Vegetables are an important supplementary source of food and nutrition. Due to their wide adaptability and availability, vegetables can fit into cropping systems under diverse agro-ecological conditions. Thailand depends also to a large extent on the production of root and tuber crops, which contribute to food security as staple substitutes. The local diet comprises of the staple rice and an accompaniment of meat, seafood, fresh water fish and several vegetables. The latter provides bulk and fibre to the diet and supplies major nutrients. In times of crisis and natural disasters, vegetables can be produced for consumption within a short period of time to avert food deficit situations.
Vegetables as a food group constitute an important component of the Thai diet. They enrich the local diet with essential nutrients such as vitamins and minerals (Table 2).
Leafy vegetables such as amaranth, spinach and piper constitute good sources of iron and calcium, essential for the growth and development of bones and teeth, and to prevent iron deficiency anemia. Vegetables are rich sources of Vitamin A, B, and C, essential for the prevention of Scurvy and Vitamin B deficiency in the body. Dark, green leafy and yellow vegetables (sweet basil, carrot and awl tree) are rich in Provitamin A (Beta-Carotene) with the young shoots containing more than the mature leaves. Vegetables such as torvum eggplant and acacia shoot are rich sources of fibre in the diet. Although fibre is not considered as a nutrient and is not absorbed in the body, it is essential for normal digestion and satiety. Fibre is known to lower incidence of blood cholesterol levels, high BP, heart disease, diabetes, gallstones and colon cancer. It is also used effectively in diets preventing and treating obesity because of its bulk and low energy value.
In addition to the nutritional importance, vegetables provide variety and taste to everyday meals.
Table 2. Vegetables rich in vitamins and minerals (common English names, with Thai names in parents thesis)
(listed in decreasing order of amounts per 100 gm of edible portion)
Vitamin A above 7,600 international units (IU)
Awl tree leaves (yo baan), white basil (maeng lak), sweet basil (horapa.), carrot, coccinia (phak tamlueng), spinach (phak khom), sesban tree (khae baan), amaranth (phak khom nham). Asiatic pennywort (boa Bok), roselle (krachiap prieo), acacia shoot (cha-om), piper (chaa phluu), ipil-ipil (kra thin Thai), and Siamese cassia (kheelek).
Niacin (B-complex)-above 1.9 mg
Piper (chaa phluu), acacia shoot (cha-om), coccinia, and spinach.
Vitamin C-above 100 mg
Horseradish tree (ma rum), coriander (phak chee), Chinese kale (kha Na), hot pepper (prik yuak), spinach, and leaf mustard (phakkat khieo plee).
Calcium (Ca)-above 200 mg
Piper, amaranth, neem flower (sadao), awl tree leaves, sesban tree, water mimosa (phak krachet), sweet basil, and spinach.
Iron (Fe) -above 150 mg
Sesban tree/shoot, spinach, sweet basil, amaranth, white basil, neem flower, Chinese celery (kuen chai), and pepper mint (Sara nhae).
Many vegetables such as celery, eryngo and lettuce, add flavor and taste to bland dishes, making them more attractive and appetizing.
Some vegetables such as starchy roots and tubers are good sources of calories, and are often used as substitutes for staple grains. With the exception of legumes, vegetables are poor sources of protein. Soybeans (legume) contain as much as 20–40 percent protein and contribute a substantial intake of protein in the Thai diet. Legumes also contribute an inexpensive source of protein to diets, when meat and fish are very expensive. They have also been extensively used in alternative forms of medicine and health foods.
Vegetables also aid digestion due to the high fibre content and are believed to have therapeutic and medicinal benefits.
Over-cooking vegetables may destroy essential vitamins and minerals. For example, about 35 percent of Vitamin C is lost on boiling for ten minutes. Water-soluble Vitamin B is lost if water used for cooking is thrown away. Other vitamins like A, D, E, and K are also lost in varying amounts through the cooking process.
Figure 1. Kangkong : served with papaya salad, sticky rice
Thailand utilizes vegetables in different ways : the uncooked vegetables are commonly used as a side dish; cooked vegetables are often eaten as a side dish or mixed in stew with meat, fish and other foods; other variations include curried, fried, broiled or baked vegetables. During the festive season, some vegetables like parsley (from highlands), carrot, radish, onion and tomato are used as a garnish to decorate meat or fish dishes and may or may not be eaten.
A common Thai meal consists of rice, cooked vegetables, and a curry dish. Vegetables are often cooked with water, oil, coconut milk and sometimes wine, blanched and served with traditional chili sauces, and even eaten in the raw form. Chili sauce was believed to have been originally prepared with local bird peppers as the major ingredient rather than chili pepper or hot pepper. It is believed that foreign traders around the middle of the Ayutthaya period introduced the two latter types to Thailand.
A low-income meal consists of at least plain or glutinous rice, indigenous vegetables consumed with traditional chili sauces and dry fish or roast chicken. Most vegetables are consumed unprocessed. Canned, pickled and dehydrated vegetables are mainly used as ingredients in making soups.
