Wednesday June 2 2010
Many women do not consume the recommended levels of nutrients
Millions of British women face health risks because they are “shunning nutritious foods”, says the Daily Mail. The Daily Express says that the dangers of a love of junk food and obsession with “food fads” even affect their unborn babies.
These reports are based on research examining evidence on the quality of the diets of UK women throughout their lives. It found that, among most age groups, intakes of key micronutrients, particularly iron, vitamin D, calcium and folate, remain below recommended levels. Many women’s diets are also too high in saturated fat and salt, and low in fibre, oily fish and fruit and vegetables.
This narrative review was not a systematic analysis of research in this field, but its finding are in line with a body of quality evidence that suggests that many women (as well as men and children) are not consuming recommended levels of nutrients and, generally, do not have healthy diets. This is a serious, recognised issue that clearly needs to be addressed. However, while this study concludes that fortified foods or vitamin and mineral supplements may have a role to play in improving women’s nutrition, it is important to have a systematic approach to the evidence on supplementation and nutritional health.
Where did the story come from?
The review was carried out by Carrie Ruxton, a dietitian who runs a nutrition consultancy, and Emma Derbyshire, a researcher from Manchester Metropolitan University. The study was funded by the Health Supplements Information Service (HSIS), an online information programme funded by the Proprietary Association of Great Britain, which is the trade association for manufacturers of food supplements and over-the-counter medicines.
The study was published in Nutrition Bulletin, a publication of the British Nutrition Foundation, a registered charity.
The review’s overall finding that many women eat poorly was generally reported accurately, if somewhat sensationally, in the media. The Daily Telegraph’s headline about millions on “danger diets” and claims in the Daily Express about “food fads” are not borne out by the evidence presented in this study. The newspapers also failed to mention the fact that there is evidence for some improvements in dietary quality over the last few years. Stories in some papers used phrasing and quotes that were identical to those found in the press release on the review. The Daily Mail correctly pointed out (near the end of its report) that the study was industry-funded, but the Express incorrectly called HSIS an “independent body”.
What kind of research was this?
This was a non-systematic narrative review discussing women’s diets. It used supporting evidence from various studies of nutrition. It also referenced studies on the relationship between diet and health. It relied heavily on data from the main source of dietary information in the UK, the National Diet and Nutrition Survey (NDNS), as collated by the Scientific Advisory Committee on Nutrition (SACN). This evidence was supplemented by other studies of women’s diet. The government surveys of nutrition are reputable and generally thought to be accurate.
The study also describes evidence that a poor diet and high alcohol intake are both related to diseases such as cancer, cardiovascular disease, diabetes, osteoporosis and mental health problems. It does not systematically examine the quality of all this evidence, but uses some of it as part of an argument for the importance of improving women’s diets. Some research experts might describe this method for selecting evidence as ‘cherry picking’.
What did the research involve?
The review summarised over 100 studies addressing women’s diets and dietary deficiencies, and also how diet relates to other aspects of health. The review did not state how it identified and selected the studies to be included and, therefore, may not identify or include all relevant studies. The studies that were not included may not agree with the findings of studies that were included. Those studies that were included were summarised in a narrative way.
What were the basic results?
The review of UK dietary surveys broadly found that, while some improvements have occurred, intakes of key micronutrients, particularly iron, vitamin D, calcium and folate, remain below recommended levels across most age groups. Women's diets are also too high in saturated fat and salt, and low in fibre, oily fish and fruit and vegetables.
The authors also make numerous specific observations on nutrition, such as:
- Among girls of school age, 52% have low intakes of magnesium, 25% have low intakes of zinc and about a quarter have poor iron status.
- Among women in their childbearing years 20% fail to meet the Lower Reference Nutrient Intake (LRNI) for iron and 83% eat more than the maximum recommended salt intake of 6g daily.
- The authors also think vitamin D intake may be inadequate, although there is no consensus about recommended intake (the body can obtain vitamin D through either dietary intake of certain foods or by producing it when the skin is exposed to sunlight).
- On average, pregnant women do not meet recommendations for vitamin D or folate.
- Middle-aged women (aged 50-64) tend to eat better quality diets and meet recommended levels of most nutrients.
- Older women (over 65 years) have low intakes of calcium, magnesium and zinc, and vitamin D status is poor.
The researchers also conclude that the evidence suggests that certain chronic conditions are influenced by dietary components. For example, they say that:
- inadequate calcium and vitamin D intakes reduce bone density
- salt and saturated fat increase cardiovascular disease risk
- excessive alcohol intakes increase cancer risk
- low intakes of long-chain n-3 fatty acids may adversely affect foetal development and mental health
- adequate folic acid reduces the risk of birth defects
How did the researchers interpret the results?
The authors conclude that, although there have been positive changes in UK women’s diets, “there is still room for improvement”. High intakes of salt, saturated fat and alcohol remain a problem, as do low intakes of fibre, long-chain n-3 fatty acids, iron, calcium, folate and vitamin D. They say that women need to make better dietary choices in order to ensure adequate levels of micronutrients and, thus, safeguard health.
However, they suggest that attaining optimal levels of some vitamins and minerals from food sources may be “challenging” for some groups of women and, therefore, fortified foods and supplements should continue to play a role in public health campaigns. They argue that, because of insufficient year-round exposure to sunlight and because few foods are naturally rich in vitamin D, vitamin supplements play an important role in helping vulnerable groups achieve acceptable vitamin D status.
This review does not tell us anything new, but it does highlight the worrying fact that many women in the UK of all ages have poor diets. Diet and food choices are complex issues and are also influenced by many environmental factors such as income, lifestyle and access to cheap, nutritious food, some of which are not entirely within an individual’s control.
Sticking to a healthy diet is easier said than done, but it’s important to try to make healthy choices. The current advice is to:
- Eat a variety of food, including plenty of fruit, vegetables and starchy foods, such as wholemeal bread and wholegrain cereals; some protein-rich foods, such as meat, fish, eggs and lentils; and some milk and dairy foods.
- Eat more fish, including one portion of oily fish a week.
- Cut down on sugar and saturated fats (found in butter, cream, cheese and many processed foods).
- Eat less salt (no more than 6g a day).
As a review of nutrition, the authors do not pay much attention to sunlight as a source of vitamin D.
While some groups may benefit from vitamin supplements (women who are pregnant or planning to be for example, are advised to take supplements of folic acid and vitamin D), it is not clear from this report which subgroups of women can get nutrients from eating a healthy diet and who may need supplementation.
It is worth considering the commercially-affiliated funding source of this review and the choice of evidence presented before deciding what role vitamins, mineral supplements or fortified foods may have in improving the health of women.