Fatty Acids
Part 5

How fat consumption can influence the course of HD

Getting the right type of unsaturated fat - essential fatty acids.

In general, it is true that any type of unsaturated fat is better for the brain and body than either saturated fat or trans fat. However, there are many different types of unsaturated fat and some types of unsaturated fat are better for you than others. Monounsaturated fatty acids have only one double bound and thus only one gap in the fatty acid chain. Polyunsaturated fatty acids have many double bonds and many gaps within the fatty acid chain. All saturated and monounsaturated fats can be made within the body and, therefore, they do not need to be supplied through the diet. However, the body is unable to make two types of polyunsaturated fat and these must be obtained through the diet. The first type of polyunsaturated fat is alpha-linolenic acid (ALA), which belongs to the omega-3 family of fatty acids. ALA is found abundantly in flax seed (a fiber derived from plants) and flax oil, and is found in small quantities in canola oil, wheat germ, and dark green leafy vegetables such as spinach and broccoli. The second type of polyunsaturated fat that the body cannot make is linoleic acid (LA) and it belongs to the omega-6 family of fatty acids. LA is found in soy oil, sesame seeds, corn oil, and in most nuts. Because the body is unable to make these two fatty acids, they are an essential part of the diet. Hence, they are called essential fatty acids (EFA´s).

ALA

Once the body is supplied with the essential fatty acid ALA, it can convert it into DHA (docosahexaenoic acid) and EPA (eicosapentaenoic acid). Both DHA and EPA are great at lowering one´s risk for heart disease. In addition, DHA is essential for nervous system maintenance and development. Infants who have low amounts of DHA in their diet have reduced brain development. Accordingly, human milk is extremely rich in DHA. DHA is the most abundant fatty acid in nerve cell membranes and is thought to contribute significantly to the fluidity of the cell membrane. DHA is also found in the synapses between nerve cells and is thought to greatly aid the nerve cells in sending signals to each other. The problem is that DHA levels naturally decline as one gets older. If DHA is not supplied through the diet (from consuming ALA), then the nerve cell membranes begin to function sub-optimally. Perhaps this may explain why societies whose diets are high in DHA (such as the Inuit of the arctic who eat a lot of fish, a great source of DHA) have a lower incidence of neurodegenerative disorders.

LA

The other essential fatty acid, LA, is converted to GLA (gamma linoleic acid) within the body. GLA eventually leads to the production of prostaglandins, which are molecules that help regulate inflammation and blood pressure. (For more information on essential fatty acids and inflammation, click here.) While LA is termed "essential," it is not entirely good for the body. In fact, Americans tend to consume way too much of it. This overconsumption is a problem because it turns out that both ALA and LA compete for the same enzymes to produce their final product. In other words, if there is too much LA, then the enzymes will be busy converting LA into GLA and there will be no enzymes left to convert ALA into DHA. (For more information on how ALA and LA compete for enzymes, click here.)Thus, a balance of ALA and LA is essential for proper health. Studies show that the optimal ratio of LA to ALA is somewhere between 2:1 and 1:1. It is estimated that the ratio of LA to ALA for most Americans is around 20:1. This imbalance makes sense because typical foods such as cereal, eggs, poultry, bread, and baked goods are made from oils rich in LA. Foods rich in ALA are much harder to find. Often, dietary supplementation may be needed in order to get enough ALA.

In addition to consuming enough ALA, humans must be able to absorb it. Findings suggest that an inadequate intake of vitamin E results in decreased absorption of ALA. Thus, some experts suggest that vitamin E supplementation may be useful in conjunction with ALA supplementation.

As mentioned earlier, nerve cell membranes are critical in terms of maintaining the safety of the nerve cell. Not only are they responsible for letting in essential nutrients and expelling harmful substances, but they also help nerve cells communicate with each other. Thus, in a person with HD, it is especially important for the nerve cell membranes to be operating optimally because it can greatly aid in the survival of the nerve cells. DHA, a product of ALA, has been shown to keep nerve cell membranes operating at an optimal level. It stands to reason that if a person with HD obtains adequate amounts of ALA and fixes the skewed imbalance of LA to ALA, he or she may be able to prolong the life of his or her nerve cells, and this too would likely delay the progression of the disease.

Last Modified: 04/12/2007

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