Addressing hunger is a key global priority. Over 733 million people suffered from hunger in 2023, a number too high to achieve current eradication goals.

When we think of hunger, we often picture undernutrition: children and adults showing the physical consequences of being underfed, reflecting inequality globally. Undernutrition is when people aren’t taking in enough energy or nutrients from food.

Alongside this calorie-based hunger, however, is an invisible hunger impacting an estimated 2 billion people. That’s one in four people globally – if not more.

Hidden hunger is when the body has enough energy (calories) to function but lacks important micronutrients such as iron, zinc, vitamin B12 and vitamin D among others to maintain good health.

Even in developed countries, including here in the UK where the Quadram Institute is located, micronutrient deficiencies can occur, including rare but severe cases where children come to school with bowed legs because they lack key vitamins. This puts pressure on the NHS, with rising numbers of people in England admitted to hospital due to poor micronutrient levels.

Hidden hunger is nutrient deficiency, and it’s hard to detect.

What is nutrient deficiency?

Nutrient deficiency happens because we don’t eat enough nutrient-rich food. Energy dense but nutrient-poor foods are becoming more popular, accessible and cheaper than the fruits, vegetables and wholegrains that are abundant in nutrients. The quality of the food we eat matters, not just the quantity.

Nutrient deficiency impacts health and wellbeing

Research shows minerals and vitamins are key to maintaining a healthy life. Without these micronutrients, essential functions in the body are limited.

Here are some important micronutrients and their importance to our health:

Iron

Is essential for oxygen transport. It produces haemoglobin, the protein in our red blood cells that helps move the oxygen we need. Iron deficiency results in anaemia, with symptoms like tiredness and lack of energy. Anaemia prevalence is higher in women of childbearing age, pregnant women and vegetarian women in the UK. Good sources include red meat, red kidney beans and nuts.

Zinc

Is important for growth, playing a role in the production of new cells and enzymes in the body. It also helps us heal wounds and maintain a healthy immune system. Deficiency can result in symptoms like loss of smell and taste, poor wound healing and hair loss. Good sources include meat, shellfish and dairy.

Vitamin B12

Is key to red blood cell production, energy release and maintaining a healthy nervous system. Lacking B12 can cause anaemia, depression and neurological symptoms. 1 in 10 vegans in the UK is deficient. Good sources include meat, fish and dairy products.

Vitamin D

Helps maintain calcium and phosphate levels in our bodies. This keeps our bones, teeth and muscles healthy. Deficiencies are prevalent in the UK, with 1 in 5 adults impacted. The sun is the most important source of vitamin D, so these rates reflect winter periods. Public health advice is to consider taking supplements from September to March.

Not everyone is impacted by nutrient deficiency the same way

It’s important to remember that nutritional requirements to maintain good health can vary between different groups. For example, menstruating women need more iron than men due to monthly blood loss. 

In the UK, over 50% of Asians are severely deficient in vitamin D and more than a third of Black Africans have high levels of vitamin D deficiency. Multiple factors, including higher levels of melanin (a skin pigment), can reduce vitamin D production in the skin.

Also, the bioavailability, or how easily our bodies can absorb and use these important nutrients, can change depending on the food we eat. For example, iron from animal origin is more easily absorbed than from plant sources.

Here at the Quadram Institute, our research is uncovering how microbes in our guts can help us absorb more iron from plant-based diets. We also provide advice on the best plant sources to contribute to healthy iron intake.

What is biofortification and how can it help?

Biofortification increases the nutritional content of common food items already incorporated in our diets, so eating habits remain unchanged. This is done by selectively breeding plants with desirable traits, editing plant genomes or other techniques like aeroponics (growing plants without soil).

At the Quadram Institute, we jointly host with the John Innes Centre the BioFortification Hub, which carries out innovative research into solving hidden hunger alongside industry partners and policymakers.

Peas can I get more B12!

Pea shoots, a common salad ingredient, are successfully being biofortified with vitamin B12. Vitamin B12 is produced by microbe activity in animal guts, so we get our fill by eating animal products. But plant-based diets are becoming more widespread, so obtaining enough B12 is more difficult and a quiet deficiency epidemic is growing.

To mitigate this, our researchers, in collaboration with the John Innes Centre and LettUs Grow, have fortified pea shoots with B12 using an aeroponic system that sprays the plants with water and B12.

‘Sunshine’ tomatoes with extra vitamin D

Collaborating with the John Innes Centre, our researchers are testing the health benefits of tomatoes that accumulate a form of vitamin D, vitamin D3, that could help alleviate vitamin D deficiencies.

Over 20% of the population is vitamin D deficient. UV exposure from the sun on our skin is the main source of vitamin D, but this source disappears in winter for people living in the UK.

There are also currently very few plant sources of vitamin D, so following plant-based diets makes it more difficult to get the recommended daily amounts. This makes these tomatoes a key piece of the puzzle to solve hidden hunger in the UK.

Zero Hidden Hunger

The Food and Nutrition National Bioscience Research Infrastructure (F&N NBRI) team at the Quadram Institute manages the nutrition and food bioactive data that can help tackle hidden hunger.

They’re collaborating on a project, called Zero Hidden Hunger EU, to understand the prevalence of hidden hunger in Europe. This project looks to develop food-based strategies which reduce deficiencies within population groups.

In particular, the team are looking at iron and zinc, focusing on the bioavailability of these nutrients from plant foods and identifying how we can maximise the sustainability of current dietary patterns without risking iron and zinc inadequacy.

What is the difference between biofortification and fortification?

While biofortification introduces beneficial micronutrients during plant growth, fortification adds these benefits during plant processing. Despite being less efficient, fortification is also key in tacking hidden hunger.

Last year, our researchers welcomed the announcement that non-wholemeal flour would be fortified with folic acid from 2026. Folic acid is a version of vitamin B9 important for brain and skull development in babies. This new legislation will help protect babies from neural tube defects, which cause serious brain and spine problems.

Is nutrient deficiency related to ultra-processed food?

The definition of ultra-processed food (UPF) can be unhelpful, as processing itself is not an indicator of nutritional content, including fats and sugars. 

Last year, the Quadram Institute submitted evidence to a House of Lords select committee on food diets and obesity, highlighting the very broad definition of UPF and the complexities around labelling all UPF as unhealthy.

Researchers at the Quadram Institute think it’s critical to consider both structure (matrix) and ingredients when assessing food. The two are interlinked, as structure affects how quickly nutrients are digested and the quality of nutrients delivered to the microbes in our guts, so both should be considered.

What can I do to get enough nutrients and tackle hidden hunger?

The NHS Eatwell Guide details the food groups we should eat as part of a healthy diet. These food groups, including wholegrains, fruits, vegetables and pulses, are rich in different micronutrients. It’s important to incorporate all these different groups in moderation in our diets to ensure nutrient needs are met. Our researchers have also shared their tips to make nutritious snacks and produced a healthy eating guide for children.

If you’re vegan or vegetarian, you need to ensure that you’re getting enough of the micronutrients iron and vitamin B12, both low in plant sources, to avoid hidden hunger.

Finally, you can take part in research here at the Quadram Institute to better understand why and how nutrients are important for our health.