Seed Oils


Conclusions

Some seed oils are specifically marketed as a source of n-3 PUFAs. These oils are not comparable to fish oil because they contain ALA rather than EPA and DHA.

The specific health benefits of ALA are less well researched and understood than those associated with EPA and DHA. ALA consumption is considered important for maintaining a healthy n-3 to n-6 intake ratio and is particularly effective where LA consumption is simultaneously reduced.

A Question of Balance: Where seed oils are used cold, as in salad dressings, substituting ALA-rich oils for those high in LA will help you to achieve a much healthier PUFA balance and should thus enhance your n-3 highly unsaturated fatty acid (HUFA) status.


Introduction

Most seed oils commonly found in the western diet are high in LA and contain only small amounts of ALA. They are not ideal from a health perspective because they help to promote an unhealthy tissue PUFA balance and could therefore contribute to inflammation. Some seed oils, however, are rich sources of ALA and have a very beneficial n-3 to n-6 ratio. These include:
Check the ALA content and n-3 to n-6 ratio of seed oils made from chia seeds and flaxseed

We set out to answer the following questions during this project:

What is the importance to our health of ALA?
What is the recommended daily intake of ALA?
How can we benefit from seed oil supplementation?
What side effects are there?



What is the importance to our health of ALA?

Seed oils provide their n-3 PUFAs exclusively in the form of ALA as they do not contain either EPA or DHA.

It is widely acknowledged that although EPA and DHA are metabolic products of ALA, the human body can only manufacture EPA in small quantities and DHA in minute quantities. ALA should therefore be seen as a significant, but minor, source of EPA and a negligible source of DHA. Both of these highly unsaturated fatty acids (HUFA) are most efficiently provided directly through your diet, either by eating fatty fish or by taking fish oil supplements.

As the benefits of seed oil supplements relate mainly to ALA, we need to examine the health effects of ALA.

Much more research has been directed at EPA and DHA than ALA because these two highly unsaturated fatty acid derivatives of ALA have more clearly demonstrated beneficial effects against a range of serious health problems.

The health benefits of ALA are nevertheless believed to be significant and can be considered under the following three headings.


Conversion of ALA into its long chain metabolites

Even though EPA and DHA are much more efficiently obtained by direct consumption through your diet, EPA is nevertheless manufactured by the body from ALA in small but significant quantities, while DHA is also created, albeit in very small amounts.

Some of the beneficial effects attributed to ALA may be produced indirectly through EPA, its metabolic product.


Direct effects of ALA on health

Based on existing research, it is likely that ALA produces a range of beneficial effects that help to prevent cardiovascular disease (CVD) by protecting against cardiac arrhythmias and inflammation associated with atherosclerosis.

It is also believed that ALA consumption helps to moderate triglyceride levels, which is a major factor for coronary heart disease (CHD).

There is some evidence that ALA may provide beneficial in preventing high blood pressure, although this is far from conclusive.

As the physiological functions of ALA are still poorly understood, it is possible that future research will reveal other specific health benefits associated with ALA supplementation.


Role of ALA in maintaining healthy PUFA balance

It is now widely accepted that maintenance of optimum PUFA balance in all body tissues is an important health factor. PUFAs are incorporated into cell membranes and are also components of triglycerides, which circulate in blood plasma.

The actual PUFA composition of tissues depends on the amounts and ratios of different PUFAs consumed in the diet.

Although DHA status does not appear to be significantly improved by ALA supplementation, a number of studies have shown that DHA status can be enhanced by increasing ALA consumption while at the same time reducing LA intake. This has the effect of reducing n-6 competition, both for desaturase and elongase enzymes and for PUFA inclusion in cell membranes.


What is the recommended daily intake of ALA?

ISSFAL has issued a statement summarizing the recommended amounts of various PUFA to be consumed in the diet. The recommendation for ALA is 2.0g, equivalent to 0.7% of energy. The ISSFAL statement relating to ALA was based on a survey of 10 studies dated between 1968 and 2003. Cardiovascular disease (CVD) was the main outcome in 9 of these studies.


How can we benefit from seed oil supplementation?

The greatest benefits of ALA supplementation in the form of seed oils would be gained by substituting them in your diet for oils that are high in LA and low in ALA, such as those made from corn, cottonseed, peanut, safflower and sunflower.

These benefits are only available where the oils are used cold, because oils rich in n-3 PUFA are not suitable for cooking. The PUFAs are rapidly transformed by heat into trans fats and other harmful substances.

Using seed oils rich in ALA for salad dressings, and incorporating them into other dishes without the need for heat, would be an effective way of improving n-3 to n-n-6 balance.

Find out which oils are suitable for cooking


What side effects are there?

No significant adverse effects for ALA supplementation were encountered during our research.

Although some studies have suggested that increased ALA consumption may be correlated with higher risk of prostate cancer, the evidence for this has so far proven inconclusive.