On my homepage, I reviewed the components of the much anticipated publication of the 2015-2020 Dietary Guidelines for Americans. These updated Dietary Guidelines are released every five years to reflect the latest nutritional and medical evidence set forth by the Dietary Guidelines Advisory Committee (DGAC)’s Advisory Report. (You can read the summary and get a link to full guidelines here.)
There were some very good points to the latest guidelines including a “food as medicine” approach, a focus on overall dietary patterns versus isolated nutrients, the ease of cholesterol guidelines, and the recommendation to reduce sugar and excess sodium. (The latter being more positive if it is focused on reducing processed foods and getting enough potassium.)
Now, in this blog, let’s review some of the controversies and caveats to the 2015-2020 Dietary Guidelines for Americans.
The Not-So-Good or Agreed Upon Guidelines
1. The Saturated Fat Attack is Back: It’s Complicated
The new Dietary Guidelines recommend a reduction of saturated fat to 10% of total calories. Some experts believe that dietary fat and saturated fat should both be reduced. Many of them feel that the reason red meat is still considered healthy, along seafood and lean meats, is due to the meat industry’s (pocketbook) influence…
Others argue there’s no evidence for saturated fat, from good quality sources, causing heart disease or major health concerns…
The updated nutritional guidelines do acknowledge that the body does need some saturated fat for physiological purposes and states:
Some evidence has shown that replacing saturated fats with plant sources of monounsaturated fats, such as olive oil and nuts, may be associated with a reduced risk of CVD. However, the evidence base for monounsaturated fats is not as strong as the evidence base for replacement with polyunsaturated fats. Evidence has also shown that replacing saturated fats with carbohydrates reduces blood levels of total and LDL-cholesterol, but increases blood levels of triglycerides and reduces high-density lipoprotein-cholesterol (HDL-cholesterol). Replacing total fat or saturated fats with carbohydrates is
not associated with reduced risk of CVD. Additional research is needed to determine whether this relationship is consistent across categories of carbohydrates (e.g., whole versus refined grains; intrinsic versus added sugars), as they may have different associations with various health outcomes.
Therefore, saturated fats in the diet should be replaced with polyunsaturated and monounsaturated fats.
The Good Saturated Fat Side:
According to a meta-analysis of six trials published before 1983 in the journal, Open Heart, there exists little evidence to support that saturated fat is associated with cardiovascular disease and all-cause
mortality. In their discussion, the authors report that the studies for dietary change may be more supportive of multiple lifestyle changes verses a cure-all diet for heart health. It was concluded: “Dietary recommendations were introduced for 220 million US and 56 million UK citizens by 1983, in the absence of supporting evidence from RCTs.”
Furthermore, sources such as coconut, butter, and full-fat dairy may have their own metabolic benefits. (see below).
The Bad Saturated Fat Side
Still, there is some evidence that excess consumption of meat, which contains saturated fat, could be a health risk. A few months ago, the IARC (International Agency of Research on Cancer), a part of the World Health Organization (WHO), issued a statement to the public that consumption of processed meat and red meat could be linked to cancer based on findings of a working group of 22 experts who reviewed over 800 studies.
However, many argue that the information that the experts based these conclusions wasn’t complete. It may be that meat, itself, isn’t harmful, but the following factors could affect its health benefits: the process of cooking meat could cause the release of toxic chemicals, the state of a person’s digestive tract (specifically their microbiome), the quality of the meat (poor sources of meat contains antibiotics and hormones which effect immune health), and other issues discussed here.
There’s also the impact of consuming a diet with an unhealthy ratio of polyunsaturated fats to replace these saturated fats. This leads us to controversy two.
2. Vegetable oils and Omega 6’s
The guidelines encourage consumption of polyunsaturated fats and oils. Studies have shown benefits of optimizing the ratio of omega-3 fatty acids to omega-6 fatty acids. Unfortunately, the American diet is already skewed too high in a ratio favoring omega-6 fatty acids. In short, this can cause inflammation and lead to a whole host of diseases. Although our bodies need omega-6 fatty acids, it would be better to specify increasing quality sources of omega-3 fatty acids and accounting for ratios in individuals before recommending blindly to increase omega-6 fatty acids. A 2009 study reports:
Linoleic acid (LA) and alpha linolenic acid (ALA) belong to the n-6 (omega-6) and n-3 (omega-3) series of polyunsaturated fatty acids (PUFA), respectively. They are defined “essential” fatty acids since they are not synthesized in the human body and are mostly obtained from the diet. Food sources of ALA and LA are most vegetable oils, cereals and walnuts. This review critically revises the most significant epidemiological and interventional studies on the cardioprotective activity of PUFAs, linking their biological functions to biochemistry and metabolism. In fact, a complex series of desaturation and elongation reactions acting in concert transform LA and ALA to their higher unsaturated derivatives: arachidonic acid (AA) from LA, eicosapentaenoic (EPA) and docosahexaenoic acids (DHA) from ALA. EPA and DHA are abundantly present in fish and fish oil. AA and EPA are precursors of different classes of pro-inflammatory or anti-inflammatory eicosanoids, respectively, whose biological activities have been evoked to justify risks and benefits of PUFA consumption. The controversial origin and clinical role of the n-6/n-3 ratio as a potential risk factor in cardiovascular diseases is also examined. This review highlights the important cardioprotective effect of n-3 in the secondary prevention of sudden cardiac death due to arrhythmias, but suggests caution to recommend dietary supplementation of PUFAs to the general population, without considering, at the individual level, the intake of total energy and fats.
