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People Need to Eat More Beta Carotene to Get Enough Vitamin AReturn to Spinach News & Research Index (April 26, 2004) - According to most nutritionists a ½ cup of carrots a day may help improve vision, lower the risk of cancer and other diseases but recently researchers at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University have shown that this may not be enough. But how much beta-carotene does one need to consume daily to maintain adequate vitamin A? New research, lead by Guangwen Tang, PhD and colleagues, showed that men who ate a diet that contained 100 grams (about ½ cup) of pureed carrots absorbed less beta carotene (a precursor to vitamin A) than the researchers previously thought. Previously, the conversion factor for beta carotene was 12 micrograms for one retinol activity equivalent. In this study, Tang and colleagues found that this number increased to 15 micrograms of beta carotene for one retinol activity equivalent, meaning more food needs to be consumed to get adequate vitamin A. Additionally, the researchers found this conversion factor became even more significant when they tested this theory with the beta carotene in spinach, giving 300 grams (about 1 ¼ cups) of pureed spinach to the same study volunteers five months later. They found that like the carrots, the beta carotene in spinach was also not as well absorbed, in fact, it was even less well absorbed than from carrots. For spinach, like carrots, the old beta carotene to vitamin A conversion factor was 12 units of beta carotene for one unit of vitamin A, but the researchers now contend that the conversion factor for beta carotene in spinach is 22 units to one. These new findings may influence the next set of US dietary guidelines for beta carotene and vitamin A. Experimental Biology 2004, Washington D.C. |
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