Is the link between nutrients and foods understood? The case of fibre and folate.

OBJECTIVES: To assess and contrast awareness of the link between dietary fibre and folate and their major food sources (fruit, vegetables, bread and cereals). DESIGN: Mailed questionnaire investigating changes made to dietary intake of fibre, folate, fruit, vegetables, bread and cereals in the previous six months. SETTING: The survey was conducted between June and November 1998 in the Australian Capital Territory. SUBJECTS: One thousand one hundred and twenty-six adults randomly selected from the electoral roll. RESULTS: More women than men in both older (50+ years) and younger (18-49 years) age groups reported increasing their consumption of folate, fibre, fruit and vegetables in the prior six months. In contrast, more men than women reported increased consumption of bread, cereals, rice and pasta in the previous six months. For food categories and fibre, less than 4% of respondents were unsure about changes in these food habits. However, 26% of men and women were 'not sure' about changes to folate intake. Similar proportions of men and women (about 33%) reported consuming more fruit, vegetables or cereal-based foods over the prior six months, yet only 6% of these men and 14% of these women reported consuming more folate. In contrast, 44% of men and 51% of women who reported consuming more plant foods also reported consuming more dietary fibre. CONCLUSIONS: The results suggested that subjects, particularly the younger age group, had a poor understanding of the relationship between folate intake and its major food sources. The understanding of the relationship between fibre intake and its food sources appeared substantial, but confusion about specific food sources was still evident. These outcomes question the effectiveness of nutrition education used to date, particularly for the current priority of increasing folate intake in younger women in the new, 'health claims' environment.

Milk choices made by women: what influences them, and does it impact on calcium intake?

OBJECTIVE: : To identify influences on type of milk consumed and the impact of milk choice on calcium intakes in Australian women of pre- and postmenopausal age. DESIGN AND SETTING: : Questionnaires covering calcium intake, health-related dietary issues and priorities self-completed in a group setting. SUBJECTS: : A total of 300 women recruited from community groups and government departments. RESULTS: : Mean milk and calcium intake were higher in older (> or = 50 years) compared to younger women. Milk provided over 50% of calcium intake for both groups. Participants rated the importance of eating foods low in fat, energy or cholesterol, high in calcium or dietary fibre or of 'limiting their intake of added sugar or sugary foods'. Younger and older women ranked eating foods low in fat as the most important food habit for their health, then ranked dietary fibre next in importance. Calcium ranked third for younger women, and fourth for older women. These rankings were reflected in the higher proportion of older women choosing fat-reduced milk in general, and skim milk in particular. This concern about eating foods low in fat was consistent with the choices made of skim, reduced fat/higher calcium or whole milk. CONCLUSIONS: : Results from this study suggest that concerns about fat are prejudicing the type of milk and amount of calcium consumed. Public health strategies targeting calcium intake need to address age-related differences in quantity and type of milk consumed, including the food attribute conflicts influencing these.

Iron status and diet in athletes.

Plasma ferritin (F) concentrations were measured (range 12-245 ng.ml-1) as an indicator of iron status in 24 male and 45 female healthy, nonanemic athletes. Usual food intake was assessed using a self-completed but supervised food frequency questionnaire. Linear regression was applied to determine the relationship between log F (as data was skewed) and average daily intake of iron (Fe), meat (M), protein (Pr), carbohydrate (CHO), fat (Fa), fiber (Fi), and kilojoules (Kj). There were negative correlations between F and each of Kj (P < 0.01) and CHO (P < 0.001), and a positive correlation between F and Pr/Kj (P < 0.01). No significant relationship existed between F and any of Fe, M, Fa, or Fi. These data suggest that iron or meat intake may not be important determinants of iron status in these athletes. Instead, the percentage of protein in the diet may be more influential on F, as may the (negative) effect of Kj and CHO intake, or at least their reflection of energy expenditure.

Plasma ferritin concentration and physical work capacity in athletes.

