From 1986 to 1990 the composition of people's diets has changed. In 1986 the amount of grain, fruit, and vegetables was higher while the meat and dairy consumption was lower. The next four years, however, shows an increase in the amount of dairy and meat consumed and a decrease in the amount grain, fruit, and vegetables.
There are several possible explanations for these changes. One is that the supply of grain, fruit, and vegetables has decreased while the supply of meat and milk has increased. Obviously if milk and meat are more readily available than other food, then it would be cheaper and more economical to consume more of it. Another explanation is that people's incomes have increased over the last five years. Grain, fruit, and vegetables are typically cheaper in price than milk and meat so if income is low then more of the inexpensive food is consumed. With people earning more money they can afford to consume more milk and meat than they could previously.
I feel that the reason for the dietary changes over the last few years is that people's standard of living has increased. People now have more disposable income, which allows them to spend the extra money on more expensive food such as milk and meat.