Dietary sources of niacin

Other Additives. Cats cannot convert tryptophan to niacin (22), or carotene to vitamin A in sufficient amounts to meet thein needs (23). These deviations, as compared with other animals, need not produce problems because added dietary sources of niacin and vitamin A provide the needs of cats. 

The RDA for niacin is expressed in terms of energy intake 6.6 mg niacin equivalent (NE, 1 mg niacin or 60 mg tryptophan) per 1000 kcal (4186 kJ) per day is recommended (13NEday-1 minimum). This is approximately equivalent to 19 and 15 mg NE day -1 for men and women, respectively. The UK RNI value for niacin is 6.6 mg NE per 1000 kcal (4186 kJ) per day for adults. The richest dietary sources of niacin are meat, poultry, fish and whole-grain cereals. 

Routes of exposure are oral and intravenous. It can also be given intramuscularly or subcutaneously but intravenous administration is recommended when possible. Dietary sources of niacin are green vegetables, eggs, milk, and other dairy products, legumes, yeast, whole grains, lean meats, liver, and fish. 

Davis, R. G., 1978, Increased bitter taste detection thresholds in Yucatan inhabitants related to coffee as a dietary source of niacin, Chem. Senses Flav., 3 423. 

Trigonellln 1-methylnicotinic acid, a metabolite of nicotinic acid or nicotinamide found in many plants. It is both a hormone and a storage form of nicotinic acid. It is apparently not a niacin metabolite in animals, although it is found in the urine of coffee drinkers. Green coffee beans contain relatively large (> 500 mg/kg) amounts of X roasting the beans converts T. to nicotinic acid. Coffee is a significant dietary source of niacin (see Vitamins) in South and Central America. 

The RDA for niacin is based on the concept that niacin coen2ymes participate in respiratory en2yme function and 6.6 niacin equivalents (NE) are needed per intake of 239 kj (1000 kcal). One NE is equivalent to 1 mg of niacin. Signs of niacin deficiency have been observed when less than 4.9 NE/239 kj or less than 8.8 NE per day were consumed. Dietary tryptophan is a rich source of niacin and the average diet in the United States contains 500—1000 mg of tryptophan. In addition, the average diet contains approximately 8—17 mg of niacin. In total, these two quantities total 16—34 NE daily. Table 5 Hsts the RDA and U.S. RDA for niacin (69). 

Good dietary sources of this vitamin are liver, kidney, lean meat, chicken, fish, wheat, barley, rye, green peas, yeast, peanuts, and leafy vegetables. In animal tissues, the predominant form of niacin is the amide. Niacin content of some foods are listed in Table 9-22. 

Niacin is present in tissues, and therefore in foods, iargeiy as the nicotinamide nucleotides. The postmortem hydrolysis of NAD(P) is extremely rapid in animal tissues, and it is likely that much of the niacin of meat (a major dietary source of the vitamin) is free nicotinamide. 

Cats, which have some 30- to 50-fold higher activity of picolinate carboxylase than other species, are entirely reliant on a dietary source of preformed niacin, and are not capable of any significant synthesis of NAD from tryptophan. 

Niacin (nicotinic acid and nicotinamide) is also known as vitamin B3. Both nicotinic acid and nicotinamide can serve as the dietary source of vitamin B3. 

Q-35 What is dietary requirement of Niacin and what are dietary sources of it ... 

Nicotinic acid is also known as niacin, and the deficiency syndrome pellagra occurs when dietary niacin is lacking. It is thought that about 15mg/day of niacin is needed for an adult. The main sources of niacin in the diet are tryptophan-containing proteins, like meats and foods that also contain nicotinic acid itself. However, a very small amount of tryptophan is included in corn. So, pellagra will occur frequently on a diet derived from corn as a main food. 

The main dietary sources of nicotinamide are meat, fish, and egg yolks. During World War II, when the restrictions mainly involved these substances, the primary sources of vitamin PP were bread, tomatoes, spinach, and fruit. Some cereals—rice, wheat, bran, and corn—have a low biological activity with respect to niacin activity because these cereals contain niacin in the form of niacinogen. The vitamin is not freed by the gastric or intestinal juices and is therefore not... 

There are numerous sources of niacin that are essential and these include poultry, fish (tuna, salmon), meat (beef), yeast, legumes, milk and fortified eereals. In addition, niacin is naturally occurring in tiny amounts and the human body can make nicotinic acid from the metabolism of dietary tryptophan (Vosper 2009). The body requires tryptophan for two main reasons (i) for the synthesis of niacin and (ii) to raise serotonin levels, which is essential for the regulation of sleep, appetite and mood. The vast majority of proteins contain about 1 % of tryptophan and it is suggested that approximately 100 g of protein intake a day will be sufficient to ensure optimum levels of niacin in the body. The recommended dose of niacin is higher when there is an increase in physiological states such as pregnancy and lactation. Importantly, the Committee of Medical Aspects of Food Policy (COMA) in the UK stated that the Reference Nutrient Intake (RNI) for niacin was 17 mg/day and 13 mg/day. 

