Our understanding of how dietary fat causes cardiovascular disease changed in the last few years, and dietary guidelines reflect this change. It now appears that the type of dietary fat is as important as the quantity of dietary fat. Earlier recommendations emphasised lowering the total amount of fat in the diet to less than 30 per cent of daily calories. Newer guidelines recommend a range of 25 to 35 percent of total calories from fat, with less than 7 per cent coming from saturated fat, up to 10 per cent of total calories from polyunsaturated fat, and up to 20 per cent of total calories from monounsaturated fat.
There are several reasons why it is difficult to stress on reduction in quantity of dietary fat. The evidence that a high total fat intake is harmful is weak. Earlier studies focussed on the relationship of total dietary fat to total blood cholesterol. Today, knowledge of the different components of cholesterol — “good” HDL and “bad” LDL — makes old assumptions about fat and heart disease untenable. The people of the Mediterranean take a high fat diet (chiefly from olive oil, nuts and fish), and yet have very low prevalence of cardiovascular disease.
Similarly, the apparent relationship between high fat diet and cancer rests on imperfect evidence. For example, the link between fat intake and colon cancer may be due to red meat rather than total fat intake.
Even if it was right to focus on total fat intake, it is nearly impossible to get patients to implement such restrictions. Patients ignore advice that includes numbers and percentages. Furthermore, food manufacturers often turn limits on dietary fat into a marketing tool: refined carbohydrates, which play a role in the genesis of type-2 diabetes, are sold as “fat free” foods.
So here is the latest advice on dietary fat, minus the numbers: take a diet rich in fresh fruit and vegetables, legumes and whole grains. Eat nuts and seeds in moderate amounts. Have fish twice a week. Cook food in sunflower oil, olive oil, canola oil or, as a last resort, soybean oil. Avoid vanaspati, palm oil and coconut oil. Use ghee sparingly. Reduce intake of commercially baked foods and deep fried foods. Avoid foods cooked in reused oil. Limit intake of red meat to a few times a month. Drink skim milk rather than whole milk.
(The writer is a specialist in Internal Medicine)