- Email: [email protected]
Women and food FAQs
FREQUENTLY ASKED QUESTIONS
Women and food FAQs
Are red wine and chocolate really good for you? Red wine and chocolate are rich sources of flavonoids: a range of bioactive phenolic compounds with antioxidant activity. The specific types of flavonoids contained in red wine and chocolate are anthocyanins, catechins and proanthocyanidins (also known as condensed tannins). Red wine also contains quercetin and myricetin. Proanthocyanidins are responsible for the astringent character of wine and the bitterness of chocolate. Antioxidants are hypothesized to play a role in reducing the risk of a range of chronic diseases including: • cardiovascular disease • cancer • age-related macular degeneration • asthma. Free radicals produced through oxidative metabolism are believed to be involved in these chronic diseases through attack on a variety of cellular targets and processes including low-density lipoprotein (LDL) oxidation and damage to DNA, proteins and enzymes. Flavonoids and other polyphenols are effective antioxidants. They have been shown in experimental studies to have free radical scavenging abilities and act as chelators of metal ions. However, their role in disease prevention may also be through their other biological actions. Flavonoids have been shown to have antithrombotic, anti-inflammatory and vasodilatory actions. These effects have been shown with both red wine and grape juice which suggests that the effect is independent of the presence of alcohol. Both red wine and chocolate have been shown to inhibit oxidation of LDL in vitro and to increase the antioxidant capacity of plasma in humans. In epidemiological studies, the intake of flavonoids from all foods has been shown to be inversely related to risk of cardiovascular disease, and some cancers, although the evidence is contradictory for cancer. Flavonoids may also be protective with respect to type 2 diabetes and asthma although further research in these areas is necessary. The health benefits of antioxidants in chocolate and red wine need to be considered in context of the overall diet. Chocolate is an energy-dense food, which should be consumed only in small amounts to avoid excess energy consumption that can lead to weight gain. Chocolate also contains high levels of saturated fat that is associated with increasing cholesterol levels. The damaging effects of excessive alcohol consumption are also well established. Fruit, vegetables and tea are also rich sources of flavonoids and other antioxidants. For example, apples, onions, kale and broccoli are rich in quercetin, while all types of berries, currants and stone fruit (e.g. peaches, apricots and nectarines) are rich in
WOMEN’S HEALTH MEDICINE 1:1
anthocyanins, catechins and proanthocyanidins. Tea and green tea are rich in catechins. In addition, fruit and vegetables are also rich in other antioxidants (e.g. vitamin C, E, carotenoids) and other protective compounds (e.g. fibre). Individuals should be encouraged to eat fruits and vegetables to increase antioxidant intake rather than excessive amounts of chocolate and red wine. An intake of at least five portions of vegetables and fruit per day is recommended to help reduce the risk of some cancers, heart disease and many other chronic conditions. Sarah McNaughton
Do pregnant teenagers need specific nutrition advice? The health and nutritional status of a pregnant woman can determine whether she and her baby have a healthy pregnancy and may also influence the future health of the unborn baby. Pregnancy during the teenage years creates competition for nutrients between the mother, who is still growing, and the developing foetus. This produces a number of specific nutritional challenges for the pregnant teenager. Weight gain Teenage mothers tend to have lower gestational weight gains compared to older women. Often they attempt to restrict weight gain to delay discovery of an unplanned pregnancy. Low weight gains are associated with low birth weight infants who are at higher risk of morbidity and mortality. Weight gain of around 12.5 kg is associated with the lowest risk of complications during pregnancy and labour. Pregnant teenagers should be advised not to restrict energy intakes during pregnancy. It may be useful to monitor weight gain.
49
© 2004 The Medicine Publishing Company Ltd
FREQUENTLY ASKED QUESTIONS
Can fish oil supplements reduce the risk of cardiovascular disease in women?
