Latent poison in the food we devour
- Oxalate rich Indigenous Vegetables vis-à-vis kidney stones -

Senjam Jinus Singh *

Food is often seen the gracious gift of God. Unequivocally, the meiteis traditional cuisine engirds of multifarious delicious-vegetables dishes; most notable examples are sinju-bora, kangshoi, eromba, chagem-pomba and various others. Since time immemorial, to cinch our daily aliments, there are various indigenous vegetables which have always been dish out our tummy without foxiness—from hilly tribes to city kin alike. Ironically, when it comes to devouring, we do not realize what we eat as long as it is ambrosial. Things can get crappy, when the food we eat becomes the reason for our bodily dysfunction. But the realm of fact is vegetables often also contain many toxic substances and antinutritive factors, which are noxious for human health.

At first, it sounds like gibberish, but here are some of the vegetables which contain potentially harmful levels of the toxic compound. These toxic substances include oxalate acid (amaranthus-chengkrup), calcium oxalate crystal (acridity in colocasia-paan), tetracyclic triterpenoid cucubitacins (bitterness in cucurbits-cucumber, bottle gourd-khongdrum, pumpkin and melon. They are considered one of the healthiest vegetables but they can turn lethal, if bitter; drinking one or two glasses of fresh bottle gourd juice in the morning on an empty stomach is one such practice particularly in India.

However, the advisory council to the Department of Indian Alternative Medicines has suggested that a small piece of bottle gourd should be tasted before extracting its juice and if it tastes bitter it should not be used as juice to drink), saponin (spinach, soy bean, tomato), While tomatoes (the fruit) are non-toxic, atropine is present in the stems and leaves, solanin (do discard any potatoes that have green eyes, sprouts, or greenish skins, rather than prepare and serve them, especially to children), linamarin (lima beans-hawai apakpi/thampak), linustatin & neolinustain (in seeds of lotus), cyanogenic glucosides (cassava-umaangra), phytohaemagglutinin (kidney Beans-rajma), chaconine (potato naturally produced toxicant in green potatoes & gives the potato a bitter taste), trypsin and chymotrypsin inhibitor, amylase inhibitors, phytohemag-glutinins, cyanogenic glycosides, and perhaps saponins (winged bean-tenoumanbi), nelumbins (lotus-petioles, pedicels and embryo contains the alkaloid which acts as a cardiac poison), sinigrin (mustard-unpleasant smell in seeds pod and inflorescence-flowers), canavins (sword bean-debhi), cyanogenic compounds-linamarin and lotaustralis (lotus-thambal, from leaves, stem, flowers, root), piperine (black pepper), capsaicin (pungency in hot pepper, The neurotoxic effect of capsaicin in rats was investigated in a study by Sugimoto et al. in 1998.

Numerous fragments of DNA were seen in the neonatal rats, 18 to 24 hrs after capsaicin injection. For now the neural toxic effects found in neonatal rat suggests that capsaicin containing foods should not be given to children because of the potential damage to the developing neuroanatomy. A population-based, case-controlled study was conducted in Mexico City from 1989 to 1990 to evaluate the relationship between chili pepper consumption and risk for gastric cancer (Lopez-Carillo et al. 1994). Chili pepper consumption may be a risk factor for gastric cancer, but further studies are needed to test this hypothesis.

Although the debate continues over whether the affects of capsaicin are good or bad, many people currently use capsaicin as an herbal remedy), allyl isothiocynate (oil of mustard), tripsin inhibitors and lectin (taro-palukabi), vicine ( broadbean-hawai mubi, consumption of uncooked broad bean causes "favism", which is characterised by haemolytic anaemia, haemoglobinasia and jaundice), hamagglutinin, goitrogen (substances that cause goiters), tannins, phyto estrogens, flatus producing oligosaccharides (carbohydrates of small molecular weight that cause flatulence-gas), phytates (soy bean), saponins & tannins ( tree bean-yongchak, though these constituents are known to inhibit digestion and absorption in the ruminants, they could be removed through processing), bamboo shoots (soibum, soidon) of some species are known to contain cyanogenic glycosides (HCN), called taxiphyllin and are therefore very bitter. Different indigenous methods of reducing acidity/bitterness from fresh bamboo shoots has been reported, boiling in water/salt water and draining or keeping shoots in hot water for 10-15 minutes for a week at ambient temperature. The optimum cooking conditions that resulted in 97% reduction of HCN were 98-1020C for 148-180 minutes.

