Fat: Friend or Foe?
We have a complicated relationship with fat. Experts demonized fat in the 1970s, ‘80s, and ‘90s, and now we are entering a new pro-fat era. Popular knowledge is slowly slowly shifting back in favor of butter over margarine, olive oil over canola, the whole egg over just the white, and whole milk over skim. The benefits of Omega 3 fatty acids for brain functioning have been noted in the press, and there have been research articles published that point to its efficacy as a possible treatment for depression (Grosso, 2014).
So is fat friend or foe? Questions about fat are exploding across the news, research, blogs and maybe even across your own kitchen table. We are learning that fat is good, that the kinds of fat you eat matter, and that the link between saturated fat consumption and heart disease is tenuous.
Let’s look a snapshot of where the US stands with fat today, and then we’ll talk about why.
The USDA publishes food supply data detailing the amount of fat available in the domestic market, and while it is difficult to deduce from this data the actual amount of fat consumed by Americans, it does give a sense of the demand for fats and the change in types of fat on the market.
- As of 2000 there was more fat in the US food supply than ever before- 170 grams per person, per day, compared to just 122 grams in 1909- that’s a 39% increase (Gerrior, 2004).
- The fat in the food supply and the fat being consumed by Americans is increasingly coming from vegetable sources and less from animal products.
- Red meat used to account for about ⅓ of total fat consumed, but now that number is down to 16%.
- We are eating 73% less butter and 77% less lard than we did in 1909, but 1038% more margarine, 170% more shortening, 1163% more soybean oil and 167% more canola oil since its introduction in 1986 (Blasbalg, 2011).
- As of 2000, “salad oils” (most notably soybean oil) accounted for 27% of fats consumed, up from 2% in 1909 (Gerrior, 2004).
Vegetable Vs. Animal Fat
The increase in vegetable fat consumption is driven by several factors- medical, social, and sometimes even political. One reason that we are eating more vegetable fat is that we are eating outside of the home way more often. Partially hydrogenated vegetable fat is used to make a variety of processed foods like cookies, crackers and other snacks because of its stability and long shelf life. The restaurant and fast food industry also uses large quantities of vegetable oils for frying, and with the explosion of these types of establishments in the past 100 years, the demand for fats has also increased (it is important to note that 50% of this frying oil is discarded after use, and overall it is estimated that 1/3 of the total fats and oils in the food supply are lost through foodservice and “consumer venues”, and not actually consumed) (Gerrior, 2004).
A second reason for the rise in the consumption of vegetable fats, and perhaps the more widely known one, is that dietary guidelines that have been advising Americans to eat less saturated fat derived from animal products for the last 50 years. These recommendations have directly impacted the types of fat available in the food supply.
Unsaturated fats are found mainly in fish and efall into two categories: monounsaturated and polyunsaturated. Monounsaturated fats are found in nuts, olive oil, peanut oil and canola oil. Polyunsaturated fats come from flax seeds, walnuts and canola oil (all of these contain omega 3 fats) as well as vegetable oils like soybean, sunflower and corn (all of these contain omega 6 fats).
Trends in Fat Consumption
- Polyunsaturated fat In 1909 polyunsaturated fats accounted for just 11% of total fats available for consumption, and as of 2006 that number jumped to 22%.
- Monounsaturated fat: Monounsaturated fat has been a relatively constant share, though there is a lot more of it in the food supply overall- from 47 grams per capita in 1909 to 77 grams in 2006.
- Saturated fat accounts for a smaller share of total fat in the food supply- from 43% in 1909 to 30% in 2006, and unsaturated fats have taken their place.
It is important to note the overall trend that all of these fats are coming less from meat, poultry fish and dairy products and increasingly from solid fats and vegetable oils (Gerroir, 2004).
