contradictory findings. The study on coronary artery calcium scores mentioned above found an increase in risk associated with calcium supplementation in pariticipants with a CAC of zero at baseline, but not in those who had CAC greater than zero at baseline.11 A pooled analysis of nine 18-24-month imaging studies using intravascular ultrasound found no significant differences in changes per year in plaque volume or calcification between those taking and not taking calcium supplements. However, calcium supplementation was significantly associated with a increase in coronary artery calcification over the duration of the studies.6 There is enough evidence to be cautious, but not enough to be certain that high-dose calcium supplements are dangerous.
I advocate a cautious, conservative approach to calcium supplementation
Despite the disagreement in research findings, there is enough evidence to be cautious about high-dose calcium supplements and to ensure adequate vitamin D intake. The focus should still be on obtaining adequate calcium primarily with food, especially since high-dose calcium supplements provide minimal (if any) benefit for osteoporosis prevention.
For many people, green vegetables, beans, nuts and seeds most likely provide enough calcium without the need for supplements (see table). A small dose of supplemental calcium could be helpful for older adults or people with lower food calcium intakes to meet their daily requirements. For example, vegans, pregnant women, or postmenopausal women, especially those with smaller appetites or lower calorie needs could benefit from 300-600 mg calcium/day, split between meals. Research from the UK has found that vegans had higher rates of hip fracture than omnivores,21,22 and data from the Adventist Health Study 2 found that vegans who took calcium and vitamin D reduced their risk.23
For these populations, I recommend using lower dose, whole food calcium supplements (whole powdered seaweed, for example) to more closely replicate getting calcium from foods.
Shop: Osteo Biotect delivers food-based, lower-dose calcium (200 mg per capsule) plus magnesium and vegan vitamin D3 to support bone building.
Most green vegetables are good sources of absorbable calcium, except for those high in oxalate (spinach, chard, and beet greens), which reduces calcium absorption.
Food (serving size)
Calcium/serving (mg)
Fractional absorption (%)
Estimated absorbable calcium/serving (mg)
Tofu (1/2 cup, firm, prepared with calcium sulfate)
Joel Fuhrman, M.D. is a board-certified family physician, seven-time New York Times bestselling author and internationally recognized expert on nutrition and natural healing, who specializes in preventing and reversing disease through nutritional methods. Dr. Fuhrman coined the term “Nutritarian” to describe his longevity-promoting, nutrient dense, plant-rich eating style.
For over 30 years, Dr. Fuhrman has shown that it is possible to achieve sustainable weight loss and reverse heart disease, diabetes and many other illnesses using smart nutrition. In his medical practice, and through his books and PBS television specials, he continues to bring this life-saving message to hundreds of thousands of people around the world.
High-dose calcium supplements may damage the cardiovascular system
July 14, 2025 by Joel Fuhrman, MD
Although adequate calcium is essential for cardiovascular and bone health, a steady stream of research has questioned the safety of high-dose calcium supplements for the cardiovascular system, in addition to questioning their value for preventing osteoporosis. About 50% of American women and 48% of adults over 60 consume less than the recommended amount of calcium each day, even with supplements.1 However, the research suggests that taking a large dose of supplemental calcium all at once is not the best way to meet your calcium needs.
A 2020 meta-analysis found no association between higher calcium intake from food (up to 1500 mg/day) and coronary heart disease or stroke in data from 26 prospective cohort (observational) studies. However, in 16 randomized controlled trials, calcium supplementation (1000-1400 mg/day) was associated with an 8% increase in risk of coronary heart disease and a 14% increase in heart attack risk. Notably, supplements containing calcium alone (without vitamin D) were associated with greater increases in risk, 20% for coronary heart disease and 21% for heart attack.2
Sources:
Trends in Calcium Intake among the US Population: Results from the NHANES (1999-2018)
The Evidence and Controversy Between Dietary Calcium Intake and Calcium Supplementation and the Risk of Cardiovascular Disease: A Systematic Review and Meta-Analysis of Cohort Studies and Randomized Controlled Trials
Why are the results for food calcium different from those for calcium supplements?
The primary difference seems to be the size of the dose taken at one time. Many calcium supplements contain 1000 mg or more, which is much more than would be found in a typical meal.
Blood calcium is very tightly regulated, always kept in a narrow range. However, large doses of supplemental calcium have been shown to overwhelm the body’s natural regulatory mechanisms and increase blood calcium levels.3,4 The extra calcium in the bloodstream could contribute to vascular calcification, which is a risk factor for cardiovascular disease, or calcification of atherosclerotic plaque. Another possibility is an increase in blood coagulation due to increased circulating calcium.5 Calcification stiffens the arteries, increases the vulnerability of atherosclerotic plaques, and increases cardiovascular risk.6,7 Observational studies suggest that elevations in blood calcium contribute to atherosclerotic plaque thickness, coronary artery calcification, and cardiovascular events.6-10 Only high dose supplemental calcium can raise blood calcium significantly.
In a large study published in 2016, participants answered questions on their diet, medications, and supplements, and their coronary artery calcium (CAC) was measured. Ten years later, CAC was measured again. Among the participants who had a CAC score of zero at baseline, those with the highest total calcium intake had a lower risk of coronary artery calcium greater than zero at 10 years, whereas the use of calcium supplements was associated with an increase in risk.
Splitting participants into users and non-users of calcium supplements, the greatest risk of coronary artery calcification at 10 years was in supplement users in the lowest fifth of total calcium intake – the group that had the lowest food calcium intake but took calcium supplements.11 These findings, like those of the meta-analysis above, suggest that dietary calcium is protective, but conventional, high-dose calcium supplements may have negative effects.
