Overview

Cranberries are a popular fruit consumed in many forms, from juices to sauces found during Christmas dinner, or eaten raw. The official genus of the cranberry is Vaccinium and comes in two forms: the most common one, Vaccinium Oxycoccos, is found in northern and central Europe and grows in the wild, while its cousin, the American Vaccinium Marcocarpon, is the most commonly cultivated and consumed among the general population worldwide.

Cranberries have been known to positively prevent the risk of urinary tract infection (UTI). Recent experts have begun to believe that cranberries can help people with metabolic syndromes like obesity and diabetes, and can manage their weight. With an increasing number of studies are being produced to find evidence of any weight management effects on patients with diabetes or obesity. 

Nutritional profile of cranberries

Cranberries are generally a good source of potassium or fibre, with potassium being important for fluid balance, nerve function, and muscle contraction, and fibre being important for bowel movement and a feeling of fullness to prevent excess calorie intake. They also contain other minerals, including:¹

• Manganese: involved in bone health, metabolism, and antioxidant defence
• Copper: Involved in various enzymatic reactions and the formation of connective tissues
• Calcium and magnesium: essential for bone health and various physiological functions

Cranberries also contain multiple vitamins, which are:

• Vitamin A: important for vision, immune function, and skin health
• Vitamin E: A fat-soluble antioxidant that plays a role in maintaining healthy skin and immune function
• Vitamin B: supports energy metabolism, cellular processes, and overall health

The most important parts of cranberries, which researchers have identified as important for weight management, are phytochemicals and antioxidants, including:

• Flavonoids: quercetin, myricetin, and kaempferol, which possess antioxidant and anti-inflammatory properties
• Phenolic acids: Examples include hydroxycinnamic acids and hydroxybenzoic acid, which are important for the overall antioxidant activity of cranberries
• Proanthocyanidins (PACs): known for their role in preventing a urinary tract infection 
• Anthocyanins: responsible for the vibrant red colour of cranberries and possess antioxidant and anti-inflammatory properties

The content of each nutrient varies and can also vary depending on different methods of consumption. Pappas and Schaich (2009) reported that anthocyanin contents can range from 13.6-171 mg/100 g of fresh weight (FW), and the content depends on the ripeness and size of the fruit. Phenolic acid content also ranges, with cranberries containing high amounts of benzoic acid ranging from 474‒557 mg/100 g FW. While the content of flavonols in cranberries is much larger than other plant foods, containing 20–40 mg/100 g FW.² 

It’s also important to note that how cranberries are consumed can also have differing effects, as the effect of food processing can affect the cranberries’ nutrient contents. For example, when cranberries are processed into juice, they significantly lose their phytochemicals. 30–40% of flavonols are lost when the skin and seeds are removed, and when juices are thermally degraded in manufacturing, more than 50% of anthocyanins are also lost. Furthermore, mixing cranberry juice with other fruit juices diminishes the phytochemical contents.

The current facts about cranberries and weight management

There have been many animal and human studies that have found that cranberries have a positive effect on cardiovascular health and its risk factors, as well as metabolic syndromes like diabetes and obesity. A study with Golden Syrian hamsters fed with a high-fat diet and then given cranberries had an improved lipid profile (2010). Another clinical study tested 150 participants with hypercholesterolemia and found that giving them a mixture of anthocyanin phytochemicals lowered the ‘bad’ low-density lipoprotein (LDL) cholesterol and the ‘good’ high-density lipoprotein (HDL) cholesterol. The mechanism isn’t particularly unclear, but it is hypothesised that it inhibits LDL oxidation and inhibits cholesterol ester transfer protein (CETP), which increases HDL and enhances reverse cholesterol transport.³ 

Other studies also looked at the effects of cranberries on diabetes or obesity. Anhe et al., (2017) showed that mice with a high-fat diet were given cranberry extracts, which reversed hepatic steatosis and insulin resistance, biological factors of obesity. Lee et al., (2008) investigated the effect of cranberry extract on lipid profiles in type 2 diabetic patients for 12 weeks. They exhibited a lowering in the atherosclerotic cholesterol profile, and their total cholesterol, LDL, and total HDL cholesterol ratios decreased considerably compared to the placebo patients.

