Cholesterol is the most demonized, misunderstood and controversial substance in both our bodies and our diets. New and recent cholesterol guidelines, in particular, have sparked headlines and hot medical debate about its role in heart disease.
The Dietary Guidelines Advisory Committee (DGAC) ignited fresh controversy this month by suggesting that cholesterol-rich foods–such as eggs, shellfish and liver–may not be a heart attack menace after all. In fact, a new report on proposed 2015 guidelines, issued by a DGAC subcommittee, concludes that, “cholesterol is not considered a nutrient of concern for overconsumption.”
A new study challenges the widely held belief that eggs are particularly dangerous.
Yale researchers reported with when adults with diagnosed coronary artery disease ate eggs daily for six weeks, no adverse effects on cardiac risk factors were observed. The same team previously reported that egg consumption didn’t harm endothelial function or raise lipid levels in participants who already had high cholesterol.
Here’s a look at some facts and myths about cholesterol, a waxy substance produced by the liver that plays essential roles in our body, from waterproofing cell membranes to helping produce vitamin D, bile acids that help us digest fat, and many types of hormones, including the sex hormones testosterone, estrogen, and progesterone.
Myth #1: Conventional lipid testing checks for all cholesterol abnormalities that raise risk for cardiovascular disease (CVD).
Fact: The conventional test doesn’t measure a dangerous type of cholesterol that has been shown to actually cause CVD: lipoprotein (a), or Lp(a).
In three studies with nearly 45,000 participants, high levels of Lp(a) tripled heart attack risk, compared to people with low levels. Elevated levels (a genetically-influenced condition found in about 20 percent of the population) also raise risk for developing CVD at a relatively young age, according to 2010 guidelines from the European Atherosclerosis Society, which recommend routine. Lp(a) screening and treatment as a “a priority for reducing cardiovascular risk.” A simple blood test is available.
A new study, published in Journal of the American College of Cardiology, highlights the added value of Lp(a) assessment. In 1995, Lp(a) was measured in 826 men and women from the general community who were then tracked for 15 years. The study found that this test significantly improved the accuracy of CVD risk prediction in all subjects, compared to assessments based on Framingham Risk Score and Reynolds Risk Score. Among those thought to be at intermediate risk for heart attacks and strokes based on their risk scores, factoring in Lp(a) levels resulted in nearly 40 percent of this group being reclassified as high or low risk, thus dramatically improving the accuracy of 15-year CVD risk prediction.
Myth #2: Elevated LDL (bad) cholesterol is the villain in most heart attacks.
Fact: About half of people who suffer these events have “normal” LDL levels.
A number of studies have implicated chronic, low-grade vascular inflammation as a key culprit in heart attacks and strokes because it contributes to both vulnerable plaque formation and plaque rupture.
Research also shows that increased levels of a lipid marker of inflammation, oxidized LDL, (OxLDL), can signify higher risk for heart attack and CVD. Assessing OxLDL levels (which can be easily measured with a blood test) can provide early warning of future cardiac danger in patients who appear otherwise healthy. Studies have shown that:
- People with high levels of OxLDL are 3.5 times more likely to develop metabolic syndrome in the next 5 years. This dangerous gang of 5 metabolic thugs quintuples risk for type 2 diabetes and triples it for heart attack.
- In healthy middle-aged men, high OxLDL levels are linked to four times higher risk for developing heart disease.
Myth #3: Low LDL cholesterol is always a sign of good health.
Fact: Low LDL has been linked to increased risk for certain disorders.
For example, a 2012 study reported that on average, people who develop cancer had lower serum levels of LDL during the 18 years prior to their diagnosis than those without the disease. The researchers examined data from the Framingham Offspring Study, comparing cancer patients to a control group of cancer-free patients matched by age, smoking status, blood pressure, diabetes, and body mass index. None of the patients had taken statins.
A recent study by French researchers found that older men with lower levels of LDL had double the risk for developing clinical depression over the next seven years, compared to men of the same age with higher levels, while in older women lower levels of HDL (good) cholesterol was linked to increased depression risk. The researchers suggest that careful management of lipids, through a combination of diet and medication, may help prevent depression in the elderly. As we reported recently, inflammation also plays a role in clinical depression, a discovery that could lead to new therapies for the mood disorder.