Calcium supplements and spinach carotenoid absorption in men
What it found
In 23 healthy men, taking calcium supplements with a spinach meal did not change how much carotenoid was absorbed into the blood.
The trial tested 500 mg and 1000 mg of calcium against a placebo.
What they found
Studies in people
Carotenoid absorption
Calcium supplements at 500 mg or 1000 mg did not significantly change the amount of lutein, beta-carotene or beta-cryptoxanthin absorbed from the spinach meal. The authors say the differences between the groups were not statistically significant.
Blood fat levels
Blood levels of triglycerides (a type of fat) also showed no significant difference between the meals with or without calcium supplements.
Washout effect
After two weeks of avoiding carotenoid-rich foods, total blood carotenoid levels dropped by about 38% on average. This confirmed that the washout diet worked.
Participant differences
The amount of carotenoid absorbed varied a lot between individual men, and also from week to week for the same person. This variability was seen even without calcium supplements.
Comparison to other study
The authors note that a different study with tomato paste found a large drop in lycopene absorption when calcium was taken. They suggest the effect may depend on the type of food and carotenoid.
What the authors conclude
“In conclusion, Ca - the most abundant divalent mineral in the diet - given at high but physiological concentrations, does not appear to have repercussions on the bioavailability of carotenoids from a spinach-based meal.”
Also in their conclusions
- They conclude that calcium, given at high but physiological doses, does not appear to affect the absorption of carotenoids from a spinach-based meal.
- They say that further investigations are necessary to fully understand the complex interactions between minerals and carotenoids during digestion.
How it was done
Earlier lab tests suggested that minerals like calcium might bind to bile salts and fatty acids in the gut, which could reduce the absorption of carotenoids from vegetables. The authors wanted to test this in people.
Twenty-five healthy, non-obese men aged 20 to 46 ate a 270 g spinach meal with 0, 500 or 1000 mg of calcium (as calcium carbonate) on three separate visits, each a week apart. Blood samples were taken for up to 10 hours after each meal to measure carotenoid levels in the blood.
What it can’t tell you
- This trial only tested a single spinach meal with calcium supplements in healthy men, so it cannot show what happens with long-term calcium supplement use or with other foods.
- The study did not measure how much fat was excreted in stool, so it cannot rule out that calcium affected fat absorption without changing blood carotenoid levels.
Who paid
- Authors work at
- Luxembourg Institute of Health, Luxembourg; Luxembourg Institute of Science and Technology, Luxembourg; University of Kaiserslautern, Germany
The paper
- Title
- No influence of supplemental dietary calcium intake on the bioavailability of spinach carotenoids in humans
- Type
- Randomised controlled trial
- Evidence
- Studies in people
- Summarised from
- Full text
- Cite
- Corte-Real J, Guignard C, Gantenbein M, et al (2017). No influence of supplemental dietary calcium intake on the bioavailability of spinach carotenoids in humans. The British journal of nutrition. doi:10.1017/S0007114517001532Free full textPubMed 28651681DOI
Summary written 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error