Can you get enough iron from a plant-based diet?

Author: Daniele Vani, Dietitian-in-training

You may have heard that iron from animal products is absorbed more easily than iron from plant foods. Have you ever wondered why?

One reason is due to so-called anti-nutrients found in plant foods (tannins, phytates and oxalates to name a few). They can trap some of the iron in your digestive tract and block its absorption. You should know that these molecules are not inherently bad; for instance, tannins are part of a molecular group called polyphenols that are known for their health-promoting antioxidant and anti-inflammatory properties [1].

The chemical environment of our gut also affects absorption of plant-based iron. Although the stomach is famously acidic, the next part of the digestive tract that food moves through - the small intestine - is actually basic (a.k.a alkaline). In a basic environment, plant-based iron will clump together and some of it will escape absorption [2].

Iron from meat is not susceptible to being trapped by anti-nutrients and will not clump in an alkaline environment [3]. Does this mean plant-based iron is inferior? No, not really. Your body will always absorb some iron and you’ll meet your daily requirement on a plant-based diet as long as you compensate by eating more iron-containing foods.

But there’s also a handy trick for getting more iron!

Think vitamin C

The bioavailability (i.e. the ease with which a nutrient is absorbed) of plant-based iron is increased substantially by vitamin C when you eat them together.

Here’s the science: vitamin C will transform the iron into an easily absorbable form. Studies have shown that vitamin C will reverse the negative effects caused by anti-nutrients [3]. Pretty cool, right?

Achieving this benefit can be as simple as squeezing a wedge of lime over your meal or having a glass of lemon water with lunch. Not a fan of citrus? Just about every fruit, vegetable and leafy green contains vitamin C, so you have an abudance of choices. Some particularly potent veggies are bell peppers, brussel sprouts, broccoli, potatoes and red cabbage. If you’re eating your iron-rich beans in a salad, you’re all set.

Where’s the iron?

When you’re eating plant-based, make it a point to know which foods are particularly high in iron so they can make it onto your plate.

Next time you’re grocery shopping, make sure to pick up:

• Soy foods like tofu, tempeh and soy milk.
• Pulses (beans and lentils) are packed with iron, protein and fiber, and also happen to be inexpensive; talk about great value! Consider rotating dried beans, peas, chickpeas, and lentils into your weekly meals.
• Trail mix that contains cashews, almonds, pumpkin seeds and dried apricots or raisins. Keep some on hand at work or school for when you need a snack.
• Whole grains (or pseudograins) like oats, barley, buckwheat and quinoa. They’re not as rich in iron as pulses, but they will still contribute to your iron count.
• Some breakfast cereals are fortified with iron. Many of them are also full of empty calories, sugar and ultra-processed ingredients, so look for brands that contain whole grains, fiber and less than 6-7 grams of sugar.
• Those of you with a sweet-tooth are fortunate that dark chocolate can be a good source of iron! Look for brands which list cocoa mass as the first ingredient.

The take-home

To easily meet your iron needs on a plant-based diet, know which foods have iron and eat them daily. Incorporate soy foods, whole grains and nuts and seeds into your diet, and be sure to include a source of vitamin C with every meal to maximize iron absorption.

References

1. Hussain, T., et al., Oxidative Stress and Inflammation: What Polyphenols Can Do for Us? Oxidative Medicine and Cellular Longevity, 2016. 2016: p. 7432797.
2. Spiro, T.G., L. Pape, and P. Saltman, Hydrolytic polymerization of ferric citrate. I. Chemistry of the polymer. Journal of the American Chemical Society, 1967. 89(22): p. 5555-5559.
3. West, A.R. and P.S. Oates, Mechanisms of heme iron absorption: Current questions and          controversies. World Journal of Gastroenterology: WJG, 2008. 14(26): p. 4101-4110