Healthy Hearts: each month Prof Christian Hamilton-Craig, local cardiologist living in Noosa Shire, talks about important issues for maintaining your heart health.
This week’s column he is joined by plant-based nutrition expert and author Tammy Fry from seed-blog.com
Carbohydrates are in important staple of a balanced diet. However, in recent years there has been a trend towards low carb, “zero carb” ketogenic, or LCHF low-carb-high/healthy-Fat diets.
What is the evidence around these approaches to carbohydrates, and what is the optimal diet for a healthy hearts?
When absorbed in the gut, all carbohydrates are broken down into various sugars which are been metabolized through the liver and into the bloodstream.
It is true to say that unrefined simple carbohydrates, such as rice, white bread and sugary carbohydrates are broken down into various sugars and the body “sees” them as sugar.
Some people have equated eating a piece of white bread to a cup of white sugar, which is not entirely true, but the concept is an accurate reflection of the way in which carbohydrates are metabolized.
Therefore, it is not surprising to see that high-carbohydrate diet, particularly those with high sugar intake such as the American diet rich with donuts and candy bars, increases the glucose handling required by the liver and pancreas, and increases diabetes.
For patients who are pre-diabetic, a very low carbohydrate or even ketogenic diet may be helpful. The downside of no-carb or “keto” diet is that it goes hand-in-hand with an increase in saturated fats or “bad fats”.
Fat intake increases satiety and reduces appetite, helping with weight loss in the short-medium term, but often causes an increase in blood cholesterol, which for patients with established coronary disease (stents bypass or previous heart attack) may be potentially dangerous over the long term.
It should be noted that animal based proteins are almost always packaged with saturated fat and cholesterol, whereas protein from plants contains no cholesterol. In fact, substituting animal protein with plant protein can actually help lower LDL cholesterol.
Furthermore, when switching to a more plant-based diet (including plant proteins like soy, nuts, pulses and legumes, as well as vegetables), you naturally increase your fibre intake.
Soluble fibre supports the reduction of cholesterol as it “grabs” onto the fat and dietary cholesterol as it moves through the gut, to be excreted.
The diet with the best evidence for healthy heart is a Mediterranean diet rich in plant-based foods, vegetables, lean meat and high intake of olive oil and nuts.
The PREDIMED trial randomized patients to a low-fat diet against a Mediterranean style diet with 30 g/day of tree nuts or 1L per week of olive oil (including cooking). This showed a significant decrease in cardiac mortality, heart attack and stroke. One litre of olive oil per week is a lot! It is fair to point out that the trial was sponsored by the manufacturers of both olive oil and nuts. However, the data are compelling for a Mediterranean diet low in carbohydrates, high in plant-based foods, and lean meat. A more recent trial published in January 2022 showed that higher olive oil intake was associated with lower risk of death, heart attack and stroke. Replacing margarine, butter, mayonnaise, and dairy fat with olive oil was associated with lower risk of death.
A balanced Mediterranean-style diet can be ‘tweaked’ for lower carbohydrates or increase protein options depending on the person’s level of activity/training and the background metabolic needs including diabetes or pre-diabetes.
Before starting any diet to talk to your local doctor and consider seeing a dietitian or nutritionist who can provide you with expert tailored advice for your particular health needs.
