Yin, yang and why hot food can cool

Suffering from indigestion? Instead of popping a pill, chewing on a chalky tablet or chugging a viscous liquid, wouldn't you rather tuck into a dish of delicious sliced radish fried with garlic paste or sip a steaming hot cup of fragrant ginger tea?

In traditional Chinese medicine, all foods can have therapeutic benefits for the body, and the lines between an edible item's nutritional and medicinal properties are often blurred.

Knowing how to harness food's medicinal powers can yield significant health dividends.

Professor Lin Zhixiu of Chinese University's School of Chinese Medicine gives credit for Hongkongers' relative longevity and good health in part to a general understanding among the Chinese population of how to use food therapeutically.

'Hongkongers really pay attention to the foods they eat and often incorporate Chinese herbs into their diet,' he says.

'This practice helps strengthen their immune system, ward off minor infections and strengthen their qi and digestive system.'

Michele Ong, 37, is a believer in the therapeutic power of food.

'My grandmother and mother often made nourishing soups for me when I was feeling tired and prepared cooling teas when the weather was too hot,' she says.

'They also told me what food to avoid when I had a bit of a sore throat or if I had to stay up late to study or work.

'As a result, I rarely fell sick, even as a child.'

Food therapy is a particularly useful approach for the very young, very old, and pregnant or lactating women who may not tolerate medicine or other therapies as well as others, says Dr Dang Yi, associate director of the master's programme in personal health management (Chinese medicine) at Baptist University's School of Chinese Medicine.

She adds that those who are recovering from an illness, suffer from chronic conditions or have subclinical health problems - that is, are not diagnosed with an illness but do not feel well - benefit greatly from a diet tailored according to the therapeutic properties of food.

The medicinal function of food was documented at least two millennia ago in Chinese medical classics such as the Yellow Emperor's Internal Classic and the Divine Farmer's Materia Medica, Lin says.

Instead of focusing on the nutritional value of food, Chinese medicine characterises food as having four natures (hot, warm, cool and cold) and five flavours (sweet, salty, sour, bitter and pungent).

The hot or cool nature of food does not refer to the temperature of the food but to the type of energy that it generates within the body after consumption.

For instance, green tea may be drunk hot, but the body feels cool afterwards, so it is considered a cool beverage. Mutton generates a great deal of heat energy within the body after consumption and hence is considered a hot food.

Each of the five flavours of food is thought to have a specific effect on the body. They correspond with the five organ systems (liver/gallbladder, heart/small intestine, spleen/stomach, lung/large intestine and kidney/bladder), and help each system to function better.

The application of food's medicinal properties is then guided by foundational theories in Chinese medicine such as yin/yang and the five element theory, all with the aim of achieving balance and, therefore, health.

Perhaps the easiest of these theories to grasp is that of yin and yang, where yin embodies qualities such as passivity, cold, dark and the feminine while activity, heat, light and masculine qualities characterise yang. Yin and yang exist in relation to, and mutually counteract, each other to achieve a dynamic balance.

They are present in and characterise all things, including the inherent nature of food, the weather and the human body.

So health and balance can be achieved by eating the right types of foods at the right times of the year, according to the condition of one's body.

Lin explains that yin foods are those that generate cold or cool energy in the body, such as watermelon, bitter gourd, crab and most green vegetables.

Yang foods, such as red meat, ginger, pepper and garlic, generate warm or hot energy.

If you're experiencing a heat syndrome (excessive yang in the body) and have symptoms such as a rapid pulse, a red tongue with yellow coating, flushed face, thirst, irritability, fever, yellow phlegm and constipation, and excrete scanty, yellow urine, take yin foods that generate cool or cold energy in the body to counteract the excessive heat, says Lin. Chow Yuen-pin, a Chinese medicine practitioner, says to avoid foods like mutton or chicken.

Conversely, Lin says, if you have a cold syndrome (excessive yin in the body) you may experience diarrhoea or loose stools, stomach pains that are relieved by warmth or pressure to the abdomen, a pale complexion, a pale tongue with white coating, an aversion to cold or feeling cold, white or clear phlegm and copious amounts of light-coloured urine. Treat this by consuming yang foods. Dang suggests avoiding cold drinks and green tea, which have a very cooling effect.

Eat foods appropriate to the weather. During winter, eat more warming foods to build up the yang energy in the body. During summer, eat more yin foods to maintain balance internally.

When Stephanie Lau's children start to show signs of being too hot, or yang, she will boil tea made from dried chrysanthemum flowers, barley or water chestnut, which have a cooling effect.

'After drinking the tea, their lips will quickly return to a normal colour, and they start feeling more comfortable again,' says Lau, 39. When her children have a cough, she avoids giving them chicken, which is supposed to make a cough worse.

Although observing general guidelines for eating correctly is helpful, it is also important to consider one's personal body type or constitution. Chinese medicine has identified nine types of constitution, including yang type, yin type, heat-deficient or blood-deficient, and diet can be used to correct imbalances in each type.

Dang advises consulting an experienced Chinese medicine practitioner to have a proper assessment of your body type and condition in order to obtain the right advice on the appropriate foods and food combinations to consume for optimal health.

'Soups and tonics are all very good, but you must take the right ones for your body type, or you could inadvertently create more problems for yourself,' Dang says.