Depending on the concentration, such compounds may reduce the edibility, nutritional value, and health benefits of dietary vegetables. Properly cooking and / or other processing may be necessary to eliminate or reduce them. Even so, cooking has a relatively small impact on the oxalate content of foods. Repeated food chemistry studies have shown no statistically significant lowering of oxalate content following the blanching or boiling of green leafy vegetables. A lowering of oxalate content by about 5-15 % is the most we should expect when cooking a high-oxalate food. It does not make sense to overcook oxalate-containing foods in order to reduce their oxalate content. Because many vitamins and minerals are lost from overcooking more quickly than are oxalates, the overcooking of foods (particularly vegetables) will simply result in a far less nutritious diet that is minimally lower in oxalates. Despite of trifling results, a conscious effort should be taken to cut down foods that cause damage to our body.

Above all, the dietary intake of oxalate is of interest for several reasons. So, let us check over together tangibly about the vegetables which content high oxalate that we should conscious about them in our daily diets. Have you ever checked the oxalate content of your food? If you haven't, it's time to wake up. Eating high oxalate food exposes us to certain irregularities in some of the functions of our body. Since, consumption of foods high in oxalate results in a disorder of the urinary tract, commonly known as "kidney stones".

The kidneys are one of the most vital parts of our body. Malfunction of the kidneys due the blockage of urine by stones causes severe pain. If you have any kidney stones, your doctor or dietician may talk with you about an eating plan to prevent new stones. The most common types of kidney stones are calcium and oxalate. Each type may require a different eating plan. There are certain foods you can have, and other foods you should avoid, to reduce the chance that you will get kidney stone again.

Oxalate is an organic acid, primarily found in plants, animals and humans. The occurrence and distribution of oxalate vary enormously among the organisms. For instance, in plants the highest oxalate concentrations commonly occur in the leaves and the lowest in roots. It is not an essential molecule and is excreted from our body in an unchanged form. Our body either produces oxalate on its own or it converts other molecules like vitamin C — high in agathi (chuchurangmei-169mg/100g); Capsicum (shimla morok-137mg/100g), coriander leaves (phadigom-135mg/100g), king chilli (umorok-115.67mg/100g), broccoli (113mg/100g), cabbage (124mg/100g), chilli (111mg/100g) and tomato (31mg/100g of edible portion), Parkia roxburghii (yongchak-26mg/100) — to oxalate. Vitamin C is one of the substances that our cells routinely convert into oxalates. External sources like the foods we eat also contribute to the accumulation of oxalate in our body. The oxalate present in the body is excreted in our urine as a waste. Too much of oxalate in our urine, results in a medical condition called as hyperoxaluria, commonly referred to as kidney stones.

Vegetables can be divided fairly readily into those containing high concentration of oxalate acid and those containing small or negligible amounts. No close correlation was found between the oxalic acid content and the content of calcium, magnesium or phosphorous, although the concentration of calcium and magnesium tend to be high in those plants or parts of plants that contain large amounts of oxalate. Indeed, totally avoiding foods high in oxalate would be something next to impossible. Howbeit, care has to be taken to keep a check on the consumption of high oxalate foods. The oxalate amount should be restricted to 40 to 50 mg per day.

The following some list given and quantum in the parenthesis will help you to avoid certain oxalate containing foods. Food with an oxalate content exceeding 10 mg/100 g of the edible portion are spinach-palangshak (412mg), amaranths-chengkrup (280.62mg), amaranthus tricolor-chengkrup marangbi (131.4mg), sweet potato leaves-maangra (48.6mg), bitter gourd (26.631mg), wild lotus (20.88mg), okra-belendri (20.547mg), French beans-rajma (22.8-30.2mg), beetroot (121.0mg). Foods with oxalate content of 1-10 mg/100g; leek flower-tilhau (9.63mg), celery (9.504mg), luffa-shebot (7.866mg), chayote leaves-dashkush (6.03mg), lotus root-thambau (5.6691mg), chives-nakupi (4.05 mg), eggplant-khamen (3.51mg), wax gourd-torbot (2.7mg), chinese yam (2.691mg), carrot (7.4mg), tomato (5.3mg) etc. Spinach is a well known high oxalate vegetable; it belongs to the family chenopodiaceae. Another well known high oxalate food in this family is sugar beet. Many vegetables from the family Amaranthaceae are high in oxalate content.