Dietary advice for pregnant teenagers
Omega-3 or n-3 polyunsaturated fatty acids (PUFAs) are essential fatty acids. This means that they must be supplied as part of the diet because the body cannot produce them. The long-chain n-3 PUFAs, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are of particular interest and are hypothesized to be protective against a number of chronic diseases. In epidemiological studies, high consumption of oily fish is inversely related to a number of cardiovascular disease risk factors and to coronary heart disease mortality in women. Compared with women who rarely ate fish (less than once per month), the risk for CHD death was 21%, 29%, 31%, and 34% lower for fish consumption 1 to 3 times per month, once per week, 2 to 4 times per week, and >5 times per week, respectively. Whilst there are no primary prevention trials to date, secondary prevention studies have shown that in individuals with a history of myocardial infarction, long-chain n-3 PUFAs reduced the risk of cardiovascular mortality. The GISSI Prevenzione trial, which provided a daily supplement of 1 g long-chain n-3 PUFAs per day for 2 years, reduced the occurrence of cardiovascular disease end points (cardiovascular death, non-fatal MI, and stroke) by 20%. In relation to cardiovascular disease risk factors, the most common finding is a reduction in triglycerides, both in individuals with and without pre-existing hyperlipidaemia. Other effects of long-chain n-3 PUFAs include: • reduction of platelet clotting • reduction of blood pressure • reduced heart arrhythmia • an anti-inflammatory action. Effects of long-chain n-3 PUFAs in other chronic diseases are less conclusive, although there is some evidence to suggest that insulin sensitivity may be improved, thus reducing the risk of type 2 diabetes. The most potent dietary sources of long-chain n-3 PUFAs are oily fish (e.g. mackerel, salmon, herring and tuna). Recent government recommendations (www.food.gov.uk) state that up to four portions of oily fish per week are recommended for all men, and post-menopausal women. However, up to two portions per week are recommended for girls, women who are likely to become pregnant and pregnant or breastfeeding women. This is slightly lower in order to reduce the risk of potential harm caused by the dioxin and PCB (polychlorinated biphenyl) content of oily fish, whilst maintaining the benefits in relation to foetal brain development. A 140 g serving of a typical oily fish would provide 2.8 g of long-chain n-3 PUFAs. Oily fish consumption in the UK is low. On average a third of a portion of oily fish is eaten per week, with seven out of ten people not eating fish at all. The alternative, fish oil supplements, are readily available and provide these long-chain n-3 PUFAs at a dose of between 0.3 and 1 g per capsule. Women with a high risk of cardiovascular disease (e.g. women with hyperlipidaemia) who have a low intake of fish, may derive particular benefit from fish-oil supplements in order to reduce their cardiovascular disease risk.
• Encourage a healthy, balanced diet and monitor this if necessary • Advise her not to restrict energy intake • Monitor weight gain • Advise folic acid supplementation, especially in the first trimester and pre-conception if possible • Encourage intake of iron-rich foods, prescribe iron supplements if necessary • Encourage intake of low-fat dairy products • A multivitamin and mineral supplement tailored for pregnancy may be advisable
Nutrient intake The National Diet and Nutrition Survey of young people aged 4–18 years (NDNS) showed that some teenage girls have low intakes of many nutrients that are important during pregnancy, including iron, folate, calcium and zinc. Because most teenage pregnancies are unplanned and they often present relatively late for antenatal care, pre-conception and first trimester folic acid supplementation is often unlikely. About 80% of females aged 15–18 years had intakes of iron below the average recommended intake. Whilst it is assumed that extra demand for iron is met because menstruation has ceased and intestinal absorption increases, low iron stores at the start of pregnancy may increase the risk of iron deficiency anaemia. Encouragement should be given to consume dietary sources of iron (e.g. lean red meat, pulses). However, iron supplementation may be required if iron status is persistently low. Calcium requirement for teenage females is 800 mg/day and reflects their greater need compared to adults, as they have yet to attain peak bone mass. Whilst the production of vitamin D increases during pregnancy to enhance calcium absorption, many pregnant teenagers may need encouragement to consume adequate amounts of dairy products to meet requirements for both growth and development of the foetus and to meet their own needs for bone maturation. Dairy products are an important source of calcium in the diet but are often perceived as fattening among adolescent girls preoccupied with body shape. Encourage low fat dairy products to maintain calcium and vitamin D intakes. Furthermore, 10 µg a day vitamin D is recommended during pregnancy and a supplement is often advised. Generally, a diet that is adequate in energy, with a supply of protein (from lean meat, dairy products and pulses), a variety of fruit and vegetables and plenty of unrefined carbohydrates (including those rich in dietary fibre to prevent constipation) applies to pregnant women of all ages. However, extra encouragement and monitoring may be required in this vulnerable group. In cases of poor dietary quality, a multivitamin and mineral supplement tailored for pregnancy may be advisable. Toni Steer
WOMEN’S HEALTH MEDICINE 1:1
50
© 2004 The Medicine Publishing Company Ltd
FREQUENTLY ASKED QUESTIONS
and offers substitutes for commonly consumed foods that help to lower the overall GI of the diet. For example, pasta instead of potatoes, basmati rice rather than easy-cook short grain rice and whole oat-based cereals rather than highly refined varieties (e.g. cornflakes). Including more pulses and beans in the diet and avoiding highly refined, sugar-rich foods will also favourably affect the glycaemic load of the diet.
