- Antioxidant activity in certain plant-based foods such as green tea and olive oil can decrease over time, especially when stored for more than six months.
- When stored for six months, green tea could see a decrease in antioxidant compounds known as catechins by around 32% according to a study.
- Antioxidant properties in extra-virgin olive oil were found to diminish by about 40% after six months of storage, as per another study.
- It is recommended to buy fresh foods only in quantities that can be consumed in a short time to maximize nutritional value.
- To protect antioxidants and other nutrients from sunlight exposure, it is suggested to prefer tinted containers over clear ones. For extra virgin olive oil, it’s suggested to store in small glass bottles in a dark setting at room temperatures between 68-77 degrees Fahrenheit.
Advocates of plant-based, antioxidant-rich foods should heed new studies suggesting their nutritional benefits may diminish with extended storage time.
Impact of Time on Antioxidant Properties
A couple of recent studies investigated how the antioxidant activity of commercial green tea bags and olive oil were affected when stored unexposed to light or moisture. Both cases revealed substantial drops in antioxidant activity within the first six months.
“To maximize the nutritional value of our food, it’s best to buy only what can be consumed in a short period,” recommended Connie Diekman, a registered dietitian and director of nutrition at Washington University in St. Louis who was not involved in the studies.
The Effect on Green Tea
An intriguing set of organic compounds known as catechins, commonly found in green tea leaves, were the focus of one study. These antioxidant units are considered to have the ability to fight bacteria and viruses, as well as limiting cancer cell activity.
Commercial green tea has a prolonged shelf life, leading Mendel Friedman and his team to question the stability of catechins during extended storage. Their study found a significant decrease, around 32 percent, in catechin concentrations after six months.
Friedman feels that this preliminary research could stimulate more expansive exploration into the issue, considering the wide variety of teas available and consumed across the globe.
Understanding Olive Oil Nutritional Decay
The second study analysed the durability of antioxidants found in extra-virgin olive oil. Known to be rich in a blend of fatty acids and phenolic compounds acting as antioxidants, regular consumption of olive oil is linked to a lower risk of heart disease, stroke, and several types of cancer.
The researchers discovered that while antioxidant activity remained constant for the first three months, most oils had lost about 40 percent of their antioxidant properties by the six-month mark.
The Fragility of Nutrients
“Antioxidants are quite fragile and it’s common knowledge that the nutritional value is best in fresh plant foods,” noted Diekman. Her advice: think about the quantity of fresh foods purchased. Large quantities may not provide a real dollar savings when considering the potential loss of nutritional value over time.
Keeping Freshness Intact
As a general guideline, Diekman suggested consumers prefer tinted containers over clear ones to protect antioxidants, vitamins, and minerals from exposure to sunlight. Extra virgin olive oil should ideally be stored in small glass bottles placed in a dark setting at room temperatures between 68-77 degrees Fahrenheit.
Get more information on antioxidants from the U.S. National Library of Medicine.