CALCIUM ON THE TONGUE Researchers have found that rodent tongues have receptors, or sensors, that respond to calcium. This image shows one of the calcium-sensing receptors stained in the center of a bright green onion-shaped taste bud.
Image: Courtesy Michael Tordoff
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Mice, and most likely humans, have the ability to taste calcium—and most do not like it, according to new research presented today at the American Chemical Society's semiannual national meeting, held this week in Philadelphia. Scientists say the findings could explain why, according to the U.S. Department of Agriculture, 80 percent of Americans do not get enough calcium when it is so important for our health.
Michael Tordoff, a biologist at the Monell Chemical Senses Center in Philadelphia, suspected that calcium's unpleasant flavor—imagine the bitter taste of chalk, which is mostly calcium—makes people avoid calcium-rich foods like spinach, brussel sprouts and collard greens. He started by trying to figure out whether the tongue could taste calcium.
Tordoff and his colleagues gave 40 different strains of mice a choice: They could drink water or a calcium-rich liquid. Most preferred water once they tried both.
There was, however, one exception—a mouse strain called PWK actually preferred the calcium-enriched liquid. Those mice, it turned out, had a different version of genes that are responsible for taste receptors on the tongue. (Taste buds, which contain approximately 50 to 100 taste cells, comprise receptors for at least five specific tastes—salty, sour, bitter, sweet and umami, or savory.)
Even more surprising: one of the genes was identical to a portion of the receptor that detects both sweet and savory, or hearty, flavors. "That was a totally unexpected, out-of-left-field finding," Tordoff says. "Nobody in their right mind would have ever thought that the sweet-taste receptor was involved in calcium taste because the taste is so different." Although this sweet and savory receptor subunit is involved in calcium taste, it does not seem to trigger the perception of either flavor.
Tordoff has so far studied these genes only in mice, but he speculates that they also play a role in human's calcium taste perception. He suggests that we do have a calcium "appetite" that kicks in when our intake is dangerously low -– for example during pregnancy or dialysis, which depletes calcium levels. People in those states tend to have a strong craving for chalky, calcium-rich cheeses.
Tordoff's findings could inspire technologies that would make calcium-rich foods more palatable, according to Eugene Delay, a taste biologist at the University of Vermont in Burlington. Indeed, San Diego–based biotechnology company Senomyx is currently developing "bitter blockers" that prevent bitter taste cells from responding, so it's not crazy to think the same could be done to block calcium taste, Tordoff says.
The fact that people can taste calcium may also help scientists better understand—and prevent—diseases like osteoporosis. "It would be interesting to see if individuals that are susceptible to osteoporosis have mutations in these [calcium receptor genes]," says Debi Fadool, a biologist at Florida State University in Tallahassee. "Maybe they're supersensitive to calcium, so they just don't want to consume it."
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15 Comments
Add CommentI was so fascinated with this article because I have a terrible problem with calcium. I am supposed to take no more than six 250 mg. of calcium plus vitamin D tablets per day since my roux n y gastric bypass surgery four years ago. In the last 6 months, I have begun craving calcium tablets so badly that I am up to taking 12 tablets a day. I worry that this will harm me. I would rather have a calcium tablet than sweets or anything else. I let them dissolve in my mouth and crunch them up. I love the taste. I told my doctor about this, but neither she nor my gastric bypass surgeon had anything of help to say. I also crave Magnesium to a lesser degree--I take 500 mg. per day, and I let them dissolve in my mouth. I love the taste of the Magnesium also. I take a multivitamin and mineral supplement and B-12 everyday as well due to my bypass surgery.
Reply | Report Abuse | Link to thisMy mother tells me that when I was a child I used to eat the dirt from my Grandmother's flower pots and I told them it tasted good. I also ate chalk and library paste at school when I went to school. I am now 54 years old, but when I was pregnant in my early 20's, I craved Magnesium and dairy products then as ferociously as I crave the calcium now. I am a nurse and I know that taking too much calcium can be lifethreatening, but I still have to eat at least 12 tablets a day.
I read somewhere that 30% of patients who undergo gastric bypass develop hypoparathyroidism. Could this be the cause for my craving? I have CMP's and BMP's twice yearly to quarterly. My last BMP one month ago showed that my calcium was in the low normal range in spite of the fact that I have been taking large amounts of calcium. All other electrolytes were normal. The only abnormal in any of my labs was that I was very slightly anemic. Can anyone help me? I am desperate for an answer.
This article is fascinating to me because I have a terrible problem. I crave calcium supplement pills with an almost unbearable craving. I take 12 of them a day when I am only supposed to take six at the most. I let them dissolve in my mouth and I crunch up the crunchy bits. They taste wonderful to me. I would as soon have a calcium pill as chocolate or ice cream. I have discussed this craving with my doctor and several nurses with no help at all. I am afraid I will end up taking too much and harming myself, but it is like an addiction; I can't stop. When I was six years old my Mother said I used to eat dirt from my grandmother's flower pots. When they slapped my hand to make me stop, I just said: "It's good!" Four years ago I had roux n y gastric bypass surgery and lost 100 lbs. But the calcium craving just developed over the last six months. I have my calcium levels tested at least every six months. I had a BMP three weeks ago and my calcium level was low normal in spite of the large amount of calcium I am taking. I also crave Magnesium, but not as much as the calcium, only 500 mg. a day. Years ago when I was pregnant, I craved Magnesium tablets then also. 30% of patients who have gastric bypass surgery end up developing hypoparathyroidism. I wonder if this has happened to me? Is there anyone out there who can help me?
