Vegan for Life - Jack Norris [28]
CHAPTER 6
IRON, ZINC, IODINE, AND VITAMIN A
Maximizing Vegan Sources
Protein, calcium, and vitamins B12 and D get most of the attention in vegan diets. But there is a handful of other nutrients that deserve consideration, namely iron, zinc, iodine, and vitamin A. We’ll touch briefly on vitamin K, riboflavin, potassium, and selenium too.
MINERAL ABSORPTION ON VEGAN DIETS
Minerals like iron and zinc are absorbed less well from plant foods than from animal products. There are a number of reasons for this, but the most important is the presence of phytate in the diet. This phosphorus-containing compound is found in whole grains, legumes, seeds, and nuts. (Smaller amounts are found in vegetables too.) Phytate binds minerals, making them less absorbable. Refining grains reduces their phytate content, but it also reduces the mineral content of a food, so isn’t much of a solution.
A number of food preparation techniques help liberate minerals from phytate and can greatly increase absorption. Fermentation, which includes the activity of both yeast and sourdough starters in bread making, as well as the production of fermented foods like tempeh and miso, greatly increases mineral availability. This makes leavened bread a better source of well-absorbed iron and zinc than crackers and flat breads.
The addition of citrus fruits to meals can also boost mineral absorption. Foods that contain vitamin C are especially effective for increasing iron absorption. Toasting nuts and seeds, and sprouting beans and grains, reduces the effects of phytate. So does soaking these foods and discarding the water before using them in a recipe.
Phytate isn’t all bad, though. It’s an antioxidant that acts in ways that could reduce cancer risk. This suggests a benefit to getting minerals from plant foods. If you use food preparation techniques to break the bond between phytate and iron or zinc, you’ll improve mineral absorption while getting the potential health benefits of phytate.
IRON
You might be surprised to know that vegans typically consume more iron than either lacto-ovo vegetarians or meat-eaters.1 The issue for vegans is how well that iron is absorbed.
This essential mineral is a part of hemoglobin, the component of red blood cells that is needed to ferry oxygen to the cells. It’s also a part of many enzymes involved in energy production and immune function. Even among Americans who eat meat, iron deficiency is the most common nutrient deficiency.
We need a constant supply of iron in our diets because we lose it through daily sloughing off of intestinal and other cells. Premenopausal women lose more iron than men because of menstrual losses. Therefore, their iron needs are more than twice what men require. The recommended daily iron intake is 18 milligrams for premenopausal women and 8 milligrams for men and postmenopausal women. In the government’s ongoing survey of American eating habits, 12 percent of women between the ages of twelve and forty-nine had poor iron status.2
Iron Deficiency
There are two stages of iron deficiency. In the first, iron stores become depleted and there may be a decrease in hemoglobin levels and mild symptoms. In the next stage—overt iron deficiency anemia—hemoglobin drops to subnormal levels, which can cause symptoms such as pale skin, fatigue, weakness, shortness of breath, an inability to maintain body temperature, loss of appetite, and hair loss. But these symptoms can also be due to other nutritional deficiencies or conditions, and true iron-deficiency anemia can be diagnosed only through a blood test. It’s relatively inexpensive to have your iron levels tested by a doctor. A blood test can also help your physician differentiate between anemia due to iron deficiency and anemia due to vitamin B12 deficiency.
Meat Iron versus Plant