However, there wasn’t any positive or negative effect on glycaemic control in the type 2 diabetic patients taking the cranberry supplements. The main phytochemical involved with these effects is believed to be anthocyanin, which Xie et al., (2020) found possesses plasma pancreatic lipase inhibiting activity by interacting with the active site of pancreatic lipase, preventing the absorption of lipids, and facilitating the prevention of obesity.

A large study done by Fang et al.,⁴ tried to investigate and determine the health effects of cranberries, particularly on obese mice. When the high-fat diet (HFD) mice were given a purified cranberry extract, they had significantly reduced body weight gain compared to the HFD control group, and further analysis found the cranberry extract prevented the fat depositing in white adipose tissue (WAT), which stores excess lipid molecules and is shown to contribute to the negative effects of cardiovascular health and obesity. Additionally, hyperinsulinemia, an indication of type 2 diabetes, was inhibited in the treatment group.

However, they found no significant difference in energy intake compared with control and HFD mice not fed with cranberries, and they also found no insulin sensitivity between treatment and control. Furthermore, a study looking at the effects of cranberries on insulin control found rats had a delayed decline in basal insulin, which is a response when you aren’t eating, and an improved pancreatic beta-cell response, which produces insulin to uptake glucose into cells.⁵

Furthermore, the mechanism by which they affect adipose tissue is by changing the expression levels of adipocytokines, which regulate the metabolism of adipose tissue. Takashi et al., (2015) demonstrated that fruits rich in anthocyanin could suppress visceral fat accumulation and hyperglycaemia through the inhibition of pancreatic lipase activity and lead to the reduction of intestinal fat absorption in rats. A cell study (2014) used adipocytes, cells that stored fats, and found direct induction of lipolysis and downregulation of genes that express the adipogenesis pathway, which is responsible for the formation of the adipocytes. 

Human studies also back up the claim, with Lee et al., (2008) finding that cranberry juice given to healthy volunteers selectively decreased biomarkers of lipid oxidation and inflammation and Simao et al., (2013) reporting that there was an improvement in dyslipidemia, hyperglycaemia and oxidative stress in individuals with metabolic syndrome.

The myths of cranberries and weight management

Despite positive animal and human studies, the jury is still out on whether cranberries are effective in managing a person’s weight. Some review studies provide mixed, fluctuating results on the benefits of anthocyanin supplements for overweight and obese people. Furthermore, as mentioned above, cranberries don’t affect someone’s energy intake, so experts caution that just because you eat cranberries doesn’t give you an excuse to stuff yourself with sweets and cakes, calorie-dense foods.

Moreover, forms of consumption like cranberry juice may not be beneficial, and it’s recommended to eat fruits raw to absorb as much of the nutrients the cranberry provides. Additionally, the effects of consuming excessive amounts of cranberries are still unknown, and experts caution against overeating within one sitting due to their high sugar content and the possibility of toxicity.

FAQs

What are the symptoms of eating too many cranberries?

According to MedicineNet, ‘Although cranberry juice is safe to consume in moderation, drinking too much can cause side effects such as upset stomach, diarrhoea, and blood sugar spikes.’. So, make sure to look at the recommended daily intake of any cranberry product to avoid situations like this. Furthermore, people who suffer from a history of kidney stones or are allergic to cranberries shouldn’t consume any cranberry products.

Are dried cranberries as healthy as fresh ones?

Due to the production process, dried cranberries contain high amounts of sugar, overall, dried cranberries and fresh cranberries provide the same health benefits, so it’s important to consume dried cranberries in moderation.

Do cranberries have other beneficial effects?

As mentioned above, cranberries can prevent urinary tract infections, with many studies backing up the statement. They can also prevent the formation of certain types of cancer, improve our immune systems, decrease blood pressure, and have been known to elevate oestrogen in women.

Summary

Cranberries and their association with weight management is a new field of interest in which more research still needs to be done. But currently, there’s quite promising evidence that cranberries can decrease the risk of cardiovascular disease, diabetes, and obesity. Cranberries have been shown to lower the ‘bad’ cholesterol and increase the ‘good’ cholesterol in the blood by inhibiting the pancreas’ lipase activity and preventing the formation of adipocytes. While also preventing blood glucose levels from getting too high and preventing hyperglycaemia. However, cranberries on their own won’t help with weight management; an overall diet and exercise are required, and consuming too much may prove more detrimental than beneficial.