The habitual Asian diet is cereal based, with an energy intake of 2 513 kilocalories, the average for Central and Southeast Asia, and 2 389 kilocalories the average for South Asia, amounting to over 60 percent of dietary supply (DES). The Thai diet in particular relies heavily on rice as the main source of calories and protein. Thailand's average per capita availability of calories was 2 351 kilocalories per day during 1994-96.
Like most developing countries in Southeast Asia, the majority of Thailand's under five-year old population is under-weight. In 1987 almost 25.8 percent of under five-year old children in Thailand were under weight, 22.4 percent were stunted and 5.7 percent were wasted. The average infant mortality rate (1995–2000) was estimated to be 3.0 percent (Table 3).
Table 3. Some population indicators affecting nutritional status (1995-2000)
| Country | Estimated population (1 000) 1997 | Average annual rate of change percent 1995–2000 | Infant mortality rate 1995–2000 | < 5 children suffering from (percent) | ||||
|---|---|---|---|---|---|---|---|---|
| Year of surveys | Sample size | Under weight | Stunting | Wasting | ||||
| Cambodia | 10 515 | 2.23 | 102 | - | - | - | - | - |
| Indonesia | 203 479 | 1.47 | 48 | 1987 | 28 169 | 39.9 | - | - |
| Laos | 5 195 | 3.07 | 86 | 1984 | 6 055 | 36.7 | 40.1 | 10.5 |
| Malaysia | 21 018 | 2.04 | 11 | |||||
| Myanmar | 46 765 | 1.8 | 78 | 1983–85 | 6 255 | 38 | 49.7 | 11 |
| Philippines | 70 724 | 2.02 | 35 | 1987 | 2 250 | 32.9 | 38.6 | 4.5 |
| Thailand | 59 159 | 0.76 | 30 | 1987 | 1 856 | 25.8 | 22.4 | 5.7 |
| Vietnam | 76 548 | 1.75 | 37 | 1987–89 | 7 044 | 45 | 56.5 | 9.4 |
Source : FAO, 1998.
The per capita consumption of vegetables in Thailand is lower than in other countries of the region. The general population is often unaware of the micronutrient content of foods, and as a result the most common nutritional deficiencies prevalent in the country are Vitamin A deficiency (VAD), Iron deficiency Anemia (IDA) and Iodine Deficiency Disorders (IDD). People need to be made aware of micronutrient food sources and advised towards making the right choice of food, food groups and food combinations, which will provide an essential ‘package’ of balanced nutrients.
Thailand has faced a micronutrient deficiency of varying degrees of severity. Though clinical VAD is not a problem in Thailand, sub-clinical deficiencies exist in many rural areas. About 17 percent of pre-school and school age children in the Northern province of Ubonratchathani, and 5.7 to 10.8 percent in the Southern provinces are estimated to exhibit sub-clinical symptoms of Vitamin A deficiency (Table 4 and 5). The prevalence of Vitamin A deficiency amongst preschool children varies within the provinces. The highest prevalence was reported in Pattani province (Table 5).
Table 4. Rates of VAD in pre-school children of Ubonratchathani province, 1977
| Vitamin A deficiency status | Prevalence |
|---|---|
| Normal (percent) | 13 |
| Low (percent) | 70 |
| Deficiency (percent) | 17 |
| Total | 100 |
Source : Wangthong, 1997.
Table 5. Vitamin A deficiency status among pre-school children in 5 provinces
| Percent prevalence in provinces | ||||||
|---|---|---|---|---|---|---|
| Status | Narathivat | Yala | Pattani | Song Khla | Satun | Average |
| Normal | 90.2 | 92.2 | 89.2 | 93.8 | 94.3 | 92.0 |
| Deficiency | 9.8 | 7.8 | 10.8 | 6.2 | 5.7 | 8.0 |
| Total | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
Source : Sinawat and Maleevong 1998.
Sub-clinical Vitamin A deficiency may be caused due to food insufficiency that stems from a reliance on i) purchased foods, ii) seasonal variations in food availability, iii) unstable food consumption patterns and iv) limited bioavailability of Vitamin A in foods consumed.
A possible factor in the etiology of VAD, apart from other factors, is the poor intake of green leafy vegetables and yellow-orange vegetables. Dietary food combinations, with the use of traditional cooking practices which have nutritional benefits in terms of improving micronutrient bioavailability, should be encouraged to prevent VAD.
In 1992, the assessment on iron deficiency anemia (IDA) in school children (6–14 years) by regions recorded the highest prevalence (20.9 percent) in the Northeast with an average prevalence of 18.3 percent in the country (Table 6). By 1993, the prevalence of IDA was reduced to 7.3 percent as a result of the School of Agriculture Lunch Project (Table 7), which provides school children with more access to food and vegetables in the daily diet.
