Eating fresh spinach that has been sitting in your refrigerator for a few days may not make you as strong as your mother told you. According to Penn State food scientists, by eight days after being harvested, spinach has lost about half of its nutrient content.

If the spinach is coming from the other side of the country, then the produce might be kept at a warm temperature in a shipping truck for an extended period of time. By the time the spinach reaches the dinner table, much of the nutrient content might already be gone.

Luke LaBorde, associate professor of food science, found that spinach stored at 4 degrees Celsius loses its folate and carotenoid content at a slower rate than spinach stored at higher temperatures. However, the spinach at 4 degrees still loses much of its nutrients after eight days.

Also, an attractive appearance does not mean that the spinach is still rich in nutrients. Sticking spinach in water to fluff it up does not change anything because nutrient loss is irreversible.

Spinach, the second best source of folate and carotenoids behind kale, is prized because of its high nutrient content.

Folate is responsible for producing and maintaining new cells in the body. Folate deficiency in pregnant women can lead to birth defects such as spina bifida. Carotenoids, commonly associated with carrots and other red and orange vegetables, help support vision and protect eyes from UV damage. Spinach is high in both nutrients.

Unless you can find local fresh greens, you may be better off with canned or frozen alternatives. “There is also a fallacy that fresh spinach is always better than canned,” said LaBorde.

Despite the damage done during the heating process for canned spinach, it may retain more of its nutrients than fresh spinach kept in the refrigerator for a few days. The same holds true for frozen spinach.

Storage Time and Temperature Effects Nutrients in Spinach
March 18, 2005, Journal of Food Science, vol 69, no. 9