For people whose eyes are bigger than their stomachs, a big meal with lots of different tastes usually satisfies. But some foods do not go with others. When the mix is wrong, people will not be able to assimilate the nutrients in the food. Sometimes there are risks of more serious side effects.

Crabs and persimmons are a well-known example. When the two are eaten together, they cause diarrhea.

Li Hongyan, a senior nutritionist from Shanghai Tongmai Food Co Ltd, suggests that when mixing different foods, people have to look out for those that might result in bad reactions.

She offers some tips.

Category 1: Soybean and milk products

Bean curd and spinach

When bean curd and spinach are eaten at the same time, they affect absorption of calcium and may lead to blockages in the abdomen. Spinach contains oxalic acid, which can react with the calcium in bean curd in the intestines and form insoluble precipitates of calcium oxalate. The foods taken together affect the absorption of calcium.

Bean curd and green onion

The combination of bean curd and green onions may affect the absorption of calcium. Bean curd contains plenty of nutrition like protein and calcium. But green onions contain a great deal of oxalic acid. When calcium meets oxalic acid, the calcium oxalate they form destroys calcium. If one eats bean curd mixed with green onions over a long time, it can lead to a lack of calcium causing spasms, osteomalacia and fractures.

Milk and chocolate

Believe it or not, milk and chocolate do not match. While milk is rich in protein and calcium, chocolate contains oxalic acid. Eaten together, the calcium from milk and the oxalic acid of chocolate can combine and form insoluble calcium oxalate, which is not only indigestible but also can cause diarrhea.

Milk and pomelo

The protein in milk can react with the fruit acids in pomelos and make one's stomach feel bloated. The acid can also over-stimulate the stomach and cause diarrhea.

Lactic acid drink and ham

Many people like having a sandwich with yogurt. However, ham and bacon in sandwiches, when taken with yogurt, could cause cancer. To extend the preservation of meat products, producers add nitrate to prevent decay and botulinus. But when nitrate meets organic acid, it can turn into nitrosamine, a carcinogen.

Soy milk and egg

Soy milk contains nutrition including vegetable proteins, fats, carbohydrates, vitamins and minerals. If drunk by itself, it is very nourishing. However, if taken together with eggs, it can reduce the activity of protease, which helps the body assimilate protein. Eggs are, of course, very rich in protein.

Category 2: Meat

Mutton and vinegar

Mutton is a "hot" food, while vinegar is "warm" and like alcohol. When the two are cooked together, they can over-activate yang energy and the circulation. According to Compendium of Materia Medica, a book on Chinese herbal medicine, eating mutton and vinegar at the same time harms the heart.

Mutton and watermelon

Watermelon is a "cold" food. When taken together with mutton, the "heat," the nourishing effect of the mutton will be dramatically decreased. For those who suffer from asthenia of the spleen, it can harm their energy and upset the spleen and stomach.

Beef and chestnut

Beef and chestnuts are good for the stomach. However, chestnuts contains vitamin C, which can react with microelements in the beef and lessen the chestnuts' nutrition. The combination is not good for digestion and can cause dyspepsia.

Category 3: Seafood

Crab and tea

Some people might get used to drinking tea after eating crabs, thinking that it is good for the digestion. On the contrary it can cause indigestion. Gastric juices are diluted after drinking tea while eating crabs, and this not only disturbs assimilation but also reduces the ability of the gastric juices to sterilize. On the other hand, tea has as much tannic acid as persimmons.

Shrimp and vitamin C

If someone eats shrimps and also takes a lot of vitamin C on the same day, he or she is taking a serious risk. Shrimps contain a compound which reacts with vitamin C becoming the poison arsenic.

Catergory 4: Vegetable

White radish and carrot

The ferment in carrot can destroy the vitamin C in the white radish. To get the best nutrition, it is better to eat them separately.

Persimmon and sweet potato

Having persimmon and sweet potato at the same time can cause blockages in the stomach. The sugar in the sweet potato gets fermented in stomach, which increases stomach acid. Together they could even cause a gastric hemorrhage or gastric ulcers.

(Shanghai Daily February 24, 2009)