Vegan for Life - Jack Norris [33]
Vitamin K is essential for blood clotting, and most people get enough to support that function. But research suggests that vitamin K also contributes to bone health. Older people with higher vitamin K intakes and higher blood levels of vitamin K appear to be at lower risk for hip fracture.9
Because of some errors in measuring vitamin K content of foods, there is evidence now that people have lower vitamin K intakes than previously thought. This isn’t an issue for blood clotting but it may be for bone health. The best sources of vitamin K are leafy green vegetables.
Soy, canola, and olive oils are also good sources. Since vitamin K is fat soluble, cooking greens in a small amount of oil can help your body absorb more.
There isn’t much information about the vitamin K intake of vegetarians or vegans, but what we know suggests that people eating plant-based diets get plenty. So why have we singled it out for discussion? The answer has to do with claims that have been made about vitamin K from those who question the adequacy of vegan diets.
The term “vitamin K” actually refers to two slightly different compounds with vitamin K activity. One, called phylloquinone or vitamin K1, is found in both plant and animal foods. The other, menaquinone or vitamin K2, is produced by bacteria and found in animal foods; plants don’t contain any. While some have claimed that vitamin K2 is a separate vitamin with its own role in the body, no research supports this.
A study comparing blood-clotting rates (a measure of vitamin K activity) showed no difference between vegans and meat-eaters, which suggests that vegans are getting plenty of vitamin K.10 And studies have shown that vitamin K1 supplements are effective in older people for reducing bone fracture risk.
Since bacteria in the colon produces vitamin K2, vegans are getting this form of the vitamin anyway. Finally, the Institute of Medicine has not established any specific recommendations for vitamin K2. We can say with assurance that vitamin K2 is not a separate nutrient, and vegans do not need it in their diet.
OTHER VITAMINS AND MINERALS
Over the years, there has been some discussion about riboflavin (vitamin B2) in a vegan diet since the main source of this nutrient in American diets is milk. But while riboflavin is found in only small amounts in many plant foods, a varied diet of grains, legumes, and vegetables provides plenty. Soyfoods are a particularly good source of riboflavin. We don’t have a great deal of information about vegan intake, but the few studies that have been done show that vegans meet the RDA for riboflavin. Choosing soy (or other plant) milks that are fortified with this nutrient can provide extra insurance, but we don’t think that vegans need to worry about riboflavin. We’ve listed the riboflavin content of plant foods on page 77.
Both vegans and omnivores need to pay attention to the mineral potassium. Since legumes are a good source of this nutrient, vegans tend to have somewhat higher intakes than meat-eaters. But it’s not easy for anyone to meet the recommended daily intake of potassium, which is 4,700 milligrams, without a bit of planning. Including plenty of vegetables in your diet is the easiest way to meet potassium needs, but it’s important to choose those that are especially potassium-rich. Best sources are certain leafy greens (beet greens, spinach, and Swiss chard), cooked tomato products and tomato juice, orange juice, sea vegetables, bananas, and legumes. The table on page 78 shows the best sources of potassium for vegans.
The mineral selenium is the only other nutrient that may be an issue for some vegans. It depends on where you live—or where your food comes from—since the amount of selenium in plant foods is dependent on the amount in the soil where the foods are grown. Evidence suggests that vegans in the United States and Canada get enough selenium. In parts of northern Europe, the selenium content