While searching for relief from migraines and general malaise, a friend recently consulted a nutritionist who told her, matter-of-factly, that because she has Type O blood, she should be eating lots of meat and eliminating gluten, dairy and many grains. A Chinese medicine doctor she consulted confirmed the advice, saying, basically: Duh.

For someone who had hoped to go vegetarian — and who is among the 45 percent of people in the U.S. with Type O blood — the news was surprising.

But was it true?

The idea of eating according to your blood type became popular with the 1996 book “Eat Right 4 Your Type” (Putnam Adult) by Peter D’Adamo, a naturopath physician. The theory is that the genes behind blood type also are behind the expression of other proteins in our body, which relate to how we digest foods.

Type O’s, having the oldest blood type, draw on our hunter roots and perform best on lean meats (including fish), fruits and vegetables, as well as with intense exercise, while gluten, some beans and dairy lead to weight gain, sickness and sluggishness, the theory posits. The proteins in legumes and dairy tend to cause inflammation in Type O’s, goes the theory, so without meat it’s difficult to fulfill their protein needs.

Rather than banning Type O’s from being vegetarians, D’Adamo said, “a more helpful way of thinking is that people who are blood Type O may want to explore a more high-protein, lower-carbohydrate lifestyle in lieu of their current dietary choices, should they suffer from signs that they are not getting enough protein in their diets: digestive disorders, fatigue, low immunity or slow metabolism.”

Meantime, people with blood Type A do best as vegetarians, B’s are hardier omnivores and ABs are a combination.

Most nutritionists do not subscribe to eating by blood type because it is not backed by hard scientific data, said Marjorie Nolan, a dietitian and spokeswoman for the American Dietetic Association.

The evidence supporting the blood-type diet is based largely on anecdotes and research showing links between blood type and certain illnesses (for example, Type O’s are more likely to have stomach ulcers). There have been no peer-reviewed studies published that show different blood types perform better on certain foods.