- Essential nutrient requirements
- Glycaemic index and glycaemic load
- Special features about women and nutrition
- Medical conditions
- Ways to maintain a healthy lifestyle
Nutrition is essential for growth and development, health and well-being. Eating a healthy diet contributes to preventing future illness and death. Dietary factors are associated with leading causes of death among women, such as coronary heart disease, some types of cancer, stroke, and type 2 diabetes mellitus. Nutrition is defined as the processes by which an animal or plant takes in and utilizes food substances. Essential nutrients include protein, carbohydrate and fat in varying amounts, and electrolytes. Normally, 85% of daily energy use is from fat and carbohydrates, and 15% is from protein. In humans, nutrition is mainly achieved through the process of putting food into our mouths, chewing, and swallowing it. The required amounts of the essential nutrients differ with age and the state of the body. In females, required components of nutrition are affected by special states of the body such as pregnancy and lactation, what our diet consists of, and any existing diseases (eg. breast cancer or weakened bones – known as osteoporosis).
For weight to remain stable, the total amount of calories that are consumed must not exceed the total that we use up through metabolic processes (eg. exercising, sweating and breathing). Energy intake must match energy output. The average energy intake is about 1800 kcal/day for women, although this varies with body size and activity level.
Protein is important for the production, maintenance and repair of tissues in the body. When energy intake is insufficient, protein intake must be raised. This is because ingested proteins are preferentially directed towards pathways of glucose (sugar) synthesis and oxidation. For adults, the recommended dietary allowance for protein is about 0.6 g/kg body weight per day. Animal proteins tend to include highest amounts of proteins, followed by legumes (beans), cereals (rice, wheat, corn), and roots.
Fats are a concentrated and rich source of energy. It is recommended that fat intake totals no more than 30% of calories. Polyunsaturated fats should be limited to less than 10% of calories, and saturated and trans-fats together to less than 10%. The rest of your fat intake should consist of monounsaturated fats.
- Trans-fats: These fats are artificially created through a chemical process. This solidifies the oil and limits the body’s ability to regulate its cholesterol. These fats are considered to be harmful to your health. Trans-fats are found mainly in deep-fried fast foods and processed foods made with margarine.
- Saturated fats: This type of fat is found in foods such as butter and beef fat.
- Polyunsaturated fats: This group includes omega 3 and 6 essential fatty acids (EFA’s).There are high levels found in fish oil, vegetable and nut oils.
- Monounsaturated fatty acids: This is found mainly in chicken fat and vegetable oils such as olive, canola and peanut oil.
Carbohydrates should make up at least 55% of total calories. The brain is a special part of the body that depends primarily on glucose for it’s energy and requires about 100 g/day of glucose for fuel. In some situations, the body can compensate for decreased levels of carbohydrates by using alternative energy pathways, such as burning fatty acids.
For adults, 1 to 1.5 mL water per kcal of energy expenditure is usually sufficient to allow for normal changes in physical activity, sweating, and solute load of the diet. Water losses consist of 50-100 mL/day through faeces (stools), 500-1000 mL/day by evaporation, and approximately 1000 mL/day through urine. If external losses increase, we must increase the amount of water we ingest. In special circumstances such as diarrhoea and vomiting, water requirements further increase.
As discussed above, carbohydrates should make up at least 55% of total daily calories. In more recent times, the quality and also quantity of these carbohydrates has been shown to be important in blood sugar control. Even though different foods may contain the same amounts of carbohydrates, the effects on blood sugar control may be totally different. This has lead to the development of measures such as the glycaemic index (GI) and glycaemic load (GL) of a food product. Low GI and GL foods are associated with health advantages such as a decrease in blood sugar levels. This is particularly important if you are pregnant, to provide good blood sugar level control for the developing baby. Leading causes of death among women include heart disease, stroke, and type 2 diabetes. Long term control of blood sugar levels helps control risk factors for these conditions, such as high cholesterol and blood pressure. The glycaemic index is obtained by measuring the effect that a carbohydrate containing food has on blood sugar levels, compared to the effect of the same amount of pure sugar. The following ranges are usually applied to determine the GI of a particular food:
- Low GI – 55 or less.
