Abstract
High milk consumption might shorten life span through increased oxidative stress. We aimed to determine whether higher mortality rates with high milk consumption are modified by fruit and vegetable intake or total antioxidant intake (oxygen radical absorbance capacity). We used information from food frequency questionnaires completed by 61,420 women in a Swedish cohort (22,391 deaths from the 1987–1990 baseline onward), 36,714 women from a second survey (1997) of this cohort, and 45,280 Swedish men (15,478 deaths from the 1998 baseline onward). Compared with low consumption of milk (<1 glass/day) and high consumption of fruits/vegetables (≥5 servings/day), time-updated information revealed an adjusted hazard ratio for death of 2.79 (95% confidence interval (CI): 2.42, 3.21) in women who consumed ≥3 glasses of milk/day and <1 serving/day of fruit/vegetables and a hazard ratio of 1.60 (95% CI: 1.40, 1.82) in women who consumed the same amount of milk but ≥5 servings/day of fruits/vegetables. The same comparisons in men, based on a single food frequency questionnaire, displayed hazard ratios of 1.31 (95% CI: 1.14, 1.51) and 1.07 (95% CI: 0.97, 1.18), respectively. Total antioxidant consumption showed similar patterns as fruit/vegetable intakes. Dietary
Generated Summary
This study investigates the relationship between milk, fruit, vegetable, and total antioxidant intake with mortality rates in cohort studies of women and men. The research utilized data from two previously described population-based cohort studies: the Swedish Mammography Cohort (SMC) and the Cohort of Swedish Men. The SMC, initiated in 1987-1990, involved 61,240 women, while the Cohort of Swedish Men, established in 1997, included 45,280 men. The study aimed to determine if fruit, vegetable, or total antioxidant intake modifies the previously observed relationship between milk consumption and death. Participants reported their average consumption frequency of up to 96 foods and beverages through a valid and reproducible food frequency questionnaire (FFQ). Time-updated information was used to assess the impact of various dietary factors on mortality rates, with statistical analyses including restricted cubic-spline Cox regression and multivariable-adjusted hazard ratios. The study’s scope encompassed data from 1987 to 2015, allowing for comprehensive assessments of long-term dietary impacts on mortality. The study explored how the combined intake of milk, fruits, vegetables, and antioxidants affects mortality, considering that high milk consumption might shorten lifespan through increased oxidative stress.
Key Findings & Statistics
- In women who consumed ≥3 glasses of milk per day and <1 serving/day of fruit/vegetables, the adjusted hazard ratio for death was 2.79 (95% confidence interval (CI): 2.42, 3.21).
- Women consuming the same amount of milk but ≥5 servings/day of fruits/vegetables had a hazard ratio of 1.60 (95% CI: 1.40, 1.82).
- In men, similar comparisons displayed hazard ratios of 1.31 (95% CI: 1.14, 1.51) and 1.07 (95% CI: 0.97, 1.18), respectively.
- Approximately 9% of women reported milk consumption of ≥3 glasses/day in 1987–1990 (Table 1), while only 2% reported such intake in 1997 (Table 2). Men had higher milk consumption, with 15% drinking ≥3 glasses/day in 1997 (Table 3).
- The average reported consumption of fruits and vegetables among women was 3.5 servings/day (standard deviation (SD), 2.0) at baseline and 5.3 servings/day (SD, 3.0) at follow-up.
- Men reported an average consumption of 4.1 servings/day (SD, 2.5).
- During a mean follow-up of 23 years (maximum 29 years), 22,391 women died.
- From January 1, 1998, onward, 10,314 women (581,785 person-years) and 15,478 men (687,688 person-years) died during a mean follow-up of 15 years (maximum 17 years).
- The rate of mortality was highest among persons consuming less than 1 serving of fruit and vegetables per day (or in the lowest quartile of ORAC) combined with high milk consumption in both men and women.
Other Important Findings
- Total antioxidant consumption showed similar patterns as fruit/vegetable intakes.
- The study hypothesized that a high intake of fruits and vegetables or a high total antioxidant intake may counteract the observed associations of milk intake with mortality.
- In time-updated analysis of the SMC, a high intake of milk (≥3 glasses/day) with a low intake of fruit and vegetables (<1 serving/day) conferred a multivariable-adjusted hazard ratio of 2.79 (95% CI: 2.42, 3.21).
- With a combined high intake of fruit and vegetables, the hazard ratio was 1.60 (95% CI: 1.40, 1.82) in women.
- In men, the same comparisons revealed a hazard ratio of 1.31 (95% CI: 1.14, 1.51) for high milk consumers with low fruit and vegetable intake and a hazard ratio of 1.07 (95% CI: 0.97, 1.18) for high milk consumers with 5 or more servings of fruits and vegetables per day.
- The relative excess risk of interaction estimate of 0.37 (95% CI: 0.01, 1.27) in the time-updated analysis of women indicated a modest additive interaction, while no significant interaction was discovered among men.
Limitations Noted in the Document
- The study’s findings may not apply to people of other ethnic origins, such as those with a high prevalence of lactose intolerance, or to children and adolescents.
- The study’s observational nature limits the ability to establish causal relationships definitively.
- Exclusion of the first two years of follow-up and those with extreme BMI values (greater than 35) and current smokers in additional sensitivity analyses may have affected the results.
- The generalizability of the results is limited by the fact that the study was conducted with Swedish adults only.
Conclusion
The study’s findings indicate that high milk consumption, particularly when combined with low fruit and vegetable intake, is associated with increased mortality rates in both women and men. “Compared with low consumption of milk (<1 glass/day) and high consumption of fruits/vegetables (≥5 servings/day), time-updated information revealed an adjusted hazard ratio for death of 2.79 (95% confidence interval (CI): 2.42, 3.21) in women who consumed ≥3 glasses of milk/day and <1 serving/day of fruit/vegetables.” This effect was more pronounced in women, where the combination of high milk intake and low fruit and vegetable intake significantly increased the risk of mortality. The association of milk intake with increased mortality was not clearly modified by fruit and vegetable intake in men. The study’s results underscore the potential role of diet in influencing lifespan, with the additive interaction between milk consumption and fruit and vegetable intake highlighting the importance of dietary patterns. These findings suggest that dietary guidelines may need to be re-evaluated, especially for women, considering the combined effects of milk consumption and the intake of protective foods. The study’s findings, therefore, question the value of recommending high consumption of milk, especially in women not meeting the recommended intakes of fruit and vegetables. The results support the idea that dietary choices, particularly the combination of milk consumption and the intake of fruits and vegetables, play a significant role in mortality risk.
IFFS Team Summary
- study of over 140 000 men and women over years in Sweden
- Compared to sex matched subjects who consumed maximum one glass of milk per day, but 5 or more serving of fruits and vegetables
- Women consuming three or more glasses of milk , and one or less servings of vegetables had a mortality HR of 2.79
- Women consuming three or more glasses of milk , and five or more servings of vegetables had a mortality HR of 1.60
- In men, the same comparison yielded HR of 1.31 and 1.07 – the latter not been statistically significant
- possibly hard to find a distinction in men if overall animal protein consumption is high