Adolescence is the stage between childhood and adulthood. It is the period of life starting with the appearance of secondary sex characteristics and ending with the cessation of somatic growth. This is one of the most challenging periods in human development due to the rapid and uneven growth.

Puberty marks the beginning of adolescence. It is initiated by physiologic factors and includes maturation of the total body. The onset of puberty usually takes place at age 8-13 in girls and 9.5-13.5 in boys, and continues for another 3-4 years. During this period, teenagers experience a major growth spurt, thus require increased nutrient needs.

Increased height involves bone growth and enhanced bone mineral composition. The final stage of skeletal bone maturation takes place at about age 17 in females and 21 in males – bones stop growing but its composition continues to increase until they are in their twenties.

During childhood, the amount of lean body mass is the same for both sexes, but changes during adolescence. The final lean body mass for males is 50% more than that of their female counterparts. This is because they have a more active and longer growth spurt. In fact, lean body mass for females decline during this period due to the high increase of fat. Girls have twice the amount of fat compared to boys.

Nutrient requirements

Growth and development are rapid during the teenage years, and the demand for energy and most nutrients is relatively high. This requirement differs between boys and girls – boys need more energy and protein due to their greater growth spurt.

Calories are simply a way to measure energy. Energy is required for growth and physical activities. A person’s caloric intake depends on their sex, size and activity level.

Protein requirements increase with age, reaching adult levels by late adolescence. Its consumption should not be overly emphasized – sufficient protein is usually obtained in our everyday diet. Some teenage boys double their protein intakes as they believe extra protein will increase their muscle mass, thus giving them an advantage in sports. The truth is once the protein needs are met, the extra amounts will be stored as fat in the body, and not muscle.

Carbohydrate and fat intakes should be sufficient to achieve the protein-sparing effect. If possible, energy must be obtained from carbohydrate in the diet. If the carbohydrate is slightly insufficient, fat will be converted into energy. If the fat is not enough, then protein will be used instead – and this must be avoided.

Calcium requirements during adolescence depend on the skeletal bone growth. Since 45% of the skeletal bone growth occurs during this period, the demand for calcium is very high. Inadequate calcium during skeletal bone formation and maturation is associated with a decrease in peak bone mass. This often leads to osteoporosis (brittle bone disease) later in life especially in postmenopausal women. Sufficient amount of vitamin D, potassium, magnesium, protein and vitamin C helps in the absorption of calcium.

The demand for iron increases during puberty. In males, the build-up of muscle mass is accompanied by greater blood volume. Females require even more iron due to their monthly menstrual cycle. Vitamin C enhances iron absorption. On the other hand, tannin, oxalic acid and phytate interfere with its absorption.

Zinc is known to be essential for growth and good sexual maturation. Zinc retention increases significantly during the growth spurt, leading to a more efficient use of dietary sources.

Thiamin (B 1), riboflavin (B 2­) and niacin (B 3) are recommended in large amounts to meet the high-energy requirements. In most cases, the increased food intake demanded by higher energy needs will be accompanied by increased and adequate levels of B vitamins. The requirements for vitamin B 6, folate and B 12 increase due to the elevated protein metabolism and also to accommodate the synthesis of DNA and RNA. Vitamin D is especially needed for rapid skeletal growth.

In an American study of some 600 people under 20, they were found to be short of iron, magnesium, zinc, and vitamins A, B 6­, D and E. Other surveys of nutrient intake have indicated that adolescence are likely to acquire less vitamin A, B 6, folate, riboflavin, iron, calcium, and zinc. Young women are also likely to obtain less magnesium, copper, and manganese. On the other hand, studies shown that the intakes of teenagers are higher than optimal in fat, saturated fat, protein and sodium.

Dietary habits

The teenage eating habits are complex. The generally busy schedule of adolescence influence their eating habits. They often eat rapidly and away from the home. They eat what they want and when; they are hard to feed and harder to influence regarding dietary changes. Meal patterns of adolescence are often chaotic. Teenagers miss more meals as they get older, often skipping breakfast and lunch altogether. Females tend to miss more meals.

