Heart disease – a catch-all phrase for a variety of conditions that affect the heart’s structure and function – is the leading cause of death in the United States and responsible for a third of all deaths worldwide. For nearly a century much of the blame for the prevalence of heart disease lay with saturated fat, a type of fat commonly found in meats, such as beef, pork, and lamb, and in whole fat dairy products, such as cheese, butter, or cream. But recent scientific studies have challenged that idea, raising the question: Does saturated fat cause heart disease?
Much of the confusion surrounding the saturated fat/heart disease debate stems from the types of studies from which the conclusions were drawn. Although the findings of a large meta-analysis published in the journal Annals of Internal Medicine indicated that there was no evidence to support the notion that consumption of saturated fat increased the risk of heart disease, the studies on which their conclusions were based were primarily observational. These types of studies can show an association, but not causation. It’s important, then, to look at findings from studies that get more to the heart of the problem – specifically, randomized controlled trials, or RCTs.
At first glance, however, the data from RCTs seem to be inconsistent. But when we consider one unifying characteristic exhibited by the subjects of these studies – inflammation – it becomes obvious that there’s more to this debate. High systemic inflammation underlies processes fundamental to nearly all diseases of aging and even cancer, which is a disease of aging. This elephant in the room can’t be ignored when answering the question about diet and heart disease.
A diet high in saturated fat sets us up for a litany of ills related to fat metabolism. But it’s only in the setting of a diet high in refined sugar that these bad things happen. In particular, when we eat saturated fat, our large, buoyant LDL increases – step number one. By itself (the randomized controlled trials seem to suggest) this first step is not enough. Only when we convert that large buoyant LDL into small, dense LDL – step number two, most likely due to consuming refined sugars and, in doing so, increasing our systemic inflammation. Then we have a problem. Saturated fat might be the smoking gun, but refined sugar is surely the trigger.
To say that dietary intake of refined sugar is to blame for heart disease is tempting. But the reality is that the way our bodies respond to food is also complicated by our genetics, microbiome, and lifestyle factors. Until scientists learn more about the role these different factors play, moderating saturated fat consumption and boosting polyunsaturated and monounsaturated fat consumption seems prudent.
In this episode, Rhonda digs deeper into the links between diet and heart disease and suggests ways to reduce individual risk.
Interested in learning more about your raw genetic data you got from a provider like 23andMe? The genes mentioned in this podcast can be found in the report at foundmyfitness.com/genetics.
A large meta-analysis of more than 70 studies showed that there wasn’t enough evidence to support the notion that saturated fat increased risk of coronary heart disease. Study
Many of the studies that have been used to determine risk are observational, which can’t be used to establish causation.
A randomized controlled trial showed that a diet high in saturated fat and low in refined sugar and processed foods led to reduced fat storage in the liver and heart and improved metabolic markers. Study
A randomized controlled trial showed that when normal, healthy weight men drank a sugar-sweetened drink every day for 3 weeks, their small LDL particles increased in number and their C-reactive protein, a marker of inflammation, increased by 60%-100%. Study
Rhonda provides a little background on LDL and HDL particles.
Hear Dr. Ronald Krauss talk about LDL cholesterol, particle size, heart disease, and atherogenic dyslipidemia. Episode
Your ancestral origins and genetic makeup play huge roles in determining your risk of heart disease.
The blood glucose response to a particular food varies from person to person based on their genetics, microbiome, and other lifestyle factors. Study
A genome wide association study identified single nucleotide polymorphisms in FTO (the fat mass and obesity associated gene), indicating that variation in FTO strongly contributes to early onset obesity and high polyunsaturated fat and low saturated fat intake may decrease risk. Study
Transcription factors PPAR-alpha and PPAR-gamma are essential for fatty acid metabolism, and polymorphisms in these genes influence diabetes and obesity risk.
The APOE4 gene is associated with higher blood concentrations of LDL particles.
How to get your genome tested and analyzed.
Trans-fats cause stiffening of cell membranes and increased risk of heart disease.
