Scientists have known for some time that in adults, low levels of vitamin D are associated with high blood pressure, high blood sugar and metabolic syndrome — a collection of risk factors for diabetes and heart disease that includes high waist circumference and elevated cholesterol and triglycerides. Now we know that too little of the sunshine vitamin causes those same problems in tweens and teens.

Kids ages 12 to 19 with the lowest levels of vitamin D (less than 15 nanograms per milliliter) were more than twice as likely to have high blood pressure and blood sugar, and nearly four times as likely to have metabolic syndrome as those with the highest amounts (more than 26 nanograms per milliliter), according to research presented yesterday at this week's American Heart Association Conference on Cardiovascular Disease Epidemiology and Prevention in Palm Harbor, Fla. Levels of 30 nanograms per milliliter are considered sufficient. The results are based on 3,577 teens who participated in the National Health and Nutrition Examination Survey (NHANES) conducted between 2001 and 2004.

Got milk? Then drink to this: A new study has linked high calcium intake to lower incidence of cancers, including colon cancer, in men and women between the ages of 50 and 78.

In surveys of nearly 300,000 men and 200,000 women, researchers found that women who got about 1300 milligrams per day or more of calcium -- the equivalent of about four and a half cups of milk -- had a 7 percent lower risk of developing any type of cancer than those with the lowest intake -- about 500 milligrams per day, the equivalent of about one and a half cups of milk.

Is sunshine more than just a home remedy for a cold? New research suggests it may be: In a study that will be published tomorrow, people with low levels of vitamin D — also known as the "sunshine vitamin" — were more likely to catch cold and flu than folks with adequate amounts. The effect of the vitamin was strongest in people with asthma and other lung diseases who are predisposed to respiratory infections.

People with the worst vitamin D deficiency were 36 percent more likely to suffer respiratory infections than those with sufficient levels, according to the research in this week's Archives of Internal Medicine. Among asthmatics, those who were vitamin D deficient were five times more likely to get sick than their counterparts with healthy levels. And the risk of respiratory infection was twice as high among vitamin D-deficient patients with chronic obstructive pulmonary disease (COPD) than in lung patients with normal levels of the vitamin.

Vitamin D is the vitamin du jour these days, with many doctors urging more sun exposure following years of campaigns advising us to cover up and use sunscreen to prevent skin cancer. Many of us, especially in cloudier areas, don’t get enough of the sunshine vitamin. The elderly and post-menopausal women are more at risk for deficiency, as are those who live in northern climes.

But today comes news that one group seems to be at particular risk, doctors report in the journal Endocrine Practice. Arab-American women who wore the hijab (a Koran-derived dress code that includes a scarf or veil over their hair and modest dress) and didn’t get enough vitamin D through their diet had half the levels of the vitamin of those who didn’t adhere as closely to the dress code. There was no difference in rates of health problems linked to vitamin D deficiency, such as bone or joint pain or breaks, or muscle weakness. The study involved 87 women in Dearborn, Mich., which has a large Arab population.

Pregnant women with vitamin D deficiencies are more likely than other expectant moms to deliver their babies via cesarean section.

"Women with a vitamin D deficiency were almost 4 times more likely to have a cesarean than those with [normal] vitamin D levels," says senior study author Anne Merewood, an assistant pediatrics professor at Boston University School of Medicine. "Vitamin D is definitely involved in muscle strength…. contractions of the uterus [which is made of smooth muscle] may not be performing as well as they could be," making it difficult for the woman to help push the baby out herself.

This research was actually part of a larger study (the findings of which are yet to be published) of the prevalence of vitamin D deficiencies among women of childbearing age. Merewood told ScientificAmerican.com that 156 (36 percent) of the 433 women in the larger study were found to be vitamin D deficient and 100 (23 percent) severely deficient. This translates into a potentially major public health problem, as vitamin D deficiency was recently linked to a number of chronic diseases, including cancer and multiple sclerosis.

Autism is more common in rainy, coastal areas of the Pacific Northwest than in drier, inland parts of three states in the region, according to new research that suggests a possible link between the brain disorder and precipitation.

Autism was twice as common in the damp counties west of the Cascade Mountains than in those east of the range, which get four times less rain, the study in Archives of Pediatric and Adolescent Medicine shows. Kids in counties in California where rainfall was heavier also had higher rates of the disorder than children whose first three years of life were spent in drier weather.

Autism causes impaired social interactions, delayed speech, and repetitive movements or behaviors. For unknown reasons, autism prevalence has surged over the past 30 years from an estimated one in 2,500 to one in 150 U.S. children, according to the Centers for Disease Control and Prevention (CDC). It's not clear why those rates are more elevated in damp areas — including states not in the study such as New Jersey, Massachusetts, Maine and Minnesota — but bad weather that keeps genetically vulnerable kids indoors could play a role, the study authors write.