Nutrition can be complicated sometimes. You're told to get all your vitamins and minerals – Huel helps with that – but did you know some can actually lessen the benefits of other nutrients? We take a look at the mineral iron and the potential 'antinutrients' that can affect our body's absorption of it.
Crucial for oxygen transport, cognitive function and your immune system, iron is an important mineral that we should all check we're getting enough of in our diet. But just how much is enough?
The Nutrient Reference Value (NRV) for iron is 14mg per day. The NRV of a nutrient refers to the amount that covers requirements of that nutrient for most of the population. A good intake of iron is essential for the transport of oxygen around the body by red blood cells, muscle contraction and nerve impulses. If we have too low levels of iron in our blood, then we have iron-deficiency anaemia.
Haemochromatosis is a condition where the body accumulates iron. Most commonly it is genetic and uncontrolled and has been linked to liver cirrhosis, cardiomyopathy, arthritis and diabetes. It is most common in people of Northern European origin, possibly as many as one in 250 people; many people who have the condition are undiagnosed and may display no symptoms unless they’re exposed to a high iron intake.
There are substances in foods that inhibit the absorption of iron and some other minerals and adversely affect their bioavailability. Consequently, there is a valid concern that the level of iron in Huel Products is not enough. Bioavailability refers to the amount of a nutrient that is absorbed and goes on to have an effect in the body. These substances that negatively affect absorption of nutrients are known as antinutrients – constituents of food that reduce the nutritional value of other nutrients even though they themselves provide nutritional benefits.
Huel Powders contain around 39mg iron (based on a 2,000kcal intake) which works out at 280% of the NRV. Although this may seem high, there are a number of factors that come into play that affect iron status, and it’s important to look at these to demonstrate that regular Hueligans are supplied with the optimal amount of iron from Huel Products.
Haem iron is a type of iron that’s primarily found in animal products and at a level of around 40% of the total amount of iron in them with the rest being non-haem iron. The form of iron that’s found in most plant products is non-haem. All the iron in Huel Products is naturally occurring and is provided by the main ingredients with no additional added. As there are no animal derivied ingredients in Huel Products, all the iron present is non-haem iron.
The bioavailability of non-haem iron is more significantly influenced by other dietary factors than that of haem iron[4, 5], and the amount of non-haem iron that’s absorbed depends on how much iron is in your body already; if your iron status is low, your body absorbs more of it from food and if your stores are adequate, then it won’t absorb so much. Typically, haem iron is more readily absorbed than non-haem iron at levels of 15-35% and 2-20% respectively[7, 8]. The absorption of haem iron isn't down-regulated, so if you consume too much, you may still absorb more than you need, and this is an advantage a vegan diet has in people with haemochromatosis.
The most notable antinutrient that affects levels of iron and some other minerals is phytic acid. Phytic acid, also known as inositol hexakisphosphate, is a naturally occurring storage form of phosphorus in plant seeds, and the bound form is known as phytate. The oats, flaxseeds, quinoa, brown rice and black beans in Huel Products are rich in phytic acid. Phytic acid is often portrayed in a bad light due to its antinutrient effect where it reduces the absorption of a few minerals including iron, zinc and manganese.
However, its health benefits are often overlooked. Phytic acid is an antioxidant[9-11] and has been shown to be anticarcinogenic. Iron can behave as a free-radical, contributing to oxidative stress which can be damaging to the body, so phytic acid’s ability to sequester and trap iron is beneficial. Phytic acid can also bind heavy metals (e.g. cadmium and lead) and help prevent their accumulation in the body. Read more in our article Phytonutrients in Huel.
The extent to which phytic acid reduces the bioavailability of iron varies, and there are other constituents in food that come into play and affect the rate. On the basis of intake data and isotope studies, iron bioavailability has been estimated to be in the range of 14-18% for mixed diets and 5-12% for vegetarian diets in subjects with no iron stores[4, 5]. Recommendations for iron for vegetarians may be as much as 1.8 times higher than for non-vegetarians[5, 14]. However, a vegetarian diet does not appear to be associated with an increased risk of iron deficiency, so there are clearly other factors coming into play such as well as other constituents of food that promote iron absorption (see below).
Milling grains and removing the bran decreases the phytic acid content of cereals and seeds and the oats in Huel Products are finely milled significantly lowering the phytic acid. In addition, most phytic acid (37-66%) is degraded in the stomach and small intestines.
Calcium has been shown to reduce the absorption of both haem and non-haem iron but has a greater effect on the latter[18, 19]. However, its effect is not as significant as that of phytic acid, and there is a minimum level of calcium that’s required to cause an inhibitory effect. Furthermore, there is adaptation over time; calcium supplementation was shown to have a reduced effect up to 12 weeks, after which it was not found to change iron nutritional status, due to the compensatory increase in non-haem iron absorption[6, 21].
Huel Products contain a high level of calcium, some naturally occurring, and some added in the micronutrient blend in the form of calcium carbonate, but as the level of iron in Huel Products is high and there is adaptation, the effect of calcium has on iron absorption is not particularly strong.
Some polyphenols have also been shown to reduce iron bioavailability. Huel Products contain some polyphenolic antioxidants from the main ingredients so there may be some inhibition. However, their effect is minimal.
It’s well researched that vitamin C significantly promotes the absorption and bioavailability of iron and that supplementation with vitamin C has been shown to be more effective at increasing iron status than iron supplements. Vitamin C – also known as ascorbic acid – is therefore a vital substance in combating the effects of antinutrients, especially in vegetarians. Indeed, the effect of vitamin C, which is itself also an antioxidant, is that strong that it has been shown to significantly counteract the effect of phytic acid. In one study, phytic acid reduced iron absorption by up to 50%, but adding 30mg of vitamin C counteracted it.
All the iron in Huel Products is non-haem iron and is all naturally occurring from the main ingredients. The amount of iron in Huel Powder v3.1 and Black Edition is high at approximately 40mg per 2,000kcal, which works out at 280% of the NRV. The amount of iron in Huel Ready-to-Drink and Instant Meals is significantly lower but still more than adequate and above the NRV.
In theory, at a 2,300kcal per day intake of the Huel Powders you could be approaching the safe upper limit of iron that could potentially be too high. Therefore, it would be reasonable for some people, especially those with haemochromatosis, to be concerned that the high level of iron in Huel products could be dangerous over time. How can we be sure that Hueligans are not at risk of iron toxicity?
The safe upper limit value is based on mixed diets and therefore doesn’t take sufficient account of the large effects of antinutrients; so, equally, some people could be justified in being concerned that they’re not absorbing sufficient iron. How can we be sure we’re absorbing enough, that phytic acid isn’t having a detrimental effect and Hueligans aren’t at risk of iron-deficiency anaemia?
It has been shown that the effect of phytic acid on iron absorption is dose-dependent, but in composite meals with certain vegetables that contain ascorbic acid, there is a much higher uptake[4,24]; considering Huel Products contain a larger amount of ascorbic acid (300mg per 2,000kcal) than most ascorbic acid-rich vegetables, the absorption of iron from a Huel meal is at an optimum level.
Based on this, you can see that the effect of vitamin C compensates adequately for the negative effects of phytic acid and Huel Products provide an optimum level of iron for absorption.
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