Ask Tufts Experts

In your January issue you state that “yogurt, while a good source of calcium, doesn’t deliver the vitamin D benefit that milk does.” This has me puzzled. I make yogurt regularly from skim milk with added dry milk, both of which have added vitamin D. Why would the yogurt not deliver the vitamin D benefit that milk does?

Sorry for the confusion! The reference was to commercial, store-bought yogurt. If you make your own yogurt from fortified milk, the result will have the added benefit of vitamin D just as the original milk does. We’ve also had readers ask about the effect of heat, as in making yogurt (where the milk is typically heated to 185 degrees Fahrenheit), on vitamin D. Unlike some water-soluble vitamins such as vitamin C and B-complex, fat-soluble vitamins such as D are not damaged by moderate heat exposure. (Vitamin D is destroyed by exposure to light, however, which is why milkmen used to deliver into doorstep boxes.)

Like other commercial dairy products made from milk, such as most cheese and ice cream, store-bought yogurt is ordinarily not fortified with vitamin D as milk is. While optional, most milk marketed in the US is fortified with vitamin D to a standardized amount of 400 IU per quart. The acceptable range allowed for vitamin D fortification of milk is not less than 100% and not more than 150% of label claims—that is, 400-600 IU per quart. But if you want to use yogurt as a source of vitamin D, you’ll have to make it at home—or seek out the new, vitamin D-fortified yogurt varieties.

Often you extol the virtues of canola and olive oils, but grapeseed oil is never mentioned. I have read that it lowers LDL and raises HDL—unlike any other oils available. It has less saturated fat than other commonly used oils. Since you never mention it, though, I wonder if there are negative health aspects that I should be aware of?

The only negative aspect of grapeseed oil compared to other oils is that it tends to be more expensive and harder to find. It is among the lowest available oils in saturated fat, with only 10% (canola oil has the least at 7%). Grapeseed oil is also high in vitamin E, with more than canola or olive oil although less than safflower oil. From the cook’s perspective, grapeseed oil is an excellent choice because of its high smoke point—about 420 degrees Fahrenheit (a temperature that will, however, destroy that vitamin E)—and light, “nutty” taste.

As an oil high in polyunsaturated fat (71%), grapeseed oil will tend to reduce dangerous LDL cholesterol a bit more than mostly monosaturated alternatives such as olive oil. But some studies have suggested that polyunsaturated fats may also lower the “good” HDL cholesterol at the same time. The claims that grapeseed oil actually raises HDL levels are based on two studies published in 1990, in the Journal of Arteriosclerosis, and 1993, in the Journal of the American College of Cardiology. Because grapeseed oil is far less common than other oils, its effects on health have not been as thoroughly studied, and these findings—more than a decade old—have not subsequently been confirmed by other research.

So, while you shouldn’t expect miracles from grapeseed oil, it’s a suitable alternative vegetable oil and a big improvement over cooking with fats that are solid at room temperature such as butter. But like all fats, grapeseed oil contains 120 calories per tablespoon, so use in moderation.