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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 Nutrient Reference Value (NRV) for iron is 14mg per day (1). 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 (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 contains around 39.2mg iron (based on a 2,000-calorie intake of v2.2) 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 Huelers are supplied with the optimal amount of iron from Huel.

Huel contains non-haem iron

Haem iron is a type of iron that’s only 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 only form of iron that’s found in 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 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 (6). Typically, haem iron is more readily absorbed than 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.

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 flaxseeds 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 (9,10,11) 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. 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 (15), so there are clearly other factors coming into play, including the fact that vegetarians have a higher dietary intake of iron than meat-eaters (16), 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 (17) and both the oats and flaxseeds 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 (18).

Calcium and iron

Calcium has been shown to reduce the absorption of both haem and non-haem iron but has a greater effect on the latter (19,20). 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 (21). 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 (6,22).

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 flaxseeds 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 (23). 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 (24).

Is the amount of iron in Huel optimal?

All the iron in Huel is non-haem iron and is all naturally occurring from the main ingredients. The amount of iron in Huel v2.2 is high at approximately 39.2mg per 2,000 calories, which works out at 280% of the NRV.

In theory, at a 2,300 calorie 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 Huelers 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 Huelers aren’t at risk of iron-deficiency anaemia?

The amount of phytic acid in Huel that the oats and flaxseeds 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 (2010), in the more extreme case, Huelers would be absorbing 5% of the iron in Huel (3), i.e. 2mg per day (based on 2,000 calories of v2.2). Compare this to someone consuming the NRV of 14mg 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 2.5mg 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 (4,25). The ratio of phytic acid to iron in Huel is around 3.3:1; considering Huel contains a larger amount of ascorbic acid (310mg per 2,000 calories of v2.2)  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 39.2mg per 2,000 calories or 7.9mg per 100g (based on vanilla Huel v2.2)
  • 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


  1. Food Drink Europe. Guidance on the Provision of Food Information to Consumers, Regulation (EU) No. 1169/2011. 2013.
  2. Bacon BR, et al. Diagnosis and management of hemochromatosis: 2011 practice guideline by the American Association for the Study of Liver Diseases. Hepatol. 2011; 54(1): 328-43.
  3. Anderson J & Fitzgerald C. Iron: An Essential Nutrient. Colorado State University. Fact sheet 9.356.
  4. Hurrell R & Egli I. Iron bioavailability and dietary reference values. Am J Clin Nutr. 2010; 91(5):1461S-7S.
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  13. Schlemmer U, et al. Phytate in foods and significance for humans: Food sources, intake, processing, bioavailability, protective role and analysis. Mol Nutr Food Res 2009; 53: S330-S75.
  14. Institute of Medicine, Food and Nutrition Board. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. Washington, DC: National Academy Press, 2001.
  15. Saunders AV, et al. Iron and vegetarian diets. Med J Aust. 2013; 199(4): S11-6.
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