A person's nutritional needs vary throughout life. Our age, activity and health can affect our needs and even individual bodies can process foods differently, meaning that some people need more of certain nutrients than others. Even the foods we eat can affect this as some foods contain elements that 'bind' or prevent the body using elements of other foods.
Regardless, there are some basic guidelines laid down by the National Health and Research Council of Australia and these too are revised from time to time, an indication that nutritional knowledge and understanding is always growing.
While often the needs may vary, all people, men and women should make sure that they eat adequate calcium, particularly early in life. Osteoporosis, while more common in post-menopausal women, can also affect men as they age.

Babies

At no other stage of live do we grow and change as rapidly as when we are children. For this reason babies from birth to 6 months whether breast or bottle-fed need over half the vitamin A intake recommended for adults, small amounts of other vitamins, and 2g of protein for every kilogram of body weight, over twice the ratio for adults.

Calculating a baby's kilojoule needs are not considered to be important so long as the infant is  growing satisfactorily. Obviously much of the protein and vitamin A will come from milk, but once a child is eating solids, foods rich in vitamin A such as orange and green leafy vegetables should be included regularly. As a baby grows, the need for vitamin A drops a little and from 7-12 months, only 1g protein per kilogram of body weight is recommended.

Children

From 1-3 years most children will be eating small quantities of much the same foods as other members of the family. So long as these meals are well balanced and the child is healthy and growing, there is little need to spend much time calculating their nutritional intake, but care should still be taken to keep up their intake of green and orange vegetables, whole grains and good quality protein foods as well as milk. Older children, until puberty, slowly increase their kilojoule intake, but as long as they are active and of average weight, there is no need for kilojoule counting.

Adolescents

Girls usually experience a growth spurt, and consequent increased nutritional needs, earlier than boys. Once menstruation commences they should take care too that they eat more foods rich in iron such as lean meats, pulses, cereals and green leafy vegetables. Both boys and girls need increased energy (carbohydrate) and protein at puberty, but care should be taken that in doing so they are not also overeating saturated fats.

Pregnancy and Lactation

During these periods, a woman's nutritional needs  increase although not to the old adage of 'eating for two'. In fact most women's kilojoule increase should only be to about 9000kJ, a rise of about 600kJ over the recommended normal intake. Pregnant women should double their intake of folate, a vitamin needed for the proliferation of cells and important in the production of red blood cells. Folate is found in liver, whole grains, green vegetables, nuts (especially peanuts), legumes and yeast extract.

They should increase their intake of vitamin C and B calcium and iron, as much as possible by increasing their intake of natural foods containing these vitamins and minerals. Lactating mothers need additional potassium, calcium, magnesium, iodine, selenium and phosphorus as well as most vitamins. Kilojoule and protein needs rise quite dramatically also, when breastfeeding. If in doubt, women should seek advice from whoever is managing their pregnancy, or post-natal health.

Women

All women of childbearing age need adequate iron (about twice that needed by a man), preferably from a natural food source. If this iron is from a non-flesh source, care should be taken that vitamin C-rich foods are also included in the diet. After menopause a woman's iron needs are the same as that of a man, but her calcium needs are higher.

Older People

Perhaps the main change nutritionally for older men and women is the reduced energy needs. From 55-75 years of age men  need a daily intake of 8800kJ and women need 6400kJ. Protein needs remain the same, so it makes sense to decrease those foods that supply fat or carbohydrate that is not linked to protein. Older people still need much the same amount of vitamins and minerals as younger people so if anything a balanced, natural diet is even more important later in life.

Food For Kids

Children can cause headaches at the meal table. While some will eat anything that is put in front of them, others push even the most tasty food around until it goes grey and cold. And parents worry: "Is my child getting enough to eat?" they fret, "What can I do to make him or her eat?" Chances are their child is perfectly well-fed and will eat when he or she is good and ready.

Children's taste buds are more sensitive that an adults. Also there are many foods they are not familiar with and are cautious of trying. We need to present foods to them in attractive ways, in small portions and without tension and nagging. If a child does not like a food, fine. There are dozens of alternatives.

Yet the opposite side of the coin is allowing a child to call the tune, so that a parent is forced to keep presenting delicious morsels until a child deigns to eat. This is not necessary either.

Just understand that a child is a little human. They get hungry and need food. Like adults, they are attracted by sweet foods, fatty foods, crunchy foods and food that just plain looks good. Sweets, chocolate, potato crisps and biscuits fit these categories well, and if they are at hand, a child will quite happily eat them and then turn away from a nourishing meal later. Then, they are just not hungry, thankyou.

Many children go through a 'fasting' stage, often around 2 years old and many parents become very worried about them then. But if a child is active and happy, not losing weight and sleeping well, the chances are that there is nothing seriously wrong and their appetite will return. Often these children are actually eating plenty, but it maybe more in the form of snacks rather than formal meals, which is also fine, so long as those snacks are full of nutrition. Hide the biscuits and make sure that there are only such things as dried and fresh fruit, juices, cheese, and raw vegetables when the child is ready to eat. So long as there are only healthy natural foods available, the young child will almost certainly be getting enough for his or her needs. Nature sees to that.

When a child goes to school, another problem may develop. School lunches should follow the balance of home meals, but need to travel well, keep at room temperature, and be appealing to look at. While there are no absolute formulas for ‘they-will-love-this’ lunch boxes, there are a few rules:

• make it fresh and keep it fresh. Invest in good quality lunch boxes and wrapping that will keep food cool and airtight. If you have to make the sandwiches the night before, refrigerate them overnight.

• give variety. Look for small packs of low-sugar fruit treats, and healthy biscuit snacks to slip into lunch boxes. Vary the fruit and drinks you send. Always include food from each of the food groups - fruit and vegetables, grains, dairy and protein.

• surprise them occasionally.  A special treat, a little note if there is a worrying test or some other problem, a cartoon picture or a flower all add an element of excitement to the meal.

• add a touch of home. Home-cooked lunch box specials make your child’s meal different and appealing. A piece of special pie or cake, a chunk of health candy or a tiny bag of your own mix of fruit and nuts all say ‘You’re special’.

Children do not need much special catering, but they appreciate fun in shapes and flavours and  often can be encouraged to eat food just because it looks good – just like us! Make a face on a serving of mashed vegetables or on a bowl of oatmeal; take time to cut fish into shapes; or serve vegetables in different ways. Chances are you'll find that picky eater will grow up with a greater appreciation of good food, and a healthy appetite.

Recommended Daily Intake (RDI)

The National Health and Medical Research Council of Australia has established, and regularly reviews, the recommended daily intake of the major nutrients in our foods. The amount is calculated on a daily basis, because many nutrients, especially vitamins and minerals, cannot be stored in the body.
The age and sex of a person has much bearing on the amounts needed daily and there are differing needs too for pregnant and lactating women. The tables exist as a guide and, within each category, individuals may sometimes need more or less of a particular nutrient.