3. Dairy- Low Fat Versus Full Fat
The Dietary Guidelines also support low fat dairy as a healthy source of calcium and nutrition and advise against consuming full fat dairy. However, several studies have shown that full-fat dairy leads to better outcomes in weight loss, diabetes, and cardiovascular health. In fact, a recent study just supported better cardiovascular effects with replacing low fat dairy for full fat dairy into the DASH (Dietary Approaches to Stop Hypertension) diet. The DASH diet is considered the most nutritious diet by experts, according to U.S. News & World Report‘s 2016 Best Diets ranking.
The study concluded the following regarding the high fat DASH diet (HF-DASH), “The HF-DASH diet lowered blood pressure to the same extent as the DASH diet but also reduced plasma triglyceride and VLDL concentrations without significantly increasing LDL cholesterol.”
According to the recent press release on the Dietary Guidelines,
“The Dietary Guidelines for Americans is one of many important tools that help to support a healthier next generation of Americans,” said Secretary Vilsack. “The latest edition of the Dietary Guidelines provides individuals with the flexibility to make healthy food choices that are right for them and their
families and take advantage of the diversity of products available, thanks to America’s farmers and ranchers.”
Nutritional science isn’t perfect. and considering all the controversy, theories, and various experts’ opinions, these guidelines are a good place to start. However, they don’t replace individualizing nutritional plans and focusing on biochemical individuality. For example, someone with a genetic variation in how they process fats may actually do better with low fat dairy, but a diabetic may need full fat… and the dietary wars march on…
(Make sure to read the bonus article on my homepage on personalized nutrition.)
U.S. Department of Health and Human Services and U.S. Department of Agriculture. 2015 – 2020 Dietary Guidelines for Americans. 8th Edition. December 2015. Available at http://health.gov/dietaryguidelines/2015/guidelines/.
U.S. Department of Health and Human Services. Press Release: HHS and USDA Release New Dietary Guidelines to Encourage Healthy Eating Patterns to Prevent Chronic Diseases. January 7, 2016. Available at: http://health.gov/dietaryguidelines/2015/
New U.S. Dietary Guidelines: Limit Sugar and Salt, Boost Fruit and Veggie
Intake. Health Day: Consumer News. January 7, 2016.
Office of Disease Prevention and Health Promotion (ODPHP). 2015 Dietary Guidelines. Advisory Committee. Health.gov Web site. Available at: http://health.gov/dietaryguidelines/2015-scientific-report/
Center for Disease Control and Prevention. Chronic Disease Overview: Chronic Diseases: The Leading Causes of Death and Disability in the United States. CDC Web site. August 15, 2015.
Seven Healthy Habits May Reduce Heart Failure Risk. Reuters. December 23, 2015.
Traditional and Emerging Lifestyle Risk Behaviors and All-Cause Mortality in Middle-Aged and Older Adults: Evidence from a Large Population-Based Australian Cohort. PLOS One. December 8, 2015
American Heart Association. My Life Check – Life’s Simple 7. http://www.heart.org/HEARTORG/Conditions/My-Life-Check—Lifes-Simple 7_UCM_471453_Article.jsp#
Aerobic fitness in late adolescence and the risk of early death: a prospective cohort study of 1.3 million Swedish men. Int. J. Epidemiol. December 20, 2015. doi: 10.1093/ije/dyv321
Hansel B. Why Dietary Cholesterol Is No Longer Enemy Number One. Medscape Diabetes &
Endocrinology. March 19, 2015.
Fernandez ML. Dietary cholesterol provided by eggs and plasma lipoproteins in healthy populations. Curr Opin Clin Nutr Metab Care. 2006 Jan;9(1):8-12.