Reply | Report Abuse | Link to thisSorry, I didn't mean to post this twice. I thought the first one didn't go through.
Reply | Report Abuse | Link to thisSorry for the repeat postings.
Reply | Report Abuse | Link to thisguess i'm the only one who read this article
Reply | Report Abuse | Link to thisAs a student doing human genetics research with PTC bitter tasting ability I found this article very interesting. I also have a grandmother with crippling arthritis and found the link to osteoarthritis informing. I hope that seraphsong2 finds a solution to her questions. I will look out for more info about this important topic. I hope that we can, with the advancement of science find out more about this life impacting issue of society.
Reply | Report Abuse | Link to thisHi!: If I remember well, the behaviour of eating ground is called "pica", sometimes it may reflect a defect in the intake of some essential vitamins and minerals, others consider it a mental misbehaving. Some children engage in ground or plant eating experiences until they meet an urticating or poisonous one. May be an endocrinologist is good for you?. Regards
Reply | Report Abuse | Link to thisHi seraphsong2:
Reply | Report Abuse | Link to thisI'm the scientist involved in the story reported here, and I have received several dozen e-mails from people over the last few days who report likings for calcium as strong as the one you describe. It sounds like your high calcium intake is not a problem for you, and there are very few bad things that can come from consuming too much calcium, but what you describe is similar to "milk alkali syndrome" that you might want to discuss with your doctor.
Hi c.mguirk13:
Reply | Report Abuse | Link to thisPTC bitter taste is a neat classroom demonstration. For those who don't know what you are talking about, roughly a quarter of the population cannot taste PTC, about half find it bitter, and a quarter find it intensely bitter. The different groups gave rise to the idea of nontasters, tasters, and supertasters. In fact, this is the second-most studied genetic trait (blood group being the most studied). My group has found there is no relationship between PTC status and calcium taste detection.
Hi jgrosay:
Reply | Report Abuse | Link to thisYes, you are correct about pica. We forget that many societies eat dirt, particularly those in Africa. I've read that the idea that eating dirt is "mental misbehaving" came out of the slave trade. Owners feared that eating dirt would give their slaves worms, which would make them eat more food, adding to their expenses. They therefore tried to beat this behavior out. In fact, the fear of worm was unwarranted. The dirt eaten is usually free of pathogens and high in calcium. There are several reasons for pica, including the fact that dirt binds toxins and may reduce stomach irritation. There is a very interesting paper showing that African societies that do not have dairying (i.e., cows) are more likely to eat dirt than those that do. The implication is that dirt is a source of calcium when milk (or other sources) are not available.
This article has made more sense than the other health articles i've seen on SciAmerica, although i'd rather advise it, if people eat more greens than diary products.
Reply | Report Abuse | Link to thisHi, so glad to hear chalk eating or craving is not related to any mental misbehaving! I use to ear dirt & chalk when I was small, then left it & did nt crave for a long time. the cravings started again when I was pregnant the first time but went away without me eating any chalks. second pregnancy same cravings but much stronger, even though I was on Calcium & Iron tablets. still I just had a few chalks in all that time. But now the cravings have come back & I am not pregnant. I eat about one chalk everyday, thats after i restrict myself & use lot of self control..i love the taste & texture of chalk. I dont like the crayola ones, they are bit...creamy in texture & taste bit chemical. I only eat white chalk. Discussed with my doctor & she thinks I m probably anaemic, so I have recently started taking iron tablets...like a week ago & so far the cravings have nt stopped!
Reply | Report Abuse | Link to thisi eat chalk...sidewalk chalk, have been for 2yrs now...ive also noticed that sometimes while knawing on a stick i can actually taste a sweetness in the chalk. I like how the crunchiness feels on my teeth and it also helps my stomach when i have acids in there, it helps me burp and i especially want it when im stressing or on my menstrual. My husband is in the army and he is in very good shape and he tried the chalk ..he doesnt eat it like i do but he does say that when he eats a little bit of it that it has a calming effect on him
Reply | Report Abuse | Link to thisi forgot to add that i only eat the white side walk chalk not the colored ones as theyve been tainted dye or something
Reply | Report Abuse | Link to this---"It would be interesting to see if individuals that are susceptible to osteoporosis have mutations in these [calcium receptor genes]," says Debi Fadool, a biologist at Florida State University in Tallahassee. "Maybe they're supersensitive to calcium, so they just don't want to consume it."---
Reply | Report Abuse | Link to this^Perhaps there is something in that, I think maybe those who can taste calcium actually seek it. My mother has osteoperosis, and I have chalk cravings. Perhaps the body knows it needs the calcium for that reason.