Table 6. Assessment on iron deficiency anemia (IDA) in school children (6–14 yr.) by regions, 1988–92
(in percent)
| Region/Year | 1988 | 1989 | 1990 | 1991 | 1992 |
|---|---|---|---|---|---|
| Central | 23.4 | 12.7 | 16.7 | 17.0 | 12.6 |
| North | 26.3 | 19.2 | 18.4 | 15.9 | 16.1 |
| East | 24.5 | 25.1 | 16.6 | 19.7 | 18.7 |
| Northeast | 35.6 | 14.6 | 18.1 | 19.6 | 20.9 |
| South | 26.3 | 19.2 | 18.4 | 15.9 | 16.1 |
| Average | 27.3 | 16.5 | 18.6 | 19.0 | 18.3 |
Source : Wangthong, 1997.
Table 7. Iron deficiency anemia in school children under the School of Agriculture for Lunch Project. 1986–1993.
(in percent)
| Prevalence of Iron deficiency Anemia | 1986 | 1987 | 1988 | 1993 |
|---|---|---|---|---|
| 26.4 | 15.8 | 12.1 | 7.3 |
Source : Wangthong, 1997.
The lack of utilization of a suitable food combination is an important cause for the poor bioavailability of iron in diets. The Thai diet requires the incorporation of the right kind of food combination to promote iron absorption by the body. For example, a typical Thai meal consisting of rice, vegetables and spices will yield 0.16 mg of absorbed iron, but this can be doubled to 0.4 mg with the inclusion of fish. The inclusion of citrus fruits, sour fruits, and food rich in Vitamin C, such as tamarind, soy bean, fermented foods and fresh foods are also beneficial in enhancing the absorption of iron from the diet.
The share of fruits and vegetables in dietary energy supply (DES) in the region is shown in Table 8.
Table 8. Fruits and vegetables in percentage of total dietary energy supply (DES) in the Asian region, 1994–96 averages.
| Percent of DES by region | ||
|---|---|---|
| Food group | South Asia | Southeast Asia |
| Fruits | 2.7 | 2.8 |
| Vegetables | 1.5 | 1.1 |
Source : FAO, 1998.
The data indicates that the contribution of vegetables to daily per capita energy supply in South Asia is higher than in Southeast Asia. In the case of Thailand, vegetables contribute to the daily per capita energy supply next to fruits. The per capita availability of fruits and vegetables in South and Southeast Asia from 1994 to 1996 is shown in Table 9.
Table 9. Asian average daily per capita availability from fruits and vegetables, 1994–96
(in kilocalories)
| Food group | South Asia | Southeast Asia |
|---|---|---|
| Fruits | 65.70 | 68.25 |
| Vegetables | 35.00 | 30.00 |
Source : FAO, 1998.
Recent data on fruit and vegetable intake in Thailand is lacking. Research studies, on 60 home gardens in Thailand show that 230 different species of plants are available, and there is a need for sustainable farming and reliance on a wide range of crops, especially horticultural crops which are a good source of micronutrients.
The national nutrition survey (MPH, 1986) revealed that dietary intakes of micronutrients was generally adequate while calcium intake was inadequate. However, in view of the likely impact of the current economic crisis and the need to provide healthy diets and lifestyles as part of the FAO's mandate in improving nutritional status of the population, it is essential that vegetable and fruit consumption should be enhanced in the daily diet.
The FBDGs highlight the nutritional benefits of vegetables in alleviating micronutrient deficiencies and promote their daily consumption in the diet (MPH, 1998).
There is a need to promote dietary food combinations through the FBDGs developed for the region. Production of micronutrient rich fruits and vegetables for consumption is a priority, with an emphasis on local horticultural crops indigenous to the region e.g. leafy vegetables (all varieties of spinach, leaves of the horseradish tree, colocasia leaves, etc.), sweet tamarind, guava, papaya, mango and others. Various green leaves and plants, which are typically used in Thai diets such as coccinia (phak tamlueng), and which can be grown even in home gardens are a rich source of Vitamin A.
FBDGs should emphasize on developing food combinations, food preparation methods and traditional cooking practices that enhance nutrient intake and absorption. As part of the FBDGs in Thailand, certain practical suggestions have been given for the population to improve micronutrient intake in their diets.
A recommended dietary intake for Thai people is outlined below (MPH, 1986):
Eat a variety of foods from each of the five food groups and maintain proper body weight.
Eat an adequate amount of rice or alternative carbohydrate source.
Eat plenty of vegetables and fruits regularly.
Eat fish, lean meat, eggs, legumes and pulses regularly.
Drink milk in an appropriate quality and quantity for one's age.
Follow a diet containing appropriate amounts of fats.
Avoid sweet and salty foods.
Eat clean and safe foods.
Avoid or reduce the consumption of alcoholic beverages.
Fibres present in vegetables and fruits help the body to remove waste, eliminate carcinogenic compounds and reduce cholesterol levels. Raw vegetables such as carrots, green vegetables (including crucifers) and tomatoes are found to be protective against the risk of developing certain types of cancer. Substances that may also help include dithiolthiones, isothiocynates, indole-3-carbinol, allium compounds, isoflavones, saponins, phytosterols, lutein, folic acid, betacarotene, selenium, Vitamin E, flavonoids and dietary fibres. The FBDGs advise the population to increase vegetable and fruit intake in the diet.
