There are people who have unusual genetic conditions causing excess cholesterol, but that would be a long shot. The body does produce some cholesterol, but a high level of cholesterol is usually because of excess consumption of animal based food products.
Rather than go on statin drugs, which have huge and dangerous side effects, a competent doctor will recommend changes to diet and lifestyle first. If your boyfriend can't do it, then he needs to listen to his doctor about medications.
I would recommend that you both read books on diet by Dr. Dean Ornish or Dr. Neal Barnard. The latter is more technical, but the first author is more accessible and popular.
I personally went from high cholesterol and other abnormal blood work to excellent levels within 3-6 months after switching to a plant based diet. I also lost 50 pounds very easily. The healthiest diet in the world is a 100% plant based diet. You do not need the following foods for a balance diet, despite what industry disinformation promotes through educational institutions and media:
+ Dairy - Many people are intolerant or allergic to dairy. It is not required for a healthy diet. Calcium is more available through leafy green vegetables. Vitamin D is available through skin exposure to the sun for about 10 minutes a day.
+ Meat - Eliminate all animal flesh. All proteins can be built from legumes (cooked or sprouted) and whole grains (brown rice, coos coos, and non-gluten whole grains are excellent). You should take a vitamin B12 supplement, however. You should also make sure to take an Omega-3 fatty oil every day as well.
+ Eggs - Some people advocate for eating egg whites since this is almost all protein and no cholesterol, however, animal protein consumption is associated with cancers. Eggs can also carry bacteria and other contaminants. Again, all proteins are available through a combination of legumes and whole grains.
Please look for "The China Study" by T. Colin Campbell. He has studies animal proteins for his entire career. He has published 350 peer reviewed articles. His studies are solid. A vegetarian diet can eliminate a large part of the risk for the following diseases:
+ Heart Disease - This includes the symptoms of high cholesterol and obesity.
+ Cancer - Campbell showed the correlation between animal protein consumption and cancer in laboratory rats and mice. He verified the effect in humans by studying dietary patterns and disease patterns in China over a period of decades.
+ Diabetes - Vegetarians are far less likely to develop diabetes and all of the associated complications. A population of vegans in California live 7-10 years longer than other Californians.
+ Osteoporosis - Eating animal proteins leads to an acid condition in the blood. The Nurses' Study showed that drinking 3 glass of milk was more likely to lead to this disease and hip fractures. The New York Times published an article about new research yesterday.
I believe that the food industry and other parties have deliberately spread disinformation in order to protect their profitable franchises. Industry has focused research on narrow questions that avoids disclosure of a very simple fact:
A whole foods vegetarian diet is the healthiest diet in the world.
Corporations do not profit by this truth, so they will push what has the lowest cost, longest shelf life, best marketability, and addictive taste. Human health plays no role in the marketing of convenience foods, like a KFC meal. By the way KFC uses MSG in just about every food they offer. (MSG and aspartame are excitotoxins and are linked to neurological problems in many people.)
By the way, if it is a lipid disorder, as suggested by the next poster, then he should still make diet and lifestyle changes. Here is what Google Health suggests for a lipid disorder:
"High cholesterol and other lipid disorders can be inherited (passed down through families) or associated with:"
"* Fatty diets"
"* Disease such as diabetes, hypothyroidism, Cushing syndrome, and kidney failure"
"* Certain medications, including birth control pills, estrogen, corticosteroids, certain diuretics, and beta blockers"
"* Lifestyle factors, including inactivity and regular, excessive alcohol use"
https://health.google.com/health/ref/High+blood+cholesterol+and+triglycerides
In other words, your boyfriend should go on a healthy and mostly vegetarian diet. Checkout the writings of the researchers I listed above if you don't trust me or the next poster. Physicians certainly know what is best: Diet and lifestyle changes.
If that isn't enough, consider medications.
Signing up for a clinical trial is a very bad idea because you have about a 0.5 chance of being in the control group where you will be given a placebo. Drugs are less effective than lifestyle changes anyway.