Ebbeling CB, Swain J, Feldman HA, et al. Effects of Dietary Composition on Energy Expenditure During Weight-Loss Maintenance. JAMA. 2012;307(24):2627-2634. doi:10.1001/jama.2012.6607.
National Institute of Health. NIH study finds cutting dietary fat reduces body fat more than cutting carbs. August 13, 2015. http://www.nih.gov/news-events/news-releases/nih-study-finds-cutting-dietary-fat-reduces-body-fat-more-cutting-carb
Harcombe Z, Baker JS, Cooper SM, et al. Evidence from randomized controlled trials did not support the introduction of dietary fat guidelines in 1977 and 1983: a systematic review and meta-analysis. Open Heart 2015; DOI:10.1136/openhrt-2014-000196.
Ward, T. Saturated Fat and CAD: It’s Complicated. theheart.org on Medscape. February 9,
O’Riordan. No Evidence to Support Dietary Fat Recommendations, Meta-Analysis Finds. February
12, 2015. http://www.medscape.com/viewarticle/839708?src=wnl_edit_specol&uac=146852BY#vp_2
Kuetipers RS et al. Saturated fat, carbohydrates and cardiovascular disease. Neth J Med. 2011 Sep;69(9):372-8.
Gunnars K. 10 Proven Health Benefits of Coconut Oil (No. 3 is Best). Authority Nutrition. December, 2015
International Agency of Research on Cancer. IARC Monographs evaluate consumption of red meat
and processed meat. Press Release. October 26, 2015. http://www.iarc.fr/en/media-centre/pr/2015/pdfs/pr240_E.pdf
Foster R. Processed Meat Can Cause Cancer: WHO. Health Day. October 26, 2015. http://consumer.healthday.com/cancer-information-5/colon-cancer-news-96/processed-meat-can cause-cancer-who-704606.html
NRDC. Meat + Drugs= Superbugs. http://www.nrdc.org/food/saving-antibiotics.asp
CDC. Understanding CAFOs and their Impact on Communities. Accessed at:
Graham M, Crooke R, Edwards PA, Hazen SL, Lusis AJ. Trimethylamine-N-oxide, a metabolite
associated with atherosclerosis, exhibits complex genetic and dietary regulation (abstract). Cell Metab. 2013 Jan 8;17(1):49-60. doi: 10.1016/j.cmet.2012.12.011.
Turning Down The Heat When Cooking Meat May Reduce Cancer Risk: http://www.npr.org/sections/thesalt/2015/11/23/456654768/turning-down-the-heat-when-cooking-meat-may-reduce-cancer-risk?utm_medium=RSS&utm_campaign=health
Melkonian, S. C., Daniel, C. R., Ye, Y., Tannir, N. M., Karam, J. A., Matin, S. F., Wood, C. G. and Wu, X. (2016), Gene-environment interaction of genome-wide association study-identified susceptibility loci and meat-cooking mutagens in the etiology of renal cell carcinoma. Cancer. 122: 108-115. doi: 10.1002/cncr.29543
Hibbeln JR, et al. Healthy intakes of n−3 and n−6 fatty acids: estimations considering
worldwide diversity. Am J Clin Nutr. June 2006; 83(6): S1483-1493S
Kris-Etherton PM, et al. Polyunsaturated fatty acids in the food chain in the United States. Am
J Clin Nutr. January 2000; 71(1): 179S-188S.
Kresser C. How too much omega-6 and not enough omega-3 is making us sick. Chris Kresser Web site. May 8, 2010.
Russo G. Dietary n-6 and n-3 polyunsaturated fatty acids: from biochemistry to clinical implications in cardiovascular prevention. Biochem Pharmacol. 2009 Mar 15;77(6):937-46. doi: 10.1016/j.bcp.2008.10.020. Epub 2008 Oct 28.
Milk intake and risk of mortality and fractures in women and men: cohort studies. BMJ. 2014; 349 doi:
http://dx.doi.org/10.1136/bmj.g6015 (Published 28 October 2014)
The relationship between high-fat dairy consumption and obesity, cardiovascular, and metabolic disease. European Journal of Nutrition. February 2013; 52(1): 1-24.
Mercola J. Is Whole Milk Dairy Better Than Low Fat? Mercola Web site. November 18, 2015.
Dallas ME. Report: DASH Diet Best Overall Eating Plan. Health Day Web site. January 5, 2016.
Chiu S, et al. Comparison of the DASH (Dietary Approaches to Stop Hypertension) diet and a higher-fat DASH diet on blood pressure and lipids and lipoproteins: a randomized controlled trial. Am J Clin Nutr. December 30, 2015, doi: 10.3945/ajcn.115.123281