- Medium GI – 56 to 69.
- High GI – 70 or more.
Foods with a low GI (less than 55) cause a slower and lower rise in blood sugar levels. These include: breads such as mixed-grain and oat breads, barley, pasta, noodles, beans, sweet potatoes, green peas and milk. Foods with a high GI (greater than 70) cause a faster and higher rise in blood sugar levels. High GI foods include: white bread, steamed white rice, chips and coffee. By aiming to incorporate low GI foods into your diet, you will help to bring down the average GI of your meal and prevent sudden increases in blood sugar levels. Foods with a low GI are often more healthy and nutritious. These foods allow blood sugar levels to be sustained at a lower level over a longer period of time. After you consume carbohydrate containing foods, the body signals the pancreas to secrete a hormone called insulin to break the carbohydrate down. Insulin acts to lower the body’s sugar levels. When the blood sugar levels decrease to a particular level, the brain is sent a signal and you become hungry again. By consuming low GI foods, you are more likely to be satisfied and feel full for longer periods of time. This helps you to maintain a healthy weight and avoiding the development of diseases such as high cholesterol, increased blood pressure levels and heart disease. The glycaemic load of a food ranks the effect of a specific serving size of that food on the blood sugar levels.
The following ranges are usually applied to determine the GL of a particular food:
- Low GL – 10 or less.
- Medium GL – 11 to 19.
- High GL – 20 or more.
The following values are applied to define the GL per day:
- Low GL – less than 80.
- High GL – more than 120.
Foods with a low GL cause a steadier, lower rise in blood sugar levels. These include many fruits and vegetables. Foods with a high GL cause a faster and higher rise in blood sugar levels. High GL foods include white rice and refined snack foods, such as chips and sweetened drinks. Generally, foods with a low fibre content and high carbohydrate levels have high GI and GL values, whereas those with high fibre contents have lower GLs. For more information and tips on how to incorporate foods with a low GL into your lifestyle, visit these pages on glycaemic index (GI) and glycaemic load (GL).
There is no doubt about the importance of diet and nutrition in pregnancy. At one end, malnutrition can result in decreased growth of the baby whilst in the womb and problems such as prematurity and anaemia (lack of red blood cells which results in decreased oxygen in the bloodstream). Changes in the diet should occur prior to pregnancy.
Special features to consider in pregnancy
- The mother is carrying and supporting another individual, and therefore needs to increase her nutritional intake and calories. A pregnant woman should receive at least 2000-2500 kcal/day. This is particularly important in the last two trimesters of pregnancy, because of increased demands on both the baby and the mother.
- Routine supplementation with vitamins and iron should not be necessary during pregnancy, but where there is evidence of dietary insufficiency, iron and vitamin supplements should be given from the first trimester onwards. Pregnant women should avoid excess amounts of vitamin A (more than 10,000 IU per day) as this has been linked to birth defects.
- Folic acid supplementation prior to pregnancy is recommended, particularly in diabetics, to reduce the risk of neural tube defects. These defects refer to conditions such as spina bifida and anencephaly, which are problems with the development of the spine or brain. They occur very early in pregnancy, often before a woman knows she is pregnant. Many babies with neural tube defects have problems with walking and with bowel and bladder control. In severe cases, it can also be a cause of death. About 1 in every 500 pregnancies is affected by a neural tube defect. The cause for this condition has been linked to lack of folic acid in the mother. Therefore, it is important to ensure folic acid supplementation prior to and especially during the first three months of pregnancy.
- Carbohydrates are the primary energy source for both the mother and the baby. There is a close correlation between the mother’s blood sugar (glucose) level and her baby’s sugar levels. Glucose is a major source of energy for the baby.
- Essential fatty acids play an important part in growth during pregnancy and are an important source of energy. They are also a source of fat soluble vitamins such as Vitamins A, D and K.
- Substance abuse – smoking, alcohol and recreational drugs not only pose direct health risks, but affect intake of an adequate and balanced diet. For example, smoking has adverse effects on the baby’s growth and development due to harmful chemicals such as nicotine and carbon monoxide.
