Can the secret to weight loss be found in the spice aisle?

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Obesity is recognised as a worldwide health crisis, and more than 50% of the South African population is overweight, which increases the risk of heart disease, stroke and diabetes.

An exciting prospect is that the risks of obesity may be lessened by the potential weight-loss effects of certain spices found in your local grocery store.

These include turmeric, chilli, cinnamon, ginger and garlic, and they may provide safe and inexpensive additions to medications or eating plans for weight loss and metabolic disease management.

Research on turmeric (Curcuma longa) and its bioactive ingredient curcumin has demonstrated several health benefits, including anti-inflammatory, anti-oxidant and anti-diabetic effects, as well as improved brain and heart health, but unfortunately does not appear to include weight loss.

A systematic review and meta-analysis of 21 randomised controlled trials (RCTs) found that curcumin supplementation brought about weight loss of only 1 to 2 kg in obese individuals with metabolic syndrome, and numerous other trials found no weight loss associated with curcumin intake.

The individuals in these studies received supplementation in the form of either turmeric powder or curcumin capsules, ranging from a dosage of 70 to 3000 mg/day, and the duration of the trials varied from short (4 weeks) to quite long (8 months).

On the plus side, several trials showed that curcumin improved cholesterol profiles and reduced inflammation, which may be beneficial for people with diabetes and cardiovascular disease.

However, curcumin only constitutes a small fraction of turmeric powder, and therefore either large amounts of turmeric or smaller amounts of purified curcumin need to be consumed to have any metabolic effects.

Chilli, of the Capsicum genus, is enjoyed by some and dreaded by others, but scientists have been exploring its fat-burning properties instead of its mouth-burning consequences.

Some studies have suggested that capsaicin, the active ingredient of chilli, can promote a feeling of fullness (satiety), thereby decreasing food intake, but others have suggested that this may simply be due to gut discomfort.

Either way, it does not seem like these effects translate into meaningful weight loss. A meta-analysis of 6 short (4 to 12 weeks) RCTs on capsaicin, varying from 3 mg/day to 135 mg/day, only demonstrated 500g weight loss, although a few other studies have suggested that slightly increased weight loss (1.5 to 2 kg) can be achieved by combining capsaicin with other products such as ginger and green tea.

Ginger alone was found to bring about minimal (less than 1 kg) weight loss in overweight and obese persons, but it decreased fasting blood glucose, improved insulin sensitivity and normalised cholesterol levels, although surprisingly, lower quantities of ginger (up to 1 g per day) appeared to be more effective than higher quantities.

Other spices

Cinnamon, obtained from different tree species in the Cinnamomum genus, is another spice which has been considered for use against obesity.

However, human trials on using cinnamon for weight loss have mostly been performed in persons with type 2 diabetes, where the combined findings of 18 RCTs indicated that cinnamon intake, usually varying between 1 mg/day and 3 mg/day, over two to four months could reduce fasting blood sugar levels.

However, cinnamon had no effect on body weight, waist circumference, or other indicators of diabetic status such as insulin resistance in these study subjects.

On the plus side, a meta-analysis of 13 RCTs found that cinnamon supplementation could reduce blood cholesterol levels in persons with type 2 diabetes.

However, the effects of cinnamon on weight loss or cholesterol levels in otherwise healthy people have not been explored in clinical studies.

In addition, cinnamon contains a toxic ingredient, coumarin, of which the levels vary depending on the specific Cinnamomum species and the method of cinnamon preparation used.

Therefore, in this case, it is certainly not a case of “if a little is good, more must be better”!

Another loved seasoning is garlic (Allium sativum), which has been used since ancient times to supposedly cure everything from cancer to the common cold.

An analysis of 13 RCTs found that garlic supplementation had very little effect on body weight, but resulted in a small but significant decrease in waist circumference, indicating that garlic may target metabolically dangerous belly fat.

In addition, one trial involving 40 patients with obesity and metabolic syndrome found that eating raw crushed garlic twice a day relieved their high blood pressure and high fasting blood glucose levels, reduced their waist circumference and improved their cholesterol levels. 

Overall, even when the data from all available trials are combined, the usefulness of these spices to bring about weight loss has only been tested in small numbers of people, usually less than a thousand, across the world.

From these studies, it appears that these spices are not effective for weight loss, although they have other health benefits that may help to manage diabetes and heart disease.

There is also the possibility that a combination of these spices may be more effective for weight loss, although this has not been tested.

Just remember that these products cannot replace medications prescribed by your doctor; at best, they can provide support while also spicing up your meal-times.

*Logan Smith and Dr Hanél Sadie-Van Gijsen are affiliated with the Centre for Cardio-metabolic Research in Africa (CARMA) in the Division of Medical Physiology at the Faculty of Medicine and Health Sciences at Stellenbosch University.

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