FURTHER READING Hu F B, Bronner L, Willett W C, et al. Fish and omega-3 fatty acid intake and risk of coronary heart disease in women. JAMA 2002; 287: 1815–1821. Knekt P, Kumpulainen J, Jarvinen R et al. Flavonoid intake and risk of chronic diseases. Am J Clin Nutr 2002; 76: 560−568. Kris-Etherton PM, Hecker KD, Bonanome A et al. Bioactive compounds in foods: their role in the prevention of cardiovascular disease and cancer. Am J Med 2002; 113: 71S−88S. Marchioli R, Barzi F, Bomba E, et al. Early protection against sudden death by n-3 polyunsaturated fatty acids after myocardial infarction: time-course analysis of the results of the Gruppo Italiano per lo Studio della Sopravvivenza nell’Infarto Miocardico (GISSI) – Prevenzione. Circulation 2002; 105: 1897–903.
FURTHER READING Brand-Miller J C. Glycaemic load and chronic disease. Nutrition Reviews 2003; 61: S49–55. Pawlak D B, Ebbeling C B, Ludwig D S. Should obese patients be counselled to follow a low-glycaemic index diet? Yes. Obesity Reviews 2002, 3: 233. Raben A. Should obese patients be counselled to follow a low-glycaemic index diet? Obesity Reviews 2002; 3: 245–56.
Toni Steer
Susan Jebb
Should we be recommending low glycaemic index diets? The glycaemic index (GI) is a method of ranking individual foods according to their effect on blood glucose levels. • A portion of food containing 50 g of carbohydrate is given to an individual and blood glucose levels are monitored over the following 3-hour period. • Blood glucose levels are ranked relative to the rise in blood glucose from a reference food (usually glucose or white bread), which is given an arbitrary score of 100. The GI concept was originally used to help individuals with diabetes. Foods with a low GI are absorbed more slowly and, therefore, help maintain a more stable blood glucose for a longer period. Beyond this, further research has looked at whether low GI diets can prevent chronic diseases. Large epidemiological analyses (e.g. the Nurses’ Health Study from the USA) have shown a reduced risk of developing type 2 diabetes and cardiovascular disease in people habitually consuming a low GI diet. More controversially, it has been claimed that low GI foods aid weight loss. Cross-sectional data from some epidemiological studies, such as the EURO-DIAB Complications Study, have shown a lower GI diet is associated with a smaller waist circumference. However, evidence of the effects on body weight from controlled intervention studies are inconsistent. It is argued that the slow rate of digestion of low GI foods could help by boosting satiety and may help people to feel fuller for longer. Moderating fluctuations in blood glucose might also help to alleviate hunger. But in most cases weight loss requires cognitive controls over total energy intake and low GI foods alone are rarely sufficient to achieve sustained weight loss. In many studies, low GI interventions have also led to an increase in the consumption of fibre-rich or wholegrain foods, increases in fruits and vegetables and decreases in refined carbohydrates (e.g. biscuits, cakes and soft drinks). It is difficult to isolate the impact on body weight of low GI foods per se. Low GI diets may provide a focus for broader changes in dietary habits leading to real improvements in health. One of the drawbacks to this approach in clinical practice is the complexity of the GI concept. Individuals eat mixed diets rather than single foods with a known GI. The most practical advice avoids quantitative calculations based on the GI of specific foods
WOMEN’S HEALTH MEDICINE 1:1
51
© 2004 The Medicine Publishing Company Ltd
Women and food FAQs