Women should be encouraged to eat at least three healthy meals a day, consisting of servings of food from all five food groups (eg. fruits and vegetables, cereals and wholegrains).
Women who are breastfeeding should increase their daily caloric intake by 300-500 kcal above pre-pregnancy levels and consume 1200 mg/day of calcium.
Foods containing high levels of calcium include:
- Dairy products such as milk, buttermilk, yoghurt and cheese. These products are very high in calcium and contain a form of calcium that is easily and efficiently absorbed by the body.
- Green vegetables such as broccoli, bok choy or pak choy, Chinese cabbage, turnip greens and kale.
- Canned fish such as sardines or salmon which contain soft bones.
- Some juices, cereals and breads which have been fortified with extra calcium to help people whose calcium intake from dairy products is inadequate.
There is strong evidence that Western style diets, rich in fatty foods, red meats and high salt and sugar levels, are associated with a substantially increased risk for obesity, type 2 diabetes mellitus, and heart disease. There are particular groups of women at high risk for these conditions: those with a family history of diabetes or heart disease, high blood pressure, high cholesterol, smokers and a past history of heart problems or impaired sugar tolerance. In these groups of women, it is very important to maintain a healthy diet and lifestyle to decrease both morbidity and mortality.
- Osteoporosis: There is an increased incidence of osteoporosis (progressive loss of and weakening of bone) in women. During early adolescence and adulthood, it is important for women to eat foods rich in calcium, to build up peak bone mass and reduce the later likelihood of developing osteoporosis.
- Anorexia Nervosa: Anorexia nervosa (loss of appetite due to a combination of psychological or nervous factors) is a condition affecting mainly younger women. Anorexic patients are often malnourished and deficient in both calories and nutrients. They may also be involved in excessive or vigorous exercise or use laxatives, which leads to further weight loss. People with this syndrome should receive prompt treatment, with education, emotional support and dietary advice.
- Obesity: This occurs when the total amount of calories that are consumed exceed the total that we use up through metabolic processes (such as exercising, sweating and breathing). Excess weight is associated with many medical conditions on its own such as type 2 diabetes, heart disease, high blood pressure and high cholesterol. A gross measure of the degree of obesity can be determined by the Body Mass Index (BMI). The BMI is caculated by diving the body weight (kg) by the height (m) squared. According to the WHO classification, a BMI from 25-30 is classified as overweight and a BMI>30 is classified as obese.Body Mass Index (BMI) Calculator
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- Iron Deficiency Anaemia: Iron deficiency anaemia (IDA) is a condition where a woman has inadequate amounts iron to meet body demands. The blood in an anaemic person does not carry enough oxygen to the tissues and body organs. This can result in decreased ability to function properly. Iron is important particularly during periods of growth and in pregnancy. IDA is usually due to low levels of iron in the diet or from blood loss. Blood loss can occur during an accident or over a longer period of time, such as in heavy menstruation (monthly loss of blood in women). During their reproductive years, women are more likely to become iron deficient, as they loose 20-40mg of iron per month during menstruation.
A well balanced diet is needed to maintain adequate amounts of iron. Foods rich in iron include lean meat, dried fruits and nuts, wholegrain breads and green leafy vegetables.
Good nutrition is important to help us feel our best and maintain our health. However, our lifestyles may be quite hectic and fast paced, leaving us little time to concentrate on eating well. The National Health and Medical Research Council (NHMRC) have released a set of recommended dietary guidelines for Australian adults. The aim of these guidelines is to improve health and wellbeing of the community as a whole. The following recommendations are based on the NHMRC guidelines.
1. Enjoy a wide variety of nutritious foods
No single food can provide you with all the nutrients you need, thus it is important that you choose a wide range of foods from:
- different food groups e.g. fruits and vegetables; meats; dairy products; and breads and cereals.
- within each food group. fruits such as apples, bananas, or oranges.
Variation provides nutrients required to keep healthy, increases consumption of protective factors and minimizes toxicant exposure.
