I went to give blood last week and to my surprise, I was denied because my hemoglobin was too low. This is not the first time and it is probably due to my vegetarian diet. I consume large amounts of green, leafy vegetables such as kale, collards, and spinach – foods that are high in iron so I just assumed, given our garden’s harvest, that I would have no problem. But this is the third time I’ve been unable to give blood in the last year so I decided it was time to see how I could improve my levels.

What bears explaining is that I couldn’t give blood the last time I tried either. My hospital’s blood bank uses an automated hemoglobin machine that reads a drop of blood that comes from a quick finger prick. My hemoglobin read around 11. Because of medications I’m on I get my blood checked every three months so the next day I decided to get a venous blood draw – that is, blood that comes from a vein rather than a finger stick. The results were decidedly better and showed that I wasn’t anemic at all. Technology being what it is though, the hospital computer kicked me out of donating until 1 week had passed – it couldn’t be manually overridden.

Capillary blood testing (finger sticks) have shown equivalency when testing using either capillary or venous blood on such measures as blood sugar levels and cholesterol and I wasn’t able to find anything that suggested that measuring hemoglobin using finger stick rather than a venous blood draw would be any different.

Nonetheless, the hemoglobin machine results read 11 and I needed 12.5 in order to donate – so I decided to double check the foods I had remembered to be high in iron. As I thought, dark, green leafy vegetables are high in iron but what I didn’t know was that the iron from plant based foods, are less readily absorbed unlike animal based sources of iron (ie, red meat, chicken, pork etc) which is more readily absorbed.

Called non-heme iron, the iron found in plant foods, is what our foods tend to be enriched with, as in iron-enriched cereal for example. Yet as I mentioned above, this is the iron that is harder for the body to absorb. In fact, 15-35% of iron from animal meat will be absorbed but astonishingly, only 2-20% of non-heme iron get absorbed by our bodies and that will depend on the type of protein consumed with the meal as well as other food components.

Vitamin C greatly enhances the absorption of iron so citrus fruits consumed with your meal will help your body boost iron absorption. Foods that negatively impact iron absorption include tannins (found in tea), calcium, phytates (found in legumes and whole grains) and polyphenols (found in wine, beer, chocolate, walnuts, peanuts… sigh, the list goes on). And as a vegetarian, I consume a lot of tofu but it turns out that some of the proteins found in soybeans actually inhibit iron absorption.

So I will be much more mindful of the combinations of foods I eat in order to maximize the absorption of vitamins and minerals. I found two excellent sources of information – one is a dietary supplement fact sheet on iron that includes 2 tables, one for animal sources of iron, the other for plant based sources of iron.

The other source I found very useful is a web page called Natural Food Hub. It had an excellent page on the Vitamin C content of many fruits including lots of interesting side facts. Happy reading!