Average intakes of tryptophan in Western diets will more than meet requirements without the need for a dietary source of preformed niacin. 

They are the major dietary source of vitamin B-12 and vitamin B-6, and they supply appreciable amounts of vitamin A, biotin, niacin, pantothenic acid, riboflavin, and thiamin. 

When considering sources of niacin, it should be noted that niacin can be, and is, synthesized by the intestinal flora. However, the amount produced is only of minor importance in the human. By contrast, as with thiamin and riboflavin, ruminants (cattle, sheep, etc.) have no dietary requirements for niacin because of bacterial synthesis in the rumen. 

PORK AS A FOOD. Pork is an important food and a rich source of many essential nutrients. An average 3.5 oz (99.4 g) serving of cooked pork ham provides 37 g of protein (that s 2/ 3 of the recommended daily allowance of protein) and 8.8 g of fat, along with being an excellent source of minerals and vitamins. Its high-quality protein contains all the essential amino acids needed to build, maintain, and repair body tissues. Pork is rich in iron, and the iron is readily used in the formation and maintenance of red blood cells. Also, pork is a major dietary source of the B vitamins, especially thiamin, riboflavin, and niacin. Also pork is about 98% digestible. 

As can be seen from Table 1, different types of foods differ considerably, not only in their total contribution to nicotinic acid equivalents, but also in the ratio of the contribution from preformed niacin and from tryptophan. In a typical Western diet, it has been calculated that if the 60 mg tryptophan = 1 mg niacin formula is applied, then preformed niacin provides about 50% of the niacin supply in the diet. In practice it seems possible for all of the niacin requirement to be provided by dietary tryptophan in Western diets. As is the case for the other B vitamins, meat, poultry, and fish are excellent sources of niacin equivalents, followed by dairy and grain products, but as noted above, certain grains such as maize, and whole highly polished rice, can be very poor sources and may be associated with clinical deficiency if the diets are otherwise poor and monotonous. 

NAD% the oxidized form of NADH, is a biological oxidizing agent capable of oxidizing alcohols to carbonyl compounds (it forms NADH in the process). NAD is synthesized from the vitamin niacin, which can be obtained from soybeans among other dietary sources. Breakfast cereals are fortified with niacin to help people consume their recommended daily allowance of this B vitamin. 

A 70-B. Although dietary niacin is the major source of the nicotinamide ring of NAD, it may also be produced from tryptophan. 

Red raspberries are one of the plant worlds richest sources of vitamins C and K, the essential mineral manganese, and dietary fiber. Contents of vitamin A (from seed carotenoids), B vitamins 1 through 3 (thiamin, riboflavin, niacin, respectively), iron, calcium, and potassium are also at good levels. 

Tree nuts can be good dietary sources (>10% of recommended dietary allowances [RDA] or adequate intake [Al]) of most vitamins except vitamins A and cobalamin (B,2). At suggested consumption level (1.5 ounces or 42.5g/day), acorn and pine nuts are excellent sources of folate and vitamin K (Table 2.7). In case of thiamin (Bj), niacin (B3), and pyridoxine (Bg), tree nuts offer alternative sources of these vitamins when more abundant animal sources are not available or are not consumed. 

Synthesis of NAD and NADP Is compromised in vitamin Bg deficient, see dietary sources fi>r niacin (Chapter 53)... 

In the organism that Is required In small amounts In food to sustain the normal metabolic functions of life. The key to this definition Is that this chemical compound must be supplied to the organism because the animal cannot synthesize vitamins. Lack of It produces a specific deficiency syndrome and supplying It cures that deficiency. An exception to this definition Is vitamin D, which can be made In the skin upon adequate exposure to sunlight. However, without adequate exposure, the animal Is dependent on a dietary source. Biotin, panthothenlc acid, and vitamin R are made by bacteria In the human Intestine, based on a symbiotic relation-ship and, thus, are not required by the human. Niacin can also be synthesized In humans from the amino acid tryptophane. 

Because tryptophan is a precursor of niacin and thus an additional source, dietary requirements for niacin are usually given in terms of total niacin or niacin equivalents. Niacin equivalent is the total niacin available from the diet including (1) preformed niacin, plus (2) niacin derived from the metabolism of tryptophan (60 mg tryptophan = 1 mg niacin). 

---