Calcium supplements and carotenoid absorption from spinach in men
What it found
Adding 500 or 1000 mg of calcium to a spinach meal made no difference to how much lutein, beta-carotene or beta-cryptoxanthin entered the blood.
This was measured in 23 healthy men over 10 hours after eating.
What they found
Studies in people
Carotenoid absorption unchanged
Adding 500 or 1000 mg of calcium to the spinach meal did not change the amount of lutein, beta-carotene or beta-cryptoxanthin found in the blood over 10 hours. The levels were about the same across all three test days.
Fat levels in blood
Blood fat levels followed a similar pattern after every meal, peaking around 2 hours and again around 6 hours. The extra calcium did not change these fat levels.
Washout diet lowered pigments
Before the trial, participants avoided colourful fruits and vegetables for 2 weeks. Their total blood carotenoid levels dropped by about 38 percent during that time.
Studies in people and animals
Lab tests showed different results
In earlier lab tests using simulated digestion and gut cells, high doses of calcium reduced carotenoid uptake by over 60 percent. That effect did not show up in these human participants.
What the authors conclude
- They found no evidence that calcium supplements at 500 or 1000 mg reduce the absorption of carotenoids from a spinach meal in humans.
- They suggest the effect of minerals on nutrient uptake may depend on the type of food eaten and the form of the supplement.
- They call for more research to understand how minerals and plant pigments interact during digestion.
How it was done
Earlier lab tests suggested that minerals like calcium might bind to fats and bile salts in the gut, blocking the body from taking in plant pigments called carotenoids. The authors wanted to check if this actually happens when people eat real food.
Twenty-five healthy men aged 20 to 46 ate 270 g of spinach on three separate days, each time with either 0, 500 or 1000 mg of added calcium. Blood samples were taken for up to 10 hours after each meal to measure newly absorbed carotenoids.
What it can’t tell you
- This trial only tested men, so it cannot show whether women would respond the same way.
- It only looked at spinach, so the results might differ for other foods rich in carotenoids like tomatoes or carrots.
- The study measured what happened over a single day, so it cannot show the effects of taking calcium supplements every day for months or years.
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 · animals · lab
- 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 30 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error