Beware of naughty nutrition percentages.
Recently, I saw a brief note hailing the fact that red grapefruit has 40 percent more beta-carotene than white grapefruit, the implication being that red grapefruit is a great source of beta-carotene.
Beta-carotene in food becomes vitamin A in your body. We have known for many years that adequate intake of vitamin A is essential for vision, growth, differentiation and proliferation of cells, and the integrity of the immune system.
For these purposes, it doesn't matter whether you get your vitamin A already formed (as in liver, cod liver oil, whole and fortified milk, and eggs) or from vitamin A precursors such as beta-carotene, which eventually are converted to vitamin A in your body.
But recent research suggests that, over time, consuming foods high in beta-carotene (but not necessarily foods high in preformed vitamin A) may help prevent some kinds of cancer. So getting enough beta-carotene can be important to your health.
But how much do you need? We don't exactly know.
We do know that women need 800 Retinol Equivalents (RE) of vitamin A daily (retinol is a form of vitamin A). Men need 1,000. We also know that six micrograms of beta-carotene equal 1 RE of vitamin A. However, while all beta-carotene becomes vitamin A, not all vitamin A comes from beta-carotene.
The USDA has evaluated the retinol equivalents of most fruits.
Some of your best bets include:
3 medium apricots (277 RE vitamin A)
1 cup cantaloupe (516 RE)
1 medium mango (806 RE)
Before Retinol Equivalents, International Units of vitamin A were the standard for evaluation. Requirements were set at 5,000 I.U.'s for men and 4,000 I.U.'s for women. One International Unit of vitamin A is equal to 0.6 micrograms of beta-carotene.
Best-bet vegetables include:
1 stalk of broccoli (2,500 I.U.)
1 large carrot (11,000 I.U.)
1/2 cup collards (5,400 I.U.)
3/4 cup cooked kale (7,400 I.U.)
3 1/2 ounces Romaine lettuce (1,900 I.U.)
1/2 cup mustard greens (5,800 I.U.)
1/2 cup pumpkin (33,990 I.U.)
1/2 cup cooked spinach (7,300 I.U.)
1 cup butternut squash (13,120 I.U.)
1 large sweet potato (14,600 I.U.)
1 medium tomato (1,350 I.U.)
So how does grapefruit stack up?
According to "Food Values" by Pennington and Church, half a medium red or pink grapefruit contains 32 RE of vitamin A. Half a white grapefruit contains only 1 RE of vitamin A.
While it's obvious that red grapefruit must contain a higher percentage of beta-carotene than white grapefruit, neither contains very much.
It would take 13 red grapefruits to meet the Recommended Dietary Allowance for vitamin A.
Half a carrot or two stalks of broccoli will easily do the same thing.
Watch out for naughty nutrition percentages. They can be very misleading.
The easiest rule of thumb for getting adequate beta-carotene is to eat a wide variety of deep orange and dark green leafy vegetables and orange-colored fruit. Except oranges and tangerines, the exception that proves the rule.
Colleen Pierre, a registered dietitian, is the nutrition consultant to the Union Memorial Sports Medicine Center in Baltimore and national spokeswoman for the American Dietetic Association.