Sunday, October 5, 2008

The truth about trans fat

This topic may seem a bit un-hip at the moment as various items in nutrition news become hot and then not in no time. However, trans fat still interests me. I teach my students about it, and I still get asked about it a lot in practice. I thought I'd write about it this week because it still seems to be an area of interest for many. In fact, in July 2008 California lawmakers approved legislation for a ban on trans fat in foods from restaurants and bakeries, and the law will take effect in 2010. This follows the somewhat controversial ban on trans fat in restaurants in New York City and others.

First of all, what is trans fat? Well, it's a type of fatty acid in which the chemical structure has been changed. This can be done industrially in order to enhance the shelf life and texture of foods. There are two types of trans fats: industrially produced (usually found in margarines, shortening, baked and fried foods) and naturally occurring (found in beef fat and milk). It appears that it's the industrially-produced type that poses the most health risk.

Why all the hype? Well, let me count the ways.

First and foremost, intake of trans fat is linked with increased risk of coronary artery disease, risk of fatal and nonfatal heart attacks, and sudden cardiac death. It is associated with increasing total and LDL (bad) cholesterol, lowering HDL (good) cholesterol, and increasing total to HDL and LDL to HDL cholesterol ratios. Plus, the effect on LDL cholesterol appears to be dose-dependent meaning that trans fat has an affect at varying doses rather than starting at say an intake of X grams/day.

It doesn't stop there. There are several other avenues through which it possibly contributes to heart disease including causing the arterial walls to be less flexible and activating inflammatory responses, which is increasingly associated with heart disease.

The shocker for me was the effect on the unborn fetus and breastfed infant. Of course, this is a potential risk, but it may adversely affect growth and development by interfering with the metabolism of essential fatty acids needed for growth and brain development (DHA and ARA). However, it may also just be that women who consume a diet high in trans fat may also not eat sources of healthy fat (omega-3 fatty acids like fish, fish oil). In one study, newborns with high levels of trans fat in their blood system tended to have smaller head circumferences, which can be an indicator of brain growth/development. This was a small study with several limitations, but the data are intriguing. What I don't believe a lot of pregnant and/or breastfeeding women realize is that what they eat really can affect their babies negatively. The ONLY way a fetus or solely breastfed infant can have trans fat in their bodies is through the mother's dietary consumption.

Other studies show either no or some positive association between trans fat and cancer and diabetes. There are also studies linking trans fat with impaired insulin sensitivity or insulin resistance. This appears to be mostly in obese subjects and/or those who already have diabetes and/or insulin resistance.

The good news is that the FDA started requiring placement of trans fat content in foods on the Nutrition Facts Panel as of Jan. '06. So even before then, companies were scurrying to remove or reduce trans fat from their foods. This was done in other countries well before us, and the average trans fat intake in those countries declined with this change. That's good news for us! At the same time, in order to make up for this reduction in trans fat, many food manufacturers utilized fat sources that are high in almost equally unhealthy -- saturated fat. Be careful! Read the label. In addition, something can say it has 0 grams trans fat or 'trans fat free' and still contain trans fat. In order to state these things, it has to contain <0.5g trans fat per serving. Check the ingredients list, and if you see the words "partially hydrogenated" and whatever type of vegetable oil listed, it contains some trans fat. Be aware that the trans fat content includes both industrially produced ("partially hydrogenated") and naturally-occurring. Also, supplements may contain trans fat as well. They are also required to list this info on their Supplement Facts Panel. In fact, one woman I know saw that her child's Flintstone gummy vitamins contained "partially hydrogenated vegetable oil".

As for the ban on trans fats, I have no problem seeing industrially-produced trans fat disappear from the food supply. There is no real human need for it other than to offer a dense source of energy (calories), and there are other nutrients and types of fat that can serve that purpose. It is simply not an essential nutrient meaning our body does not need trans fat for survival or to function properly AND it is actually potentially harmful. Yet another reason to get a little closer to mother nature when it comes to the food we eat:)

Here's to a healthy week!


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