Do new studies change our understanding?
Cardiovascular disease is anything but boring; what we know about it is constantly evolving. New information comes along all the time, which on the whole is a good thing. Even though this disease has been on the decline, it is still the number one killer of Americans, responsible for about one million deaths per year.1 However, not all studies nor all analyses on the topic are created equal. Therefore, I thought it apropos to present a quiz on cardiovascular disease myths and truths.
Without further ado, here is a challenge to your cardiovascular disease IQ. The questions below are true or false. The answers and evidence are provided after.
1) Saturated fat is good for us, but processed foods and trans-fats are unhealthy.
2) Fish oil supplements will help reduce the risk of cardiovascular disease and mortality.
3) Fiber has significantly beneficial effects on heart disease prevention.
4) Unlike sugary sodas and drinks, diet soda is most likely not a contributor to this disease.
5) Vitamin D deficiency may contribute to cardiovascular disease.
Now that was not so difficult. Or was it? The answers are as follows: 1-F, 2-F, 3-T, 4-F, 5-T. So how did you do? Regardless of whether you know the answers, the reasons are even more important to know. Let’s look at the evidence.
Most of the medical community has been under the impression that saturated fat is not good for us. We need to limit the amount to no more than 10% of our diet. But is this true? The results of a newly published meta-analysis (a group of 72 randomized clinical trials and observational studies) would upend this paradigm.2 While saturated fat did not decrease the risk of cardiovascular disease, it did not significantly increase the risk either. Also, the results showed that trans-fats increase the risk of this disease. Of course trans-fats are a processed fat, so this is something that most of us would agree upon. And in the clinical trials portion of the meta-analysis, omega-3 and omega-6 polyunsaturated fats did not significantly reduce the risk of cardiovascular disease.
Does this mean that we can go back to eating saturated fats with impunity? Well, there were weaknesses and flaws with this study. The authors only looked at the one dimension of fat. Their comparison was based on the upper-third of intake of one type of fat versus the lower-third of intake of the same type of fat (whether it was saturated fat or a type of unsaturated fat). It did not consider whether saturated fat was substituted with refined grains or unsaturated fatty acids. Also, what was the source of saturated fats, animal or plant, and did these sources also contain unsaturated fats as well, like olive oil or nuts which contain good fats? Therefore, there are many unanswered questions and potentially several significant flaws with this study.
While I respect the New York Times, I was a bit surprised to see Mark Bittman’s March 25, 2014 column, “Butter is Back,” referencing the new meta-analysis above. Many of his articles in the past have contributed to the health and wellness of his readers. However, he misses the boat by promoting butter and other sources of saturated animal fat, such as cheese, pork and the skin from chicken. I think he does a disservice to his readers, making statements that are downright dangerous and hopefully will not result in more cardiovascular disease.
The meta-analysis above, which Bittman uses to buoy his arguments, does not differentiate among plant or animal saturated fat sources. But in one that does, the researchers found saturated fats from animal sources increased cholesterol and the risk of cardiovascular disease.3 Also in another study, specifically using unsaturated fats in place of saturated fat reduced the risk of this disease.4, 5
There is whole industry built around fish oil and reducing the risk of cardiovascular disease. Yet the data don’t seem to confirm this theory. In the latest study, the age-related eye disease study 2 (AREDS2), unfortunately, 1 g of fish oil (long chain omega-3 fatty acids) daily did not demonstrate any benefit in the prevention of cardiovascular disease nor its resultant mortality.6 This study was done over a five-year period in the elderly with macular degeneration. The cardiovascular primary endpoint was a tangential portion of the ophthalmic AREDS2. This does not mean that fish, itself, falls into that same category, but for now there does not seem to be a need to take fish oil supplements for heart disease, except potentially for those with very high triglycerides. Fish oil, at best, is controversial ; at worst, it has no benefit with cardiovascular disease.
We know that fiber tends to be important for a number of diseases, and cardiovascular disease does not appear to be an exception. In a meta-analysis, involving 22 observational studies, the results showed a linear relationship between fiber intake and decreased in risk for developing cardiovascular disease.7 In other words, for every 7 grams of fiber consumed, there was 9% reduced risk in developing the disease. It did not matter the source of the fiber from plant foods; vegetables, grains and fruit all decreased the risk of cardiovascular disease. This did not involve supplemental fiber, like that found in Fiber One or Metamucil. To give you an idea about how easy it is to get a significant amount of fiber, one cup of lentils has 15.6 grams of fiber, one cup of raspberries or green peas has almost 9 grams, and one medium-size apple has 4.4 grams. Americans are sorely deficient in fiber. 8
An upcoming presentation at the American College of Cardiology examines the Women’s Health Initiative: the study suggests that diet soda may increase the risk of heart disease.9 In those drinking two or more cans per day, defined as 12 ounces per can, there was a 30% increased risk of a cardiovascular event, such as an a stroke or heart attack, but an even greater risk of cardiovascular mortality, 50%, over 10 years. These results took into account confounding factors like smoking, diabetes, high blood pressure, and obesity. This study involved over 56,000 postmenopausal women for almost a nine-year duration.
The results of a recent observational study in the elderly suggest that vitamin D deficiency may be associated with cardiovascular disease risk. The study showed that those whose vitamin D levels were low had increased inflammation, demonstrated by elevated biomarkers including C-reactive protein (CRP).10 This biomarker is related to inflammation of the heart, though is not as specific as one would hope.
Beware in regards to saturated fat. If a study looks like an outlier or too good to be true, then probably it is. I would not run out and get a cheeseburger just yet. However, study after study has shown benefit with fiber. So if you want to reduce the risk of cardiovascular disease, consume as much whole food fiber as possible. Also, since we live in the northeast, consider taking at least 1000 IUs of vitamin D daily. This is a simple way to help thwart the risk of the number one killer.
1 uptodate.com. 2 Ann Intern Med. 2014;160(6):398-406. 3 JAMA 1986;256(20):2623. 4 Am J Clin Nutr. 2009;99(5):1425-32. 5 Cochrane Database Syst Rev. 2012:5;CD002137. 6 JAMA Intern Med. Online March 17, 2014. 7 BMJ 2013; 347:f6879. 8 Am J Med. 2013 Dec;126(12):1059-67.e1-4. 9 ACC Scientific Sessions 2014; Abstract 917-05. 10 J Clin Endocrinol Metab online February 24, 2014.