This investigation aimed to determine whether the physical work capacity of nonanemic athletes could be improved when plasma ferritin concentrations of below 30 ng/ml were raised at least 15 ng/ml. The experimental group consisted of 15 training athletes, each of whose plasma ferritin concentration was less than 30 ng/ml (mean and SD of 19.8 +/- 8.4 ng/ml). In a control group of 16, each was measured with a plasma ferritin concentration of more than 40 ng/ml (mean and SD of 83.3 +/- 37.6 ng/ml). All participated in submaximal and maximal tests for aerobic and anaerobic power. Following iron supplementation, plasma ferritin concentration in each experimental subject increased by at least 15 ng/ml to more than 30 ng/ml, to a new mean of 46.3 +/- 15.5 ng/ml. The performance measures were also repeated, but no significant overall effects were associated with the increased plasma ferritin concentrations. These data provide no sound evidence that physical work capacity of athletes is enhanced when plasma ferritin concentrations of around 20 ng/ml are increased by at least 15 ng/ml.

The effect of 7 to 8 months of vitamin/mineral supplementation on the vitamin and mineral status of athletes.

Blood indicators of eight vitamins (B1, B2, B6, C, E, A, B12, folate) and six minerals (Cu, Mg, Zn, Ca, P, Al) were measured in 86 athletes before and after a 7- to 8-month period of training. During this period half consumed a multivitamin/mineral supplement and a matched group took a placebo. Following the supplementation period, blood biochemical indicators of B1, B6, B12, and folate status all increased but there were no significant effects of supplementation on B2, C, E, and A, or on the blood levels of any of the minerals. The supplementation had no effect on red or white cell counts or on hemoglobin levels. Irrespective of the supplementation, some blood measures varied according to sex, females evidencing significantly higher values than males for vitamins C, E, copper, magnesium, and aluminium, with B2 being higher in males. It is concluded that 7 to 8 months of multivitamin/mineral supplementation increased the blood nutritional status of some vitamins but did not affect any blood mineral levels, and that some blood nutritional indicators may vary according to sex.

The effect of 7 to 8 months of vitamin/mineral supplementation on athletic performance.

The effect of vitamin and mineral supplementation was studied over 7 to 8 months of training and competition in 82 athletes from four sports: basketball, gymnastics, rowing, and swimming. Matched subgroups were formed and a double-blind design used, with subgroups being given either the supplementation or a placebo. All athletes were monitored to ensure that the recommended daily intakes (RDI) of vitamins and minerals were provided by diet alone. Sport-specific and some common tests of strength as well as aerobic and anaerobic fitness were performed. Coaches' assessment of improvement was also obtained. The only significant effect of supplementation was observed in the female basketball players, in which the supplementation was associated with increased body weight, skinfold sum, and jumping ability. A significant increase in skinfold sum was also demonstrated over the whole group as a result of supplementation. In general, however, this study provided little evidence of any effect of supplementation to athletic performance for athletes consuming the dietary RDIs.

Bone density of élite female athletes with stress fractures.

To investigate whether stress fractures occurring in élite female athletes are related to reductions in bone mineral density (BMD), we measured BMD in nine athletes with such fractures and nine athletes without fractures who were matched for age, weight, height and sport. BMD was measured in three regions: upper limbs (distal radius), axial skeleton (lumbar spine) and lower limbs (femoral neck) by photon absorptiometry. The number of menses per year was significantly less (P less than 0.04) and the age of menarche was significantly delayed (mean +/- SD; 16.1 +/- 0.4 v. 14.4 +/- 1.5 years, P less than 0.02) in the fracture group compared with the non-fracture group. There was no significant difference in BMD between the two groups at any of the measurement sites. Moreover although the fractures occurred mainly in lower limb bones, at sites characterised by predominantly cortical bone, all athletes had femoral neck BMD values within the 95% confidence limits for normal non-athletic women. We conclude that stress fractures in élite female athletes are largely independent of BMD.