Increased consumption of high fructose corn syrup and sucrose linked to 35% greater risk of heart disease. Study
People with the highest intake of refined sugar had a 4-fold increase in heart attacks. Study
Learn more about how refined sugar harms health and influences disease risk. Episode
The primary apolipoprotein of chylomicrons, VLDL, IDL, and LDL particles. Apolipoprotein B is produced in the small intestine and the liver. It transports fat molecules (such as cholesterol) to all the body's cells and tissues. High levels of ApoB, especially when LDL particle concentrations are also high, are the primary driver of the formation of plaques that cause vascular disease.
A lipoprotein produced in the liver and the brain. In the brain, ApoE transports fatty acids and cholesterol to neurons. In the bloodstream, it binds and transports cholesterol, bringing it to tissues and recycling it back to the liver. Approximately 25% of people carry a genetic variant of this lipoprotein called ApoE4, which is associated with higher circulating levels of LDL cholesterol and a 2- to 3-fold increased risk of developing Alzheimer's disease.
The tendency for something to promote the formation of fatty deposits called plaques in the arteries.
A disease characterized by the deposition of fatty plaques on the inner walls of arteries. Something is said to be atherogenic when it promotes the formation of fatty plaques in the arteries. Atherosclerosis causes coronary artery disease.
One of two types of fat, or adipose, tissue (the other being white adipose tissue, or white fat) found in mammals. The primary function of brown adipose tissue is to generate body heat. In contrast to white adipocytes (fat cells), which contain a single lipid droplet, brown adipocytes contain numerous smaller droplets and a much higher number of mitochondria, which make it brown. Brown fat also contains more capillaries than white fat, since it has a greater need for oxygen than most tissues.
A molecule composed of carboxylic acid with a long hydrocarbon chain that is either saturated or unsaturated. Fatty acids are important components of cell membranes and are key sources of fuel because they yield large quantities of ATP when metabolized. Most cells can use either glucose or fatty acids for this purpose.
A value (between 0 and 100) assigned to a defined amount of a carbohydrate-containing food based on how much the food increases a person’s blood glucose level within two hours of eating, compared to eating an equivalent amount of pure glucose. Glucose has a glycemic index value of 100. Whereas eating high glycemic index foods induces a sharp increase in blood glucose levels that declines rapidly, eating low glycemic index foods generally results in a lower blood glucose concentration that declines gradually.
An estimate of the effects of carbohydrate consumption using the glycemic index (GI) while taking into account the amount of carbohydrate that is consumed. In other words, glycemic load is a GI-weighted measure of carbohydrate content that is defined as the grams of available carbohydrate in the food, multiplied by the food's GI.
A circulating lipoprotein that picks up cholesterol in the arteries and deposits it in the liver for reprocessing or excretion. HDL is often referred to as the "good cholesterol."
A critical element of the body’s immune response. Inflammation occurs when the body is exposed to harmful stimuli, such as pathogens, damaged cells, or irritants. It is a protective response that involves immune cells, cell-signaling proteins, and pro-inflammatory factors. Acute inflammation occurs after minor injuries or infections and is characterized by local redness, swelling, or fever. Chronic inflammation occurs on the cellular level in response to toxins or other stressors and is often “invisible.” It plays a key role in the development of many chronic diseases, including cancer, cardiovascular disease, and diabetes.
A peptide hormone secreted by the beta cells of the pancreatic islets cells. Insulin maintains normal blood glucose levels by facilitating the uptake of glucose into cells; regulating carbohydrate, lipid, and protein metabolism; and promoting cell division and growth. Insulin resistance, a characteristic of type 2 diabetes, is a condition in which normal insulin levels do not produce a biological response, which can lead to high blood glucose levels.
A diet that causes the body to oxidize fat to produce ketones for energy. A ketogenic diet is low in carbohydrates and high in proteins and fats. For many years, the ketogenic diet has been used in the clinical setting to reduce seizures in children. It is currently being investigated for the treatment of traumatic brain injury, Alzheimer's disease, weight loss, and cancer.
