Plants, in their green leaves, bring together carbon dioxide from the air, water from the soil and the energy of sunlight to form the simplest form of carbohydrate called glucose. The chlorophyll in the green leaves serves as a catalyst for this reaction.
By this reaction, the energy of sunlight is stored in the carbohydrate which the plant uses and is obtained by animals when the plant is consumed by them. It is this same energy of sunlight in carbohydrates that we get when we eat plants or animals.
In other words, the energy you and I use to move around every day originates from the sun.
Carbohydrates exist in various natural forms such as Glucose, Fructose, Sucrose, Lactose (milk sugar) produced by lactating animals, Starch, Cellulose, Hemicellulose, Pectin, Gums and Mucilages.
In a more complex way carbohydrates can be split into Monosaccharides, Disaccharides, Oligosaccharides and Polysaccharides; Glucose and Fructose are monosaccharides.
Finally carbohydrates can also be divided into Sugars (Glucose, Fructose, Sucrose, Lactose); Starches and Fibres (Cellulose, Hemi-cellulose, Pectin, Gums and Mucilages).
Foods rich in carbohydrates are table sugar, honey, jam, jelly, potatoes, cornflakes, rice, bread, yam, cassava products, fruits, vegetables, pasta, plantain, millet, wheat products, peas, fat-free milk, oats, beans and many others. Foods which do not contain carbohydrates include beef, eggs, chicken, fish, vegetable oils, butter and margarine.
The main use of carbohydrates is provision of energy.
As said above there are three main forms of carbohydrate:- sugars, starches and fibres. The energy derivable from food eaten depends on the type of carbohydrate contained in the food; the more simple carbohydrate in the food, the more the energy derivable. Thus food containing more fibres will give less energy, while food containing more sugars will give more energy. If the energy produced is more than the amount required by the body, the liver will cover the excess into glycogen for storage in the liver and the muscle cells and into fatty acids for storage in the adipose tissue which can lead to obesity.
The source of carbohydrate is therefore very important for weight maintenance and in the management of diabetes. The diabetic needs carbohydrates for energy and so must choose what will give the required energy but still feels full.
The foods discussed here are readily available in the Tropics; I have left out Quinoa which is quite healthy but expensive and not readily available. The writer takes it regularly.
1. Sweet Potatoes
Sweet potato is a root vegetable with origin in South America; from there it spread to Polynesia, Australia, Hawaii and thence to the rest of the world. It is called yam in some parts of the world although the real yam and sweet potato are quite different. Sweet potato is also different from the common potato (Irish potato) though slightly related.
Sweet potato grows very well in tropical and warm temperate climates where there is enough rain to nourish it; the tubers mature in two to nine months.
Of the carbohydrate sources available in Nigeria and most of the tropics, sweet potato is the best.
It has about 21 percent of carbohydrate comprising starch, sugars and fibres; more importantly it has only 86Kcals of energy in every 100gram weight, it is therefore difficult to obtain excess energy even if you consumed 1000grams of sweet potatoes in one day.
Sweet potato has 2 percent protein, lots of Vitamin A, B5, B6 and C and minerals; 3 percent of sweet potato is fibre.
Sweet potato is therefore a very healthy source of carbohydrate.
The biggest producer of sweet potato in the world is China followed by Uganda and Nigeria
Like sweet potato, yam is a root vegetable; unlike sweet potato it contains little sugar so the taste is starchy, It can grow to be in exceptional cases quite large (70 kg) and long (5 feet), the tuber is usually covered with rough skin; colour varying from brown to purple.
Yam is native to Africa and Asia; Nigeria is the biggest producer of yam in the world
Yam is a very healthy source of carbohydrate, it is 27.5 percent carbohydrate, 4 percent fibre, 1.5 percent protein, fat-nil, and sugar—0.5 percent. Yam is rich in Vitamins B6 and C and some minerals (Manganese and potassium). The energy in 100 grams of yam is 118Kcals, while the daily recommended calorie from carbohydrate in the average adult is about 1200Kcals; imagine how much yam you have to eat to get there.
In the line of preference, yam is number 2.
3. Green Plantain
Green plantain belongs to the banana family but unlike the common banana it has to be cooked before eating. It is slightly bigger than banana but contains less sugar. Its origin is in the Oceania and Southeast Asia but it now very common in West Africa and the Caribbean.
Mature (yellow) plantain is softer, its skin is easier to remove but contains more sugar, it is usually fried, baked, boiled or grilled.
