Your Genes May Influence How Your LDL Cholesterol Responds to a Low-Carb Diet, Study Finds – Medical Daily
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Two people can follow the same low-carb diet and see very different results on their cholesterol tests.
For some, LDL cholesterol may change little. For others, it can rise substantially. New research suggests that genetic differences may help explain why, particularly when a low-carb diet is higher in saturated fat.
Researchers analyzed genetic and dietary data from participants in the DIETFITS trial and found that people with a stronger inherited tendency towards higher LDL cholesterol were more likely to experience an increase in LDL while following a low-carbohydrate diet. The relationship was particularly noticeable among those consuming more saturated fat.
The finding does not mean that genes decide whether a low-carb diet will raise someone’s cholesterol. Instead, it points to a more complicated relationship between what people eat and how their bodies respond.
The analysis came from the DIETFITS trial, a randomized study that compared healthy low-carbohydrate and low-fat diets.
For the new analysis, researchers examined 431 participants with available genetic data. They examined participants’ genetic predisposition to higher LDL cholesterol alongside their dietary intake and changes in LDL levels during the first six months.
LDL, short for low-density lipoprotein, is often called “bad” cholesterol. When too much circulates in the blood, it can contribute to the buildup of fatty deposits inside the arteries, increasing cardiovascular risk over time.
The researchers were interested in whether inherited differences could help explain why LDL responds differently when people change their diets.
What they found pointed towards an interaction between genetics and the type of fat people consumed.
Among people following the low-carb diet, participants with a greater genetic predisposition to higher LDL tended to experience larger increases in LDL when their diets contained more saturated fat.
That distinction matters because low-carb does not describe one particular diet.
Removing carbohydrates can mean eating more nuts, seeds, fish, and unsaturated oils. It can also mean eating more butter, fatty meats, and other foods that contain substantial amounts of saturated fat.
Those choices can produce very different nutritional profiles even though both diets may be labeled low-carb.
The study, therefore, does not suggest that cutting carbohydrates automatically causes LDL cholesterol to rise. Instead, the results indicate that a person’s genetic background may influence how strongly their LDL responds to the saturated fat consumed as part of a low-carb eating pattern.
The researchers also examined participants assigned to the healthy low-fat diet.
They did not find the same relationship between genetic predisposition, saturated fat intake, and LDL changes in that group.
That comparison is important because it suggests the finding was not simply about people who happened to have genes associated with higher cholesterol. The dietary pattern appeared to matter too.
Still, the results do not provide a simple formula for predicting exactly what will happen to one person’s cholesterol after changing their diet.
Genetics may be part of the explanation, but it is only one factor among many.
Rather than looking for a single “cholesterol gene”, the researchers considered thousands of genetic variants.
They combined these differences into what is called a polygenic score. In simple terms, the score estimates how strongly a person’s collection of genetic variants is associated with a particular trait, such as higher LDL cholesterol.
This approach can help researchers detect patterns that might be missed by studying one gene at a time.
But it is not yet a tool that can tell someone which diet they should follow.
The study was also based on a relatively small genetic subgroup of the larger DIETFITS trial, meaning the findings need to be tested in other populations before scientists can determine how widely they apply.
The results do not make low-carb diets inherently good or bad.
Instead, they add another reason to look beyond the amount of carbohydrate on a person’s plate.
Someone who replaces bread, rice, or pasta with foods rich in unsaturated fats may have a very different cholesterol response from someone who replaces those foods primarily with butter, fatty meat, or other sources of saturated fat.
That distinction is already reflected in dietary guidance, which generally recommends limiting saturated fat and choosing more unsaturated fat sources.
For people concerned about cholesterol, an LDL blood test can provide a clearer picture than assuming a particular diet will produce a particular result.
And because people can respond differently to the same eating pattern, a diet that produces good results for one person may not produce identical results for another.
That is one of the more interesting possibilities raised by the research.
Nutrition advice is often built around broad recommendations that apply to large groups of people. But studies like this suggest that inherited biology may help explain some of the variation between individuals.
Researchers could eventually learn to identify people who are more likely to experience a substantial increase in LDL from particular dietary patterns.
That possibility remains some way off, however. The current findings do not justify routine genetic testing to decide whether someone should follow a low-carb diet.
For now, the research offers a more nuanced explanation for something doctors and patients have long observed: dietary changes do not affect everyone’s cholesterol in exactly the same way.
A low-carb label alone cannot tell the whole story. What replaces the carbohydrates, how much saturated fat is involved, and, potentially, the genes a person carries may all help
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