Rubidium intake

The transfer of rubidium in the food chain from flora to fauna is without problems, as it was shown to occur in two species of herbivorous mice. On average, mice and voles accumulated 9 mg, and carnivores 5 rag Rbkg DM. The difference between both groups was highly significant and showed the different rubidium intake (Anke et al. 1997). 

In fact, beverages account for 45% of the rubidium intake of women and men with mixed diets in Europe, followed by vegetable foodstuffs (34%) and animal foodstuffs (21%) (Anke and Angelow 1995). 

In Germany, the rubidium intake of adults with mixed diet was investigated in 10 populations using the duplicate portion technique (Table 1.4-4). 

Tab. 1.4-4 Rubidium intake of German adults with mixed diets at different times ( Jgday )...

Despite apparently similar foodstuffs being available at all supermarkets, the location affected rubidium intake because of the different rubidium contents of drinking water. Notably, those people who drank rubidium-rich drinking water from rubidium-rich gneiss regions took in significantly more rubidium than those in other areas. 

On average, the rubidium intake of both sexes decreased by about 15% from age 20 to age 60 years, but body weight had no... 

Following consumption, rubidium is mainly excreted via the kidneys. The apparent absorption of rubidium was very high, at about 85%. During both examination periods, the rubidium intake of both sexes followed a Gaussian distribution (Figure 1.4-1). 

Anke etal. 1997b). Worldwide, the rubidium intake of adults with mixed diets was shown to range from 1.2 to 7 mg per day (Parr et al. 1992, Kavas-Ogli et al. 1995). 

A comparison of rubidium intake analyzed by the duplicate portion technique and calculated by the market basket method showed that, on average, the latter overestimates the intake by about 75% (Anke et al. 1997b). 

Tab. 1.4-6 Rubidium intake, excretion, apparent absorption rate and balance of people with mixed diets...

Evans WH, Read Jl, Caughlin D. 1985. Quantifications of results for estimating elemental dietary intakes of lithium, rubidium, strontium, molybdenum, vanadium and silver. Analyst 110 873-877. 

DOT CLASSIFICATION 4.3 Label Dangerous When Wet SAFETY PROFILE Moderately toxic by intraperitoneal route. A ver reactive alkaK metal (more reactive than potassium or cesium). In the body, rubidium substitutes for potassium as an intracellular ion. The ratio of Rb/K intake is important in the toxicology of rubidium. A ratio above 40% is dangerous. In rats, a failure to gain weight is the first symptom, followed by ataxia and hyperirritabihty. Symptoms include skin ulcers, poor hair coat, sensitivity, and extreme nervousness leading to convulsions and death. 

Anke M, Angelow L, Glei M, Muller M, Gunstheimer U, Rohrig B, Rother C and Schmidt P (1997a) Rubidium in the food chain of humans Origins and intakes. In Eischer PWE, U Abbe MR, Cockell KA and Gibson RS, eds. Trace Elements in Man and Animals-9. NRC Research Press,... 

Beverages provide humans with 28% of their magnesium intake, 27% of nickel, 24% of copper, 33% of strontium, 40% of uranium, 45% of rubidium, and 58% of vanadium consumption. Drinking water, home-made beverages (tea, coffee) and beer are important suppliers of inorganic body components. 

Rubidium is also incorporated into hen s eggs. Hens were found to excrete only 25% of their intake via the feces and urine (Sarudi et al. 1995). 

Rubidium retained in the tissues, as a result of either high dietary intake or from injections, is slowly lost from the body. Following intravenous administration of Rb, < 5% remained in blood for a long time while the elimination half-life of rubidium was found to range between 39 and 134 days (Nielsen 1986). 

Following the exhaustion of their rubidium stores, the feed intake of goats with a rubidium-poor nutrition decreased significantly (Anke et al. 1993) such that, on average, adult goats with rubidium-poor rations, when studied over six generations and with intrauterine rubidium depletion, consumed 16% less feed (see Table 1.4-7). 

Tab. 1.4-7 Influence of a rubidium-poor nutrition on feed intake, growth, reproduction, milk production and mortality of goats...

Kavas-OglyA, Luteuliaev F, Raeiev A, Onishchenko V, Abbasova B, Mamatkulov K and Rish M (1995) Bromine, rubidium and cesium intakes from self-selected diets by residents of the Samarkand oasis. Mengen- und Spurenelemente 15 735-740. 

Messiha FS (1978a) Cesium and rubidium salts ffects on voluntary intake of ethanol by the rat. Pharmacol Biochem Behavior 9 647—651. Messiha FS (1978b) Voluntary drinking of ethanol by the rat biogenic amines and possible underlying mechanism. Pharmacol Biochem Behavior 9 379-384. 

Metz R and Fanck AE (1978) Antlitz edler Steine, Mineralien-Kristalle. Chr Belser Verlag Stuttgart. Nielsen FH (1986) Rubidium. In Mertz W, ed. Trace Elements in Human and Animal Nutrition, pp. 431-434. Academy Press, Inc Orlando. Parr RM, Crawley H, Abdulla M, Iyengar GV and Kumpulainen J (1992) Human Dietary Intakes of Trace Elements A Global Literature Survey Mainly for the Period 1970-1991. International Atomic Energy Agency 12. 

The mean dietary intake for a normal Utah male has been calculated at 2.55 mg/day [39]. This is obviously influenced by diet, with different foods containing markedly variable amounts of rubidium. Soybean, containing 225 ppm, has one of the highest concentrations, with beef muscle (140 ppm), tomatoes (140 ppm), and ground coffee (89 ppm) also containing significant amounts [40]. At the opposite end of the scale, white bread, cheese, and onion contain only about 1 ppm [40]. The total human body content of rubidium is approximately 0.32 g [41,42]. 

Rubidium is eliminated only very slowly from the body with Rb studies showing urinary and fecal excretion to be 68% and 32%, respectively [43]. The daily excretion of rubidium is variable [44] and is dependent on the dietary intake of both rubidium and potassium. However, the urinary Rb/K ratio remains fairly constant [43,44]. This consistent ratio is further evidence of the metabolic relationship between rubidium and potassium. Overall when rubidium is administered orally as RbCl, its biological half-life ranges from 30 to 60 days [45-48]. 

Rubidium deficiency in goats reportedly results in depressed food intake and life expectancy, and increased spontaneous abortions. If rubidium is required by humans, the requirement probably would be no more than a few hundred micrograms per day, based on animal data. Rubidium is a relatively nontoxic element and thus is not of toxicological concern from the nutritional point of view. 

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