The leaves and seeds of Amaranthus species are edible. Both Amaranthus and A. tricolor are high in oxalate content, and they are similar in appearance; the difference between them is that tricolor has purplish leaves. Maximum oxalate concentration is noticed in amaranth (742 mg). Bitter gourd (Karot akhabi) shows a high oxalate content. In taro (palukabi) tubers and leaves acridity is due to the presence of calcium oxalate crystal. Most of the cultivated varieties are free from acridity. However, it is best not to taste any variety raw. The acridity is destroyed by cooking. Vegetables with high oxalate content also include cucumber-thabi, green peppers-morok, parsley (salad crop) and greens of all kind. Withal, we should limit the use of condiments like black pepper, cinnamon (dalchini) and ginger.

Renal stones (kidney) have beset humans for centuries. Researchers have found evidence of kidney stone in 7,000 year old Egyptian mummy. Each year, worldly people make almost 3 million visits to health care providers and more than half a million patients go to emergency room with urolithiasis. Factors leading to initiation of calcium oxalate concentrations are still not known. In our state Manipur, a case study conducted in the Department of Biochemistry in collaboration with the Department of Urology, RIMS, Imphal was shown that urolithiasis was found to be most predominant in the age of group of 31-41 years comprising of 30.6%. It was observed that the higher incidence of urinary stones case in male (68%) than female (32%). Meanwhile, P.P. Singh et al., in their 196 stones analysis in Manipur showed calcium and oxalate were present in all the stones.

Comparatively little is known about the daily intake of oxalate, the proportion normally absorbed or the proportion of the urinary oxalate that is of dietary origin. Several extensive studies of the oxalate content of foods have been made within recent years, but the accuracy of the analytical procedure is sometimes open to question. Meanwhile, oxalate that a human body absorbs from food was thought to be an insignificant contributor to urinary oxalate excretion. However, many researchers indicated that dietary oxalate can provide up to 80% of the oxalate excreted. Some risk factors for stone disease are associated with a low calcium intake and dietary oxalate is believed to be an important contributing factor. An interesting fact to note is that, most leafy vegetables contain high levels of minerals such as calcium and iron, however, these minerals may not be readily available biologically due to the presence of oxalates which forms insoluble salts with the minerals and prevent their absorption in the digestive tract (small intestine). In addition, some of the oxalate in urine is made by the body. But eating certain foods with high levels of oxalate can increase the amount of oxalate in the urine, where it combines with calcium to form calcium oxalate stones.

For all of the above reasons, when healthcare providers recommend restriction of dietary oxalates to prevent calcium oxalate stone formation in individuals who have previously formed stones, they often suggest "limiting" or "reducing" oxalate intake rather than setting a specific milligram amount that should not be exceeded. Besides oxalate stone formation, high oxalate intake has other effects on human being. Small dose of oxalate in the body may cause headache, pain and twitching in muscle and cramps. Larger doses can cause a week an irregular heartbeat, a drop in blood pressure and sigh of heart failure. Large doses of oxalate can rapidly put a person in a shock life state, causing convulsion, coma, and possibly death. The mean lethal dose for an adult is about 15-30 g, but the lowest reported lethal dose is only g (70 mg/kg).

Of course, our region, being blessed with a variety of natural surrounding and varying climates, has a number of indigenous underutilized-vegetables, which are available seasonally, and practically no relevant information is available on the nutrient content and anti-nutritional factors, especially the oxalate content of such vegetables. So, if you have been bringing on foods that are listed as "high oxalate foods", it's time for some reality check.

In Shakespeare's one of the best-known plays, The Merchant of Venice, there is a famous adage: "All that glisters/glitters is not gold", from a secondary plot of the play, the puzzle of Portia's boxes. It's still doubtlessly conceded in every realm of life, therewith, when it comes to sporadically saying: "All that vegetables contain is not always edible or nutritious". Needless to say, think twice - or about a dozen times-before using the delicious-looking vegetables in any styles of partaking. For the food we eat today, will determines how salutiferous our society will be later on in life.