Prevailing wisdom on what’s good for the heart seems to change as quickly and as often as the weather. Recommendations to engage in regular physical activity and avoid smoking have stood the test of time, but dietary advice for cardiovascular health has shifted significantly. Let’s take a look at where the science currently stands on heart-healthy diets.
For several decades, the idea that saturated fat “clogged the arteries” prevailed. In fact, it was difficult to even find the words “saturated fat” without their being prefaced with the phrase “artery-clogging,” so that it practically became a single entity: “arterycloggingsaturatedfat.” More recently, however, several large-scale meta-analyses have debunked the fearmongering notion that delicious foods such as red meat, bacon, and cheese cause cardiovascular disease (CVD) or increase risk for heart attack. One of these, out of Harvard University, concluded “that there is no significant evidence for concluding that dietary saturated fat is associated with an increased risk of CHD or CVD.” In a separate review, the same researchers wrote, “Overall, despite the conventional wisdom that reduced dietary saturated fat intake is beneficial for cardiovascular health, the evidence for a positive, independent association is lacking.”
Owing to the belief that dietary fat—saturated fat, in particular—was bad for the heart (not to mention the waistline), many people cut back on fatty foods, but rather than replacing fat calories with calories from lean protein, vegetables, and legumes, many tended toward increased consumption of refined carbohydrates, especially high-sugar grain-based products plastered with slick marketing that they were “fat-free.” Unfortunately, this backfired for many people, leading to worse cardiovascular health. As a review in the American Journal of Clinical Nutrition put it, replacing saturated fat “with a higher carbohydrate intake, particularly refined carbohydrate, can exacerbate the atherogenic dyslipidemia associated with insulin resistance and obesity that includes increased triglycerides, small LDL particles, and reduced HDL cholesterol.” So, in trying to follow a “heart-healthy” diet, people inadvertently did the exact opposite. High triglycerides, low HDL, and abdominal obesity are among the diagnostic criteria for metabolic syndrome, so not only was cardiovascular health worsened, but people may have also negatively affected regulation of their blood glucose and insulin.
The ratio of triglycerides to HDL has emerged as a key indicator of risk for cardiovascular disease. Research indicates it’s an independent predictor for coronary heart disease (CHD), a finding that has been replicated and deepened: this ratio predicts CVD and CHD mortality. The TG:HDL ratio is a predictor of major adverse cardiac events in patients on statins, including those with lower LDL, suggesting that LDL is not the best indicator of cardiovascular status. (Some researchers have gone so far as to state outright that LDL-C does not cause CVD.)
The last several years have seen a resurgence in research on low-carbohydrate diets, and, more recently, in strict ketogenic diets. Reducing carbohydrate consumption, especially in people with type 2 diabetes or metabolic syndrome, has been shown to positively affect atherogenic dyslipidemia. Specifically, low-carb and ketogenic diets are well-known for lowering triglycerides and raising HDL—exactly what we would want for reducing risk for CVD and CHD. Carbohydrate restriction also reliably increases LDL particle size, shifting from the more atherogenic “pattern B” (small, dense particles) to the more favorable “pattern A” (large, buoyant particles).
Low carbohydrate diets are not, by definition, high in saturated fat. The majority of dietary fat can be obtained from mono- and polyunsaturated sources, such as seafood, poultry, avocados, nuts and seeds. But there’s no need to restrict saturated fat on a low-carb diet. Let’s not forget that Robert Atkins, MD—yes, that Dr. Atkins—was a cardiologist! It’s unlikely he would have risked his livelihood by telling patients with compromised heart health that it was fine for them to consume juicy steaks, bunless cheeseburgers, and rich pâté. It seems he was ahead of his time, espousing a higher fat, lower carb diet in the early 1970s.
What to Eat
Bearing in mind that pattern A LDL particles and a low TG:HDL ratio appear to be protective for heart health, and that metabolic syndrome (a.k.a. insulin resistance syndrome), is a major factor in compromised cardiovascular status, it stands to reason that a truly heart-healthy diet is one consisting of foods that allow individuals to maintain blood glucose and insulin within healthy ranges, that do not perturb the TG:HDL ratio unfavorably, and that keep LDL particles skewed toward pattern A.
Carbohydrate tolerance and glycemic response to foods varies widely among individuals. One person’s whole grain bread is another’s white flour biscuit with grape jam. There are billions of healthy, long-lived people all around the world who consume high-carb diets, so very low-carb or ketogenic diets are obviously not essential for everyone. They are a powerful intervention for those with established T2D or metabolic syndrome, but this degree of carb restriction may not be required to prevent these conditions from developing in the first place. What is likely required is maintaining overall metabolic health, low inflammation, and good insulin sensitivity. For some individuals, this leaves room for liberal amounts of grains, beans, starchy tubers, and fruit. Others will have to be more careful about total carb intake, even from foods that are wholesome and unrefined.
Advice on fat has done a major turnaround. Saturated fat is no longer public enemy #1, and a dastardly finger now points at industrial seed oils. These oils (e.g., corn, cottonseed, soybean, safflower) are high in omega-6 fatty acids. The parent n-6, linoleic acid, is an “essential” fatty acid, but we require only a very small amount of it. The glut of these polyunsaturated oils in the modern food supply means we’re getting far more than we need, and it’s crowding out the scarcer but equally important omega-3s. Moreover, overconsumption of these oils appears to play a role in the adverse health effects that were originally—but erroneously—attributed to saturated fat.
It may be that there is no one “perfect” diet, whether for the heart or any other part of the diet. Those who enjoy alcohol in moderation can do so; those who prefer to abstain can abstain. There is no one food or beverage that provides a dietary element that cannot be gotten from another source. Healthy diets consist of whole, unprocessed foods that provide the body with the vitamins, minerals, proteins and fats it needs to thrive, with carbohydrate tailored to individual tolerance and activity level.