Niacin as a food nutrient fortifier

What is niacin

Niacin is a water-soluble vitamin, also known as vitamin B3. Niacin is a general term for pyridine-3-carboxylic acid and its derivatives with biological activity. Niacinamide is its main form in animals. Niacin has a simple chemical structure, stable physical and chemical properties, and is not easily damaged by acid, alkali, and heat, so it is considered the most stable vitamin.

The physiological functions of niacin

1. Participate in the metabolism of substances and energy in the body. Niacin forms coenzyme I and coenzyme II in the form of niacinamide in the body. The niacinamide part of these two coenzyme structures has reversible hydrogenation and dehydrogenation properties and plays a role in transferring hydrogen during the biological oxidation of cells.
2. Related to the synthesis of nucleic acids. Glucose can produce 5-phosphate ribose through the pentose phosphate metabolic pathway, which is the main way to produce ribose in the body, which is an important raw material for the synthesis of nucleic acids. Coenzyme I and Coenzyme II composed of niacin is the hydrogen transmitters in the first biochemical reaction of the metabolic pathway of pentose glucose phosphate.
3. Lower blood cholesterol levels. A daily intake of 1-2g niacin can lower blood cholesterol levels. The principal may be that it interferes with the synthesis of cholesterol or lipoproteins, or it can promote the synthesis of lipoproteins.
4. The component of glucose tolerance factor. Glucose tolerance factor (GTF) is a complex composed of trivalent chromium, niacin, and glutathione. It may be a cofactor for insulin, which can increase the utilization of glucose and promote the conversion of glucose into fat.

Deficiency and excess

Residents in areas where corn is the staple food are prone to niacin deficiency. Although the content of niacin in corn is higher than that in rice, the niacin in corn is combined and not easily absorbed and utilized by the human body. However, adding alkali can make combined smoking The acid becomes free niacin, which is easily used by the body. For example, occasionally adding baking soda to cornmeal when making polenta, steamed wotou, and corn tortillas, the food made from cornmeal will not only have good color, aroma, and taste but also the combined niacin is easily absorbed and utilized by the body. (Note: Use a small amount of alkali! Alkali is a very terrible enemy for most vitamins. Vitamin B1, Vitamin B2, and Vitamin C are very sensitive to alkali, and will be destroyed in an alkaline environment and affect absorption.)

Tuberculosis patients taking a large amount of anti-tuberculosis drug isoniazid for a long time will affect the conversion of tryptophan to niacin, so it can also cause niacin deficiency.

When niacin is deficient, the synthesis of coenzyme I and coenzyme II in the body is blocked, and certain physiological oxidation processes are impaired, that is, vitamin B3 deficiency-leprosy appears. The typical symptoms are dermatitis (dermatitis), diarrhea (diarrhea), and dementia (dementia), the so-called “three-D symptoms”. Dermatitis mostly occurs on exposed parts of the body, such as the cheeks, the back of the hands, and the back of the feet. There is a clear boundary between the skin of the affected area and the healthy skin. Most of them show sunburn-like changes. The skin becomes reddish-brown, the epidermis is rough, desquamation, pigmentation, and neck dermatitis is more common. The symptoms of the digestive tract mainly include loss of appetite, indigestion, and diarrhea. At the same time, oral mucosa and tongue erosion, and scarlet tongue may occur. The neuropsychiatric symptoms include depression, anxiety, memory loss, apathy, and dementia, and some can show mania and hallucinations. Accompanied by muscle tremor, tendon reflex allergy, or disappearance. Vitamin B3 deficiency often coexists with vitamin B1 and B2 deficiency.

The side effects of excessive intake of niacin are mainly skin redness, eye discomfort, nausea and vomiting, hyperuricemia and impaired glucose tolerance, etc. Long-term large amounts of intake can cause damage to the liver.

Note: The nutritional status of the body can be evaluated by measuring the ratio of 2-pyridone/N-methylnicotinamide in urine, urine load test, the ratio of N-methylnicotinamide to creatinine, and red blood cell NAD content.

Reference intake and food sources

The reference intake of niacin should consider energy consumption and protein intake. In addition to being directly ingested from food, niacin can also be converted from tryptophan in the body. An average of 60mg tryptophan can be converted into 1mg niacin. Therefore, the reference intake of vitamin B3 in the diet should be expressed in niacin equivalent (NE).

Niacin equivalent (mgNE) = niacin (mg) + 1/60 tryptophan (mg)

Resident dietary vitamin B3 reference intake, adult male RNI is 14mg NE/d, female is 13mg NE/d, UL is 35mg NE/d.

Niacin is widely present in various animal and plant foods. Niacin is mainly present in plant foods, and niacinamide is mainly present in animal foods. Niacin and niacinamide are rich in liver, kidney, lean poultry, fish, whole grains and nuts. Although the content of niacin in milk and eggs is low, the content of tryptophan is high, which can be converted into niacin in the body.