Marc Joseph Nutrition - Blog

In a recent study published in Nutrition and Metabolism, researchers found that interesterified (IE) fat, which is being pushed as a replacement for trans fats, may actually have more negative health effects than trans fats themselves.

The negative health effects of trans fats have been widely known for some time:

• increase bad cholesterol (LDL)
• decrease good cholesterol (HDL)
• impair endothelial cell (e.g., arterial) function
• associated with greater risk for heart disease and diabetes

Beginning in 2006, the Food & Drug Administration (FDA) began requiring all food manufacturers to list trans fats separately on the Nutrition Facts labels on packaged foods:

That move certainly has helped make it easier to select healthier products at the grocery store.

And, late last year, in a move that may start a trend, New York City banned trans fat use in restaurants.

Questions remain, though. What will replace trans fat products? Many products have been developed for both frying and baking. Will the replacements be any healthier?

Interesterified (IE) fats have been developed as one alternative. These fats are made by combining liquid oils (e.g., canola oil) with solid fats (e.g., palm oil) and mixing them with acids or enzymes to form a fat of desired consistency. The process is called interesterification.

The study mentioned above put study participants in three groups using the following test fats (~30% overall fat, >70% test fat):

• palm oil (a saturated fat) - PO
• partially hydrogenated soybean oil (containing 3.2% trans fat and 6.5% palm oil) - PHSO
• and an interesterified fat (with 12.5% stearic acid, a saturated fat) - IE

Researchers found that after four weeks:

• Blood glucose levels were 40% higher after meals in individuals using the IE diet versus those using the PO or PHSO diet.
• Fasting insulin levels were 10% lower in those using the PHSO diet and 22% lower in those using the IE diet.
• HDL (or good cholesterol) fell by 8 percent for the PHSO diet and 7 percent for the IE diet.

Not so good. Although the results of this study need to be replicated (this study was funded and staffed by the Malaysian Palm Oil Board), it seems like IE fats may be ones that you’ll want to avoid.

Your best bet is including in your diet unaltered fats in healthy combinations. For example, try using olive oil (high in monounsaturated fats) as your primary dietary oil, and layering on essential fats (Omega-3 fats as found in fish oil and small amounts of Omega-6 fats as found in vegetable oils).

Many of the healthy compounds found in vegetables, including:

• carotenoids
  • beta-carotene
  • lycopene
  • lutein
• vitamin E

are fat-soluble nutrients. What that means is that these nutrients are best absorbed from the digestive tract in the presence of fat.

The differences in absorption when fat is or is not included in the meal can be large and significant. For example, as this recent article notes, when an avocado (a fatty fruit) was added to a salad, seven times the amount of lutein and 18 (!) times the amount of beta-carotene were absorbed from the other salad ingredients.

The type of fat matters. The article also mentions another study that found the consumption of unhealthy trans fats actually reduced the absorption of vitamin E.

Vitamins D and K are also fat-soluble, with the latter nutrient found in high quantities in leafy greens such as spinach and kale.

The takeaway is that it’s important to include healthy fats, such as olive oil, as a regular/moderate part of meals to help ensure the best absorption of fat-soluble nutrients. Not all fats are bad.

(Of course, fats are high in calories, so you don’t want to overdo it. The key is reducing the consumption of empty calorie foods high in sugar and refined grains, and replacing them with healthy fats, whole grains, vegetables, and lean protein.)