Are red wine and chocolate really good for you? Red wine and chocolate are rich sources of flavonoids: a range of bioactive phenolic compounds with antioxidant activity. The specific types of flavonoids contained in red wine and chocolate are anthocyanins, catechins and proanthocyanidins (also known as condensed tannins). Red wine also contains quercetin and myricetin. Proanthocyanidins are responsible for the astringent character of wine and the bitterness of chocolate. Antioxidants are hypothesized to play a role in reducing the risk of a range of chronic diseases including: • cardiovascular disease • cancer • age-related macular degeneration • asthma. Free radicals produced through oxidative metabolism are believed to be involved in these chronic diseases through attack on a variety of cellular targets and processes including low-density lipoprotein (LDL) oxidation and damage to DNA, proteins and enzymes. Flavonoids and other polyphenols are effective antioxidants. They have been shown in experimental studies to have free radical scavenging abilities and act as chelators of metal ions. However, their role in disease prevention may also be through their other biological actions. Flavonoids have been shown to have antithrombotic, anti-inflammatory and vasodilatory actions. These effects have been shown with both red wine and grape juice which suggests that the effect is independent of the presence of alcohol. Both red wine and chocolate have been shown to inhibit oxidation of LDL in vitro and to increase the antioxidant capacity of plasma in humans. In epidemiological studies, the intake of flavonoids from all foods has been shown to be inversely related to risk of cardiovascular disease, and some cancers, although the evidence is contradictory for cancer. Flavonoids may also be protective with respect to type 2 diabetes and asthma although further research in these areas is necessary. The health benefits of antioxidants in chocolate and red wine need to be considered in context of the overall diet. Chocolate is an energy-dense food, which should be consumed only in small amounts to avoid excess energy consumption that can lead to weight gain. Chocolate also contains high levels of saturated fat that is associated with increasing cholesterol levels. The damaging effects of excessive alcohol consumption are also well established. Fruit, vegetables and tea are also rich sources of flavonoids and other antioxidants. For example, apples, onions, kale and broccoli are rich in quercetin, while all types of berries, currants and stone fruit (e.g. peaches, apricots and nectarines) are rich in
WOMEN’S HEALTH MEDICINE 1:1
anthocyanins, catechins and proanthocyanidins. Tea and green tea are rich in catechins. In addition, fruit and vegetables are also rich in other antioxidants (e.g. vitamin C, E, carotenoids) and other protective compounds (e.g. fibre). Individuals should be encouraged to eat fruits and vegetables to increase antioxidant intake rather than excessive amounts of chocolate and red wine. An intake of at least five portions of vegetables and fruit per day is recommended to help reduce the risk of some cancers, heart disease and many other chronic conditions. Sarah McNaughton
Do pregnant teenagers need specific nutrition advice? The health and nutritional status of a pregnant woman can determine whether she and her baby have a healthy pregnancy and may also influence the future health of the unborn baby. Pregnancy during the teenage years creates competition for nutrients between the mother, who is still growing, and the developing foetus. This produces a number of specific nutritional challenges for the pregnant teenager. Weight gain Teenage mothers tend to have lower gestational weight gains compared to older women. Often they attempt to restrict weight gain to delay discovery of an unplanned pregnancy. Low weight gains are associated with low birth weight infants who are at higher risk of morbidity and mortality. Weight gain of around 12.5 kg is associated with the lowest risk of complications during pregnancy and labour. Pregnant teenagers should be advised not to restrict energy intakes during pregnancy. It may be useful to monitor weight gain.
49
© 2004 The Medicine Publishing Company Ltd
FREQUENTLY ASKED QUESTIONS
Can fish oil supplements reduce the risk of cardiovascular disease in women?