Sources:
Does Calcium Supplementation Increase Cardiovascular Risk?
Calcium Supplements and Risk of Cardiovascular Disease: A Meta-Analysis of Clinical Trials
Oral Calcium Supplements Associate With Serial Coronary Calcification: Insights From Intravascular Ultrasound
Carotid artery plaque thickness is associated with increased serum calcium levels: the Northern Manhattan study
Vascular calcifications as a marker of increased cardiovascular risk: a meta-analysis
Calcium Intake From Diet and Supplements and the Risk of Coronary Artery Calcification and its Progression Among Older Adults: 10-Year Follow-up of the Multi-Ethnic Study of Atherosclerosis (MESA)
Some disagreement, but cause for concern
Not every study has detected a harmful effect of calcium supplementation. Since 2020, of four meta-analyses that have pooled and analyzed many calcium supplementation trials, two reported an increase in the risk of heart disease-related outcomes, and two reported no difference in the risk between supplementation and control groups.2,12-14
Even within individual studies, there are seemingly contradictory findings. The study on coronary artery calcium scores mentioned above found an increase in risk associated with calcium supplementation in pariticipants with a CAC of zero at baseline, but not in those who had CAC greater than zero at baseline.11 A pooled analysis of nine 18-24-month imaging studies using intravascular ultrasound found no significant differences in changes per year in plaque volume or calcification between those taking and not taking calcium supplements. However, calcium supplementation was significantly associated with a increase in coronary artery calcification over the duration of the studies.6 There is enough evidence to be cautious, but not enough to be certain that high-dose calcium supplements are dangerous.
Sources:
Calcium Intake From Diet and Supplements and the Risk of Coronary Artery Calcification and its Progression Among Older Adults: 10-Year Follow-up of the Multi-Ethnic Study of Atherosclerosis (MESA)
Association Between Calcium Supplementation and the Risk of Cardiovascular Disease and Stroke: A Systematic Review and Meta-Analysis
Vitamin D, Calcium Supplements, and Implications for Cardiovascular Health: JACC Focus Seminar
Calcium Supplements and Risk of CVD: A Meta-Analysis of Randomized Trials
I advocate a cautious, conservative approach to calcium supplementation
Despite the disagreement in research findings, there is enough evidence to be cautious about high-dose calcium supplements and to ensure adequate vitamin D intake. The focus should still be on obtaining adequate calcium primarily with food, especially since high-dose calcium supplements provide minimal (if any) benefit for osteoporosis prevention.
For many people, green vegetables, beans, nuts and seeds most likely provide enough calcium without the need for supplements (see table). A small dose of supplemental calcium could be helpful for older adults or people with lower food calcium intakes to meet their daily requirements. For example, vegans, pregnant women, or postmenopausal women, especially those with smaller appetites or lower calorie needs could benefit from 300-600 mg calcium/day, split between meals. Research from the UK has found that vegans had higher rates of hip fracture than omnivores,21,22 and data from the Adventist Health Study 2 found that vegans who took calcium and vitamin D reduced their risk.23
Related: Why vegetarians and vegans could have a higher risk of bone fractures
For these populations, I recommend using lower dose, whole food calcium supplements (whole powdered seaweed, for example) to more closely replicate getting calcium from foods.
Shop: Osteo Biotect delivers food-based, lower-dose calcium (200 mg per capsule) plus magnesium and vegan vitamin D3 to support bone building.
See the Smart Supplementation Quiz for guidance on the supplements that are right for you.
Sources:
Vegetarian and vegan diets and risks of total and site-specific fractures: results from the prospective EPIC-Oxford study
Risk of hip fracture in meat-eaters, pescatarians, and vegetarians: a prospective cohort study of 413,914 UK Biobank participants
Dietary patterns and hip fracture in the Adventist Health Study 2: combined vitamin D and calcium supplementation mitigate increased hip fracture risk among vegans
Absorbable calcium in selected plant foods24-28
Most green vegetables are good sources of absorbable calcium, except for those high in oxalate (spinach, chard, and beet greens), which reduces calcium absorption.
Food (serving size)
Calcium/serving (mg)
Fractional absorption (%)
Estimated absorbable calcium/serving (mg)
Tofu (1/2 cup, firm, prepared with calcium sulfate)
861
31
266.9
Kale (1 cup cooked)
177
49.3
87.3
Bok choy (1 cup cooked)
158
53.8
85.0
Edamame (1 cup shelled)
120
36
43.2
Broccoli (1 cup cooked)
62
61.3
37.4
Brussels sprouts (1 cup cooked)
56
63.8
35.7
Green cabbage (1 cup raw, chopped)
36
64.9
23.4
White beans (1 cup cooked)
120
21.8
26.2
Pinto beans (1 cup cooked)
79
26.7
21.1
Almonds (1 ounce)
76
21
16.0
Spinach (1 cup cooked)
245
5.1
12.5
Joel Fuhrman, M.D. is a board-certified family physician, seven-time New York Times bestselling author and internationally recognized expert on nutrition and natural healing, who specializes in preventing and reversing disease through nutritional methods. Dr. Fuhrman coined the term “Nutritarian” to describe his longevity-promoting, nutrient dense, plant-rich eating style.
For over 30 years, Dr. Fuhrman has shown that it is possible to achieve sustainable weight loss and reverse heart disease, diabetes and many other illnesses using smart nutrition. In his medical practice, and through his books and PBS television specials, he continues to bring this life-saving message to hundreds of thousands of people around the world.