2. Eat plenty of vegetables, legumes and fruits
Australian Dietary Guidelines recommend at least five servings of vegetables and two of fruit a day. This food group is important because they provide:
- Helps lower blood cholesterol levels;
- Slow absorption of foods in bloodstream;
- Vitamin C
- Important for maintaining skin’s firmness and smooth texture;
- Maintaining healthy gums;
- Helping the body absorb iron;
- Substances that help the body get rid of potentially harmful molecules called free radicals and protect cells against damage.
A serving size can be:
- One medium sized fruit or vegetable;
- 1/2 cup raw, cooked, frozen or canned fruits (in 100% juice) or vegetables;
- 3/4 cup of 100% fruit or vegetable juice.
3. Eat plenty of cereals, preferably wholegrain
It is recommended that we eat a variety of cereals ranging from breads, breakfast cereals, to rice and pasta. Insoluble fibre is found mostly in wholegrain products, such as barley, oats and rye, which are important in maintaining regular bowel movements. Wholegrain products are also slowly digested and absorbed, with a lower glycaemic index (GI). Low GI foods have been shown to reduce the risk of type 2 diabetes and heart disease.
4. Include lean meat, fish, poultry and/or alternatives
Lean meat, fish and poultry are good sources of protein. The guidelines recommend that red meat (beef, lamb and veal) should be eaten 3-4 times a week. Red meat is the best source of iron (helps transport oxygen around the body) and good source of zinc (involved in immune functions) and Vitamin B12 (important in memory and concentration). Fish intake at least twice a week is also recommended, because it is rich in omega 3, which has been shown to lower the risk of heart disease and improve brain development and function.
5. Include milks, yoghurts, cheeses and/or alternatives
Dietary guidelines recommend 2-3 serves of low fat milks, yoghurts and cheeses each day. These are good sources of protein and calcium. A serving includes; 1 cup of milk or yogurt, or 2 slices (40 g) of cheese.
6. Drink plenty of water
The dietary guidelines suggest intake of between 1.5 to 2 litres of fluid per day, preferably of pure drinking water.
7. Limit saturated fat and moderate total fat intake
High levels of these fats have been associated with increased amounts of bad (LDL) cholesterol, fatty arterial deposits, heart disease, type 2 diabetes and obesity. Cut down on foods which contain saturated fats such as butter, chicken skin, cheese and fats on cuts of meat.
8. Choose foods low in salt
Salt can increase blood pressure, which is associated with a higher chance of heart disease and stroke. You can reduce levels of salt intake by: trying low salt or no added salt foods, not adding salt to cooking, reducing the amount of salty foods consumed (chips, nuts, pickled vegetables) and eating less processed foods.
9. Limit your alcohol intake if you choose to drink
It is important to limit alcohol intake because excess alcohol consumption is associated with high blood pressure and stroke. However, moderate intake of alcohol can reduce the risk of heart disease by increasing the ‘good’ type of cholesterol (HDL). It is recommended that women limit their alcohol to no more than two standard drinks a day.
10. Consume only moderate amounts of sugars and foods containing added sugar
It is recommended that we keep an eye on our total sugar intake. This is because sugars easily add to our total energy intake, increasing our risk of obesity. Sugars can also replace foods, which provide us with important vitamins and minerals.
It is important not to forget about exercise, in conjunction with healthy nutrition to maintain a balanced lifestyle.
The National Physical Activity Guidelines for Australians recommends at least 30 minutes of moderate-intensity physical activity on most, preferably all, days of the week. Regular exercise is important to maintain an optimal body weight. Best results are achieved from combining regular physical activity with a healthy, well balanced diet.
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- Healthy Eating Guidelines [online]. 2006 [cited 18th April 2006]. Available from URL: http://www.foodfacts.com.au/EatingTips.aspx
- National Womens Health Centre, Nutrition.
- NSW Health, Nutrition & Pain, Community Information Series, Hunter Integrated Pain Service; 2005.
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- Symmonds EM, Symmonds IM. Essential Obstetrics & Gynaecology. Spain: Churchill Livingstone; 2004.
- Augustin L, Franceschi S, Jenkins D, et al. Glycemic index in chronic disease: a review, European Journal of Clinical Nutrition, 2002; 56: 1049-1071.