Excess milk intake may shorten life span in women, researchers claim

16-Feb-2017 - Last updated on 16-Feb-2017 at 14:19 GMT

Researchers hypothesised that a high intake of fruits and vegetables or a high total antioxidant intake may counteract the observed associations of milk intake with mortality. ©iStock/smartin69

Drinking milk to excess may be detrimental to health and could even shorten life span in women, according to Swedish researchers.

Conclusions reached suggest large volumes of milk can promote chronic low-grade inflammation in the body.

However, the study goes further with the insinuation that there is a heightened risk based on gender.

“A sex difference in sensitivity to galactose exposure has been identified experimentally,” the study said. “Galactose elimination capacity is also higher in men than in women, but it declines with increasing age.”

The study also found evidence that an adequate fruit and vegetable intake could provide a degree of protection from the oxidative and inflammation processes caused by galactose supplementation.

Milk consumption and its effects has been an ongoing bone of contention amongst scientists. It has long been promoted as strengthening bone and reducing the likelihood of bone fractures.

On the other hand, the same team demonstrated a higher risk of fracture with high daily milk consumption in women.

This study also identified higher mortality rates in both women and men with high milk consumption.

FFQ on diet & lifestyle

Researchers from the Uppsala University and Karolinska Institute in Stockholm looked at data provided by approximately 106,000 men and women based in Sweden.

A food frequency questionnaire (FFQ) that asked about diet and lifestyle was distributed and statistical analysis was used to compare total antioxidant consumption with fruit and vegetable intake.

Results suggest for women who consumed at least three glasses of milk and ate fruit and vegetables once a day, the risk of dying was three times as high compared to those who drank no more than one glass of milk per day and ate fruit and vegetables at least five times per day.

There was a 60% higher risk of earlier death in women who consumed three glasses of milk per day and ate fruit and vegetables at least five times a day.

This figure was in comparison to women who consumed the same amount of fruit and veg but drank little to no milk at all.

Men exhibited a 30% higher risk of death only if they consumed at least three glasses of milk per day compared to those men who seldom or abstained from drinking milk.

However, the amount of fruit and vegetables consumed had no significant bearing on these outcomes.

“The gradient of risk with increasing milk consumption was more pronounced in women,” the study pointed out.

“Our postulated mechanism is that milk consumption induces oxidative stress by way of the galactose component of lactose, because galactose supplementation results in premature aging in animals through induction of oxidative stress and inflammation.”

Evolutionary mechanism

public breastfeeding breast milk infant formula mother maternal iStock Viktorcvetkovic — Researchers thoguht the lower female degradation of galactose might have been an evolutionary survival mechanism for the child. ©iStock/Viktorcvetkovic

The researchers believed that a lower rate of galactose degradation in females might have been an evolutionary survival mechanism for the child.

Galactose is used in the production of human breast milk. Most lactose in human breast milk is made from galactose taken up from the blood.

Liver glycogen in infants is formed mainly from breast milk–derived galactose.

The anti-oxidative and anti-inflammatory power of fruits and vegetables was cited as the reason behind its ability to counteract the effects of excess milk intake.

“By reducing oxidative stress and inflammation processes, higher fruit and vegetable intake has convincingly been shown to promote longevity and reduce the risk of cardiovascular disease and some cancers,” the study commented.

The study’s authors did acknowledge the limitation of the study that included a local population, which yielded results that might not apply to people of other ethnic origins, such as those with a high prevalence of lactose intolerance, or to children and adolescents.

“The findings of our observational investigation should not be evaluated in isolation and have to be interpreted cautiously,” the study concluded.

Source: American Journal of Epidemiology

Published online ahead of print: doi.org/10.1093/aje/kww124

“Milk, Fruit and Vegetable, and Total Antioxidant Intakes in Relation to Mortality Rates: Cohort Studies in Women and Men.”

Authors: Karl Michaëlsson Alicja Wolk Håkan Melhus Liisa Byberg