Butter Neutral, Unsaturated Fats Still Better for Health

Veronica Hackethal, MD

July 15, 2016

Long the villain, fat seems to be having its day in the sun. Two new studies have added fuel to the controversy about what types of fats are beneficial to long-term health and which ones to avoid.

The first study, a meta-analysis lead by Dariush Mozaffarian, MD, DrPH, of Tufts University, Boston, Massachusetts, addressed the question "Is butter back?" It found only weak or neutral effects of butter consumption on overall mortality and cardiovascular disease (CVD) risk, suggesting that butter may not be as harmful as previously thought.

The findings were published online on June 29 in PLoS One and represent the most comprehensive evaluation so far of the effects of butter consumption on long-term health.

"Even though people who eat more butter generally have worse diets and lifestyles, it seemed to be pretty neutral overall," first author Laura Pimpin, PhD, said in a Tufts University press release. Dr Pimpin is a data analyst in public-health modeling for the UK Health Forum.

"This suggests that butter may be a "middle-of-the-road" food: a more healthful choice than sugar or starch — such as the white bread or potato on which butter is commonly spread — [both of] which have been linked to higher risk of diabetes and cardiovascular disease; and a worse choice than many margarines and cooking oils — those rich in healthy fats such as soybean, canola, flaxseed, and extra virgin olive oils — which would likely lower risk compared with either butter or refined grains, starches, and sugars," she continued.

The second study, which draws from two very large databases of participants in the Nurses' Health Study and the Health Professionals Follow-up Study, who were followed for over 3 decades, was published online July 5 in JAMA Internal Medicine.

Results suggest that eating higher amounts of saturated and trans fat increases the risk for death, while eating polyunsaturated fats (PUFAs) and monounsaturated fats (MUFAs) may lower the risk of death. Replacing saturated fats with the same amount of calories from PUFAs and MUFAs was linked to a reduced risk for overall death.

"There has been widespread confusion in the biomedical community and the general public in the past couple of years about the health effects of specific types of fat in the diet. This study documents important benefits of unsaturated fats, especially when they replace saturated and trans fats," first author Dong Wang MD, MSc, of the Harvard TH Chan School of Public Health, Boston, Massachusetts, noted in a statement from that institution.

The results lend support to the 2015–2020 Dietary Guidelines for Americans, which for the first time cut out the recommendation to limit total fat, opting instead to recommend a diet low in saturated fat, as reported by Medscape Medical News.

Findings of Two Papers Not Necessarily at Odds

The findings from the two papers are not mutually exclusive, according to Keith Ayoob, EdD, of Albert Einstein College of Medicine, Bronx, New York, who was not involved in either study.

Instead, the combined message is that unsaturated oils are still overall better than saturated fats.

"The take-home message is that when you can use monounsaturated fat, use it. That's a priority," Dr Ayoob told Medscape Medical News. "Some fat sources are actually beneficial, and those are the ones we want to favor.

"It's not that butter's better, it's sort of neutral. It doesn't necessarily produce the positive results you're looking for," he added, "On the other hand, full-fat dairy food might have some positive aspects to it."

Recent evidence has suggested a possible metabolic protective effect for some dairy products, like yogurt and cheese, which are traditional parts of the Mediterranean diet.

"It's becoming clear that not all saturated fats may behave the same in the body," added Dr Ayoob.

The crux of the matter is about focusing on the individual fatty-acid profile of foods and the diversity of food sources. Increasing evidence suggests the need for dietary guidelines to shift away from a focus on isolated nutrients to the overall dietary pattern.

"Monounsaturated fat is not just neutral. It's actually really helpful. We know that diets higher in olive oil and nuts do produce positive benefits," Dr Ayoob emphasized.

For example, evidence from the PREDIMED study, a 5-year trial conducted in Spain that randomized participants to a Mediterranean diet supplemented with olive oil or nuts vs a low-fat control diet, has suggested numerous health benefits associated with the Mediterranean diet.

These include better prevention of CVD and less weight gain compared with a low-fat diet, reversal of metabolic syndrome, and decreased incidence of diabetes. The Mediterranean diet has also been linked to improved cognition and lower risk of stroke.

"Eating Fat Does Not Make You Fat"

Indeed, the National Obesity Forum in the United Kingdom recently stepped up the controversy over dietary fats with the release of a report stating, "Eating fat does not make you fat."

It quoted several trials suggesting that following a higher-fat, low-carbohydrate diet may be better than a low-fat diet for decreasing weight and cardiovascular risk.

However, it went further and advised people to stop counting calories but cut down on snacking, because different types of foods have different metabolic effects. And, it went on to say that "saturated fat does not cause heart disease," while full-fat dairy may have health benefits.

However, Dr Ayoob does not necessarily agree and would recommend an individualized approach that takes into account the eating pattern and metabolic profile of each patient.

