Researchers discovered that the time of day you take calcium supplements may affect how your body processes fats and cholesterol. In this study, mice that received calcium in the morning developed higher cholesterol and fat levels in their blood and liver compared to those given calcium in the evening. Scientists found that morning calcium triggered changes in liver genes that made it harder for the body to break down fats. This research suggests that the timing of calcium intake—not just the amount—plays an important role in how your body manages cholesterol and fat metabolism.

The Quick Take

  • What they studied: Whether taking calcium supplements at different times of day (morning versus evening) affects how the liver handles cholesterol and fat
  • Who participated: 40 female mice divided into four groups: some received calcium in the morning, some in the evening, and some served as controls with no extra calcium
  • Key finding: Mice given calcium in the morning developed significantly higher blood cholesterol and triglycerides (a type of fat), plus more fat buildup in their liver cells. Evening calcium didn’t cause these problems
  • What it means for you: If you take calcium supplements, the time of day may matter for your cholesterol and fat metabolism. However, this was tested in mice and cells in a lab, so more human studies are needed before changing when you take your calcium

The Research Details

Scientists conducted two types of experiments. First, they gave 40 mice either calcium supplements in the morning or evening for 10 weeks while feeding them a low-calcium diet, then measured their cholesterol and fat levels. Second, they used human liver cells grown in a lab and exposed them to high calcium levels during different times of day to see how the cells responded. In some experiments, they turned off a specific gene (PER1) to see if it was responsible for the fat-building effects.

The researchers measured multiple things: blood cholesterol and fat levels, how much fat accumulated in liver cells, changes in gene activity, and levels of specific proteins involved in fat metabolism. This multi-layered approach helped them understand not just what happened, but why it happened at the molecular level.

This research approach is important because it reveals that timing matters just as much as the amount of calcium you consume. Most previous studies only looked at whether calcium affected cholesterol, without considering what time of day it was taken. By testing both whole animals and isolated cells, the researchers could identify the specific biological mechanism (the PER1-PPARα pathway) responsible for the timing effect.

This study has several strengths: it used a controlled experimental design with clear comparison groups, measured multiple related outcomes, and identified a specific biological mechanism. However, the study was conducted in mice and lab cells, not humans, so results may not directly apply to people. The sample size was relatively small (40 mice), and the study didn’t test different calcium doses or durations. The findings are preliminary and require human studies to confirm whether timing matters in real-world calcium supplementation.

What the Results Show

Mice that received calcium in the morning showed dramatic increases in blood cholesterol and triglycerides compared to control mice. Their livers also accumulated more fat droplets, visible under a microscope as swollen, fatty liver cells. In contrast, mice receiving evening calcium showed normal cholesterol and fat levels similar to controls.

When scientists examined the genes in liver tissue, they found that morning calcium activated a gene called PER1, which then shut down other genes responsible for breaking down fats (PPARα, CPT1A, and APOA5). This explains why morning calcium led to fat buildup—the liver couldn’t process fats efficiently.

In the lab experiments using human liver cells, nighttime calcium exposure (which simulates evening intake) produced similar results to morning calcium in mice: increased fat accumulation and the same pattern of gene changes. When researchers artificially turned off the PER1 gene, the fat-building effects disappeared, proving that PER1 was the key player in this process.

The study found that the circadian rhythm (your body’s internal 24-hour clock) plays a critical role in how calcium affects fat metabolism. The timing effect was consistent across both animal and cell experiments, suggesting this is a fundamental biological mechanism rather than a random finding. The researchers also noted that low-density lipoprotein (LDL, the ‘bad’ cholesterol) increased specifically with morning calcium, which is particularly relevant for heart health.

Previous research has shown mixed results about whether calcium supplements affect cholesterol—some studies found benefits, others found no effect. This research helps explain those conflicting findings: the time of day calcium was taken may have differed between studies, leading to different results. This work aligns with growing evidence in ‘chrono-nutrition’ (the study of how timing affects nutrition), which shows that when you eat or supplement matters as much as what you consume.

The biggest limitation is that this research was conducted in mice and lab cells, not humans. Mice have different metabolisms and lifespans than people, so results may not directly translate. The study used only female mice, so it’s unclear if males would respond differently. The researchers used a specific type of calcium (calcium carbonate) at specific doses, so other forms or amounts might behave differently. Additionally, the study lasted only 10 weeks in mice (equivalent to a few years in human terms), so long-term effects remain unknown. Finally, the study didn’t test whether the timing effect occurs with dietary calcium from food sources, only with supplements.

The Bottom Line

Based on this preliminary research, if you take calcium supplements, consider taking them in the evening rather than the morning. However, this recommendation has low to moderate confidence because it’s based on animal and lab studies, not human trials. Before changing when you take calcium, consult your doctor, especially if you have high cholesterol or liver concerns. If you get calcium from food (dairy, leafy greens, fortified products), timing is unlikely to matter in the same way.

This research is most relevant for people who take calcium supplements, particularly those concerned about cholesterol levels or metabolic health. People with existing high cholesterol, fatty liver disease, or metabolic disorders should pay special attention. However, people who meet their calcium needs through diet alone probably don’t need to worry about timing. Pregnant women, older adults, and people with bone health concerns should discuss calcium timing with their healthcare provider.

If the timing effect applies to humans, you might expect to see changes in cholesterol levels within 4-8 weeks of switching when you take calcium, based on how quickly cholesterol typically responds to dietary changes. However, this is an estimate based on animal research, and individual responses vary significantly.

Want to Apply This Research?

  • Track the time you take calcium supplements and monitor your cholesterol levels every 6-8 weeks. Record: (1) time of day calcium is taken, (2) total cholesterol, LDL, and triglyceride levels, and (3) any digestive symptoms. This creates a personal data set to see if timing affects your individual metabolism.
  • If currently taking calcium in the morning, shift to evening intake (ideally 2-3 hours before bed). Set a daily reminder for the same evening time each day. Track how you feel and any changes in energy, digestion, or bloating. After 6-8 weeks, ask your doctor to recheck your cholesterol to see if timing made a difference for you personally.
  • Create a simple log with three columns: date, time of calcium intake, and any symptoms or notes. Every 8 weeks, compare your cholesterol results to previous tests. If you see improvement after switching to evening calcium, continue that timing. If no change occurs, discuss with your doctor whether other factors (diet, exercise, genetics) are more important for your cholesterol management.

This research was conducted in mice and laboratory cells, not humans. The findings are preliminary and should not be used to replace medical advice from your healthcare provider. If you take calcium supplements or have concerns about your cholesterol or liver health, consult your doctor before making changes to when or how you take calcium. This information is for educational purposes only and is not a substitute for professional medical diagnosis, treatment, or advice. Individual responses to calcium supplementation timing may vary significantly based on genetics, diet, lifestyle, and existing health conditions.