Welcome to Straight Talk on Health. I’m your host Dr. Chet Zelasko. Straight Talk on Health is a joint production with WGVU in Grand Rapids MI. I examine the world of health. Nutrition. Exercise. Diet. Supplementation. If there’s something new, I look at the science behind them, and let you know whether it’s real or not. You can check out other things that I do on my website Drchet.com and sign up for my free emails.
There are a few questions in nutrition that are ubiquitous. No matter whether in person or via phone and email, there are just some questions that I’m asked all the time. One of those questions is related to iron absorption: What will help absorb iron? Years ago, I came upon a research paper on the factors that affect iron absorption from the diet, especially non-heme iron. I decided to check to see if there was any progress—and there was! Some things that are interesting to nutrition geeks. First a little primer on iron.
There two primary forms of dietary iron. The first is called heme iron. As you might guess, heme is synonymous with blood and it’s the form of iron that comes from meat. With the emphasis for the past 50 years on not eating red meat, the iron in heme and myoglobin, which contribute to the red color of both, is missing from the diet. More and more people rely on vegetable sources of iron. That’s called non-heme iron and most is in the form of ferrous fumarate. The point to this is that heme iron is better absorbed than non-heme iron. That may be leaving more people deficient in iron absorption.
The average daily iron intake from diet is 10 to 15 mg with only 1 to 2 mg absorbed through the intestinal system. Nutrient–nutrient interactions may play a role in intestinal iron absorption. Dietary inhibitors such as calcium, phytates, polyphenols and enhancers such as ascorbic acid and proteins mainly influence iron bioavailability. Numerous studies have been carried out for years to enhance iron bioavailability and combat iron deficiency.
Researchers from the UK wanted to check the published research to see what factors have been examined that contribute to iron absorption and what inhibits iron absorption. Their approach interested me. Most of the absorption research on many nutrients are single meal approaches. In other words, subjects come to the lab after having not eaten overnight or sometimes longer, their nutrient levels are tested, they are fed a single meal, some with things that may enhance absorption, others which may inhibit absorption of the target nutrient, then they are retested. The results are used to make recommendations on what foods inhibit nutrient absorption. Most of the research on iron absorption being affected by calcium was done this way.
The problem is simple: most of the published iron absorption studies have been done by using the single-meal approach. In their opinion, that tends to exaggerate the effect of any types of inhibitors and enhancers. They scanned the published research to find studies that used a whole diet approach, rather than a single meal approach. Here’s what they found.
Dietary enhancers of iron absorption include vitamin C, meat as well as poultry, fish, and alcohol. The last one surprised me. I would have thought that alcohol might inhibit iron absorption. I guess the grapes in wine and bacteria and hops in beer may actually improve iron absorption. What about inhibitors? The inhibitors included tannins, which are found in tea and coffee, calcium and dairy products, polyphenols—a specific type of phytonutrient which is found in wine, phytates, animal proteins such as milk and eggs, and other minerals such as zinc and copper.
Their goal was to come up with an algorithm that could help predict iron absorption depending on the normal diet of the individuals. That’s fine but I think the results stand on their own when interpreted. In the simplest terms I can use, and understanding that there will always be factors specific to individuals, here’s what they found.
The lower the iron status of the individual, the higher the absorption of iron regardless of other factors. Simply put, if you’re iron deficient, your body is going to absorb more IF it’s in the foods you eat whether that diet includes meat or is plant-based, regardless of inhibitors or enhancers. In fact, when they plotted the data, it was apparent that as iron status decreases, iron absorption increases. The opposite was also true. If your iron status is good, you will not absorb excess iron from the food in your diet.
When looking at diets that were high in enhancers and low in inhibitors, more iron was absorbed in those subjects when compared to subjects that were low in iron enhancers than for iron inhibitors. Practical example? If you eat your vegetables that are high in iron, if you eat citrus and some meat, and avoid milk and tea, you’ll absorb more iron. The danger for you right now is that you may start constructing an optimal iron absorbing diet in your head. Don’t do that and here’s a couple of reasons why not.
First, in spite of examining all the available research, the results are based on just 19 studies. Combining all the subjects in those studies yields about 420 subjects from countries all over the world. While that’s better than all the data from the single meal studies, it’s still not extensive data. It presents guideposts for us to follow, not dogma that must be adhered to.
But second, and most importantly, the difference in iron absorption between those high in enhancers and lost in inhibitors and vice versa was about 4%. While statistically significant, that’s not a lot of difference. It’s also not enough with which to base an entire diet for maximal iron absorption.
Leap ahead 10 years. In a recent review of iron absorption, there really hasn’t been much progress. It’s not that scientists don’t have good ideas. They have used techniques such as encapsulation, emulsification, chelation, and food fortification has been shown to increase the bioavailability and absorption rate of iron. The problem has been the testing. Scientists use in vitro studies almost exclusively in mediums which mimic the human gut. The problem is twofold: the in vitro studies are not the human gut which is complex to say the least. Why use them you may ask? Human or animal trials are much more expensive to do. As discussed before, single meal trials are not great but the iron absorption issue hasn’t reached the level of importance that warrants the research expense of longer human trials. Compounding the issue is that elemental iron is a significant reactive free radical producer so it has to be combined with something to reduce the potential for doing damage.
Is this useless? Is there nothing important here? Not in the least. What it means is that before you change your diet, find out where you stand. Get your serum ferritin, hemoglobin and iron status checked. You have to know where you are before you know whether you need to do anything. Then, find a way to increase the enhancers while decreasing the inhibitors. Over the long haul, not just for single meals. If you were to increase vitamin C foods in your diet while decreasing coffee and tea, that may be all you need to do. You can also talk with your physician to see if they want you to add additional iron.
Iron is important for our body to carry oxygen in hemoglobin and to make energy in the long-term energy system. Try to construct your diet with more vegetables that are high in iron, maybe some meat if you eat it, and citrus and other fruits that will help with iron absorption. That’s a simple way to keep your iron and energy levels at healthy levels. I’m out of time. This is Dr. Chet Zelasko saying health is a choice. Choose wisely today and every day.
References:
J Zhejiang Univ Sci B. 2008 Mar; 9(3): 165–191.
