How seaweed could slow the obesity tidal wave

Monday March 3 2014

“Seaweed could be key to weight loss, study suggests,” BBC News reports.

UK researchers have looked at alginates that occur naturally in “kelp” seaweed (the variety that resembles large blades). They found that these alginates may help reduce the amount of fat the body digests.

Their study showed that, in the lab, certain types of alginates can slow down the enzyme activity of a fat digesting enzyme called pancreatic lipase. The researchers believe that if the alginates can block this enzyme, less fat would be absorbed by the body, which would stop people becoming obese.

However, the research did not draw any definitive conclusions, the most pertinent being that weight loss would not necessarily occur in humans (or even in mice). It's also unclear whether any potential effect from seaweed extract would lead to an improvement in weight-related health issues, such as reduced risk of diabetes.

Even if the alginates studied were successful in achieving weight loss, this does not mean they are safe to consume. Ultimately, ingesting a substance that slows down fat absorption is unlikely to have the same health benefits as a well-balanced diet and exercise – this is a tried and tested lifestyle choice for maintaining a healthy weight.

Nonetheless, the market for quick-fix weight loss treatments is large and extremely profitable, so research into seaweed extract will almost certainly continue.

Where did the story come from?

The study was carried out by researchers from Newcastle University and was funded through a BBSRC CASE studentship (a grant programme for bioscience researchers) with industrial sponsors Technostics Ltd.

The study was published in the peer-reviewed science journal Food Chemistry.

The UK media’s reporting of the study was generally accurate, though much of the reporting gives the impression the alginates studied had proven to be an effective weight loss supplement in humans.

What kind of research was this?

This was a laboratory study investigating how a compound called alginate could influence the digestion of fat.

Alginates are chemicals that can be extracted from the cell walls of brown seaweed or from certain bacteria. Using alginate as a food additive is not a new concept, but this latest news covers new territory: their potential as an anti-obesity treatment.

In industrialised countries, dietary fats can account for 40% of energy intake, with triacylglycerol (TAG) being the major component. An enzyme called lipase, excreted from the pancreas, plays an important role in the digestion of fats in the body, so reducing pancreatic lipase activity would reduce fat breakdown, resulting in lower amounts being absorbed by the body. This would mean the fat passes straight through the body and wouldn’t accumulate under the skin or around organs, which is bad for your health.

Laboratory research like this is useful for establishing proof of a particular concept, but many more tests are needed for potential food additives. Experiments on humans are more important and would provide more information about the potential risks and rewards of using alginate as a food additive or a weight loss agent.

What did the research involve?

This research involved seeing how different alginates reduced pancreatic lipase enzyme activity under laboratory conditions.

The researchers tested the effects of different types of alginate originating from bacteria or seaweeds on different types of fat. They used olive oil to represent naturally occurring fats and used a compound called DGGR to represent an artificial fat (similar to the type found in many types of processed food).

A series of controlled experiments were run; these included making sure the lipase enzyme was fully functional in the tests and measuring how lipase digested fats in the absence of alginate.

The primary aim of the analysis was to look for statistical differences in how the alginates affected pancreatic lipase enzyme activity.

What were the basic results?

The researchers found that:

  • not all alginates inhibited lipase to the same extent, even those from the same genus of seaweed. This appeared to be related to the structure of the alginate – specifically, the guluronate content of the seaweed, and those with higher levels being were more effective at inhibiting lipase
  • alginate inhibited pancreatic lipase by a maximum of 72.2% (±4.1) with synthetic substrate (DGGR) and 58.0% (±9.7) with natural substrate (olive oil).
  • alginates from the seaweed Laminaria hyperborea seaweed inhibited pancreatic lipase to a significantly higher degree than the alginates extracted from a different seaweed: Lessonia nigrescens
  • a dose-dependent inhibition was seen for both sets of seaweed alginates (adding more alginate led to less enzyme activity)  
  • levels of inhibition with an olive oil substrate were lower than that of the synthetic substrate, but they were not statistically different

How did the researchers interpret the results?

The researchers concluded that: “High-G [guluronate] alginates are effective inhibitors of pancreatic lipase and are used in the food industry at low levels. They could be included at higher levels in foods without altering organoleptic qualities [aspects of food experienced by the senses, such as smell and taste], potentially reduce [sic] the uptake of dietary triacylglycerol aiding in weight management.”

Conclusion

This study shows that certain types of alginates can inhibit the enzyme activity of a key fat digestive enzyme (pancreatic lipase) under specific laboratory conditions. However, it does not show that this effect can be replicated usefully in people, or that this would lead to weight loss and other improvements in health if used as an obesity treatment or prevention.

The media reports that the link between seaweed extracts and weight loss are purely speculative. This is based on the potential implications, rather than any solid evidence from the research itself.

The next stage of this research would be to test alginate-containing foods in clinical trials involving people, either to prevent weight gain or increase weight loss. Media reports suggest that the researchers plan to do just this. The BBC quotes the lead researcher as saying: "We have already added alginate to bread, and initial taste tests have been extremely encouraging […] now the next step is to carry out clinical trials to find out how effective they are when eaten as part of a normal diet."

It’s too early to tell if adding alginates to food will be effective as part of a weight loss treatment or prevention strategy, but the findings of this early stage research appear encouraging.

Analysis by Bazian
Edited by NHS Choices