Cholesterol: Can a change in diet and lifestyle really help?

Dyslipidemia is one of the most important modifiable risk factors for coronary heart disease. (CHD). Dyslipidemia is generally characterized by:
- Increased total cholesterol,
- Increased LDL cholesterol (LDL-c) and triglycerides (TG),
- in conjunction with decreased concentrations of HDL cholesterol (HDL-c).

At present, these lipid imbalances are most routinely treated with medications which beg one to ask: Are diet and lifestyle changes still relevant forms of treatment in the age of cholesterol-lowering drugs?

So what contributes to cholesterol?

Everyone produces cholesterol in their liver. Some people naturally produce more than others. Things that influence cholesterol levels are diet, exercise and cholesterol lowering medications.

A review of some of the studies combining dietary change and physical activity revealed that a low fat (<30% of daily energy) and low saturated fat diet combined with 30-60 minutes of physical activity (3-7times per week) can lower your total cholesterol by 7-18% and LDL-c by 7-15%.

Putting that into perspective, for both males and females weighing less than 90kg, it would equate to a daily fat intake of between 60-85g; not a lot when you consider a 400g tin of coconut milk contributing 50-60g of fat (the majority saturated fat) and a meat pie containing 25-30g of fat.

The effect on HDL-c was however less clear. Although some of the trials showed significant increases ranging from 5 to 14%, a majority of the trials showed no significant effect. It is important to note that some studies showed improvement in cholesterol profile with shorter trial periods, however interventions should be maintained for at least 16 weeks (or 4months) to achieve a change in cholesterol profile.

The second part of the review looked at supplementing the diet with certain foods known to enhance lipid lowering. The 3 most commonly studied and used being oat bran, fish oils and plant sterols.

Fish oil supplementation combined with exercise appears to have the most effect on TG levels. Studies over a 3-6week period were able to lower TG levels by 20-38%.

It has been suggested that the soluble fibre in oat bran is able to bind to bile acids in the digestion process thereby reducing total cholesterol. Supplementing the diet with oat products have been shown to produce significant reductions in both TC and LDL-C concentrations but having little effect on either HDL-C or TG levels (which could also be due to the shorter duration of the study periods)

In studies that have combined oat bran supplementation with exercise, consistent and substantial plasma lipid decreases were demonstrated. After 4 wk of supplementing with 35–100g oat bran/d combined with supervised endurance training for 60 min/d, reductions in TC and LDL-C of (8-26%) and (10-30%) respectively were observed.

Plant sterols, plant compounds that are structurally similar to cholesterol, were shown to lower lipid levels in humans by inhibiting cholesterol absorption from the intestine. Food sources of plant sterols include vegetable oils, seeds, and nuts. Increasing the dietary intake of these compounds is also possible through the consumption of certain products that have been supplemented with plant sterols, such as margarines and yoghurts. In a meta-analysis of 21 trials of plant sterol supplementation, it was shown that a near-maximum effect of a 10% reduction in LDL-C occurs at a dose of 2 g/d. This can be obtained fro the use of 20-25g of plant sterol enriched margarine (which roughly equates to spreading a teaspoon of margarine on 4-5slices of bread). Total cholesterol levels were shown to be reduced to a similar extent. Although the evidence suggests that these nutritional supplements have no effect on HDL-C or TG levels.

In conclusion, combination diet and lifestyle therapy is an effective means of improving cholesterol levels. For individuals who require only a 5–25% decrease in TC or LDL-C concentrations, such interventions should be implemented as a first line preliminary measure and be given at least a 3-4 month period before a review of management.