Sweet drinks and gout risk studied

“Women who drink lots of orange juice and fizzy pop are more at risk of developing painful gout," reported the Daily Mirror .

This study followed a large group of female nurses in the US for 22 years. The women had their diet assessed by questionnaires several times throughout this period and were asked whether they had been diagnosed with gout, and when the symptoms had started. Those who consumed one or more sugary fizzy drinks or glasses of fruit juice a day had an increased risk of developing gout in later life. Orange juice appeared to have a greater effect on risk than other types of juice.

Although the number of cases of gout has increased in recent years, it is still not that common, especially in women. The overall risk of developing gout is still relatively small, and a doubling in risk still only raises the lifetime risk slightly.

One glass of fruit juice still counts as one of your five a day. However, drinking fewer sugary fizzy drinks is a good idea for a number of health reasons.

Where did the story come from?

The study was carried out by researchers from Boston University Medical School and Harvard University. Funding was provided by the US National Institutes of Health. The study was published in the peer-reviewed Journal of the American Medical Association.

The study was covered by a number of newspapers. The coverage was mostly accurate with newspapers giving details about the context of the research and the general risks of gout.

What kind of research was this?

This research was part of a cohort study in which a large number of women were followed for over 20 years to see how their health changed. The Nurses’ Health Study is a large, well-established research programme in the US, which has investigated a large number of risk factors for chronic diseases. It started in 1976, when it recruited 121,700 female nurses aged between 30 to 35 years, of whom 95% were white. The participants had been regularly contacted for further assessments of their health and lifestyle. From the total cohort, 78,906 participants who had been monitored from 1984 to 2006 were included in this particular study.

Gout is a painful form of arthritis that usually develops in older people and affects about 1 to 2% of people in Western countries at some point in their lives. Historically, the condition has been considered to be more common in men, but the number of women developing gout is growing as life expectancies increase. The number of cases of gout has increased in recent years (US annual incidence was 16 new cases out of 100,000 people in 1977 and 42 new cases out of 100,000 people in 1996).

Gout is linked to high levels of a chemical called uric acid in the blood. Fructose (a type of sugar found in fruit and sugary fizzy drinks) can stimulate an increase of uric acid levels in the blood. A recent study by the same authors suggested that consumption of fructose-rich drinks increased the risk of gout in men.

What did the research involve?

Women from the Nurses’ Health Study, who had given enough information about their diet and who had not been diagnosed with gout before 1984, were included in this study.

The nurses’ diets were assessed by validated questionnaires that were sent to them on seven occasions up to 2002. Questions about how many sugary fizzy drinks, diet fizzy drinks and fruit juices they drank were included. Each woman’s average intake was then determined for a number of the periods between the questionnaires). A cumulative score of these was used to categorise the women’s consumption (less than one serving a month, one a month to one a week, two to four a week, five to six a week, one a day, two or more a day). The fructose content of the drinks was calculated and the total fructose intake for the women in these categories was estimated.

Cases of gout were identified using criteria from the American College of Rheumatology. Participants were sent questionnaires in 1982, 1984, 1986, 1988, 2002 and every two years after that. They were asked whether they had been diagnosed with gout by a doctor, and when the condition had started. From 2001 onward, an extra questionnaire was sent to anyone diagnosed with gout in 1980 or later to verify that the symptoms matched official diagnostic criteria. A total of 81% of women diagnosed with gout, and to whom this extra questionnaire was sent, replied.

Other risk factors were measured at the time women joined the study and every two years afterwards. Data were collected on weight, alcohol intake, regular use of medications and other health conditions. In the analysis, the researchers adjusted the data to take into account the possible effects of age, total energy intake, body mass index and other medical and dietary factors (such as alcohol) that are known to increase the risk of developing gout.

What were the basic results?

During the 22 years of follow up, 778 new cases of gout were identified. Women who drank one sugary fizzy drink every day had a 74% higher risk of developing gout (relative risk [RR] 1.74, 95% confidence interval [CI] 1.19 to 2.55). Women who drank two or more drinks a day had about two and a half times the risk (RR 2.39, 95% CI 1.34 to 4.26). For consumption of orange juice, the increased risk was 41% for one glass a day (RR 1.41, 95% CI 1.03 to 1.93). Two or more glasses were again associated with two and a half times the risk (RR 2.42, 95% CI 1.27 to 4.63).

When the analysis included all fruit juices, drinking one glass of juice was still associated with greater risk (RR 1.67, 95% CI 1.12 to 2.49 but two or more glasses a day was not (RR 1.14, 95% CI 0.57 to 2.27, n=11). There was no relationship between drinking diet fizzy drinks and the risk of developing gout.

Using these results, the researchers calculated that about 47 extra new cases of gout a year could be expected for every 100,000 women drinking two or more servings of orange juice compared with less than one.

How did the researchers interpret the results?

The researchers report that “the risk of incident gout increased with increasing intake of sugar-sweetened soda. In contrast, diet soda intake was not associated with risk of incident gout.” They say their findings “provide the first prospective evidence among women that fructose and fructose-rich beverages are important risk factors to be considered in the primary prevention of gout”. However, they balance this statement by saying that the overall risk of developing gout for women is low.

Conclusion

This large, well-conducted study suggests that dietary consumption of fructose may increase the risk of developing gout.

The following points should be considered:

The increased risk of gout for people who drank one or more fructose-rich drinks a day was in comparison to the group with the lowest consumption of less than one drink a month. This is a big difference in juice consumption. The difference in risk for women who drank less juice, such as one drink a week, might be less.
Diet can be hard to assess, as people sometimes do not accurately remember what they eat, or they can give the answers they think researchers want to hear. However, the methods used here to assess diet were well designed and are likely to give as accurate a picture of diet as any survey can.
Even with accurate assessment, there can be variation in the content of fructose of juices and in portion sizes. There may also be other dietary sources of fructose that were not recorded in this study.
The relationship between dietary fructose intake, levels of uric acid in the blood and the development of gout is not fully understood. Other factors affect risk, including alcohol and weight, which the researchers took into account. However, it is possible that there are other risk factors that they did not take into account in their analysis.
As all the participants in the study were nurses and the majority of them were white, it is not clear how well these findings apply to women in other ethnic groups, or to men. Also, it is worth considering whether there is anything else different about the lifestyles or risk factors that nurses experience compared to the general population.
No questionnaires assessing new cases of gout were sent between 1988 and 2002, so it is unclear whether the lack of data during this period may have affected the accuracy of the number of cases detected.
Following the women for a longer period may show a different pattern in association between fructose consumption and gout (for example, lifetime risk of gout may be the same regardless of diet, but age of onset may differ).

Despite these limitations, this is a good quality study, which appears to indicate that regularly drinking more orange juice may increase the risk of gout for women. However, the overall risk of developing gout is still relatively small, and a doubling in risk still only raises the lifetime risk very slightly.