Iron in Huel and the Effects of Antinutrients and Vitamin C

The level of iron in Huel is at an optimum level despite concerns about both the high iron content and the effects of substances that may inhibit its absorption into the body. The following information will alleviate concerns that some people have regarding the amount of iron that Huel supplies.

The Daily Values (DV) are the amounts of nutrients recommended per day for Americans, the DV for iron is 18mg per day^[1]. 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 anemia.

Hemochromatosis 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. This genetic condition is most common in the caucasian population. Possibly, as many as one in 250 people have the condition, many of which are undiagnosed and may display no symptoms unless they’re exposed to a high iron intake^[2].

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 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 Powder contains around 35mg iron (based on a 2,000kcal intake of v1.1) which works out at 194% of the DV. Although this may seem high, there are several 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.

Huel contains nonheme iron

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^[3] 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 is naturally occurring and is provided by the main ingredients with no additional added. As there are no animal products in Huel, all the iron present is non-haem iron.

The bioavailability of nonheme iron is more significantly influenced by other dietary factors than that of heme iron^{[4, 5]}, and the amount of nonheme 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^[6]. Typically, heme iron is more readily absorbed than nonheme iron at levels of 15-35% and 2-20% respectively^{[7, 8]}. The absorption of heme 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 hemochromatosis.

Phytic acid and iron

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 and flaxseed in Huel are both 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^[12]. 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^[13]. 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. Based on 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^[15], so there are clearly other factors coming into play, such 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^[16] and both the oats and flaxseed in Huel are finely milled significantly lowering the phytic acid. In addition, most phytic acid (37-66%) is degraded in the stomach and small intestines^[17].

Calcium and iron

Calcium has been shown to reduce the absorption of both heme and nonheme 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^[20]. 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 nonheme iron absorption^{[6, 21]}.

Huel contains 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 is high and there is adaptation, the effect of calcium has on iron absorption is not particularly strong.

Polyphenols and iron

Some polyphenols have also been shown to reduce iron bioavailability^[5]. Huel contains some polyphenolic antioxidants in the oats and flaxseed so there may be some inhibition. However, their effect is minimal.

Vitamin C and iron

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^[22]. 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^[23].

Is the amount of iron in Huel optimal?

All the iron in Huel is nonheme iron and is all naturally occurring from the main ingredients. The amount of iron in Huel v1.1 is high at approximately 35mg per 2,000kcal, which works out at 194% of the DV.

In theory, at a 2,500kcal per day intake of Huel you could be approaching the safe upper limit of Huel that could potentially be too high, and it would be reasonable for some people, especially those with haemochromatosis, to be concerned that the high level of iron in Huel 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 and Hueligans aren’t at risk of iron-deficiency anaemia?

The amount of phytic acid in Huel that the oats and flaxseed provide is around 310mg per 100g* and, at this level, if no other factors came into play, this would significantly reduce the amount of iron that is actually absorbed and available for use.

According to the figures provided by Hurrell & Egli^[4], in the more extreme case, Hueligans would be absorbing 5% of the iron in Huel^[3], i.e. 1.75mg per day (based on 2,000kcal of v1.1). Compare this to someone consuming the DV of 18mg per day based on a mixed non-vegetarian diet; this person, absorbing the upper amount of 18% of the iron consumed^[4], would be absorbing around 3.2mg per day. As you can see, there’s very little in it.

It has also been shown that the effect of phytic acid on iron absorption is dose-dependent and the molar ratio of phytic acid to iron can be used to estimate the effect on absorption^[4]. A ratio of <0.4:1 is required to significantly improve iron absorption in plant-based meals that do not contain any enhancers of iron absorption, or <6:1 in composite meals with certain vegetables that contain ascorbic acid^{[4, 24]}. The ratio of phytic acid to iron in Huel is around 3.3:1; considering Huel contains a larger amount of ascorbic acid (300mg per 2,000kcal of Huel v1.1) than most ascorbic acid-rich vegetables, the absorption of iron from a Huel meal is at an optimum level.

Using the above figures, you can see that the effect of vitamin C compensates adequately for the negative effects of phytic acid and that Huel provides an optimum level of iron for absorption.

Main points

• Huel has a high iron content of 35mg per 2,000kcal or 7mg per 100g (based on unflavoured unsweetened Huel v1.1)
• Huel has a high phytic acid content which could lower the bioavailability of the iron significantly
• Calcium has a small effect on reducing iron absorption
• Huel contains a high level of vitamin C and this is a potent enhancer of iron absorption
• The amount of iron in Huel is optimal considering all the factors that inhibit and enhance its absorption

* Based on EU v2.3 formula

References

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