Molecules (often simply called “ketones”) produced by the liver during the breakdown of fatty acids. Ketone production occurs during periods of low food intake (fasting), carbohydrate restrictive diets, starvation, or prolonged intense exercise. There are three types of ketone bodies: acetoacetate, beta-hydroxybutyrate, and acetone. Ketone bodies are readily used as energy by a diverse array of cell types, including neurons.
A measure of the number of small LDL particles in a person’s blood. LDL-P is thought to be a better predictor of heart attack risk than total LDL cholesterol. Apolipoprotein B (ApoB) is used as a marker for LDL-P since there is one ApoB molecule per LDL particle.
A class of saturated fats. Medium-chain triglycerides are composed of medium-length fatty acid chains (six to 12 carbons long) bound by a glycerol backbone. They occur naturally in coconut oil, palm oil, and butter, but they can also be synthesized in a laboratory or food processing setting. Evidence suggests that MCT therapy improves cognitive function in older adults with Alzheimer's disease. Examples of MCTs include caprylic acid (C8), capric acid (C10), and lauric acid (C12).
Dietary fats acids that have more than one unsaturated carbon bond in the molecule, such as omega-3 and omega-6 fatty acids. PUFAs are present in fish, nuts, and seeds and are more prone to oxidation than other fatty acids. PUFAs activate a master gene called PPAR, which is involved in lipid metabolism.
One of the three isotypes of a subfamily of nuclear receptor proteins (the PPARs) that functions as a transcription factor. PPAR-alpha is a major regulator of lipid metabolism in the liver and is activated under conditions of energy deprivation. It is necessary for the process of ketogenesis, a process that is a key adaptive response to prolonged fasting and is inducible by strict carbohydrate restriction. Activation of PPAR-alpha promotes uptake, utilization, and catabolism of fatty acids by upregulation of genes involved in fatty acid transport, fatty acid binding and activation, and peroxisomal and mitochondrial fatty acid β-oxidation. Expression of PPAR-alpha is highest in tissues that oxidize fatty acids at a rapid rate, especially the liver, but also brown adipose tissue (BAT), the heart, and kidney.
A study in which people are randomly allocated to receive one of several clinical interventions. One of these interventions is the standard of comparison or control. The control may be a standard practice, a placebo, or no intervention at all.
Highly processed grains, starches, or sugars. Refined foods are typically processed via industrial extraction, concentration/purification, or enzymatic transformation and often lack the vitamins, minerals, and dietary fiber of whole foods. Many refined foods have a high glycemic index, which can rapidly produce an elevated glucose response.
A main-step process resuming in the net movement of cholesterol from peripheral tissues back to the liver via the plasma. Excess cholesterol from cells is brought back to the liver by HDL where it is secreted in bile or otherwise converted into bile salts.
A change in one nucleotide DNA sequence in a gene that may or may not alter the function of the gene. SNPs, commonly called "snips," can affect phenotype such as hair and eye color, but they can also affect a person's disease risk, absorption and metabolism of nutrients, and much more. SNPs differ from mutations in terms of their frequency within a population: SNPs are detectable in >1 percent of the population, while mutations are detectable in <1 percent.
A metabolic disorder characterized by high blood sugar and insulin resistance. Type 2 diabetes is a progressive condition and is typically associated with overweight and low physical activity. Common symptoms include increased thirst, frequent urination, unexplained weight loss, increased hunger, fatigue, and impaired healing. Long-term complications from poorly controlled type 2 diabetes include heart disease, stroke, diabetic retinopathy (and subsequent blindness), kidney failure, and diminished peripheral blood flow which may lead to amputations.
A type of lipoprotein. VLDL enables fats and cholesterol to move within the water-based solution of the bloodstream. It is assembled in the liver from triglycerides, cholesterol, and apolipoproteins, and converted in the bloodstream to low-density lipoprotein (LDL). VLDL transports endogenous products (those made by the body), whereas chylomicrons transport exogenous products (those that come from the diet).
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