“Most people can get their daily fill of vitamin D by drinking a cup of milk and eating a 3-ounce serving of salmon.” — Dr. Susan Y Chon, dermatologist at the MD Anderson Cancer Canter at the University of Texas, as quoted in a United Press International story, “Skin expert: Get Vitamin D From Food.”

Trouble is: There’s no evidence to support the math behind Chon’s statement. So let’s add it up for her.

One cup of milk contains no vitamin D naturally. Milk is supplemented with vitamin D while being processed, but by the time milk reaches the consumer some studies show that one cup of milk may not have any vitamin D in it at all. At most, it has 100 IU of vitamin D.

Three ounces of farmed salmon may not contain that much vitamin D either, as farmed salmon do not get vitamin D from the food chain naturally like wild salmon does. While a 3-ounce serving of wild salmon may have up to 500 IU of vitamin D, some studies show that salmon from the market may only have 10-25 percent of that amount, or just 50-150 IU.

Vitamin D researchers now suggest a minimum of 2,000 IU of vitamin D daily, which you would make in just minutes outdoors in the summer with full-body sun exposure in a bathing suit.

“Some people may absorb enough vitamin D from their routine outdoor exposure,” Chon says in a statement to UPI. But routine outdoor exposure — with sunscreen on as Chon recommends, means just 10 percent of the body is exposed, making tens of units of vitamin D if the person has no sunscreen on their face. Most women wear SPF in their make-up now, cutting that amount by 95-99 percent.

So in Houston in the summer “incidental” outdoor exposure without sunscreen (10 percent of the body exposed for 10 minutes at mid-day) would make about 500 IU of vitamin D on a bright, sunny day. If the person is wearing sunscreen as Chon recommends, that amount would be cut by at least 95 percent, meaning the person would make, at most, 25 IU of vitamin D. And that amount goes down even more if the exposure comes in the morning or afternoon, when the sun contains less UVB which triggers vitamin D production.

A full-body, non-burning session in a sunbed can make 10,000-20,000 IU of vitamin D, according to clinical tests — 100-200 times what is supplemented into a glass of milk.

That’s why sunbed users have vitamin D blood levels 90 percent higher than the general population, according to Boston University research. A Canadian study published last year showed that sunbed users have the highest vitamin D levels in Canada.

To read Chon’s quote in the UPI story click here.