Kale and spinach juice found to sustain lutein absorption for up to 30 hours, study finds

Drinking cold-pressed juice made from kale and spinach raises blood lutein levels and sustains that increase for up to 30 hours, according to a new South Korean study.

According to the Korea Food Communication Forum (KOFRUM), a research team led by Professor Yoon Jeong-mi of the Department of Food and Nutrition at Chonnam National University compared how well lutein is absorbed and utilized in the bloodstream when healthy adults consumed raw vegetables, cold-pressed vegetable juice, or lutein supplements.

Participants consumed each of the three forms — supplements, raw vegetables and cold-pressed juice — at two-week intervals. The lutein content was standardized at 20 milligrams across all three trials. The raw vegetable portion consisted of 100 grams of kale, 50 grams of spinach and 150 grams of apple, while the juice trial used 200 milliliters of cold-pressed juice made from the same ingredients. The supplement trial provided 20 milligrams of lutein.

Blood lutein concentration peaked at 0.37 micrograms per milliliter 12 hours after raw vegetable consumption. With the lutein supplement, levels reached their highest point of 0.61 micrograms per milliliter at 24 hours. For the cold-pressed juice, blood lutein concentration peaked at 0.42 micrograms per milliliter at the 30-hour mark.

The researchers also tracked changes in high-sensitivity C-reactive protein (hs-CRP), a blood marker that reflects the level of inflammation in the body, with higher values generally indicating greater inflammation.

Raw vegetable consumption reduced hs-CRP by 19 percent at 12 hours compared with pre-consumption levels. The lutein supplement brought hs-CRP down by 32 percent at 24 hours. Cold-pressed juice reduced hs-CRP by 17 percent at 12 hours and 26 percent at 24 hours, with the reduction reaching as much as 39 percent at 30 hours.

"For people who do not eat enough vegetables, cold-pressed juice made from lutein-rich vegetables such as kale and spinach can be a convenient way to take in lutein and a variety of plant-based nutrients," Yoon said.

The study was published in a recent issue of Nutrition Research and Practice, an international nutrition journal.