Dietary advice for pregnant teenagers
Omega-3 or n-3 polyunsaturated fatty acids (PUFAs) are essential fatty acids. This means that they must be supplied as part of the diet because the body cannot produce them. The long-chain n-3 PUFAs, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are of particular interest and are hypothesized to be protective against a number of chronic diseases. In epidemiological studies, high consumption of oily fish is inversely related to a number of cardiovascular disease risk factors and to coronary heart disease mortality in women. Compared with women who rarely ate fish (less than once per month), the risk for CHD death was 21%, 29%, 31%, and 34% lower for fish consumption 1 to 3 times per month, once per week, 2 to 4 times per week, and >5 times per week, respectively. Whilst there are no primary prevention trials to date, secondary prevention studies have shown that in individuals with a history of myocardial infarction, long-chain n-3 PUFAs reduced the risk of cardiovascular mortality. The GISSI Prevenzione trial, which provided a daily supplement of 1 g long-chain n-3 PUFAs per day for 2 years, reduced the occurrence of cardiovascular disease end points (cardiovascular death, non-fatal MI, and stroke) by 20%. In relation to cardiovascular disease risk factors, the most common finding is a reduction in triglycerides, both in individuals with and without pre-existing hyperlipidaemia. Other effects of long-chain n-3 PUFAs include: • reduction of platelet clotting • reduction of blood pressure • reduced heart arrhythmia • an anti-inflammatory action. Effects of long-chain n-3 PUFAs in other chronic diseases are less conclusive, although there is some evidence to suggest that insulin sensitivity may be improved, thus reducing the risk of type 2 diabetes. The most potent dietary sources of long-chain n-3 PUFAs are oily fish (e.g. mackerel, salmon, herring and tuna). Recent government recommendations (www.food.gov.uk) state that up to four portions of oily fish per week are recommended for all men, and post-menopausal women. However, up to two portions per week are recommended for girls, women who are likely to become pregnant and pregnant or breastfeeding women. This is slightly lower in order to reduce the risk of potential harm caused by the dioxin and PCB (polychlorinated biphenyl) content of oily fish, whilst maintaining the benefits in relation to foetal brain development. A 140 g serving of a typical oily fish would provide 2.8 g of long-chain n-3 PUFAs. Oily fish consumption in the UK is low. On average a third of a portion of oily fish is eaten per week, with seven out of ten people not eating fish at all. The alternative, fish oil supplements, are readily available and provide these long-chain n-3 PUFAs at a dose of between 0.3 and 1 g per capsule. Women with a high risk of cardiovascular disease (e.g. women with hyperlipidaemia) who have a low intake of fish, may derive particular benefit from fish-oil supplements in order to reduce their cardiovascular disease risk.
• Encourage a healthy, balanced diet and monitor this if necessary • Advise her not to restrict energy intake • Monitor weight gain • Advise folic acid supplementation, especially in the first trimester and pre-conception if possible • Encourage intake of iron-rich foods, prescribe iron supplements if necessary • Encourage intake of low-fat dairy products • A multivitamin and mineral supplement tailored for pregnancy may be advisable
Nutrient intake The National Diet and Nutrition Survey of young people aged 4–18 years (NDNS) showed that some teenage girls have low intakes of many nutrients that are important during pregnancy, including iron, folate, calcium and zinc. Because most teenage pregnancies are unplanned and they often present relatively late for antenatal care, pre-conception and first trimester folic acid supplementation is often unlikely. About 80% of females aged 15–18 years had intakes of iron below the average recommended intake. Whilst it is assumed that extra demand for iron is met because menstruation has ceased and intestinal absorption increases, low iron stores at the start of pregnancy may increase the risk of iron deficiency anaemia. Encouragement should be given to consume dietary sources of iron (e.g. lean red meat, pulses). However, iron supplementation may be required if iron status is persistently low. Calcium requirement for teenage females is 800 mg/day and reflects their greater need compared to adults, as they have yet to attain peak bone mass. Whilst the production of vitamin D increases during pregnancy to enhance calcium absorption, many pregnant teenagers may need encouragement to consume adequate amounts of dairy products to meet requirements for both growth and development of the foetus and to meet their own needs for bone maturation. Dairy products are an important source of calcium in the diet but are often perceived as fattening among adolescent girls preoccupied with body shape. Encourage low fat dairy products to maintain calcium and vitamin D intakes. Furthermore, 10 µg a day vitamin D is recommended during pregnancy and a supplement is often advised. Generally, a diet that is adequate in energy, with a supply of protein (from lean meat, dairy products and pulses), a variety of fruit and vegetables and plenty of unrefined carbohydrates (including those rich in dietary fibre to prevent constipation) applies to pregnant women of all ages. However, extra encouragement and monitoring may be required in this vulnerable group. In cases of poor dietary quality, a multivitamin and mineral supplement tailored for pregnancy may be advisable. Toni Steer
WOMEN’S HEALTH MEDICINE 1:1
50
© 2004 The Medicine Publishing Company Ltd
FREQUENTLY ASKED QUESTIONS
and offers substitutes for commonly consumed foods that help to lower the overall GI of the diet. For example, pasta instead of potatoes, basmati rice rather than easy-cook short grain rice and whole oat-based cereals rather than highly refined varieties (e.g. cornflakes). Including more pulses and beans in the diet and avoiding highly refined, sugar-rich foods will also favourably affect the glycaemic load of the diet.