Science vs. Dogma: Choosing Our Food
Fat is abundant in our food supply and the consumption and use of vegetable oils has skyrocketed, leaving the animal fats in their wake. Today fat constitutes a smaller part of the American diet than it did in the 1970s, 33% today versus 36% in 1974 (NHANES 2010, Wells 2008). Furthermore, Americans eat less fat overall, from an average of 85.6 grams in 1977-78 to 75.2 grams in 2005-08 (Lin, 2012). Why? You guessed it- low fat diet craze.
Fat was categorized as a macronutrient in 1827, but it wasn’t really until more than a century later that people- and the government- started to take an issue with it. The emphasis on reducing fat intake began in the 1950s with the rise of the diet-heart hypothesis that linked dietary fat, specifically saturated fat, with blood cholesterol levels and cardiovascular disease. These studies spearheaded by Ancel Keys received widespread criticism at the time for being reductionist and poorly conducted, and experts actually cautioned against limiting fat intake because of its critical role in the formation and function of the brain and in cellular membranes (Taubes 2001; Kritchevsky, 1998).
In Gary Taubes’ 2001 article, The Soft Science of Dietary Fat, the author explains that the popularized idea that fat is deadly evolved from “hypothesis to dogma” because “politicians, bureaucrats, the media and the public have played as large a role in the science as the science.” Americans wanted dietary advice, government officials wanted it to be simple and straightforward, and the media wanted something to run on their 24 hour news cycle. Thus, despite the growing body of evidence that seriously challenged and even contradicted this seemingly ‘simple hypothesis,’ official fat policy was declared and for 50 years Americans have been told to eat less fat (Taubes, 2001).
The decline in fats sourced from animal products and the subsequent rise in the use of vegetable oils, margarine, and shortening was encouraged by food policy that linked saturated fats to coronary heart disease and cardiovascular disease. For example, since the 1950s there has been a significant decline in milk consumption, and by 2000 Americans were drinking 36% less milk than in the 1950s. When we do drink milk, it is usually low fat. As of 2000 whole milk accounted for just 36% of all milk consumption in the US, down from 92% in the 1950s (USDA Agriculture Fact Book, 2001-2002).
The low fat dogma inspired a new low-fat industry. In the early 1990s, 5,400 new low-fat versions of foods flooded supermarket shelves. With the anti-fat sentiment, the per capita consumption of added fats and oils actually decreased by 8% (Gerrior, 2004).
Apart from official dietary recommendations, the amount of fat Americans are eating has also been influenced by the increase of two earner households, more single parent homes, a rise in food prices, and a decrease in real income (Agricultural Fact Book, 2001-02). Americans eat out more and eat at home less. As of 2005-08 only 68% of meals were eaten at home (Lin 2012). Our reliance on restaurants, fast food, vending machines, street and snack foods is concerning as these foods are notorious for being energy dense and nutrient poor. Meals served outside the home tend to be larger portions than meals you would make at home (Lin 2012). Foods prepared at home have a fat content of 30.5% while fast food has a fat content of 41.1% (Lin 2012). As mentioned above, fats in fast food and restaurant meals are sourced from vegetable sources rather than animal sources.
Today we are facing a serious health crisis with ⅔ of Americans reported as being either overweight or obese (NHANES, 2010). The American Heart Association has shifted their dietary recommendations, and now advises Americans to have a diet with ‘moderate’ fat intake as opposed to ‘low’ recognizing that low fat diets are also high in carbohydrates, low in HDL cholesterol (the good cholesterol) and high in triglycerides, and that a diet with moderate fat intake allows for more of the ‘good fats’ (Dixon, 2001).
Ultimately, the types of fat we consume do matter, and this is important to understand for our health. Stay tuned for articles about the Diet Heart Hypothesis, and why it isn’t as clear cut as Ancel Keys would’ve liked.
Additional writing for this article by L. Smith
Blasbalg TL, Hibbeln JR, Ramsden CE, Majchrzak SF, Rawlings RR. Changes in Consumption of omega-3 and omega 6 fatty acids in the United States during the 20th century. Am J Clin Nutr. 2011 March 2; 93(5): 950-962.
