I know what you’re thinking. “With a title like ‘Your Brain on Fat’, this is going to be another sermon on the benefits of reducing dietary fat, another attempt to convince us to ditch animal foods and awkward encouragement to start making our own clothing from hemp, stop using deodorant and to regularly participate in drum circles. We all know that eating tons of fat is cause for serious concern because of the associated risk of cardiovascular disease, coronary heart disease and stroke, and that animals have rights, blah blah blah, so what more needs to be said?!” Well, if this is what you’re thinking, you would be right, to a certain degree (BTW, A+ on knowing the effects that a diet high in fat has on health). While we know that diets high in “bad” fats are proven to increase the risk for all the bad things you just mentioned, a new study out of Brigham and Women’s Hospital shows that there is also an association between dietary fat and brain function. According to the study, women who consumed the most saturated fat (generally received from animal foods), had lower levels of cognition and memory compared with those who consumed the least. On top of this, those who consumed the most “good” fat exhibited the highest levels of cognitive function over a 4 year period 1. A clear indication that if we substitute our milk and steak with flax seed and fish we will reduce risk factors associated with a number of serious health concerns and slow cognitive aging. Less clear is the course of action you should take on the other Matthew McConaughey-esk activities, which I will leave for you and your best judgement.
To improve our understanding of dietary fat, let’s take a look at the different types and attempt to understand the molecular differentiations between them and how they impact our bodies. Unsaturated fats, liquid at room temperature, contain one or more double bonds (monosaturated and polysaturated fats, respectively) between their Carbon atoms. Depending on their geometric formation, these double bonds can further classify unsaturated fats as either CIS or Trans (Yup, the evil trans fat actually starts as an unsaturated fat before it is molecularly manipulation). Without getting too specific, the CIS configuration is bent and has Hydrogen atoms on the same side, while the Trans configuration is linear where the Hydrogen atoms are on opposite sides of the bond 2. Unsaturated trans fats become partially or fully saturated when the atoms are bombarded with more hydrogen, which eliminate the existing double Carbon-Carbon bonds 3. Finally, saturated fats consist of triglycerides and have no double bonds, which are “saturated” with the maximum number of Hydrogen atoms and are solid at room temperature 4.
The differences in molecular structure between the varieties of fat may seem insignificant, but understanding their impact on the body is essential in our quest to understanding health and wellness. “Good” fats (the unsaturated variety) are considered so because of their positive effects on blood cholesterol, inflammation and heart rhythms 5. Conversely, “bad”, saturated fats were labeled this way because it was believed that their consumption raised LDL levels and, by extension, the risk for heart disease and stroke. I use past tense here because, although it is commonly believed that we need to reduce our intake of saturated fats to avoid serious health risk, the negative effects of saturated fats have recently come under fire. New evidence suggests that there is, “no significant evidence for concluding that dietary saturated fat is associated with increase risk of CHD or CVD” (coronary heart disease and cardiovascular disease) and if reducing our consumption of saturated fat, we need to place more emphasis on what we consume in its place 6. One suggestion I found is that if we replace “1% of energy from SFAs (saturated fatty acids) with PUFAs (poly unsaturated fatty acids)…it is likely to produce a reduction in CHD incidence” by 2 to 3% as opposed to replacing SFA’s with carbohydrates 7.
While the jury on saturated fats is still out, there is an overwhelming amount of evidence that the consumption of trans fat is extremely detrimental to our health and must be avoided at all costs. Trans fat is unsaturated, but differs from mono and polysaturated fats in the configuration of its Hydrogen bonds. In order to increase shelf life and to give them the ability to withstand repeated heating, trans fat (a liquid in their unaltered state) is solidified through hydrogenation which partially or completely converts it into saturated fat 8. Although trace amounts of trans fat can be found in meat and dairy products, the major dietary source is partially hydrogenated vegetable oil which is used in baked goods, processed snack foods, margarines and frying fast foods 9. Trans fats are extremely harmful because, “they not only raise LDL cholesterol levels but also lower HDL cholesterol” and with trans fat, a little goes a long way in causing catastrophic health problems 10. A daily intake of approximately 5 grams is associated with a 25% increase in heart disease which is a major concern because of the high content of industry use in certain fast foods where “it is possible to consume 10 to 25 grams…for habitual consumers of large amounts of this [fast] food.” 11 However, food labeling laws have gone a long way in reducing trans fat consumption and have produced a 58% decrease found in American blood levels between 2000 and 2009 12.
The general consensus is that dietary fat should account for roughly 25-30% of our total caloric consumption where saturated fats contribute no more than 10% and trans fats intake is as low as humanely possible 13. This “low fat” approach is believed to provide the full range of benefits to be gained from dietary fat and to greatly reduce the risk of heart disease, stroke and obesity. But, recent studies rebuke the perceived benefits of “low fat” diets and put more emphasis on the types of fat we consume as having the greater impact on overall health and wellness 14 15. “Substituting in the good fat in place of the bad fat is a fairly simple dietary modification,” that can have significant implications in the state of our public’s health 16. Safe to say a complete overhaul in the general understanding of dietary fat is needed. We need learn more about its affects on our body and be more diligent in consuming the right variety, not eliminating it completely.
It is becoming clear that as the amount of research around dietary fat consumption grows, we need to stop placing so much importance on isolating and modifying specific dietary factors to improve health. Instead, we need to shift our focus to specific dietary needs and approach nutrition holistically where good health is centered on the well being of the entire individual. Discussing nutrition mechanistically by stating that a reduction in the consumption of “x” will have “y” benefit on “z” health concern is short sighted and fails to address the big picture of how our bodies are unique and how it functions as something greater than just a collection of parts. Substituting one nutrient to mitigate localized health concerns does not foster longevity or comprehensive health and wellness.