For sixteen years, the American Institute of Nutrition Rodent Diets, AIN-76 and AIN-76A, have been used extensively around the world. Because of numerous nutritional and technical problems encountered with the diet during this period, it was revised. Two new formulations were derived: AIN-93G for growth, pregnancy and lactation, and AIN-93M for adult maintenance. Some major differences in the new formulation of AIN-93G compared with AIN-76A are as follows: 7 g soybean oil/100 g diet was substituted for 5 g corn oil/100 g diet to increase the amount of linolenic acid; cornstarch was substituted for sucrose; the amount of phosphorus was reduced to help eliminate the problem of kidney calcification in female rats; L-cystine was substituted for DL-methionine as the amino acid supplement for casein, known to be deficient in the sulfur amino acids; manganese concentration was lowered to one-fifth the amount in the old diet; the amounts of vitamin E, vitamin K and vitamin B-12 were increased; and molybdenum, silicon, fluoride, nickel, boron, lithium and vanadium were added to the mineral mix. For the AIN-93M maintenance diet, the amount of fat was lowered to 40 g/kg diet from 70 g/kg diet, and the amount of casein to 140 g/kg from 200 g/kg in the AIN-93G diet. Because of a better balance of essential nutrients, the AIN-93 diets may prove to be a better choice than AIN-76A for long-term as well as short-term studies with laboratory rodents.

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AIN-93 Purified Diets for Laboratory Rodents: Final Report of the American Institute of Nutrition Ad Hoc Writing Committee on the Reformulation of the AIN-76A Rodent Diet

Human serum albumin: from bench to bedside.

The AIN-93 rodent diets were formulated to substitute for the previous version (AIN-76A) and to improve the performance of animals that consume them. They are called AIN-93G, formulated for growth, and AIN-93M, for maintenance. Major changes included substituting cornstarch for sucrose and soybean oil for corn oil and increasing the amount in order to supply both essential fatty acids (linoleic and linolenic). L-Cystine was substituted for DL-methionine to supplement the casein component. The mineral mix was reformulated to lower the amounts of phosphorus, manganese and chromium, to increase the amount of selenium, and to add molybdenum, silicon, fluoride, nickel, boron, lithium and vanadium. The amounts of vitamins E, K-1 and B-12 were increased over those in the AIN-76A vitamin mix. The AIN-93G diet contains 200 g of casein and 70 g of soybean oil/kg diet. The maintenance diet (AIN-93M) contains 140 g of casein and 40 g of soybean oil/kg diet. The 1993 diets have a better balance of essential nutrients than the 1976 diet and are better choices for studies with laboratory rodents.

Components of the AIN-93 Diets as Improvements in the AIN-76A Diet

Trace elements in human physiology and pathology: zinc and metallothioneins.

http://www.eedu.org.cn/Article/UploadFiles/200906/2009061916001277.pdf

Health risk from heavy metals via consumption of food crops in the vicinity of Dabaoshan mine, South China.

Because of nutritional and technical problems the AIN-76A rodent diet was revised. One of the new formulations was designated AIN-93G and was suggested for use during growth, pregnancy and lactation studies. Some major differences in this new formulation compared with the AIN-76A diet are as follows: 7 g soybean oil was substituted for 5 g corn oil/100 g diet to increase the amount of linolenic acid; the amounts of vitamins E and K were increased; cornstarch was substituted for most of the sucrose; the amount of phosphorus was reduced to eliminate the problem of nephrocalcinosis in female rats; L-cystine was substituted for DL-methionine; and the manganese concentration was reduced. Various developmental modifications of the AIN-93G diet were fed to weanling rats and mice to determine effects on growth and tissue mineralization. After rats were fed the developmental version of AIN-93G for 16 wk, body weights in both male and female rats were not different from those of rats fed a cereal-based nonpurified diet. After 13 wk, male mice fed this diet weighed 13% more than those fed the nonpurified diet. Body weights of female mice were not affected. The new diet formulation prevented kidney calcification in female rats and mice during 16 wk of feeding.

Development and testing of the AIN-93 purified diets for rodents: results on growth, kidney calcification and bone mineralization in rats and mice.

We believe greater consideration should be given the agronomic and nutritional/bioavailability factors that influence risk from Cd-contaminated soils. We have argued that the ability of rice to accumulate soil Cd in grain while excluding Fe, Zn and Ca (even though the soil contains 100-times more Zn than Cd) was important in adverse effects of soil Cd is farm families in Asia. Further, polished rice grain is deficient in Fe, Zn and Ca for humans, which promotes Cd absorption into duodenal cells. New kinetic studies clarified that dietary Cd is absorbed into duodenum enterocytes; 109 Cd from a single meal remained in the duodenum for up to 16 days; part of the turnover pool 109 Cd moved to the liver and kidneys by the end of the 64-day ‘chase’ period. Thus malnutrition induced by subsistence rice diets caused a higher absorption of dietary Cd and much higher potential risk from soil Cd than other crops. Because rice-induced Fe-Zn-Ca-malnutrition is so important in soil Cd risk, it seems evident that providing nutritional supplements to populations of exposed subsistence rice farmers could protect them against soil Cd during a period of soil remediation. In the long term, high Cd rice soils need to be remediated. Remediation by removal and replacement of contaminated soil is very expensive (on the order of $3 million/ha); while phytoextraction using the high Cd accumulating ecotypes of the Zn-Cd hyperaccumulator,Thlaspi caerulescens, should provide low cost soil Cd remediation.

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An improved understanding of soil Cd risk to humans and low cost methods to phytoextract Cd from contaminated soils to prevent soil Cd risks

The diet of approximately three billion people worldwide is nutrient deficient and most of the world’s poorest people are dependent on staple food crops as their primary source of micronutrients. One component of the solution to nutrient deficiencies is collaboration among plant breeders, cereal chemists and nutritionists to produce staple crop cultivars with increased mineral nutrient concentration. Sixty-three historical and modern wheat cultivars were evaluated for grain yield and concentration of calcium, copper, iron, magnesium, manganese, phosphorus, selenium, and zinc. While grain yield has increased over time, the concentrations of all minerals except calcium have decreased. Thus a greater consumption of whole wheat bread from modern cultivars is required to achieve the same percentage of recommended dietary allowance levels contributed by most of the older cultivars. The decrease in mineral concentration over the past 120 years occurs primarily in the soft white wheat market class, whereas in the hard red market class it has remained largely constant over time. This suggests that plant breeders, through intentional selection of low ash content in soft white wheat cultivars, have contributed to the decreased mineral nutrient concentration in modern wheat cultivars. These results contradict the theory that there exists a genetically based, biological trade-off between yield and mineral concentrations. Therefore, using the abundant variation present in wheat cultivars, it should be possible to improve mineral concentrations in modern cultivars without negatively affecting yield.

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Philip G. Reeves

Papers

AIN-93 Purified Diets for Laboratory Rodents: Final Report of the American Institute of Nutrition Ad Hoc Writing Committee on the Reformulation of the AIN-76A Rodent Diet

Components of the AIN-93 Diets as Improvements in the AIN-76A Diet

Development and testing of the AIN-93 purified diets for rodents: results on growth, kidney calcification and bone mineralization in rats and mice.

An improved understanding of soil Cd risk to humans and low cost methods to phytoextract Cd from contaminated soils to prevent soil Cd risks

Relationship between yield and mineral nutrient concentrations in historical and modern spring wheat cultivars