- Raspberry ketones have developed a reputation for helping us lose weight, but is this justified ?
The raspberry ketone phenomenon where it is claimed ingestion can help reduce body fat or obesity rumbles on. The raspberry (Rubus idaeus L.) has been eaten in Europe for centuries, not only because of its flavour but because of its nutritional value. Ellagic acid is one important component but the ketone(s) have reputed health properties too.
Raspberry ketone (4-(4-hydroxyphenyl) butan-2-one; RK) is the major aroma of the fruit (Galois, 1982) and was identified back in 1903. It is found at up to 4.3 mg/kg fruit. It is widely used in fragrancies and perfurmes and a potent flavour for foods (Guichard, 1982) under the EU Flavourings Regulation (1334/2008/EC).
The ketone is also to be found in blackberries and cranberries.
Where did the weight loss idea start ?
Raspberry ketone became popular for as a weight reduction agent when it was discussed on the Dr. Oz television show during a section called “Raspberry ketone: Miracle fat-burner in a bottle” back in February 2012. Having been touted as the agent for weight loss, there is still no reliable scientific evidence that shows it actually works. It is currently banned from sale in the United Kingdom because it does not comply with the Food Safety Authority’s guidelines for declaration as a novel food. It is available however in other European countries and the United States.
Research
Its medical benefits have mainly been conducted in animal models. The chemical structure is similar to synephrine and capsaicin which might explain some of its actions. One study by the Ehime University School Of Medicine in Japan demonstrated in a male mouse model that feeding them raspberry ketone reduced levels of obesity and fatty liver as they were feeding on a high fat diet. They postulated that RK could positively influence lipid metabolism by increasing the norepinephrine induced lipolysis in white adipocytes (Morimoto et al., 2005).
Since this study in Japan, there has been renewed interest in raspberry ketone with a variety of studies in cell and animal models to understand the mechanism of action. One investigation found using immunoassays that RK increased the expression and secretion of adiponectin. Adiponectin is a cytokine which is secreted by fat tissue (adipose tissue) that regulates both glucose and lipid metabolism and thus regulates body weight and homeostasis. A low concentration of adiponectin is linked with obesity and metabolic disease (Hu et al., 1996). One other study found similar effects in reducing fatty liver in the same type of mouse model (Wang et al., 2012).
Toxicity
The toxicological studies on raspberry ketone are limited to acute and subchronic studies in rats. When the lowest recommended daily dose of raspberry ketone (100 mg) as a food supplement is consumed, it is 56 times the established threshold of toxicological concern (TTC) of 1800 μg/day for Class 1 substances (Bredsdorff et al., 2015). The margin of safety (MOS) based on a NOAEL of 280 mg/kg bw/day for lower weight gain in rats is 165 at 100 mg and 12 at 1400 mg.
Clearly a cautionary note is sounded. There are not enough studies yet, let alone those that tackle human feeding studies and weight loss using raspberry ketone (Lee, 2016). There are some conditions which may even be exacerbated by RK – various types of cancer for example. If it acts like synephrine it could increase levels of anxiety or raise heartbeat. All these effects need thorough investigation and so a healthy dose of scepticism is required at the moment into its properties.
Products
There are a number of products on offer which are sold as pure raspberry ketone and are made available in health food shops as tablets even though they are not meant to be so especially in the European Union. One of the most significant is sold European wide as part of a weight loss program using Raspberry Ketones Max® in capsules and another from Holland & Barrett combined with other ingredients. The recommended intake is between 100 and 1,400 mg per day.
References
Gallois, A. (1982) Quantitative evaluation of raspberry ketone using thin-layer chromatography. Sciences des Aliments 2, pp. 99–106.
Guichard, E. (1982) Identification of the flavoured volatile components of the raspberry cultivar lloyd george. Sciences des Aliments 2, pp. 173–185.
Hu, E., Liang, P., Spiegelman, B.M. (1996) AdipoQ is a novel adipose-specific gene dysregulated in obesity. J. Biol Chem. 271 pp. 10697–10703
Morimoto, C., Satoh, Y., Hara, M., Inoue, S., Tsujita, T., Okuda, H. (2005). Anti-obese action of raspberry ketone. Life sciences, 77(2), pp. 194-204.
Wang, L., Meng, X., Zhang, F. (2012) Raspberry ketone protects rats fed high-fat diets against nonalcoholic steatohepatitis. J Med Food. May;15(5) pp. 495-503.
Weyer, C., Funahashi, T., Tanaka, S., Hotta, K., Matsuzawa, Y., Pratley, R.E., Tataranni, P.A. (2001) Hypoadiponectinemia in obesity and type 2 diabetes: close association with insulin resistance and hyperinsulinemia. J. Clin. Endocrinol. Metab. 86 pp. 1930–1935
Revised 28th January 2016
It’s a strange subject. What happens if I eat loads of raspberries ?