Constantly tired, unfocused, weak? These nutrient deficiencies could be the cause
Fatigue, concentration problems, and muscle weakness are among the most common everyday complaints – across all age groups. They are often attributed to stress, lack of sleep, or lack of exercise. But even those who get enough sleep, eat a balanced diet, and exercise can experience these symptoms.
One possible reason: an undetected nutrient deficiency . Many of these complaints can be traced back to a deficiency in certain vitamins, minerals, or essential fatty acids. This article highlights the most common deficiencies, typical symptoms, and explains when nutritional supplementation may be beneficial.
What is a nutrient deficiency – and why does it often go unnoticed?
A nutrient deficiency occurs when the body is not adequately supplied with certain vitamins, minerals, or other vital substances over an extended period of time. A distinction is made between an acute deficiency with clear symptoms and a latent deficiency – an undersupply that initially remains unnoticeable but can become noticeable in the long term.
The causes are varied: an unbalanced diet, chronic stress, certain medications or illnesses, limited nutrient absorption in the intestines, and increased nutrient requirements, for example, due to physical activity or pregnancy. Particularly insidious is the fact that not all deficiencies can be reliably detected through traditional blood tests. For example, serum levels of magnesium or vitamin D may appear normal, even though the levels in the body's cells are too low.
Five common nutrient deficiencies and their typical symptoms
1. Vitamin D
Vitamin D deficiency is one of the most common nutritional deficiencies worldwide – and not only in regions with low sunlight. Since the body produces most of its vitamin D in the skin via UVB radiation, levels often drop significantly, especially during the winter months or when staying indoors for extended periods. Sunscreen, dark skin types, and a low body's own conversion rate also contribute to the fact that adequate supply is not always guaranteed.
Low vitamin D levels can manifest themselves in a variety of ways. The most common symptoms include chronic listlessness and a deep feeling of exhaustion that is not fully compensated for by rest or sleep. Many affected individuals also report muscle weakness or a general loss of strength, which is particularly noticeable in everyday life or during exercise. Psychological symptoms such as low mood, irritability, or depressive moods are also associated with a deficiency – not least because vitamin D is also involved in the production of mood-regulating neurotransmitters. It also influences the immune system: An increased susceptibility to infections, especially during cold season, can therefore be an additional indication of an inadequate supply.
2. Iron
Iron is a key trace element for oxygen transport in the blood and cellular respiration. Women of childbearing age, people with chronic inflammation, endurance athletes, and vegetarians or vegans are particularly affected by iron deficiency – often without knowing it. A common but often underestimated risk factor is menstruation : Regular blood loss – especially during heavy or prolonged periods – can lead to gradual iron deficiency if the losses are not adequately compensated for through diet or supplements.
Impaired iron absorption due to gastrointestinal diseases or interactions with foods (e.g., coffee, black tea) can also contribute to iron deficiency. Typical symptoms include persistent fatigue and a feeling of not being able to perform properly despite sufficient sleep. The skin may appear paler, and mental performance—especially concentration and attention—is often reduced. Physical signs such as brittle nails, hair loss, or increased sensitivity to cold can also indicate iron deficiency, especially when several symptoms occur simultaneously.
3. Omega-3 fatty acids
Omega-3 fatty acids—especially EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid)—perform key functions in the body: They regulate inflammation, promote cellular health, and are crucial for brain and heart function. The main sources are fatty cold-water fish such as salmon, herring, and mackerel. Since these are rarely consumed in many diets, omega-3 deficiency is widespread.
A deficiency often manifests itself subtly at first: concentration problems, rapid mental fatigue, and a general lack of performance are typical early signs. The skin may appear dry, flaky, or irritated—a sign of impaired cell membrane function. Research is also increasingly linking emotional symptoms such as mood swings, irritability, or depressive moods to an imbalanced omega-3 status. Laboratory results often reveal an unfavorable ratio of omega-6 to omega-3 fatty acids or a low omega-3 index.
4. Magnesium
Magnesium is involved in over 300 metabolic processes and is essential for the function of muscles, nerves, heart, and brain. The need for magnesium increases particularly during physical exertion, regular exercise, high levels of stress, and certain life phases such as pregnancy or growth. At the same time, dietary intake is not always sufficient—especially with high consumption of highly processed foods or when taking certain medications.
Magnesium plays a particularly crucial role for athletic individuals. It supports muscle relaxation after contractions and thus helps prevent muscle cramps and tension. Studies also show that adequate magnesium intake can reduce muscle soreness due to its anti-inflammatory properties and improved recovery. Therefore, during intense physical exertion or when high sweat loss occurs (e.g., in endurance sports), particular attention should be paid to ensuring adequate magnesium intake.
