Hydroxytyrosol is a phenolic compound found in nature, recognized for its antioxidant capabilities and role in health. This compound is produced by the olive tree and its derivatives are found in various natural sources, most notably olive oil.
Natural Sources of Hydroxytyrosol
The primary natural source of hydroxytyrosol is the olive tree, Olea europaea, where the compound is present in the fruit, leaves, and pulp. In nature, hydroxytyrosol is formed through the hydrolysis of another compound called oleuropein as the olive ripens. This process also occurs when an enzyme acts on oleuropein as the olive tissue matures or is damaged.
The concentration of hydroxytyrosol varies significantly depending on the product derived from the olive. Extra virgin olive oil (EVOO) contains the highest amounts among oils because it is extracted through mechanical means without chemicals or high heat, which preserves the phenolic compounds. The amount can range from around 14 mg/kg in some extra virgin olive oils. The taste of high-quality EVOO, often described as bitter and pungent, is partly due to the presence of these compounds.
Conversely, the processing and refinement of olive oil can lead to a substantial decrease in its hydroxytyrosol content. For example, processed table olives, particularly those treated with iron salts for color, contain very little hydroxytyrosol because these salts act as catalysts for its oxidation. The ripeness of the olive also plays a part; unprocessed ripe, black olives can contain significantly more hydroxytyrosol than unripe green olives.
Biological Activity in the Body
The main function of hydroxytyrosol in the body is its potent antioxidant activity. It scavenges free radicals, which are unstable molecules that cause cellular damage through a process called oxidative stress. By neutralizing these radicals, hydroxytyrosol helps protect cells and tissues from this damage. Its antioxidant capacity is considered one of the highest among natural antioxidants.
For cardiovascular health, this antioxidant activity helps protect low-density lipoprotein (LDL) cholesterol particles from oxidation. The oxidation of LDL is a step in the development of atherosclerosis, a condition where plaque builds up inside arteries. By preventing this oxidation, hydroxytyrosol contributes to maintaining the health of blood vessels.
The compound also exhibits anti-inflammatory effects. It can influence the expression of various components involved in the inflammatory response by modulating specific cellular pathways. This includes inhibiting the production of certain pro-inflammatory molecules while increasing the secretion of anti-inflammatory ones. This dual action as an antioxidant and anti-inflammatory agent benefits skin health by protecting it from environmental stressors and offers neuroprotection, as it is one of the few polyphenols that can cross the blood-brain barrier.
Commercial Forms and Dosage
Beyond its natural occurrence in olive products, hydroxytyrosol is available as a dietary supplement. These supplements are produced from extracts of the olive fruit or leaf. When selecting a supplement, it is useful to look for products that are standardized, meaning the label specifies the exact amount of hydroxytyrosol per serving to ensure a consistent intake.
There is no official Recommended Daily Allowance (RDA) for hydroxytyrosol. Dosages in supplements can vary widely, often ranging from 5 mg to 50 mg per serving. The European Food Safety Authority (EFSA) has evaluated it as safe, with a no-observed-adverse-effect level of 50 mg/kg of body weight per day. In the United States, it is considered a generally recognized as safe (GRAS) ingredient in processed foods at levels of 5 mg per serving.
Hydroxytyrosol has high bioavailability, meaning that when consumed, it is efficiently absorbed and utilized by the body. This is not always the case with other plant-derived polyphenols. This efficiency allows it to be effective even at the lower concentrations found in a diet rich in high-quality olive oil.
Safety Profile and Considerations
Hydroxytyrosol is considered safe, especially when consumed as part of whole foods like extra virgin olive oil. Its presence in the Mediterranean diet, which has been associated with longevity and health for centuries, speaks to its long history of safe consumption.
Dietary supplements containing hydroxytyrosol are also well-tolerated by most people. At very high doses, some individuals might experience mild side effects, such as stomach upset, though this is not common. The compound has been studied for its various health benefits without significant reports of adverse reactions within the typical dosage ranges found in supplements.
It is advisable for individuals to consult with a healthcare provider before beginning any new supplement regimen. This is particularly important for those who are pregnant, nursing, or taking prescription medications. There is a potential for interaction with certain drugs, such as blood thinners or medications for blood pressure, and professional medical advice can help ensure safe and appropriate use.