A surprising study contradicting all previous research found that being fat in middle age appears to cut the risk of developing dementia rather than increase it, the Lancet scientific journal has reported.

A study of two million people found that the underweight were far more likely to develop dementia, a growing problem among the elderly in the Western world.

The underweight had a 34 percent higher risk of developing dementia than those of a normal weight, the study found, while the very obese had a 29 percent lower risk of becoming forgetful and confused and showing other signs of senility.

The exhaustive study, published in the Lancet Diabetes and Endocrinology Journal, flies in the face of previous smaller studies — and much modern health advice — that what is good for the heart is also good for the head.

Researchers said that if other studies confirm the findings, the next step would be to examine if people who eat more unknowingly take in dementia-fighting nutrients. But Nawab Qizilbash of Oxon Epidemiology, who led the study, cautioned: “Even if there is a protective effect against dementia from being overweight or obese, you’re not living long enough to benefit from it.”


Breast milk bought online may be risky

People who buy human breast milk over the Internet may be getting less than they bargained for. A study in Pediatrics found that more than 10 percent of samples of breast milk bought online contained cow’s milk.

Researchers bought 102 samples from sites that use classified ads to connect milk buyers with sellers. They isolated mitochondrial DNA from the samples by polymerase chain reaction, the same technique used for forensic and medical purposes. Every sample contained human DNA, but 11 of them contained cow’s milk, 10 of them at levels higher than 10 percent.

“This was high enough to rule out minor or accidental contamination,” said the lead author, Sarah A. Keim, a principal investigator at Nationwide Children’s Hospital in Columbus, Ohio.


Bleach tied to respiratory ills

Cleaning with bleach at home is associated with higher rates of respiratory illness in children, a study found.

Researchers studied the use of bleach in the homes of 9,102 9- and 10-year-olds in Spain, Finland and the Netherlands and assessed its effects on respiratory health. The study is in Occupational & Environmental Medicine.

The researchers found that the use of bleach in homes at least once a week increased the risk of respiratory infections by 18 percent overall. But it was associated with a 20 percent increase in the risk for flu and a 35 percent increase in the risk for recurrent tonsillitis.

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