Magnesium also influences sleep quality – especially in certain forms such as magnesium bisglycinate or magnesium taurate, which are characterized by high bioavailability and a calming effect on the nervous system. These forms can positively influence the time it takes to fall asleep and the depth of sleep, which in turn supports nighttime regeneration and performance the following day. Especially in cases of high stress or restless sleep, magnesium thus offers a dual benefit – both physical and mental.
5. Essential amino acids
Amino acids are the building blocks of life: They are needed for the development and maintenance of muscle, for the production of hormones and enzymes, and for regeneration. The body cannot produce some of these amino acids itself; they must be regularly supplied through food. Especially with increasing age or with an unbalanced diet, the supply of certain essential amino acids can become insufficient.
A deficiency can manifest itself in general muscle weakness and delayed recovery after physical exertion. Slow muscle growth despite training or rapid muscle loss during inactivity also indicate an undersupply. Furthermore, poor sleep, a general performance deficit, and a weakened immune system are frequently associated in the literature with a suboptimal amino acid supply—particularly in older adults or people with chronic stress.
What to do if you suspect a deficiency?
Anyone who experiences typical symptoms such as persistent fatigue, concentration problems, or physical weakness over a prolonged period should critically examine their diet and lifestyle. The cause is often a chronic deficiency in certain micronutrients. A medical evaluation—ideally including laboratory tests—can help confirm a suspicion or rule out other causes. However, it is important to note that standard blood tests do not always provide a complete picture. Especially with magnesium or vitamin D, the cell status can differ significantly from the serum level.
As a first orientation, a simple self-check can provide valuable information:
Do you regularly serve fresh fish?
Fatty cold-water fish such as salmon, herring, and mackerel are the best natural sources of omega-3 fatty acids . Those who eat little fish or follow a purely plant-based diet run the risk of not getting enough EPA and DHA.
Is there a longer period with little sunlight or indoor daily routine?
The body only produces vitamin D when the skin is exposed to sufficient UVB radiation. People who spend most of their time indoors, rarely go out into the sun, or regularly use sunscreen can develop a deficiency over time.
Do you exercise regularly, but recovery takes an unusually long time?
Physical exertion increases the need for magnesium, protein, and other micronutrients. Delayed recovery or frequent muscle pain may indicate an imbalanced nutrient balance.
Is the diet rather one-sided or vegetarian/vegan?
A plant-based diet is healthy, but can lead to a deficiency in certain areas – such as iron, vitamin B12 or omega-3 – if careful attention is not paid to a balanced intake.
Is there a high level of stress in everyday life?
Chronic stress increases the consumption of magnesium, zinc, and B vitamins. Symptoms such as inner restlessness, sleep problems, or lack of energy can be associated with this—even with proper diet and exercise.
When nutritional supplements can be useful
Dietary supplements can help close specific nutritional gaps – especially in cases of proven deficiencies, increased needs, or limited absorption. It's not the quantity that matters, but the targeted selection. Products with scientifically proven ingredients, good bioavailability, and clear labeling offer real added value.
At the same time, supplementation should always be part of a holistic approach – including a balanced diet, exercise and stress reduction.
Conclusion: Take symptoms seriously – and think holistically
Constant fatigue, concentration problems, or muscle weakness are not trivial. They often have functional causes that can be positively influenced with simple measures. A targeted supply of critical micronutrients—whether through diet or supplementation—can make an important contribution.
If you want to keep your body healthy in the long term, you should not only pay attention to obvious deficiencies, but also recognize the “silent” deficiencies – before they become noticeable.
Sources:
- Holick, M.F. (2007). Vitamin D deficiency. New England Journal of Medicine, 357(3), 266-281.
DOI: 10.1056/NEJMra070553 - Calder, P.C. (2017). Omega-3 fatty acids and inflammatory processes: from molecules to man. Biochemical Society Transactions, 45(5), 1105–1115.
DOI: 10.1042/BST20160474 - Gröber, U., Schmidt, J., & Kisters, K. (2015). Magnesium in prevention and therapy. Nutrients, 7(9), 8199-8226.
DOI: 10.3390/nu7095388 - Wolfe, R.R. (2017). Branched-chain amino acids and muscle protein synthesis in humans: myth or reality? Journal of the International Society of Sports Nutrition, 14(1), 30.
DOI: 10.1186/s12970-017-0184-9 - Abbasi, B. et al. (2012). The effect of magnesium supplementation on primary insomnia in elderly: A double-blind placebo-controlled clinical trial.
Journal of Research in Medical Sciences, 17(12), 1161-1169.
PMID: 23853635
Image Credits: Photo by Sarah Chai: https://www.pexels.com/de-de/foto/lebensmittel-essen-gesund-apple-7263016/
