recently to ask a lot of media-related things oxalic acid in vegetables. The so-called oxalic acid, that is, a lot of spinach and vegetables caused Shibuya taste of a substance. Legend of the formation of calcium-binding it and precipitation, can cause kidney stones. The so-called spinach and tofu should not eat, should not mix the tofu小葱are using oxalic acid at said thing.
However, how many vegetables have oxalic acid in the end? What are the factors affecting the oxalate content in vegetables? Oxalic acid containing foods and eating tofu with work? I think if we want to solve these problems, we must also know what a good plant food products and the role of oxalic acid content.
what vegetables contain oxalic acid?
original, oxalic acid is a plant material which widely exist for improving plant resistance has important role. In other words, the oxalic acid content was high, while relatively strong resistance of plants. The study found that the vast majority of plants contain oxalic acid, so much more than just a few小葱spinach. The average concentration of oxalic acid up to plant dry weight by as much as 6 percent.
, however, the oxalic acid content of plants is still very large differences. For example, belong to the amaranth Amaranthaceae, Araceae belong to the taro, spinach Chenopodiaceae belong to, belong to Tetragonia Tetragonia Section (an emerging vegetables, supermarkets have to sell), belong to purslane purslane Branch and other vegetables with a high level of oxalic acid. Coriander and sweet potatoes are also many of the oxalic acid. And in general, the oxalate content of leaf vegetables is higher than other types of vegetables, melons, vegetables and oxalic acid content is relatively low, such as cucumber.
even the same type of vegetables, it's different varieties, cultivation of soil and climate conditions are different, oxalic acid content are also different. For example, in summer than in autumn spinach oxalate content of spinach; insufficient light or low temperature of the oxalic acid content of vegetables increased; wild plants of the oxalic acid content than the favorable conditions of cultivated plants high oxalic acid content.
vegetables in the relationship between oxalic acid and calcium
oxalic acid would hinder the body's calcium absorption, so people have put it as anti-nutritional factors to consider. For the high-oxalate vegetables is one of the calcium it is difficult to successfully absorb the human body, it is reported that in this kind of vegetables, vegetables contain calcium own only about 5% can be absorbed by the body.
so, even though the whole vegetables belong to high calcium foods (if by dry weight basis, the calcium content of vegetables is very impressive! ), but not every kind of vegetables can effectively assist the body calcium. For example, Brassica vegetables high calcium content, while the oxalic acid relatively small, such as small vegetables, cabbage, kale, etc., they are a good source of dietary calcium.
at life eat vegetables, the biggest natural Troublesome oxalic acid are spinach. From oxalic acid and calcium in terms of molar ratio, red beet root ratio was 5.1, spinach 4.3, 4.0 Tetragonia. Potato are 1.6, and 1.2 are amaranth, tomatoes are 0.6, cabbage and lettuce are around 0.1. That is why cabbage and lettuce category usually can be eaten raw vegetables reasons - they is not Shibuya, refreshing and delicious taste.
cocoa beans of the ratio of 2.5, also belong to a relatively high acid foods, this is the so-called "chocolate should not and drink milk together, otherwise the impact of calcium absorption, "the source of this statement.
oxalic acid content from the point of view, can not see how the "小葱should not mix the tofu," the theoretical basis.小葱because of the oxalic acid content of less than 20 mg / 100 grams, in the vegetables are lower. And amaranth content as high as 300 mg / 100 grams, no one seems to say "Can not fried tofu amaranth", we can see a lot of dietary taboos is relatively biased argument.
oxalic acid hazards and countermeasures
oxalate trouble, not only to affect the absorption of calcium, more people are worried about it cause stones. The study found that the oxalic acid in human urine about half comes from food. Oxalic acid in food absorption, the urinary excretion of oxalic acid also significantly increased. Substantial and long-term excretion of oxalic acid, may increase kidney stones (calcium oxalate stones) is dangerous.
oxalic acid and may even damage the digestive tract surface organization, caused by the human body does not. For example, eating kiwifruit, people will feel a sense of oral irritation. Except one of the protease decomposition outside the oral mucosa, the role of oxalic acid crystals also stabbed one of the reasons why. Excessive intake of oxalic acid also may cause damage to the digestive tract, and even kidney damage.
However, the modern diet which does not like the Red Army as吃糠咽菜, vegetables also reduce the total , therefore dietary intake quantity of oxalic acid with 20 years ago, there is a gradual downward trend. Even the latest research suggests that oxalic acid in plants are an important antioxidant component, if there is enough dietary calcium, the general quantity of oxalic acid intake is not caused by calcium deficiency and stones As for questions.
some survey also found that calcium intake and the incidence of kidney stones showed a negative correlation, therefore, often eating rich calcium in food, is to reduce the occurrence of kidney stones important dietary measures. People at a lot of imagination, rich in oxalic acid in spinach and tofu with cooking should not be afraid of their combination of calcium oxalate, causing the body stone. Go by the logic will be able to consider that truth just the opposite, it should be at the same time to eat vegetables eat more soy products, sesame, milk and other calcium-rich foods, since oxalic acid and calcium in pot combination of precipitation, or in the digestive tract resulting combination of precipitation, it will reduce the absorption of oxalate. - U.S. intestine, are unable to absorb precipitation status of the material.
If some out-dated in accordance with the recommendation to eat low calcium diet, put food rich in calcium and oxalate completely separate not to create more opportunities for the oxalic acid was absorbed into the human body! Food processing study found that use of calcium chloride and other calcium salts to soak vegetables, can effectively reduce the human body can absorb the volume of the Soluble oxalate, the reason being used to advance the solution to precipitate calcium oxalate, so that the human body to reduce oxalate absorption.
as long as the proper processing of cooking vegetables can be put down to the oxalic acid is not hazardous to health level. Domestic and foreign studies have found that after treatment cheuk hot soup go disposable, can effectively reduce the oxalate content in vegetables, reduce the rate at 30% ~ 87% between. However, after hot-cheuk whether the number of oxalic acid can be removed, but also their own vegetables or not a firm texture. For example, spinach leaves and soft, the removal rate can be as high as 50 ~ 70%; and Swiss chard leaves and hard, the removal rate of less than 40%.
so, in order to reduce the oxalic acid in vegetables brings trouble, should be guided by three principles:
1 All astringency heavier vegetables, the best-cheuk hot boiling water and then consumed.
2 astringency not to drink the soup, even inside the dissolution of vitamin A LITTLE, then do not have to pity.
3 substantial astringency eat leafy vegetables at the same time, it should be an increase in dietary intake of calcium-rich food, it is best able Taken together with consumption, to reduce the body's absorption of oxalate, thereby reducing the risk of calcium oxalate-type kidney stones.
References:
1 Ying-Peng Zhang, etc., plant body and its control measures against oxalic acid, Anhui Agricultural communications, 2007,13 (10) :34-39
2 Chai W. et al. Effect of different cooking methods> 3丁健桦such as, HPLC determination of oxalic acid in vegetables by the interference method of treatment, food science, 2005,26 (12) :172-175
4 Zhou Jian-lie, calcium supplements can prevent kidney stones happen evidence - read New England Journal of Medicine thesis Jackson and others experiences. Chinese Journal of Clinical Nutrition, 2006 (3): 198 -- 201
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