His interest in the topic stemmed from a 2006 study from the Slovak Republic. The researchers found that vegans had higher levels of cadmium in their blood compared to both meat-eaters and lacto-ovo vegetarians. Levels were higher in those who had been vegetarian the longest and also in those who ate the most whole grains.
High levels of cadmium are possibly associated with risk for heart disease and very high levels can impact bone health and both liver and kidney function. Whether the higher levels of the Slovakian vegans is a problem is something we don’t know. The researchers thought that the higher antioxidant content of vegan diets could counter the effects of cadmium.
But it also appears that getting adequate zinc and iron is important for reducing harmful effects of cadmium. Zinc enhances production of a protein that binds to cadmium and prevents its damaging effects. And getting adequate iron can reduce cadmium absorption.
This was particularly interesting to me because I have been hearing quite a bit from vegans who are worried about zinc and iron in their diet. They aren’t worried about getting enough, but instead are concerned about getting too much, which they fear will raise their risk for Alzheimer’s disease (AD). In fact, as Jack addresses in his article, zinc might actually help to protect against AD.
This raises the issue that I wrote about recently in relation to iron in cast iron pots. That is, when it comes to diet and health, the concerns are different for vegans. Even if excess zinc does turn out to be harmful, vegans are more likely to fall short of requirements than to get too much of this mineral. The RDAs for zinc are 11 milligrams for men and 8 milligrams for women, but it’s possible that vegans need more than this since zinc isn’t absorbed as well from plants. The best sources of zinc in vegan diets are legumes (beans, soyfoods and peanuts), nuts and seeds, with most of these foods providing around 1 milligram of zinc per serving.
Some vegans choose to eat diets that are very dependent on whole grains. They avoid nuts and sometimes even downplay legumes because of a mistaken belief that fat and protein are bad for you. Whole grains are certainly healthy foods, but replacing some of them in your diet with legumes and nuts can boost your zinc intake (and it might lower your cadmium intake, too.) Consuming some whole grains as bread may also help since leavening with yeast or sourdough improves zinc absorption.
This is not something you need to micromanage by any means. It just reinforces the benefits of eating a variety of vegan foods, rather than focusing too heavily on one particular type of food. Because I eat an antioxidant-rich diet and because I tend to favor beans, tofu, nuts, and starchy vegetables over grains (which I still eat every day) I’m not particularly worried about cadmium. And I’m on the fence about zinc supplements. But it’s possible that a low-dose zinc supplement could be beneficial for some vegans, especially women who have relatively low calorie intakes. Jack suggests that a supplement of 10 to 25 milligrams per day is safe and I agree. Take a look at his article on cadmium for a more in depth discussion of these issues.