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A balanced diet contains the most important nutrients. We need these to function every day, to be healthy and to be strong in everyday life. But what happens if you lack certain nutrients? Read all about the most important nutrients and how you can quickly and safely make up for a deficiency here.

What are nutrients? Macronutrients and micronutrients

Nutrients are the components of food that the body has to receive regularly. They supply energy, build and maintain body tissue and are needed for countless metabolic processes. Nutrition science divides them into two groups. Macronutrients are needed in large amounts: carbohydrates as the main energy source, fats and proteins. Micronutrients are needed in small amounts but are just as vital: vitamins, minerals and trace elements such as iron, zinc and selenium. Water completes the picture. An overview of all groups is given in the guide why the body needs additional nutrients. Some nutrients are called essential because the body cannot produce them itself. Of the 20 amino acids that build body proteins, nine are essential and must come from food. The same applies to certain fatty acids: the marine omega-3 fatty acids EPA and DHA lowered the risk of heart attack in a meta-analysis of 13 randomised controlled trials.

Why a nutrient deficiency develops

Hardly anyone in Europe goes hungry, yet many people fall short on single nutrients. The causes of a nutrient deficiency are well described. Across the EU, only 12% of people eat the recommended five portions of fruit and vegetables a day. Athletes, pregnant and breastfeeding women, older people, vegetarians and vegans have a higher or different need. Long-term medication acts as a nutrient robber: people who had taken acid blockers for two years or longer had a 65% higher risk of vitamin B12 deficiency, and the contraceptive pill raises the need for folic acid, B vitamins, magnesium and zinc, as the guide to nutrient robbers shows. Stress increases the need for B vitamins, zinc and vitamin C. On top of this comes the nutrient dilemma: industrially processed food is high in energy but low in nutrients. In a randomised trial, adults ate 508 calories more per day on an ultra-processed diet, and USDA data show declining levels of protein, calcium, iron, riboflavin and vitamin C in 43 garden crops between 1950 and 1999.

Which nutrients most often run short?

A handful of nutrients appear again and again in deficiency statistics. Vitamin D tops the list: 40.4% of Europeans have less than 50 nmol/L of 25-hydroxyvitamin D, the form measured in the blood, as the guide to vitamin D deficiency explains. Iron deficiency is one of the most common deficiencies worldwide and affects women in particular; in tired women with low iron stores, fatigue fell by 47.7% with iron. Vitamin B12 is critical for vegetarians and vegans: a review of 18 studies found deficiency rates of 11% to 90% among vegetarians, as the guide on recognising a vitamin B12 deficiency describes. Magnesium is part of more than 300 enzymes, and from the age of 50 many people are at risk of a deficiency. For women who could become pregnant, 400 µg of folic acid a day or an equivalent amount of folate such as 5-MTHF is advised, as the comparison folic acid vs. folate shows.

Signs of a nutrient deficiency and how it is detected

A nutrient deficiency rarely announces itself with a single clear symptom. Typical signs include cracks in the corners of the mouth, hair loss or skin rash, tingling or numbness in the hands and feet, muscle cramps, constant tiredness, a weak immune system with frequent infections, poor sleep and digestive problems. Tingling and numbness, for example, can point to a lack of B vitamins; the eight B vitamins are needed for energy metabolism, the nerves and blood formation. Because the symptoms overlap, a blood test brings clarity. For vitamin D, the decisive value is 25-hydroxyvitamin D; for magnesium, the level in the red blood cells says more than the standard serum test, because the body draws on other stores to keep the serum level stable. The typical patterns of a lack of the sunshine vitamin are summarised in the guide to vitamin D deficiency symptoms.

Food, absorption and supplements

A nutrient only counts once the body has absorbed it. Bioavailability describes the share of a nutrient that reaches the bloodstream and can be used. It depends on the form and the combination: vitamin C counteracts substances that block iron absorption, and vitamin D3 taken with a meal containing fat reached 32% higher peak blood levels than with a fat-free meal. With age the body produces fewer digestive enzymes, which makes it harder to break down food and absorb nutrients. The basis remains a varied diet: wheat bran, amaranth and spinach are among the foods richest in magnesium, oysters, beef and pumpkin seeds among the best sources of zinc, and fruit and vegetables supply vitamin C. Food supplements complement a balanced, healthy diet: they fill gaps where food, sunlight or absorption are not enough.

All nutrient guides at a glance

• Nutrients: what nutrients are, the causes of a deficiency, the most common deficits and eleven warning signs.
• Nutrient deficiency: five reasons why many people run low despite plenty of food, with figures from large population studies.
• Nutrient robbers: how diet, medication and stress lead to a vitamin deficiency and how it can be corrected.
• The nutrient dilemma: why processed food leaves people overfed but undernourished.
• Bioavailability: how form and combination decide how much of a nutrient the body can use.
• Vitamin D deficiency: thresholds, testing and how a low level is corrected.
• Vitamin B12 deficiency: risk groups, symptoms, blood values and treatment.
• Iron deficiency: tiredness, blood values and iron-rich foods.
• Magnesium: why the mineral matters with age and how a deficiency is tested.
• Folic acid vs. folate: the difference between the two forms of vitamin B9 and the advice before pregnancy.
• Amino acids: the building blocks of protein, the nine essential ones and protein needs.
• Fatty acids: saturated, unsaturated and trans fats and the role of omega-3.

Frequently asked questions

What are the 6 main types of nutrients?

The six main types are carbohydrates, fats, proteins, vitamins, minerals and water. Carbohydrates, fats and proteins are the macronutrients that supply energy and building material. Vitamins and minerals, including trace elements such as iron, zinc and selenium, are micronutrients needed in small amounts. Water is vital for every process in the body. Certain amino acids and fatty acids are essential and must come from food. More on nutrients.

What are macronutrients and micronutrients?

Macronutrients are carbohydrates, fats and proteins, which the body needs in large amounts for energy and to build tissue. Micronutrients are vitamins, minerals and trace elements, needed in much smaller amounts but involved in almost every metabolic process. Magnesium alone is part of more than 300 enzymes. Both groups have to be supplied regularly through food. More on magnesium.

How do I know if I have a nutrient deficiency?

Warning signs include constant tiredness, hair loss, cracks in the corners of the mouth, muscle cramps, tingling in the hands and feet, frequent infections and digestive problems. Because these symptoms overlap, only a blood test shows which nutrient is missing. For vitamin D, the decisive value is 25-hydroxyvitamin D; 40.4% of Europeans are below 50 nmol/L. More on nutrient deficiency.

Do I need nutrient supplements?

Food supplements complement a balanced diet, they do not replace it. They make sense where food alone falls short: for vegans and vegetarians with vitamin B12, in winter with vitamin D, with a higher need during pregnancy, sport or stress, and with long-term medication such as acid blockers. A review of 18 studies advises vegetarians to take vitamin B12 supplements regularly. More on nutrient robbers.

How can I improve nutrient absorption?

The form and the combination matter. Vitamin D3 taken with a meal containing fat reached 32% higher peak blood levels than with a fat-free meal. Vitamin C improves iron absorption, while coffee and black tea lower it, so leaving time between iron and these drinks helps. Lycopene from tomato paste with a little oil is better available than from fresh tomatoes. More on bioavailability.

Which nutrients are most important for energy?

B vitamins, iron and magnesium are central. The eight B vitamins help the enzymes that turn food into energy, iron transports oxygen to the cells and magnesium supports energy metabolism. A lack of vitamin D or vitamin C can also show up as tiredness. In tired women with low iron stores, fatigue fell by 47.7% with iron supplements. More on iron deficiency.