Skip to Content

What is the 8th taste?


For thousands of years, humans have recognized 4 main tastes: sweet, sour, bitter, and salty. In 1908, Japanese scientist Kikunae Ikeda discovered the fifth taste, umami or savoriness, often found in savory foods like cheese, meat, and mushrooms. In the 2000s, scientists identified several more tastes that the human tongue can detect:

The 6 Accepted Tastes

Sweet Detected by taste buds that sense sugars
Sour Detected by taste buds that sense acids
Salty Detected by taste buds that sense saltiness
Bitter Detected by taste buds that sense bitterness, often from alkaloids
Umami Savory, brothy, meaty taste detected by receptors that sense glutamates
Fatty Detected by taste buds that sense fatty acids

The 6 tastes described above are generally accepted by scientists. However, recently, researchers have proposed an additional “8th taste” that may also be detectable by the human tongue. This taste is called calcium taste or “calcium sensation.”

What is Calcium Taste?

Calcium taste refers to the ability to detect calcium ions (Ca2+) dissolved in water using taste receptors in the mouth. The existence of specific calcium taste receptors and transduction mechanisms are still being researched and debated.

Some studies have identified a calcium-sensing receptor (CaSR) in taste receptor cells that responds to calcium concentrations in liquids. This receptor may trigger signals to the brain that create a distinct taste sensation when calcium is present.

However, the mechanisms are complex, and not all scientists agree that humans have specific calcium taste perception. Some argue that calcium affects salty and sour taste receptors rather than acting on dedicated calcium taste buds.

So while calcium taste is not universally accepted, many researchers believe there is evidence that humans can taste and detect levels of calcium in foods and beverages. More research is still needed to fully understand the receptors and neural pathways involved.

Foods and Beverages High in Calcium

If calcium taste exists, which foods would activate these receptors most? Here are some foods naturally high in calcium that may trigger calcium taste:

Dairy products Milk, yogurt, cheese
Canned fish Sardines, salmon with bones
Fortified plant milks Soy, almond, oat milk with added calcium
Fortified cereals and juices Calcium-fortified orange juice, cereal
Calcium-set tofu Tofu coagulated with calcium salts
Edamame and soybeans Boiled immature soybeans
Dark leafy greens Kale, broccoli, bok choy
Almonds Whole raw almonds

Beverages with added calcium like calcium-fortified orange juice and milk may also deliver high levels of calcium that activate calcium taste receptors.

Some researchers have conducted studies specifically testing subjects’ ability to taste different levels of calcium in water. They found that people could discern subtle differences in calcium concentrations in plain water, providing evidence for calcium taste perception separate from sourness or bitterness.

Possible Functions of Calcium Taste

If confirmed, calcium taste may have evolved in humans and animals to detect and regulate calcium intake for key bodily functions. Here are some of the potential functions of calcium taste receptors:

Detect Calcium Levels in Foods

Having specific calcium taste receptors allows organisms to taste when foods are rich in calcium and drive consumption of calcium-containing items. This is especially important for growing children who need calcium to build bones and teeth.

Avoid Calcium Toxicity

Calcium taste receptors may also prevent excess calcium ingestion which can be harmful to health. Sensing bitter or “off” tastes from high calcium allows organisms to moderate their intake and avoid toxicity.

Regulate Calcium Homeostasis

Calcium taste buds may help the body regulate calcium homeostasis and control calcium levels in the bloodstream. Tasting calcium could trigger biological processes that maintain ideal calcium concentrations for cellular functions.

Aid Mineral Balance with Sodium

There may be a close link between calcium taste receptors and salty taste receptors that help maintain the balance between calcium and sodium. This mineral balance is vital for nerve function, muscle contraction, and water regulation in the body.

Controversy and Criticisms About Calcium Taste

Despite some compelling evidence, not all experts are convinced that humans have specific taste perception for calcium. Here are some criticisms about the hypothesis of a distinct calcium taste:

Poor Specificity

Some studies suggest the hypothesized calcium taste receptor is not very selective for calcium ions. It may respond to and be confounded by other mineral ions like magnesium and iron that elicit a similar taste.

Complex Interactions

Rather than a single receptor, the taste of calcium may involve multiple receptors and complex interactions with sour and bitter taste pathways in the mouth and brain. This makes studying calcium taste perception difficult.

Sensitivity Differences

There is huge variation in taste sensitivity between people. Not everyone may be able to discern subtle differences in calcium concentrations, bringing into question how common calcium taste perception is.

Inconclusive Identification

Attempts to definitively identify and clone calcium taste receptor cells in humans have had mixed results and remain inconclusive. Their existence is still debated.

Research on Calcium Taste Perception

Despite criticism, some compelling research exists on the potential mechanisms and effects of calcium taste in humans and animals:

Rodent Studies

Studies in mice and rats have identified specific taste cells and receptors that selectively respond to calcium but not other mineral ions. These receptors were found to connect to brain areas involved in taste perception and calcium homeostasis.

Human Psychophysics

Psychophysical studies where humans taste calibrated calcium solutions have shown the ability to detect differences in calcium levels and rateintensity of perception. This provides evidence of possible separate calcium taste beyond sourness.

Calcium Receptor Gene

Research has found taste receptor cells in humans, rats, and mice that selectively express the calcium sensing receptor gene, CASR. Silencing this gene reduced calcium taste responses, linking it to calcium perception.

Neural Pathways

Neuroscience studies have traced the neural signals from the mouth to the brain when calcium solutions are tasted. The pathways are distinct from bitter, sour, salty, and sweet, suggesting unique calcium taste processing.

While more research is still needed, these studies show evidence for specific calcium taste perception in humans and animals beyond just sourness or bitterness.

Future Research on Calcium Taste

Confirming calcium taste receptors could have many implications for nutrition and health research. Here are some ideas for future studies:

Improve Calcium Nutrition

If calcium taste aids calcium regulation, this pathway could be targeted to improve calcium intake in those who lack it like growing children and the elderly at risk of osteoporosis.

Reduce Calcium Kidney Stones

Understanding calcium taste could help prevent excessive calcium uptake that contributes to painful kidney stones in those prone to them.

Test Taste Modifiers

Compounds could be identified that amplify or mask calcium taste, helping regulate calcium ingestion. These would be useful for nutritional supplements.

Study Interactions with Sodium Taste

Researchers should better explore how calcium taste perception balances with salty taste to maintain ideal sodium and calcium levels.

Link With Gut Microbiome

The gut microbiome may influence activation of taste receptors. Studying this link may reveal ways to modulate calcium taste through probiotics.

Conclusion

In conclusion, calcium taste remains a controversial but intriguing hypothesis about an additional basic taste in humans. While findings are mixed, evidence does exist for calcium-specific taste receptor cells that help detect and regulate calcium ingestion. If confirmed, this pathway could be leveraged to optimize calcium nutrition at different life stages and improve human health. However, more research is still required to fully characterize the receptors and mechanisms behind the postulated calcium taste phenomenon. Uncovering the secrets behind this possible 8th basic taste could reveal new insights into nutrition, physiology, and how we experience the sensation of taste.