Strong defenses Stimulate the immune system with citric acid and ginger

Not only good for the taste: Lemon and ginger substances stimulate the body's defenses

Lemons and ginger are considered as two particularly healthy foods. After all, both contain large amounts of vitamin C and therefore contribute to strengthening the immune system. But they contain even more important substances: citric acid and 6-gingerol. These stimulate the molecular defenses in human saliva, as researchers have now found.

Do something good for health with lemons and ginger

If you want to do something good for your health, you should drink a glass of lemon water regularly in the morning. The body is so important vitamins and nutrients added from the lemon. In addition, the digestion is stimulated and liquid added. It is also recommended to start the day with ginger water. The spicy tuber is not only rich in vitamin C, but can also protect against diseases and help you lose weight. But lemons and ginger can do even more: as researchers have now found, flavor-giving substances of both foods stimulate the immune system.

The citric acid contained in lemon and sharp-tasting ginger gingerol 6 stimulate the molecular defenses in human saliva. (Image: Alexander / fotolia.com)

Citric acid and pungent-tasting gingerol of ginger

As reported by the Technische Universität München (TUM) in a recent release, citric acid and pungent-tasting ginger gingerol give not only food and drink a special flavor.

Both substances also stimulate the molecular defenses in human saliva. A research team from the TUM and the Leibniz Institute for Food Systems Biology has found this out.

The results of the study were recently published in the journal "Journal of Agricultural and Food Chemistry".

Saliva fulfills a variety of biological tasks

Human saliva is a complex, aqueous mixture of various components. In addition to mucosal and immune cells, it contains a large number of molecules that fulfill a wide variety of biological tasks.

Because saliva not only plays an important role in food intake, but is also crucial for the health of the teeth, the gums and the oral mucosa. At the same time it represents the first bastion against externally invading pathogens.

Therefore, the saliva contains various antimicrobial molecules, including the antibacterial lysozyme. They are part of the innate molecular immune system.

Certain factors influence the saliva composition

That factors such as age, state of health but also what someone eats and drinks affect the saliva composition, has now been proven. However, little is known about the effects of individual food ingredients.

To learn more about this, the research team led by study leader Professor Thomas Hofmann, head of the Leibniz Institute for Food Systems Biology at the TUM, investigated the influence of different flavorings on the salivary composition of humans:

Citric acid (sour), the sweetener aspartame (sweet), iso-alpha-acids (bitter), the flavor enhancer monosodium glutamate (umami), saline, 6-gingerol (spicy) and the substances contained in the Szechuan pepper hydroxy-alpha-sanshool (tingling) and hydroxy-beta-sanshool (numbing).

Flavoring substances already have biological effects in the oral cavity

As the scientists demonstrated for the first time by the combination of salivary flow measurements, proteome analyzes and bioinformatic evaluations, all investigated substances modulate the protein composition of the saliva to a greater or lesser extent.

Biological functional analysis of the salivary proteins affected by the modulation also showed that the changes induced by citric acid and 6-gingerol activate the molecular defense system in saliva.

Thus, 6-gingerol enhanced the activity of an enzyme which converts thiocyanate dissolved in saliva into hypothiocyanate, thereby approximately tripling the amount of antimicrobial and fungicidal hypothiocyanate in saliva.

In contrast, citric acid-induced changes increased lysozyme levels in saliva by up to 10 times.

As studies on bacterial cultures for the first time prove, this increase is sufficient to almost completely prevent the growth of Gram-positive bacteria. Lysozyme works against this type of bacteria by destroying their cell wall.

"Our new findings show that taste-giving substances have biological effects in the oral cavity that go far beyond their known sensory properties," says Hofmann from the Chair of Food Chemistry and Molecular Sensors at the TUM.

Researching these with the latest analytical methods is one of the goals that food systems biology has set itself, explains the food chemist.

Only in the long term would it be possible to find new approaches to the production of foods whose ingredient and function profiles are tailored to the health and sensory needs of consumers. (Ad)