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Nutritional investigations for fatigue

Fatigue—you know the feeling. You drag yourself out of bed despite getting enough hours of sleep, and find yourself relying on caffeine to get you through the day. No matter what you do, you feel sluggish and tired. It can be highly frustrating when you don’t understand why.

Fatigue is a very non-specific symptom, meaning that there are many, many possible causes. It can occur with numerous health conditions—usually alongside other symptoms—and it can also be the result of poor sleep (not enough hours of sleep overall, or a lack of quality sleep), chronic stress, and a whole range of nutritional factors.

Nutrition is a very common contributor to fatigue, so when someone presents with ongoing fatigue some nutritional investigations may be warranted. Here are some common factors that you may like to consider.

Iron levels

Iron deficiency is a common cause of fatigue. It is very common among women, particularly those who menstruate. This is one of the simplest things that can be checked via a blood test (called ‘iron studies’). It is really important to test your iron levels before taking a supplement, as both iron deficiency and iron overload in the body cause fatigue. Iron overload/excess can occur due to a hereditary condition called haemochromatosis. For some (not all) women who have this condition, it may not become known or apparent until after menopause if periods have been very heavy during the menstruation years. Regular, heavy menstruation could potentially mask the condition in some—there could even have been times when iron levels were low if menstrual blood losses were very significant. However, once menstruation has stopped, if this condition was present then iron could start to build up in the body. This is why it’s important not to assume you are iron deficient and that you need to supplement—please discuss having your iron levels tested with your GP beforehand.

Vitamin B12 and Folate

Often when people hear the word ‘anaemia’, they think of iron deficiency anaemia. However, there are other types of anaemias related to deficiencies of other nutrients, such as vitamin B12 and folate. Again, a simple blood test can check for anaemia and investigate which type it is. Vitamin B12 comes from animal foods, so deficiency is more likely to occur in people who eat a vegan diet (and do not supplement B12). However, sometimes deficiencies can occur because there are issues absorbing the vitamin B12. This can occur with some health conditions, as well as with some medications.

Overall food intake

Another reason for fatigue can be an inadequate overall energy (calorie) intake. Not consuming enough food to meet your body’s needs will certainly have you feeling less than energetic and, when it occurs consistently, has a range of flow on effects including impacting various hormones. Not eating enough may be intentional—for example, with restrictive dieting—or in some cases it can be unintentional. This might happen for people who have a poor appetite (for some, this happens with high levels of stress). It can also occur for some athletes who have a very high energy output due to long and/or hard training sessions, which can make it difficult to eat enough to fuel all of the work the body is doing

The quality of what you eat

The quality of our overall eating pattern matters when it comes to our energy levels and how we feel each day. When we eat too many highly processed foods, it is much harder to consume optimal amounts of vitamins and minerals. In fact, over time, this could contribute to multiple deficiencies. Vitamins and minerals help our body to extract the energy from food, so consuming plenty of nutrient-rich whole foods is very important for ensuring your body is getting what it needs to function properly.

Macronutrient balance

If the fatigue seems to come and go, or you tend to experience it at a certain time of day, you may like to consider the macronutrient balance of your meals. Including a source of protein, fat, and carbohydrates in your main meals, as well as plenty of vegetables, can help to provide a more sustained energy release—avoiding energy spikes and crashes. Try experimenting with the macronutrient composition of your meals and notice how satiated and energised you feel afterwards.

Blood glucose regulation

Our blood glucose (sugar) levels are closely linked to our energy levels. When we consume carbohydrates from food or drinks, this is broken down to glucose and absorbed into the bloodstream. Our body needs to maintain a certain level of glucose in the blood and then allow the rest to move into the cells to be used for energy or stored for later. This process is regulated by hormones, including insulin. Challenges with blood glucose regulation, such as insulin resistance, can contribute to fatigue. You may also experience energy spikes and crashes. Blood glucose control can be assessed by testing your fasting blood glucose and fasting insulin. There are also other tests available, such as HbA1c which provides a general indication of your overall blood glucose over the past three months. This won’t, however, assess insulin resistance. Only testing insulin itself does that.

Overreliance on caffeine

While caffeine does help to momentarily prevent us from experiencing that tired feeling, it is really a band-aid solution. Many people find that taking a break from caffeine actually leads them to feel better and have more energy (after the initial period of caffeine withdrawals). If this is not something you’re interested in experimenting with, I can’t encourage you enough to consider when you’re having caffeine—ideally not on an empty stomach or after midday.


This is an often overlooked cause of fatigue! Many people say they know they need to drink more water, but find it hard to make it a priority. This really can make a difference so take steps to make it easier for you to drink more water. For example, take a reusable water bottle with you so it is always available, or set up some new habits, such as always drinking a glass of water upon waking in the morning.

Coeliac disease

One of the symptoms of coeliac disease can be fatigue, because it can significantly affect nutrient absorption which then leads to deficiencies (when undiagnosed/untreated). Symptoms of coeliac disease can differ between individuals. For some people, this condition is only discovered because they have unexplained, ongoing iron deficiency (tested via a blood test). If you usually consume gluten-containing foods and coeliac disease is suspected, it’s important to discuss having a blood test with your GP before omitting gluten.

As you can see, there are many reasons why you might be feeling tired and sluggish. Often it can be a simple fix however if you are experiencing persistent or unexplained fatigue, it’s important to consult with your qualified healthcare practitioner.

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