FURTHER READING Hu F B, Bronner L, Willett W C, et al. Fish and omega-3 fatty acid intake and risk of coronary heart disease in women. JAMA 2002; 287: 1815–1821. Knekt P, Kumpulainen J, Jarvinen R et al. Flavonoid intake and risk of chronic diseases. Am J Clin Nutr 2002; 76: 560−568. Kris-Etherton PM, Hecker KD, Bonanome A et al. Bioactive compounds in foods: their role in the prevention of cardiovascular disease and cancer. Am J Med 2002; 113: 71S−88S. Marchioli R, Barzi F, Bomba E, et al. Early protection against sudden death by n-3 polyunsaturated fatty acids after myocardial infarction: time-course analysis of the results of the Gruppo Italiano per lo Studio della Sopravvivenza nell’Infarto Miocardico (GISSI) – Prevenzione. Circulation 2002; 105: 1897–903.
FURTHER READING Brand-Miller J C. Glycaemic load and chronic disease. Nutrition Reviews 2003; 61: S49–55. Pawlak D B, Ebbeling C B, Ludwig D S. Should obese patients be counselled to follow a low-glycaemic index diet? Yes. Obesity Reviews 2002, 3: 233. Raben A. Should obese patients be counselled to follow a low-glycaemic index diet? Obesity Reviews 2002; 3: 245–56.
Toni Steer
Susan Jebb
Should we be recommending low glycaemic index diets? The glycaemic index (GI) is a method of ranking individual foods according to their effect on blood glucose levels. • A portion of food containing 50 g of carbohydrate is given to an individual and blood glucose levels are monitored over the following 3-hour period. • Blood glucose levels are ranked relative to the rise in blood glucose from a reference food (usually glucose or white bread), which is given an arbitrary score of 100. The GI concept was originally used to help individuals with diabetes. Foods with a low GI are absorbed more slowly and, therefore, help maintain a more stable blood glucose for a longer period. Beyond this, further research has looked at whether low GI diets can prevent chronic diseases. Large epidemiological analyses (e.g. the Nurses’ Health Study from the USA) have shown a reduced risk of developing type 2 diabetes and cardiovascular disease in people habitually consuming a low GI diet. More controversially, it has been claimed that low GI foods aid weight loss. Cross-sectional data from some epidemiological studies, such as the EURO-DIAB Complications Study, have shown a lower GI diet is associated with a smaller waist circumference. However, evidence of the effects on body weight from controlled intervention studies are inconsistent. It is argued that the slow rate of digestion of low GI foods could help by boosting satiety and may help people to feel fuller for longer. Moderating fluctuations in blood glucose might also help to alleviate hunger. But in most cases weight loss requires cognitive controls over total energy intake and low GI foods alone are rarely sufficient to achieve sustained weight loss. In many studies, low GI interventions have also led to an increase in the consumption of fibre-rich or wholegrain foods, increases in fruits and vegetables and decreases in refined carbohydrates (e.g. biscuits, cakes and soft drinks). It is difficult to isolate the impact on body weight of low GI foods per se. Low GI diets may provide a focus for broader changes in dietary habits leading to real improvements in health. One of the drawbacks to this approach in clinical practice is the complexity of the GI concept. Individuals eat mixed diets rather than single foods with a known GI. The most practical advice avoids quantitative calculations based on the GI of specific foods
WOMEN’S HEALTH MEDICINE 1:1
51
© 2004 The Medicine Publishing Company Ltd