Beta-Carotene in Spinach (and How to Maximize its Bioavailability)
Most people associate beta-carotene with carrots and other orange vegetables, but this yellow-orange pigment is also abundant in a number of other plant-based foods. Spinach, for example, contains tons of beta-carotene, although in spinach and other leafy green vegetables this yellow-orange pigment is masked by the presence of the green chlorophyll.
But exactly how much beta-carotene does spinach contain?
According to data published by the U.S. Department of Agriculture (USDA), a 100-gram serving (about 3.5 ounces) of raw spinach provides roughly 5600 micrograms of beta-carotene, which corresponds to about 70% of the amount of beta-carotene found in an equal-sized serving of raw carrots. As heat reduces the water content of spinach, cooked spinach has an even higher concentration of beta-carotene: about 6300 micrograms per a 100-gram serving.
But it's not all about the amount of beta-carotene. Research suggests that a number of factors influence how much of the beta-carotene found in spinach is actually readily available for your body to use. Below, we take a look at some of these factors to help you maximize the bioavailability and absorption of beta-carotene from your spinach-containing meals.
Maximizing the Bioavailability and Absorption of Beta-Carotene from Spinach
Cooking spinach doesn't destroy its beta-carotene – quite the contrary
Many vitamins are extremely sensitive to heat, but beta-carotene is not one of them. In fact, heat actually facilitates the break-down of plants' thick cell walls and effectively releases beta-carotene, thereby making this essential nutrient more readily available for absorption into the bloodstream. A study published in the May 1998 issue of The Journal of Nutrition, for example, found that women who ate cooked spinach absorbed three times as much beta-carotene compared with those who ate raw spinach.
Mincing and liquefying make the beta-carotene in spinach more bioavailable
A study published in the February 1999 issue of The Journal of Nutrition found that the beta-carotene in spinach is more bioavailable if the spinach is minced or liquefied before consumption. Now that sounds like a pretty good reason to get one of those masticating spinach juicers, or to add some fresh baby spinach into the blender next time you are making a fruit smoothie!
Dietary fat improves beta-carotene absorption
Whether you prefer raw or cooked spinach, be sure to include a source of healthy fats in the same meal. Beta-carotene is a fat-soluble nutrient, which means it is best absorbed from food when also some fat is present in a meal. If you are using spinach in a salad, a great way to increase the absorption of beta-carotene from your meal is to dress the salad with an oil-based dressing. Or, if you are making a spinach-based green smoothie, throw some seeds or into the blender before your mix your drink. Note: Drugs that reduce fat absorption, such as cholestyramine and colestipol, may also reduce absorption of beta-carotene.
Effect of Long Storage Times on the Beta-Carotene Content of Spinach
It is also a good idea to avoid storing fresh spinach for long periods, not only because it tends to wilt rather fast but also because storing reduces its nutritional value. Although a 1991 study published in the Italian Journal of Food Science found only a small decrease in the beta-carotene content of spinach after three weeks of storage (10% loss on a wet weight basis, 23% loss on a dry weight basis), other important nutrients found in spinach are not as stable as beta-carotene. For example, a study published in the journal Food Chemistry in 1998 found that fresh spinach loses 75% of its vitamin C content within seven days of harvest when stored in the refrigerator at 4°C (39°F). Spinach also loses B vitamins during storage, albeit at a slower rate.
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