Manic depressive psychosis in India and the possible role of lithium as a natural prophylactic. II--Lithium content of diet and some biological fluids in Indian subjects.
Trace elements are known to influence a number of biological processes.  The possible role of lithium as a trace element in human nutrition and in the pathogenesis of certain diseases is presently under investigation. Information regarding the lithium content of articles of food and the daily intake of lithium in Indian subjects is limited. Lithium intake is likely to be affected by such factors as dietetic habits, type of drinking water, and soil content of this element. Such differences in intake may be responsible for the epidemiological differences observed in the incidence of manic depressive psychosis (MDP) and atherosclerotic heart disease (AHD) in different populations. The present study describes the result of estimation of lithium which was found to be present in articles of food commonly used in an Indian diet. The lithium content of serum, urine, and other biological fluids in healthy Indian volunteers is also reported.
Vegetables, fruits, spices, pulses, cereals and nonvegetarian dietary articles were purchased from the local market. The edible parts of these food items were dehydrated in an oven at 110°C and the loss in weight was determined. The dehydrated samples were crushed into a homogeneous powder with a grinder. Five to 10 gins. of the dry powder was taken in a silica crucible and ashed at 450°C in a muffle furnace for 24 hours. The ash was dissolved in 5.0 ml of 12 N hydrochloric acid and heated to dryness. The residue was dissolved in deionized water, filtered in the flask and the volume of the filtrate made up to 10 ml.
Drinking water samples were analysed according to the method described by Soman et al.
For the estimation of dietary lithium, a 24 hour cooked food sample prescribed as a full diet for inpatients in K.E.M. Hospital, Bombay was collected. This consisted of all the daily food items except drinking water. Both vegetarian and nonvegetarian diets with similar caloric values were collected for three successive days and analysed.
Serum, urine and seminal plasma samples were obtained from healthy medical student volunteers and doctors attending at the general hospital. Cerebrospinal fluid samples were obtained from patients admitted for minor disorders not known to affect the nervous system and having no psychiatric symptoms.
The quantity of lithium in the samples was estimated by a Perkin-Elmer (Model 303) Atomic Absorption Spectrophotometer (AAS). The recovery tests were carried out by adding known amounts of lithium to 11 samples, and estimating the total amount of lithium which was present before and after addition. The mean recovery was 103.4% with a range of 92-112%.
Lithium content of food:
The results of analysis of various articles of food are shown in [Table - 1]. Amongst the various leafy and non-leafy vegetables which were analysed, coriander leaves, tamarind, tomato and garlic had high amounts of lithium; while onions, green chillies, and vegetables like cauliflower had little lithium. Spices such as nutmeg, cummin seeds and coriander seeds had high lithium content. The lithium content was high in various cereals and pulses like pearl-millet, black-gram, and chawli seeds; while rice and wheat contained very little lithium.
Lithium content was also found to be high in rock salt and commonly used crude sea salt as compared to refined table salt.
The highest amount of lithium (12 µg/gm) was detected in tobacco.
The lithium content of water varied according to the source. Tap water supplied to Bombay city had a low lithium content as compared to spring water from a nearby village which had twice the amount of lithium, probably because the water supplied to Bombay is mostly soft rain water which collects in catchment reservoirs and contains less minerals.
Daily dietetic intake of lithium in Indians:
The report of the Indian Council of Medical Research describes the average values of elements in various food items per capita daily intake. The average per capita daily intake of lithium was estimated using this data, and the data showing the estimated mean lithium content of various dietary articles [Table - 1]. This daily intake of lithium was found to be 74 µg. In order to test the validity of this indirect estimate, both vegetarian and nonvegetarian diets were analysed for three successive days for their lithium content. The mean lithium content per day of the nonvegetarian diet was 135.4 µg with a range of 118.5-152.0 µg, while it was 75.8,ug with a range of. 69.95-80.0 µg for the vegetarian diet. [Table - 2]. This compares well with the average per capita daily intake values of various food items as described by the I.C.M.R. when approximately 2.6 µg of lithium per day obtained from the city water supply was added to the previous values, the daily intake of lithium in our subjects was found to be between 72.55-154.6 µg.
Serum lithium levels:
Serum samples obtained from 13 healthy volunteers between 20 and 35 years of age and consuming normal daily diet were studied for lithium content. The serum lithium values varied between 0.014-0.072 m. equiv./1. with a mean of 0.029 m. equiv./1. ± 0.025 (S.D.).
Urinary excretion of lithium:
The 24 hour urinary excretion of lithium was estimated in 8 healthy volunteers. The total daily urinary output of lithium varied between 34-201 µg. Both vegetarians and nonvegetarians showed a wide variation in lithium excretion, an(I there was no correlation with the type of diet consumed. The mean value for the amount of lithium excreted in 24 hours urine sample was 78.4 µg ± 55.60 (S.D.).
Lithium in C.S.F.:
Out of 20 samples of cerebrospinal fluid which were analysed, 15 samples did not show any lithium indicating negligible lithium content. Only 5 samples showed levels varying between 0.02-0.08 µg/ml.
Lithium in seminal plasma:
Analysis of 10 semen samples from normal individuals showed lithium value between 0.154 and 0.280 µg/ml.
Lithium content of human milk:
The mean content of lithium in 10 samples was 0.155 µg/ml with a range of 0.1-0.25 µg/ml.
Lithium as a trace element has assumed recent importance because of its role in the treatment of manic depressive psychosis, and in the genesis of atherosclerosis and goitres. Very little is known regarding its daily intake in various populations. One study from the West estimates that the daily lithium intake is 0 to 45 µg. The results reported here suggest a higher intake of lithium in Indians although the two studies may not be strictly comparable. Differences in dietary habits probably account for this. The large amount of lithium in the Indian diet is derived from cereals, pulses, spices and the type of salt used in cooking. Majority of Indians consume crude sea salt or rock salt which contains more lithium than refined table salt which is used in Western countries. The source of water supply also contributes to daily lithium intake. Water from rural wells or springs is likely to have a higher content of lithium than purified soft water. A very high amount of lithium is present in tobacco. Chewing or eating tobacco, by itself or with betel nuts and leaves, is common in India and this will add to the lithium intake.
Serum contains very little lithium, and in some samples of cerebrospinal fluid, lithium could not be estimated by AAS, which is perhaps the most sensitive method available at present. Endogeneous serum lithium levels in various psychiatric disorders do not seem to have any diagnostic value (unpublished data). It is possible that the tissue level of lithium and its daily turnover are physiologically more important than the serum level. Earlier studies have demonstrated the presence of lithium in various biological tissues. Lithium has important effects in many different organ systems, particularly those involved in ion transport and polypeptide hormone action, and it is also an effective therapeutic agent in manic depressive psychosis. There is a vast difference between the large amounts of lithium required therapeutically and the small amount of lithium which is consumed regularly in the diet. Little is known about the role of lithium intake in low doses as supplied from the diet in contemporary metropolitan health. It is possible that the epidemiological differences in diseases such as AMP among various population may be related to the dietetic intake of lithium. It is realized that the present study was carried out in the subjects from Bombay and the cooked food analysed was obtained from a general hospital in Bombay. Food habits are known to vary from state to state and from class to class and no generalised conclusion can be drawn from the above data for the entire population of India. The need for further work in this field is obvious.
The authors thank Shri S. D. Soman, Head, Health Physics Division, Bhabha Atomic Research Centre, Bombay 400 074, for providing facilities to carry out this work.