Good Fats vs. Bad Fats
Basically, there are two groups of fats: saturated and unsaturated. Within each group are several more types of fats.
Let's start with the good guys -- the unsaturated fats. Unsaturated fats include polyunsaturated fatty acids and monounsaturated fats. Both mono- and polyunsaturated fats, when eaten in moderation and used to replace saturated or trans fats, can help
lower cholesterol levels and reduce your risk of heart disease.
Polyunsaturated fats, found mostly in vegetable oils, help lower both blood cholesterol levels and triglyceride levels -- especially when you substitute them for saturated fats. One type of polyunsaturated fat is omega-3 fatty acids, whose potential heart-health benefits have gotten a lot of attention.
Omega-3s are found in fatty fish (salmon, trout, catfish, mackerel), as well as flaxseed and walnuts. And it's fish that contains the most effective, "long-chain" type of omega-3s. The American Heart Association recommends eating 2 servings of fatty fish each week.
"Plant sources are a good substitute for saturated or trans fats, but they are not as effective as fatty fish in decreasing cardiovascular disease," notes Lichtenstein. Do keep in mind that your twice-weekly fish should not be deep-fat fried!
It is best to get your omega-3s from food, not
supplements, Lichtenstein says: "Except for people with established heart disease, there is no data to suggest omega-3 supplements will decrease heart disease risk."
The other "good guy" unsaturated fats are monounsaturated fats, thought to reduce the risk of heart disease. Mediterranean countries consume lots of these -- primarily in the form of olive oil -- and this dietary component is credited with the low levels of heart disease in those countries.
Monounsaturated fats are typically liquid at room temperature but solidify if refrigerated. These heart-healthy fats are typically a good source of the antioxidant vitamin E, a nutrient often lacking in American diets. They can be found in olives; avocados; hazelnuts; almonds; Brazil nuts; cashews; sesame seeds; pumpkin seeds; and olive, canola, and peanut oils.
The 'Bad' Fats in Your Diet
Now on to the bad guys. There are two types of fat that should be eaten sparingly: saturated and trans fatty acids. Both can raise cholesterol levels, clog arteries, and increase the risk for heart disease.
Saturated fats are found in animal products (meat, poultry skin, high-fat dairy, and eggs) and in vegetable fats that are liquid at room temperature, such as coconut and palm oils. The 2005 Dietary Guidelines recommend limiting saturated fats to 10% or less of your total calories, while the American Heart Association recommends keeping them to just 7% of total calories.
Lichtenstein recommends using liquid vegetable oils in place of animal or partially hydrogenated fats.
"There is evidence that saturated fats have an effect on increasing colon and
prostate cancer risk, so we recommend whenever possible to choose healthy unsaturated fats -- and always strive to be at a healthy weight," Doyle explains.
We're also hearing a lot these days about trans fatty acids, or trans fats. There are two types of trans fats: the naturally occurring type, found in small amounts in dairy and meat; and the artificial kind that occur when liquid oils are hardened into "partially hydrogenated" fats.
Natural trans fats are not the type of concern, especially if you choose low-fat dairy products and lean meats. The real worry in the American diet is the artificial trans fats. They're used extensively in frying, baked goods, cookies, icings, crackers, packaged snack foods, microwave popcorn, and some margarines.
Some experts think these fats are even more dangerous than saturated fats.
"Trans fats are worse than any other fat, including butter or lard," says Michael Jacobson, executive director of the Center for Science in the Public Interest, a nonprofit advocacy group.
Research has shown that even small amounts of artificial trans fats can increase the risk for heart disease by increasing LDL "bad" cholesterol and decreasing HDL "good" cholesterol.
The American Heart Association (AHA) recommends limiting trans fat to less than 2 grams per day, including the naturally occurring trans fats. The U.S. Dietary Guidelines simply recommend keeping trans fats consumption as low as possible.
SO - that still means that
you still shouldn't eat more than 10 g of trans fats/day (assuming you ABSORB 20%). So I will agree with your surgeon on that account.
* Gagner M, Rogula T, Strain G, Emerson R, Biertho L, Pomp A. Decreased lipid malabsorption in both gastric bypass and biliopancreatic diversion with duodenal switch. Surgery for Obesity and Related Diseases. 2005;1(3):240-241. PII: S1550-7289(05)00173-5 [there is a typo - should be "Decreased lipid ABSORPTION ..."] - see attached.
http://www.ncbi.nlm.nih.gov/pubmedh...turated-fats-and-heart-disease-link-unproven/
Home > Behind the Headlines > Saturated fats and heart disease link...
