Iron is a double-edged sword. If we don’t absorb enough, we risk anemia, but if absorb too much we may increase our risk of cancer, heart disease, and a number of inflammatory conditions. Because the human body has no mechanism to rid itself of excess iron, one should choose plant-based (non-heme) sources over which our body has some control.
Iron is a double edged sword. If we don't absorb enough, we risk anemia, but if absorb too much… we may be increasing our risk of colorectal cancer, heart disease, infection, neurodegenerative disorders and inflammatory conditions. Other conditions that have been associated with high iron intake include Alzheimer's Parkinson's, arthritis, and diabetes. Because the human body has no mechanism to rid itself of excess iron, we evolved to tightly regulate the absorption of iron. If our iron stores are low, our intestines boost the absorption of iron, and if our iron stores are topped off, our intestines block the absorption of iron to maintain us in the sweet spot. But this only works with the primary source of iron in the human diet, the iron found in plant foods. Our digestive system can't regulate the iron in ingested blood—heme iron. The iron in animal foods can just zip right our intestinal barrier even if we already have too much; we have no control over it.
In fact some guess that iron overload may be a reason meat consumption has been tied to breast cancer risk. Iron is a pro-oxidant, and can induce oxidative stress and DNA damage. “A high intake of iron in developed societies may, over time, lead to a physiologic state of iron overload in postmenopausal women, who are no longer losing blood every month. Iron overload favors the production of free radicals, fat oxidation, DNA damage, and may contribute to breast carcinogenesis independently or by potentiating the effects of other carcinogens.”
Only people with a confirmed diagnosis of iron-deficiency anemia should consider supplementing their iron intake, and even then it can be risky. A recent study this found a significant increase in oxidative stress within the bodies of women on iron supplements, and so before going on iron supplements I would suggest talking to your physician about first trying to treat it through diet alone, by eating lots of healthy iron-rich foods like chickpeas and pumpkin seeds while consuming vitamin C-rich foods at the same meal, such as citrus, tropical fruits, broccoli, or bell peppers, which improve plant iron absorption, while avoiding drinking tea and coffee with your meals, which can impair iron absorption.
Since organic acids like vitamin C can boost iron absorption, the coca cola company commissioned a study to see if drinking coke would do the same thing, and the answer is no.
To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring watch the above video. This is just an approximation of the audio contributed by Serena
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This is another reason why Plant Protein is Preferable. For more on iron, see Iron During Pregnancy and Are Iron Pills Good For You?. For more on nutrient bioavailability, see Wednesday's NutritionFacts.org video-of-the-day New Mineral Absorption Enhancers Found along with Garden Variety Anti-Inflammation, Take Vitamin D Supplements With Meals, Calcium Absorption: Soy Milk Versus Cow Milk, Raw Food Nutrient Absorption, and Forgo Fat-Free Dressings?. For more on breast cancer see Relieving Yourself of Excess Estrogen, Flax and Fecal Flora, Broccoli Versus Breast Cancer Stem Cells and 49 other videos that touch on breast cancer. There are also videos on more than a thousand other topics.
Check out my associated blog posts for some more context: How to Enhance Mineral Absorption, Is Caffeinated Tea Really Dehydrating?, Eating Green to Prevent Cancer, How Tumors Use Meat to Grow, and Avoiding Dairy to Prevent Parkinson's