A high-fat diet does mean less food on the plate, he explained. So for someone who needs more frequent servings throughout the day, a high-fat diet might prove challenging.

"Ultimately losing weight is what's going to improve your health. Whether you lose weight on a high-, normal-, or low-fat diet, I'm more concerned with what kind of a diet each individual can follow to maintain a lower weight," he stressed, adding, "I hope people don't start overconsuming saturated fat because they think it's a free for all. You still have to pay attention to quantity."

Latest Study Results: PUFAs and MUFAs Better Than Butter

The new study by Dr Wang and colleagues included 84,349 women from the Nurses' Health Study and 42,884 men from the Health Professionals Follow-up Study. Participants reported dietary fat intake on food frequency questionnaires at baseline and every 2 to 4 years. Researchers separated participants into five groups based on increasing consumption of different types of fats. Then they evaluated overall deaths and deaths due to CVD, cancer, neurodegenerative disease, and respiratory disease.

During over 32 years of follow-up, 33,304 deaths occurred. After adjustment for 18 risk factors like smoking, hypertension, body mass index (BMI), and hypercholesterolemia [and comparing the group with highest intake in each type of fat category with the same amount of calories in carbohydrates], results showed increased risk of death with consumption of saturated and trans fats. PUFAs and MUFAs were linked to a reduced risk of death

Hazard Ratios (HRs) for the Highest Intake of Fat Category vs the Same Amount of Calories in Carbohydrates

Category HR for total mortality 95% CI P for trend
Saturated fat 1.08 1.03–1.14 < .001
Trans fat 1.13 1.07–1.18 < .001
PUFAs 0.81 0.78–0.84 < .001
MUFAs 0.89 0.84–0.94 < .001

Replacing just 5% of saturated fat calories with PUFAs and MUFAs reduced overall mortality by 27% and 13% (HR, 0.73 and 0.87, respectively).

Consumption of ω-6 PUFAs, especially plant-derived linoleic acid, was associated with reduced risk of death from most major causes. Eating fish-derived ω-3 PUFAs was linked to a modest reduction in overall death (HR comparing extreme quintiles, 0.96; P = .002 for trend).

"Our study shows the importance of eliminating trans fat and replacing saturated fat with unsaturated fats, including both omega-6 and omega-3 polyunsaturated fatty acids," said senior author Frank Hu, MD, MPH, PhD, professor of nutrition and epidemiology at Harvard Chan School and professor of medicine at Harvard Medical School.

"In practice, this can be achieved by replacing animal fats with a variety of liquid vegetable oils," he added.

In the study by Dr Mozaffarian and colleagues, researchers searched nine databases from inception to May 2015, without regard to language or setting. They identified nine cohort studies, but no randomized controlled trials. They standardized butter intake across studies to the US Department of Agriculture's recommended serving of 14 g/day (about one tablespoon).

The analysis covered 15 country-specific cohorts from the United States and Western and Northern Europe, which included 636,151 participants, 28,271 total deaths, 9783 cases of CVD, and 23,954 cases of incident diabetes.

Results showed a weak association between butter consumption and all-cause mortality, but there were no significant links between butter consumption and CVD, including coronary heart disease (CHD) and stroke. And butter consumption was associated with a slight decrease in the incidence of diabetes.

Relationship Between Butter Consumption and Selected Health Outcomes

Outcome Risk ratio 95% CI P
All-cause mortality 1.01 1.00–1.03 .045
Any CVD outcome 1.00 0.98–1.02 .704
CHD 0.99 0.96–1.03 .537
Stroke 1.01 0.98–1.03 .737
Type 2 diabetes 0.96 0.93–0.99 .021

"Overall, our results suggest that butter should be neither demonized nor considered 'back' as a route to good health," Dr Mozaffarian said in the Tufts press release.

"More research is needed to better understand the observed potential lower risk of diabetes, which has also been suggested in some other studies of dairy fat. This could be real or due to other factors linked to eating butter — our study does not prove cause and effect," he concludes.

The study by Pimpin/Mozaffarian et al was supported by a grant from the National Heart, Lung, and Blood Institute of the National Institutes of Health (NIH). Dr Mozaffarian reports ad hoc honoraria, consulting, and chapter royalties from and/or advisory board membership in Boston Heart Diagnostics, Haas Avocado Board, AstraZeneca, GOED, Life Sciences Research Organization, UpToDate, and Elysium Health. Dr Mozaffarian is one of three coinventors on a grant for "Use of trans-palmitoleic acid in identifying and treating metabolic disease." The coauthors reports no relevant financial relationships. The study by Wang et al was supported by grants from the NIH. Dr Hu reported research support from the California Walnut Commission and Metagenics. The coauthors reports no relevant financial relationships. Dr Ayoob reports no relevant financial relationships.

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PLoS One. Published online June 29, 2016. Article

JAMA Int Med. Published online July 5, 2016. Abstract


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