Behind The Headlines - Health News from NHS Choices
Saturated fats and heart disease link 'unproven'
Tue, 18 Mar 2014 14:33:00 EST
“No link found between saturated fat and heart disease,” The Daily Telegraph reports. Researchers have looked at large amounts of data and say they have found no significant link between saturated fat and heart disease.
Nutritional guidelines generally encourage low consumption of saturated fats, found in butter, cream, cheese and fatty cuts of meat, as these were thought to be linked to increased cholesterol in the blood and an increased risk of heart disease.
In contrast, unsaturated fats, found in fish and plant sources, have been encouraged (to a certain extent) as these are thought to have a protective effect on the heart and blood vessels.
This latest study finds that the evidence for these guidelines may not be definitive.
Researchers pooled the results of 72 studies that had looked at the link between fatty acids and coronary disease (including heart attack, coronary heart disease and angina).
They found no significant evidence that saturated fats increase the risk of heart disease and no significant evidence that omega-6 and omega-3 polyunsaturated fats protect the heart.
However, some of the pooled studies involved people with cardiovascular risk factors or with cardiovascular disease, so the results may not necessarily apply to the population at large.
Yet the researchers say that despite their results, further research is necessary, especially in people who are initially healthy. Until the picture becomes clearer, it is recommended people stick to the current UK guidelines on fat consumption.
Concentrating on a single food source to protect your health is never a good idea. The most important thing is to eat a healthy and balanced diet, which should include at least five portions of fruit and vegetables.
Where did the story come from?
The study was carried out by researchers from the University of Cambridge and Medical Research Council, University of Oxford, Imperial College London, University of Bristol, Erasmus University Medical Centre and Harvard School of Public Health. It was funded by the British Heart Foundation, Medical Research Council, Cambridge National Institute for Health Research Biomedical Research Centre and Gates Cambridge.
The study was published in the peer-reviewed journal Annals of Internal Medicine.
The results of the research were accurately reported by the UK media, though some of the headlines were a little too black and white. This study hasn’t “proved” that saturated fat isn't bad for the heart, rather that evidence of harm does not appear to be statistically significant.
What kind of research was this?
This was a systematic review and meta-analysis that aimed to summarise the evidence about associations between fatty acids and coronary disease. A systematic review is an overview of primary studies. Systematic reviews use explicit and reproducible methods to search for and assess studies for inclusion in the review. A meta-analysis is a mathematical synthesis of the results of the included studies.
This is an appropriate way of pooling and studying the body of available evidence on a specific topic.
What did the research involve?
The researchers first searched databases of published studies to identify prospective cohort studies related to fatty acid exposure that were at least one year long. They also searched for randomised control trials that had looked at the association between fatty acids exposures and coronary disease.
Fatty acid exposures included:
fatty acid intake, estimated by diet questionnaires or diet records
levels of fatty acid biomarkers
the effect of supplementing diets with fatty acids
Coronary disease was defined as:
fatal or nonfatal heart attack
coronary heart disease
angina
coronary insufficiency (also known as angiographic coronary stenosis) – where poor blood flow to the heart causes repeated angina attacks
sudden cardiac death (also known as coronary death)
Once the studies had been identified, the researchers assessed if there were any biases and extracted data about the characteristics and results.
The researchers transformed the results of each study, to calculate the relative risk of coronary disease when people in the top third of the fatty acid distribution were compared with people in the bottom third.
The researchers then performed a meta-analysis to combine the results of the included studies.
What were the basic results?
The researchers identified 72 studies: 45 cohort studies and 27 randomised controlled trials. 40 studies had initially healthy populations, 10 recruited people with elevated cardiovascular risk factors and 22 recruited people with cardiovascular disease.
32 cohort studies, including 530,525 people, looked at the association between dietary fatty acid intake and coronary disease. These studies looked at the intake of:
total saturated fatty acid
total monounsaturated fatty acid
total long-chain -3 polyunsaturated fatty acid
total -6 polyunsaturated fatty acid
total trans fatty acid intake
When comparing people in the top third to those in the bottom third of dietary fatty acid intake, only trans fatty acid intake was significantly associated with a risk of coronary disease.
