Thiamin , dietary sources

Thiamine was the first of the B vitamins to be identified, so it became known as vitamin B1. The absence of thiamine in the diet causes a disease called beriberi, which damages the heart and impairs nerve reflexes. In extreme cases, it causes paralysis. One major dietary source of vitamin Bj is the hulls of rice kernels (p. 1035). A deficiency is therefore most likely to occur when highly polished rice is a major component of the diet. A deficiency is also seen in alcoholics who are severely malnourished. 

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. 

On the other hand, the situation is now fairly clear with those substances which make an animal independent of dietary sources of at least several of the B. vitamins. The mechanism has been worked out best for starcih, sorbitol, and ascorbic acid, insofar as they spare thiamine, but there is no reason to suppose that the same mechanism does not apply also to the other carbohydrates and allied substances which produce the same effect and to the other vitamins which are spared. 

Microorganisms, fungi and plants synthesize thiamin but animals have to rely on exogenous dietary sources. In the absence of adequate thiamin intake, thiamin deficiency results in specific diseases. The typical thiamin deficiency syndrome in humans is beriberi, characterized by polyneuritis and paralysis of... 

Ascorbic acid is one of the most easily destroyed of vitamins, by heat and air. Destruction also seems to occur in the intestinal tract. As with thiamine and some other vitamins, the urinary excretion of ascorbic acid increases as the dietary intake increases so that there must be a point at which it is no longer economically sound to add it to the diet. Synthesis of ascorbic acid takes place in the bodies of most species man, monkeys, and guinea pigs need a dietary source. 

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. 

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. 

Thiamin is required by all species of animals. They must have a dietary source, unless it is synthesized for them by microorganisms in the digestive tract, as in the case of ruminants. 

We have in fact three reasons for adding nutrients to foods. First, we may restore all or some of the nutrients lost in preparation of the food, such as the thiamin lost in milling white flour. Secondly, we can add nutrients to a food that might reasonably be expected to contain them. Thirdly, we can use a food as a vehicle for nutrients when deficiency is likely. An example of the second is the addition of vitamins A and D to margarine, which would not otherwise contain them, because margarine is regarded as a substitute for butter, which is an important dietary source of them. Another example is the addition of vitamins A and D to skimmed cows milk as a food for children the addition of EFA will be mentioned later. 

Most foods contain a low concentration of thiamine. The most important dietary sources are Brewers yeast (1500%), pork (120%), whole wheat and other whole grains (70%) pork liver (60%), oatmeal (70%), peas (30%), asparagus (25%) and salmon (25%) (Fig. 26.3). 

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. 

Brazil nut contains small amounts of other minor bioactives and essential micronutrients such as essential minerals, phytic acid, dietary fiber, and thiamin. Brazil nut is an excellent source of magnesium, potassium, and calcium. 

Sources Dietary Reference Intakes for Calcium, Phosphorous, Magnesium, Vitamin D, and Fluoride (1997) Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin Folate, Vitamin B, Pantothenic Acid, Biotin, and Choline (1998) Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids (2000) Dietary Reference hitakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc (2001) Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (2002/2005) and Dietary Reference Intakes for Calcium and Vitamin D (2011). These reports may be accessed via www.nap.edu... 

---