Dr Frank B. Hu, professor of nutrition and epidemiology at the Harvard School of Public Health, was a member of the US 2015 Dietary Advisory Committee. In an e-mail interview, he explains the changed position on cholesterol. Excerpts from the exchange:
Why was cholesterol linked to heart disease before; what changed?
Studies in the ’50s and ’60s found a direct link between blood cholesterol levels and heart disease, prompting recommendations aimed at lowering dietary intake of cholesterol. However, in general, dietary intake of cholesterol only moderately influences blood cholesterol levels. Other dietary factors more strongly determine blood cholesterol levels.
And these other dietary factors are...
Monounsaturated and polyunsaturated fats and high-quality carbohydrates that are rich in fibre and have low glycaemic load (whole grains, fruits, vegetables, beans and legumes) are associated with an improved cholesterol profile. Saturated fats, transfats and low-quality carbohydrates are associated with worsened cholesterol profile. The current position focuses on these aspects of the diet, and does not posit a specific recommendation for dietary cholesterol. Nevertheless, high-risk populations such as individuals with diabetes or heart disease still need to monitor their cholesterol intake.
Do we still need to test blood cholesterol levels?
Blood cholesterol levels are still a risk factor for CVD, hence routine testing patients’ blood cholesterol levels continues to remain critical. Blood cholesterol levels are only modestly affected by dietary cholesterol intake. This does not imply that blood cholesterol levels do not in turn affect cvd risk.
Can we eat what we like now?
Dietary cholesterol is but one nutrient. There are many aspects of diet that can affect disease risk. It is important to consume the right types of fats, high-quality carbohydrates, healthy sources of protein, while avoiding sweetened beverages, all of which have been addressed in the advisory committee report.
How will the recommendations impact statin prescriptions?
The current recommendations have not retained the earlier limit on dietary cholesterol intake, but that is only because of its weak correlation with blood cholesterol levels. Maintaining normal blood cholesterol levels is still crucial, hence statin treatment protocols should not be impacted by these recommendations.
Can we return to eggs or whole milk?
Eggs are a major source of dietary cholesterol. However, previous studies have shown that up to one egg per day is not associated with risk of CVD among generally healthy individuals. Since whole milk contains more saturated fat than reduced fat milk, people are recommended to replace full-fat dairy with reduced fat or low-fat dairy.
And other heart-healthy recommendations?
Dietary patterns high in whole grains, fruits, vegetables, nuts, legumes, low-fat dairy and seafood, and low in red and processed meats, refined grains and sugar-sweetened beverages are strongly associated with reduced risk of CVD.