People in the top third of dietary intake of trans fatty acids had a 16% increased risk of coronary disease compared to people in the bottom third (relative risk [RR] 1.16, 95% confidence interval [CI] 1.06 to 1.27).
17 cohort studies, including 25,721 people, looked at the association between circulating fatty acid biomarkers (i.e. in the blood) and coronary disease. These studies looked at circulating levels of the same fatty acids listed above. Comparing the top third and the bottom third, there were no significant associations between circulating levels of any of these types of fatty acid and the risk of coronary disease.
However, there were significant associations for specific fatty acids. The saturated fatty acid margaric acid was significantly associated with lower risk (RR 0.77, 95% CI 0.63 to 0.93), as were the polyunsaturated fatty acids eicosapentaenoic (RR 0.78, 95% CI 0.65 to 0.94), docosahexaenoic (RR 0.79, 95% CI 0.67 to 0.93) and arachidonic acid (RR 0.83, 95% CI 0.74 to 0.92).
27 randomised controlled trials, including 103,052 people, looked at the effect of fatty acid supplementation on the risk of coronary disease. In these trials, people in the intervention group had been given linolenic acid, long-chain -3 polyunsaturated fatty acid or -6 polyunsaturated fatty acid supplements. No significant difference in the risk of coronary disease was seen for people in the intervention group compared to people in the control group.
How did the researchers interpret the results?
The researchers concluded that “current evidence does not clearly support cardiovascular guidelines that encourage high consumption of polyunsaturated fatty acids and low consumption of total saturated fats”.
Conclusion
In contrast to current recommendations, this systematic review found no evidence that saturated fat increases the risk of coronary disease, or that polyunsaturated fats have a cardioprotective effect.
Similarly, there was no significant association between the levels of total omega-3 or omega-6 polyunsaturated fatty acids and coronary disease. This lack of association was seen in both cohort studies, which looked at dietary intake or circulating levels the in blood, and in randomised controlled trials that had looked at the effect of supplementation.
There was also no significant association between total saturated fatty acids and coronary risk, both in studies using dietary intake and in those using circulating biomarkers. In addition, there was no significant association between total monounsaturated fatty acids and coronary risk – again, both in studies using dietary intake and those studying fatty acid composition.
Dietary trans fatty acid intake was associated with increased coronary disease risk, although circulating levels were not.
There are some limitations to this study:
- For the studies based on dietary intake, it is not clear over how long a period of time their diet was assessed. Dietary questionnaires can be inaccurate due to recall bias and may not be representative of diet over a number of years.
- The level of fat consumption is unclear – that is, how large the difference in fat consumption per day was between people in the top third compared with people in the bottom third.
- Some of the studies involved people with a pre-existing health condition, so the results may not be applicable to a healthy population.
Despite these limitations, this was an impressively detailed and extensive piece of research, which is likely to prompt further study.
Current UK guidelines remained unchanged:
The average man should eat no more than 30g of saturated fat a day.
The average woman should eat no more than 20g of saturated fat a day.
Even if saturated fats don’t directly harm your heart, eating too much can lead to obesity, which in turn can damage it.
The key to a healthy diet is “everything in moderation”. The occasional buttered scone or cream cake is not going to hurt you, but you need to be aware of your total calorie intake.
Eating a healthy, balanced diet, being physically active and not smoking are the best ways to keep your heart healthy.
Analysis by Bazian. Edited by NHS Choices.
Links To The Headlines
No link found between saturated fat and heart disease. The Daily Telegraph, March 18 2014
Saturated fat 'ISN'T bad for your heart': Major study questions decades of dietary advice. Daily Mail, March 18 2014
Saturated fat advice 'unclear'. BBC News, March 17 2014
Should I avoid saturated fat? BBC News, March 17 2014
'Butter may be no worse for your heart than using ‘healthy’ low-fat alternative’. Daily Mirror, March 17 2014
Links To Science
Chowdhury R, Warnakula S, Kunutsor S, et al.
Association of Dietary, Circulating, and Supplement Fatty Acids With Coronary Risk: A Systematic Review and Meta-analysis. Annals of Internal Medicine. Published online March 18 2014
