Which foods give you energy: what sugar, water and iron do, and when tiredness is about more than food

In this article you will find the answers to these questions: which foods give you energy, which foods give you energy quickly, and what drinking and iron have to do with feeling tired. That matters, because the sweet snack many people reach for in a slump is exactly what research links to more tiredness. It also matters because tiredness that lingers is sometimes a reason to see your GP, and a new menu will not change that. Tiredness is common. In the Dutch Lifelines cohort of 78,363 adults, 15 per cent of participants without a chronic illness were severely tired.⁠⁵ So feeling tired is very normal, even for people who are otherwise healthy. The BioProfile wellbeing scan gives you an indication of where you stand today in how you feel. It is self-insight, to help you make better choices in your diet and lifestyle. It is not a diagnosis. Only a doctor can give you that.

Which foods give you energy

Dutch GP advice for people who feel tired starts with ordinary food: eat healthily and choose mainly wholegrain products, pulses, vegetables, fruit, nuts and fish.⁠⁶ The same advice also mentions being active for half an hour at least five times a week, and giving up alcohol, because alcohol can make tiredness worse.⁠⁶

Put simply: the food that gives you energy is not one product. It is an ordinary, varied way of eating, with exercise alongside it and without the drink that makes tiredness worse.

Does sugar give you a quick burst of energy?

Many people grab something sweet when their energy drops. A meta-analysis brought together 31 studies, with 1,259 participants in total. The meta-analysis found no point after eating at which carbohydrates improved any aspect of mood. Compared with a placebo, people felt more tired within 30 minutes and less alert within 60 minutes.⁠¹

What this means for you: the sugar rush is mostly a story. In these studies, the quick snack was followed by a dip, and nowhere do these studies point to a food that gives you energy straight away.

Steady energy throughout the day

In a nutrition study, 82 otherwise healthy adults followed two diets in random order, each for 28 days.⁠² One diet had a high glycaemic load, which means its carbohydrates make blood sugar rise sharply; the other had a low glycaemic load. On the high glycaemic load diet, people scored about a quarter higher for tiredness and over a third higher for depressive symptoms than on the low one. The differences were larger among participants with overweight.⁠²

Put simply: what you eat week after week seems to matter more than the snack of the moment. In this study, meals whose carbohydrates raised blood sugar less sharply went together with less tiredness and a better mood.

What you drink counts too

Energy is also about what you drink. In controlled experiments, 25 healthy young women became mildly dehydrated through exercise, with a fluid loss of 1.36 per cent. The group felt worse, more tired and less energetic, both at rest and during exercise, found it harder to concentrate and had more headaches. Most measures of thinking ability did not change.⁠³ Your body loses fluid all day long through breathing, sweating and going to the toilet, and the Voedingscentrum advises adults to drink between 1.5 and 2 litres every day.⁠⁴

What this means for you: a small fluid shortfall was enough to make people feel more tired. Drinking enough throughout the day is part of the answer to an afternoon slump.

When iron is the question

Iron status often comes up when people talk about tiredness. In a French study, 198 menstruating women with unexplained tiredness, no anaemia and low iron stores (ferritin below 50 μg/L) took either iron or a placebo. After 12 weeks, tiredness in the iron group had fallen by just under half, compared with clearly less than a third in the placebo group. Compared with a placebo, iron had no clear effect on quality of life, depression or anxiety.⁠⁷ A meta-analysis of six studies pointed the same way: in tired people with low iron but no anaemia, iron reduced tiredness a little. In the general population, however, the link between low iron and tiredness was not clear.⁠⁸

Put simply: iron made a difference for tired people who really had too little iron, and only a blood test shows whether that is the case for you. The researchers behind the French study advise having your blood checked after six weeks if you try iron.⁠⁷

When tiredness is more than a matter of food

Among Lifelines participants with at least one chronic illness, 23 per cent were severely tired, and the more chronic illnesses someone had, the more likely severe tiredness became.⁠⁵ What this means: lasting tiredness can have a cause that food does nothing to change.

Tiredness usually passes on its own after a while. Call your GP if the tiredness lasts a long time, for example longer than a month, or if other symptoms come with it: more night sweats than usual, less appetite, a drop in your weight that you did not want, a change in your stools or blood in your stools, being short of breath at rest or with little effort, a lot of thirst and passing a lot of urine, heart palpitations, feeling very low with no interest in anything, or feeling very tense or restless.⁠⁶ If a low mood is part of it, the article on how long a low feeling lasts goes into this further.

What the wellbeing scan shows

The wellbeing scan gives you a picture of where you stand today. If you take the scan again later, you can see whether a change in what you eat, drink or how you move goes together with how you feel. A questionnaire cannot tell an iron deficiency apart from drinking too little water or a chronic illness. The scan is not a diagnosis.

In summary

This article showed that the food that gives you energy is an ordinary, varied way of eating with wholegrain products, pulses, vegetables, fruit, nuts and fish, and that in the research a dip follows sugar rather than a boost. The article also showed that meals that raise blood sugar less went together with less tiredness over weeks, that drinking enough counts, and that iron makes a difference for people who really have too little iron. Tiredness that lasts longer than a month, or that comes with other symptoms, is a reason to call your GP.