A survey on adolescence carried out in the UK in 1983 showed that the main sources of energy were bread, chips, milk, biscuits, meat products, cakes and puddings. While this resulted in a diet that was high in fat, the intake of many other nutrients appeared to be within the acceptable range. However, iron, calcium and riboflavin intakes were unacceptably low in the sample of girls. A study on Korean teenagers revealed that the prevalence of vitamin/mineral supplement use was 31%. Vitamin C, A and multivitamins were the most frequently used supplements. The mean vitamin/mineral intakes from supplements exceed the Korean or the U.S./Canadian recommended dietary allowances (Kim et al 2001).

Boys generally tend to eat enough food, but they may be deficient in nutrients as they often avoid vegetables, whole grains and other whole foods. Teenagers who consume more refined foods without taking supplements usually develop deficiencies. Teenage girls tend to eat less, as they are concerned about their weight. However, they eat more fruits and vegetables compared to boys.

In any urbanised society, compounded by the fact of working parents, many young people are not eating properly or depending too much on fast food. The teenage years are a time of accelerated growth and hormonal changes. Thus, a well balanced diet is fundamental and supplements are essential if fast food continues to be consumed. Although concern has been expressed about the habit of snacking, teenagers may obtain substantial nourishment from foods eaten outside traditional meals. Thus, the choice of food is more important than the time or place of eating.

Use of tobacco, alcohol, marijuana, and other drugs is a major health problem. The effect of these chemicals on nutritional status depends on the amount and length of use as well as on the individual’s general state of health. A study which looked at the eating habits of teenage smokers, found that girls had significantly lower intakes of vitamin A, C, some B vitamins, fiber and vegetables than those who did not smoke.

Eating disorders in young women are common. In adolescence, controlling weight by exercise rather than diet restriction seems to carry less risk of development of eating disorders.

Anorexia nervosa is a psychological illness. It is the refusal to eat enough to maintain a normal body weight and an intense fear of gaining weight even though the individual is of normal weight or underweight. Sufferers are of the impression that they are fat and often see themselves as being fat even though they are obviously underweight. Energy intake is reduced and output increased by excessive exercise and, at times, self-initiated vomiting or use of laxatives or diuretics.

Bulimia nervosa, a condition seen most often in older adolescents, is also a psychological illness, but does not usually lead to the seriously depleted nutritional state as seen in anorexia nervosa. Bulimics are also obsessed with fear of gaining weight. They generally maintain close to normal body weight, with recurring pattern of binge eating followed by self-induced vomiting. The foods eaten tend to be high in carbohydrate and fat. Sufferers may also use large quantities of laxatives, slimming pills or strenuous exercise to control their weight. Vomit is acidic and can erode teeth, therefore bulimics have poor teeth due to regular vomiting.

Obesity in teenagers seems to be on the rise. Obesity in adolescence usually results from poor food choices and laziness or lack of exercise. Other habits can also lead to weight gain. Many obese adolescents were overweight as children, maturing earlier than those of normal weight and achieving greater skeletal growth. Many others, however, were slim children and began accumulating excess fat only in puberty. Some accumulation of fat in existing adipose tissues is normal in girls.

Overweight teens that become overweight adults are at greater risk for developing a chronic disease, such as arthritis, cancer, diabetes, heart disease, and high blood pressure, at a younger age. Being overweight can also lead to low self-esteem. Many overweight teens isolate themselves from their peers and do not take part in outside activities. This can lead to even more weight gain.

Diet changes, sensible eating and exercise are the best ways to counteract excessive weight gain, even in youngsters. Like eating habits, exercise habits are often created early in life, and once set, are harder to change. This is also true for attitudes toward health and life. Eating and exercise patterns, plus attitudes are all important in generating long-term health.