Niacin (vitamin B3): effect, requirement & deficiency

Vitamin B3 (niacin), is a water-soluble vitamin that belongs to the eight B vitamins. It plays a central role in energy metabolism and is essential for the health of the skin, nerves and psyche.             

Niacin comes in two main forms:

• as nicotinic acid and

• as niacinamide (nicotinamide)

Both forms are converted into coenzymes in the body, which support important biochemical processes. The human body can partiallyproduce niacin from the amino acid tryptophan, but an adequate intake of niacin through food is important to meet the body's needs.

Niacin is found in many animal and plant-based foods, although the quantities vary greatly.

The best sources of niacin include:

• Animal products: lean meat (especially poultry, beef and pork), fish (e.g. tuna, salmon), eggs and offal such as liver.

• Plant sources: whole grains, legumes (e.g. peanuts, lentils), mushrooms and certain vegetables such as green leafy vegetables.

 Foods with a high niacin content:

Although plant foods contain less niacin, the requirement is usually well met with a healthy diet. It is important to note that the body can synthesise niacin from tryptophan, which is particularly important in a high-protein diet.

Niacin is often expressed in niacin equivalents (NE) to account for both directly supplied niacin and niacin synthesised from tryptophan. The conversion factor is as follows:

1 mg niacin is equivalent to 60 mg tryptophan.

Example: a high-protein meal containing 600 mg of tryptophan is equivalent to 10 mg of niacin.

This makes it clear that a high-protein diet in particular can help to meet niacin requirements, even if direct sources of the vitamin are limited.

Niacin is an all-rounder vitamin that plays a key role in many bodily processes.

Niacin is an indispensable component of coenzymes such as NAD (nicotinamide adenine dinucleotide) and NADP (nicotinamide adenine dinucleotide phosphate). The NAD precursor nicotinamide riboside (NR), a compound known from longevity research, also belongs to the class of B3 vitamins and is crucial for the body's energy supply. NADH (nicotinamide adenine dinucleotide hydride) is the biologically active form of vitamin B3. These coenzymes are responsible for a functioning metabolism, including:

• the conversion of carbohydrates, proteins and fats into energy

• cellular respiration and cell regeneration

Without sufficient niacin, the body would not be able to obtain the energy it needs from food.

Vitamin B3 contributes to the normal functioning of the nervous system. It supports the formation of neurotransmitters, which are essential for the transmission of signals between nerve cells. A niacin deficiency can therefore lead to neurological disorders and damaged nerves.

Niacin plays an important role in mental health by contributing to normal psychological function.

It contributes to:

• regulate mood swings

• reduce signs of fatigue

• increase motivation, concentration and memory

• prevent Alzheimer's disease

A sufficient supply of niacin therefore supports mental resilience and general well-being.

Niacin helps to maintain normal skin by strengthening the skin barrier and improving moisture retention.

Vitamin B3 supports the normal function of the mucous membranes and thus contributes to the functioning of the digestive system. Deficiencies can cause digestive problems such as diarrhoea, constipation, loss of appetite, vomiting or inflammatory diseases of the digestive tract.

Niacin helps to reduce tiredness and fatigue because it is involved in energy metabolism.

The daily requirement for niacin varies depending on gender, age and energy consumption. The reference values of the German Nutrition Society (DGE) are 11-17 mg niacin equivalents per day. The niacin requirement is highest in male adolescents. After that, the requirement decreases with age. In special circumstances, such as during high physical exertion, pregnancy, stress or illness, the need may be increased.

However, the dosages used in practice for general health maintenance or targeted use are often significantly higher. The European Food Safety Authority (EFSA) states the following upper limits for the total daily intake of nicotinamide:

The maximum level for nicotinamide has been set at 12.5 mg per kg of body weight per day, or about 900 mg per day for adults. This level does not apply during pregnancy or breastfeeding because there are insufficient data for this critical period of life. Maximum levels for children and adolescents have been derived based on body weight.

A niacin deficiency is in developed countries rare, but can occur with an unbalanced diet or certain illnesses. Risk groups include:

• People with alcohol dependency

• Patients with chronic bowel or liver disease

• People with congenital metabolic disorders

• People who follow a very low-protein diet

• People who suffer from anorexia

Niacin deficiency symptoms only appear when tryptophan metabolism is disturbed at the same time or the protein and vitamin B6 intake is very low.

Signs of early niacin deficiency are unspecific: exhaustion and fatigue, loss of appetite, headaches and irritability.

Severe niacin deficiency leads to pellagra, which is characterised by the following symptoms (the ‘3 Ds’):

• Dermatitis: inflammation of the skin, especially on sun-exposed areas.

• Diarrhoea: gastrointestinal complaints such as diarrhoea.

• Dementia: neurological disorders and memory loss.

Treatment involves a targeted intake of vitamin B3 through dietary supplements or dietary adjustments. In cases of severe deficiency, a doctor should be consulted to determine the correct dosage.