When people think of heart-health, they generally think of three things: dietary fat, exercise, and sodium. Yes, those things are probably the most important for your ticker’s wellbeing, but there are lots of other small things that might add up over the years. Unless you’re a vegetarian or have had a blood test showing a deficiency, you probably haven’t given too much thought to the iron content of your diet.
Iron Deficiency and the Heart
Someone who is “iron deficient” or who has “iron deficiency anemia” doesn’t have enough iron available to produce red blood cells. Red blood cells carry oxygen throughout the body. Symptoms of iron deficiency include fatigue, dizziness, fainting, shortness of breath, loss of appetite, weakness, and feeling “foggy” headed/unable to concentrate.
Iron Deficiency and Congestive Heart Failure
Iron deficiency makes it more difficult for the heart to pump blood and oxygen, so it works faster and harder to try to keep up. Rarely, this can progress to enlargement of the heart and heart failure.
For patients already in heart failure, iron status appears to be critically important. Most studies have shown that between 30 and 50 percent of patients with heart failure are also iron deficient. This deficiency is associated with worse exercise performance and a higher rate of hospitalization and death from all causes. If patients with heart failure and iron deficiency receive iron injections, they experience improved exercise capacity, kidney function, and quality of life. Recent European guidelines for heart failure recommend monitoring iron parameters in all heart failure patients.
To get technical (bear with me here):
- If someone has a “low ejection fraction,” this means that the left ventricle of the heart isn’t pumping enough blood when it contracts.
- The body tries to compensate in patients with heart failure and a low ejection fraction in many ways, two of which are:
- The Renin-Angiotensin-Aldosterone System (RAAS) becomes overactive. The RAAS is a hormone system that regulates blood pressure and fluid balance.
- The Sympathetic Nervous System (SNS), which is what stimulates the body’s fight-or-flight response also becomes overactive.
- The overactive RAAS and SNS stop a protein that is needed to carry iron into the cells. This protein is known as the transferrin receptor protein 1 (TfR1).
- Unfortunately, people with heart failure often experience blood loss because of certain medications that they take. They also tend to have impaired nutrition and some degree of nutrient malabsorption. Both blood loss and malnutrition further decrease levels of TfR1.
- Besides storing and transporting iron, TfR1 metabolizes free radicals, so you want a lot of TfR1. Free radicals, as you might know, are very hard on the body so we want them to be metabolized before they can damage DNA and RNA and cause cell death.
Iron Overload and Heart Disease
Too much iron for someone who has not been diagnosed with anemia does more harm than good.
In individuals without heart failure, high -level iron injections appear to cause constriction of blood vessels, leading some researchers to speculate that the damage caused by iron could be the first step in a cascade of events leading to the thickening and hardening of arteries (this is known as atherosclerosis).
Iron might impair endothelial function, mostly due to the oxidative stress that it provokes. The endothelium is the lining of the arteries and blood vessels that controls the contraction and dilation of the vascular system, and also plays an important role in blood clotting.
Other experts believe that iron may also act as a catalyst in the oxidation of LDL-cholesterol and cause inflammation, which is a known risk factor for heart disease and a harbinger of many other medical problems ailing modern day humans.
Individuals can develop iron overload from excessive blood transfusions, iron supplements, or iron injections. However, the most common cause of iron overload is hemochromatosis, a genetic disease characterized by a predisposition to absorb excess iron from the diet.
The manifestations of iron overload depend on which organs are affected and can include fatigue, skin color changes, abdominal pain, joint pain, reproductive problems, diabetes and problems with glucose regulations, an elevation in liver enzymes – oh, and also…heart failure and arrhythmias.
It’s long been assumed that premenopausal women were less likely to get heart disease because estrogen protected them, but maybe it’s because they lose iron every month. That would explain why giving postmenopausal women estrogen doesn’t seem to change their heart disease risk.
The Type of Iron Matters
A meta-analysis reviewing data from 21 studies involving 292,454 participants (Indiana University School Public Health in Bloomington) found that heme iron consumption increased the risk of Coronary Artery Disease by 57%, but non-heme iron appeared to have no impact.
Heme iron is found only in meat, poultry, fish, and other seafood. Non-heme iron is found in grains, beans, vegetables, fruits, nuts, and seeds, and is also found with heme iron in animal-based protein. In other words, non-heme iron is found in both animals and plants, but heme iron is only found in animals. Heme iron is absorbed at a much higher rate in comparison to non-heme iron; we’re talking 37% absorption vs. 5%!
Is it Really Iron Deficiency Anemia?
When I still practiced clinically, it drove me nuts how often anemia of chronic disease was misdiagnosed as iron deficiency. Anemia of chronic disease occurs in response to inflammation. It presents with only a mild drop in hemoglobin and it doesn’t progress. Iron deficiency gets worse and worse until it’s treated and the hemoglobin level can fall quite low. With anemia of chronic disease, total iron binding capacity (TIBC) usually drops, because there’s enough iron – it just can’t get to where it needs to be (think of insulin resistance but with iron instead of insulin). When iron stores are low, TIBC is high because there’s a lot of room for some happy little iron molecules to settle into – lots of capacity for improvement. In some cases, a doctor will need to order a serum transferrin receptor test to straighten things out – the results will be high if it’s iron deficiency anemia and low or low-normal in anemia of chronic disease. Why does it matter? Because giving someone high iron supplements if they don’t need it can be quite dangerous and technically even fatal in the case of some underlying diseases.
- If you have heart failure or know someone who does, you might want to ask if iron status can be checked if it hasn’t been recently.
- Don’t overdose on iron supplements in an attempt to be healthier and keep iron-containing supplements out of reach of small children.
- Moderate how much red meat you’re eating and try to get more iron from plant-based foods.
- As always, keep an eye on the fat and sodium content of your diet, try to squeeze in time for exercise, don’t overdo it with alcohol, and quit smoking if you haven’t already.
- If you’ve been diagnosed with iron deficiency and have underlying health problems, it’s not a bad idea to ask for a serum transferrin receptor test if your hemoglobin isn’t lower than 9.5 mg/dL or so and your TIBC is low or normal.