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Is cholesterol level in blood depends on dietary habbits only

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"hypercholesterolemia"[MeSH Terms] AND "genetics"

Quick answer

No. Diet is one of several factors that set your blood cholesterol. Genes, other medical conditions, medicines and lifestyle also matter, and in some people they matter more than diet.
1. Genetics
  • Familial hypercholesterolemia (FH) is the clearest example. It is most often caused by loss-of-function mutations in the LDL receptor gene, in about 80-85% of cases. The liver then clears LDL poorly, so LDL-C stays high even on a good diet (Robbins & Kumar Basic Pathology, Familial Hypercholesterolemia).
  • Variants in other genes, such as APOB and PCSK9, can do the same. Common variants in APOE also change how much dietary cholesterol you absorb (Sleisenger and Fordtran's GI and Liver Disease, Genetics).
  • Genes also explain why people on the same diet respond differently. Park's Textbook of Preventive and Social Medicine describes an "important interplay between dietary and genetic determinants" (Park's, Fatty acids).
2. Diet
  • Diet does matter. A diet high in saturated and trans fats lowers LDL receptor activity and raises LDL-C. Dietary cholesterol also affects plasma lipid levels (Harrison's Principles of Internal Medicine 22E, Hypercholesterolemia; Henry's Clinical Diagnosis, Biological Variation).
  • Even so, the response to diet varies a lot from person to person.
3. Medical conditions that raise cholesterol (secondary causes)
  • Hypothyroidism and estrogen deficiency reduce LDL receptor activity (Harrison's 22E).
  • Other causes I know of from general knowledge, not from the sources I pulled:
    • Nephrotic syndrome
    • Cholestatic liver disease
    • Diabetes and insulin resistance
    • Obesity
    • Chronic kidney disease
    • Cushing syndrome
4. Medicines and lifestyle
  • Some drugs raise lipids. Examples are corticosteroids, some diuretics, some antiretrovirals, and retinoids.
  • Physical inactivity, excess weight and smoking also affect lipid levels. Smoking lowers HDL.
  • Age, sex and menopause have an effect too.
  • Cholesterol varies naturally from day to day and with the season. It is slightly higher in winter (Henry's).
5. Your body makes most of it
  • The liver makes a large share of the body's cholesterol. That is why statins, which block cholesterol synthesis, work even in people with a healthy diet.
What this means for you
  • A healthy diet helps most people, but it may not normalize cholesterol if the cause is genetic or secondary.
  • Very high LDL-C (for example, above about 190 mg/dL), a family history of early heart disease, or tendon xanthomas should prompt a check for FH.
  • If your levels are high despite a good diet, ask your doctor to check for secondary causes such as thyroid disease. Medication may be needed.
Recent evidence: A quick PubMed check turned up 2025-2026 systematic reviews on FH. They cover FH risk factors, systematic identification of FH, and genetic variants and carotid atherosclerosis in FH (PMIDs 42025352, 41478251, 40510188). They reinforce that FH is under-detected, and I saw nothing contradicting the points above. I only looked at the titles and did not read the papers.
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