Green plantain is a healthy source of carbohydrate; it has about 32 percent carbohydrate comprising about 15 percent sugar, 15 percent starch and 2 percent fibre. It is also very rich in potassium, vitamin A and Beta-carotene, a precursor of vitamin A. The total energy in 100 grams of green plantain is only 120Kcals; to exceed the daily maximum energy from carbohydrate of about 1200Kcals, you need to eat about 1000grams of green plantain a day.
Green plantain can be boiled, fried, baked or grilled; it can also be blended and prepared like semolina; Diabetics to take note. Plantain grows all year round and so is staple food to much of the Tropics.
In the line of preference, green plantain is number 3.
4. White garri
White garri is made from cassava; the latter is a root vegetable widely cultivated in the tropical and sub-tropical regions of the world for its rich starch content. Its origin is South America from where it apparently spread to the rest of the world.
When dried and ground into powdery form it is called Tapioca but when fermented and ground into semi powdery form and fried it is called garri. White garri has no added palm oil hence it is a healthier source of carbohydrate than yellow garri.
White garri is 38 percent carbohydrate, fibre-1.8 percent, very little protein and fat; its energy content in 100 grams is 160 Kcals. It is poor in vitamins but moderately rich in the potassium.
To exceed the daily energy requirement you will have to consume a lot of garri; diabetics should consider that.
Cassava is the fourth biggest supplier of energy source to the world after rice, wheat and maize.
Nigeria is the biggest producer of cassava in the world
The bean seed is a legume consumed by man and animals. It is a healthy source of carbohydrate as it is 21.5 percent carbohydrate ( fibre 5.5 percent), 21 percent protein, it is also rich in vitamins and minerals. It contains 155 Kcals. of energy in 100 grams, hence it is beneficial to diabetics.
6. Wheat products
Wheat bread, Semolina, Spaghetti and Macaroni are some of the wheat products common in the market.
Of the lot, semolina has the highest amount of carbohydrate—72 percent with 360 Kcals in 100 grams, it is not a healthy source of carbohydrate for diabetics.
Wheat bread on the other hand is 47.80 percent carbohydrate but has 267 Kcals of energy in 100 grams. Its fibre content is 4 percent but it is 5.91percent sugar.
Spaghetti and macaroni are 43 percent carbohydrate with only 220 Kcals of energy in 100grams but have very little sugar.
Thus of the wheat product s mentioned above, pasta (macaroni and spaghetti) is the healthiest source of carbohydrate.
7. Quaker Oats (oat meal)
The oat plant, Avena sativa, a cereal plant, originated in the near East but it now a temperate plant; it is grown in Europe on annual basis. The plant produces seeds called oats which are consumed by man and livestock in various forms. Oat seeds can be crushed into oatmeal which is served as breakfast cereal or ground into flour which can be prepared in various forms similar to semolina.
Oat is rich in carbohydrate (67 percent), protein (17 percent), fat, minerals and vitamins.
Energy derivable from 100 grams of oats is 367Kcals which is quite high but then oats contain soluble fibre which reduces absorption of cholesterol in the gut. Because of the fibre, one feels full easily thus limiting volume consumed. Oatmeal is therefore considered healthy.
Rice is a cereal grain like wheat, oat, barley, rye and corn; it is grown in most parts of the world but mostly in the far-east. It is the staple food in India, China, and several other countries in South-east Asia.
Today, it is the most widely cultivated crop after sugar cane and maize.
Rice provides about 20 percent of energy consumed globally, superseding wheat (19 percent) and maize (5 percent).
There are several varieties of rice—white, brown, red and black.
Cooked white long grain parboiled rice is about 73 percent carbohydrate yielding about 333Kcals in every 100grams consumed. It is low in vitamins and minerals.
Cooked brown rice is about the same in carbohydrate and energy but has minerals, vitamins and little fibre.
Millet is a cereal produced by seeded grasses that grow in semiarid parts of the world, particularly in Africa and Asia. There are several varieties of millet but Pearl and finger millets are the ones found most in Africa. Millet is a very old crop with history dating back as far as 10,000 years. The earliest place millet (pearl) was grown in West Africa is Mali and that was 2500BC
Millet grows in very difficult climate but yield is much better with fertilizers; India is the largest producer of millet in the world followed by Nigeria and Niger Republic
Millet is a healthy source of carbohydrate, it is 71 percent carbohydrate (starch, very little sugar and 8.5 percent); it is 11 percent protein and fat—4.5 percent. It is also rich in vitamins and minerals. However it is high in energy, about 378 Kcals in 100 grams.
On millet, one can easily take in more energy than required on daily basis.