Briefel RR, Johnson CL. Secular Trends in Dietary Intake in the United States. Annual Rev. of Nutr. 2004 July; 24: 401-431.
Dixon LB, Ernst ND. Choose a Diet That Is Low in Saturated Fat and Cholesterol and Moderate in Total Fat: Subtle Changes to a Familiar Message. Am J Clin Nutr. 2001 Feb 1; 131(2): 510S-526S.
Gerrior, S., Bente, L., & Hiza, H. (2004). Nutrient Content of the U.S. Food Supply, 1909-2000. (Home Economics Research Report No. 56). U.S. Department of Agriculture, Center for Nutrition Policy and Promotion.
Grosso, G., Pajak, A., Marventano, S., Castellano, S., Galvano, F., Bucolo, C., Drago, F., & Caraci, F. Role of omega-3 fatty acids in the treatment of depressive disorders: a comprehensive meta-analysis of randomized clinical trials PLOS One. 2014
Jakobsen MU, Dethlefsen C, Joensen AM, Stegger J, Tjonneland A, Schmidt EB, Overvad K. Intake of carbohydrates compared with intake of saturated fatty acids and risk of myocardial infarction: importance of the glycemic index. Am J Clin Nutr. 2010;91:1764 –1768.
Kritchevsky, David. History of Recommendations to the Public about Dietary Fat. J Nutr. 1998 Feb 1; 128 (2): 449S-452S.
Kuipers RS, de Graaf DJ, Luxwolda MF, Muskiet MH, Dijck-Brouwer DA, Muskiet FA.Saturated fat, carbohydrates and cardiovascular disease. Neth J Med. 2011 Sep; 69(9):372-8.
Kuklina EV, Carroll MD, Shaw KM, Hirsch R. Trends in high LDL cholesterol, cholesterol-lowering medication use, and dietary saturated-fat intake: United States, 1976–2010. NCHS data brief, no 117. Hyattsville, MD: National Center for Health Statistics. 2013.
Meilahn, Elaine N. Low Serum Cholesterol: Hazardous to Health? Circulation. 1995; 92: 2365-2366
Mozaffarian D, Appel LJ, Van Horn L. Components of a Cardioprotective Diet: New Insights Circulation. 2011;123:2870-2891.
Oh K, Hu FB, Manson JE, Meir SJ, Willett WC. Dietary Fat Intake and Risk of Coronary Heart Disease in Women: 20 Years of Follow-up of the Nurses’ Health Study. Am. J. Epidemiol. (2005) 161 (7): 672-679.
Ravnskov U. High cholesterol may protect against infections and atherosclerosis. QJM: An International Journal of Medicine. 2003 Dec. 96(12); 927-934.
Ravnskov U. The Fallacies of the lipid hypothesis. Scandinavian Cardiovascular Journal. 2008; 42: 236-239.
Schatz IJ, Masaki K, Yano K, Chen R, Rodriguez BL, Curb JD. Cholesterol and all-cause mortality in elderly people from the Honolulu Heart Program: a cohort study. The Lancet. 2001 Aug 4; 358 (9279): 351-355.
Siri-Tarino PW, Sun Q, Hu FB, Krauss RM. Meta-analysis of prospective cohort studies evaluating the association of saturated fat with cardiovascular disease.Am J Clin Nutr. 2010 March; 91(3): 535–546.
Taubes G. Nutrition: the soft science of dietary fat. Science 291:2536–2545, 2001
Wells, Hodan F., and Jean C. Buzby. Dietary Assessment of Major Trends in U.S. Food Consumption, 1970-2005, Economic Information Bulletin No. 33. Economic Research Service, U.S. Dept. of Agriculture. March 2008.
USDA Agriculture Fact Book, 2001-2002. 2003 March. http://www.usda.gov/factbook/2002factbook.pdf