How Much of a Problem is Iron in a Vegetarian Diet?

Based on our review of the research, we do not believe that vegetarians typically have problems in getting the iron that they need. In large scale studies like the National Health and Nutrition Examination Survey (NHANES), over three-fourths of vegetarians meet their daily iron requirement, with the percentage being similar to non-vegetarians.

Many people associate strong iron intake with consumption of meat, and it is true that grass-fed beef, one of our WHFoods, provides you with approximately 2 milligrams in one 4-ounce serving. (Two milligrams is the same as 11% of our recommended 18 milligrams of iron per day.) Other meats like lamb provide you with a similar amount of iron. However, it would be wrong to associate strong iron intake with animal versus plant foods, because a wide variety of plant foods can provide at least 11% of your daily iron needs as well.

In fact, every one of our Top 25 iron-rich foods are plant foods. You can get over one-third of your daily iron from 1 cup of cooked spinach, and over 20% from 1 cup of cooked Swiss chard. And a very special mention in the iron category should go to olives. Olives can provide nearly 25% of your daily iron requirement in a single cup.

All of our legumes will provide you with 20% of your daily iron or more, with the exception of tofu and tempeh, which provide you with approximately 15%. The dark green leafy vegetables and legumes can serve as "go-to" food groups for most individuals who choose a vegetarian-type meal plan. Finally, not to be ignored as good iron resources are the Nuts & Seeds group. Foods from this group typically provide 5-15% of your daily iron per serving.

If your day included two servings of legumes, three servings of green leafy vegetables, and one serving of nuts/seeds, you intake would already be very close to our recommended daily amount.

The Iron Absorption Controversy

Some of our readers have asked us about the lesser absorption of iron from plant versus animal foods. This issue remains under active investigation in food research, and we would definitely describe this area as a controversial one.

As a general rule, the form of iron found in plant foods (non-heme iron) is different that the form found in animal foods (heme iron), and this difference in form affects absorption. Heme iron is roughly 5-10 times better absorbed than non-heme iron. However, even in meat eaters, heme iron represents a very small percent (5-10%) of total iron intake. In other words, most of the iron consumed by meat-eating individuals still comes from plant foods in the form of non-heme iron.

Recent studies on divalent metal transporter 1 (DMT1)—the protein that carries non-heme iron up into our body—have shown that the non-heme iron in plant foods must get converted from one form (ferric iron) into another form (ferrous iron) in order for absorption to take place. Since vitamin C (ascorbic acid) can help promote this step, combining iron-rich plant foods with vitamin C-rich plant foods can be a good way to increase the likelihood of non-heme iron absorption. Luckily, it is not difficult to do this kind of food combining! You can use our Recipe Assistant to find the recipes you need in this regard. Start out by picking any one of our iron-rich plants foods in the "Foods to Include" column. For example, spinach is our number one food for iron at WHFoods, so you could begin by selecting this vegetable. Next, move over to the middle column and select all of the animal foods that you would like to avoid. Finally, move over to the last column on the right and select "Vitamin C" as a "Nutrient to Include." Then click the Submit button, and you will find spinach-containing vegetarian recipes that are rich in both iron and vitamin C!

Much of the controversy surrounding iron absorption involves the degree to which iron absorption is impacted by mixed diets that contain mostly plant foods but also include some animal foods. We've seen estimates of average iron absorption in these diets that range all the way from 5-20%. At this point in the research process, relatively small amounts of animal foods in a meal plan appear to increase overall iron absorption, even though the extent of this increase is not clear. There is also evidence that other food substances—for example, lactic acid, malic acid, and citric acid—increase absorption of plant iron. These additional factors make estimates of iron absorption from mixed diets more complicated to determine.

When organizations like the National Academy of Sciences (NAS) make public health recommendations for dietary intake of iron, they are forced to make assumptions about the absorption of iron from plant versus animal foods. For example, the most recent Dietary Reference Intakes (DRIs) from the NAS proposed different daily iron requirements for vegetarians based on an assumed average of 10% iron absorption for vegetarians and an assumed average of 18% average iron absorption for non-vegetarians. This difference led to a DRI recommendation of 80% additional iron intake by vegetarians. At WHFoods, we have not seen evidence to indicate that this much larger amount of iron is needed among vegetarians to avoid unwanted risk of iron deficiency anemia or other health problems. However, persons concerned about their iron intake who consume plant foods almost exclusively may want to consult with their healthcare provider about this issue.

More Information on Vegetarian Diets

For more information on the subject of vegetarian diets, please see our overview article "A Practical Look at Vegetarian Diets" as well as the following Q+As.

References

To see the research articles we reviewed in the writing of these articles, see here.

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