Sulphides

Sulfides are sulfur-containing compounds found in a variety of foods, especially in plants of the Allium genus, such as garlic, onions, leeks and chives. These phytochemicals are known for their numerous health benefits and play an important role in traditional and modern medicine.

Chemical properties of sulphides

Sulphides are organic compounds that contain sulphur in the -2 oxidation state. They can be divided into water-soluble (e.g. S-allylcysteine) and fat-soluble (e.g. diallyl sulphide) compounds. These different solubilities influence the bioavailability and mode of action of the sulphides in the body.

Natural sources of sulphides

The main sources of sulphides in the diet are

• Garlic (Allium sativum): Contains allicin, diallyl sulfide and other sulfides known for their health-promoting properties.
• Onions (Allium cepa): Rich in various sulphides, which also have antioxidant and anti-inflammatory effects.
• Leeks (Allium porrum) and chives (Allium schoenoprasum): These contain similar sulphides to garlic and onions.
• Wild garlic (Allium ursinum): Another valuable source of sulphides found in nature.

Possible health benefits of sulphides

Sulphides offer a variety of health benefits:

1. Anti-carcinogenic effect

Sulphides have shown anti-carcinogenic properties in various studies. They act in several ways:

• Inhibition of phase I enzymes: These enzymes are often responsible for the activation of procarcinogens. Procarcinogens are chemical substances that can potentially contribute to the development of cancer, but are not directly considered carcinogenic. They must be metabolically activated in the body in order to develop their harmful effects. This activation often occurs through enzymes present in the liver and other tissues. Sulphides can inhibit their activity and thus help to potentially prevent the development of cancer cells.
• Induction of phase II enzymes: These enzymes are involved in the detoxification of carcinogens. By activating these enzymes, sulphides can help to eliminate harmful substances from the body.
• Inhibition of cell proliferation: Sulphides can help to potentially inhibit the growth of cancer cells, which has been observed in animal studies in various types of cancer such as stomach, colon and breast cancer.

2. Antioxidant effect

Sulphides, especially allicin, show strong antioxidant properties. They help to reduce oxidative damage by neutralising free radicals and increasing the activity of antioxidant enzymes such as glutathione S-transferase. These antioxidant effects are crucial for protecting cells from oxidative stress, which is associated with many chronic diseases.

3. Cardiovascular health

Sulphides can have a positive effect on the cardiovascular system:

• Cholesterol-lowering effect: studies show that sulphides can inhibit cholesterol synthesis in the body, leading to a reduction in total cholesterol and LDL cholesterol. This can reduce the risk of arteriosclerosis and heart disease.
• Platelet aggregation: Sulphides help prevent platelets from clumping together, which can reduce the risk of blood clots and associated cardiovascular disease.

4. Antimicrobial effect

Sulphides also have antimicrobial properties. They can inhibit the growth of bacteria and reduce the formation of nitrosamines, which are considered carcinogenic. This effect is particularly relevant in connection with the inhibition of nitrate-reducing bacteria in the stomach, which are responsible for the formation of nitrite. Nitrate-reducing bacteria are microorganisms that are able to reduce nitrate (NO3-) and convert it into other nitrogen compounds. This process plays an important role in the nitrogen cycle in the environment and in biological systems.

5. Support for digestion

Sulphides aid digestion by helping to stimulate the secretion of gastric juice and saliva and supporting intestinal peristalsis. This can contribute to better nutrient absorption and healthy intestinal flora.

Bioavailability and absorption of sulphides

The bioavailability of sulphides varies depending on the type of compound. S-allylcysteine has an absorption rate of 55-67%, while the bioavailability of other sulphides is less well documented. Fresh and raw preparation methods, such as eating raw garlic or onions, can maximise sulphide uptake.

Recommended intake and use

To reap the health benefits of sulphides, it is recommended to

• Consume garlic and onions raw: This maximises the content of active sulphides.
• Versatile preparation: Garlic can be used in salads, sauces or as a condiment to increase your daily intake.
• Regular consumption: A regular intake of sulphide-rich foods can provide long-term health benefits.

Possible side effects and precautions

Although sulphides offer many health benefits, they can also have side effects if consumed in excess. These include:

• Digestive discomfort: High amounts of garlic or onions can cause bloating, abdominal pain or diarrhoea.
• Odour: Eating garlic can lead to a strong body odour, which can be unpleasant for some people.
• Allergic reactions: In rare cases, people can have an allergic reaction to sulphides.

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