Fermented foods have become popular in recent years, partly due to their perceived health benefits.

For instance, there is some evidence eating or drinking fermented foods can improve blood glucose control in people with diabetes. They can lower blood lipid (fats) levels and blood pressure in people with diabetes or obesity. Fermented foods can also improve diarrhoea symptoms.

But can they help you lose weight, as a recent study suggests? Let’s look at the evidence.

Remind me, what are fermented foods?

Fermented foods are ones prepared when microbes (bacteria and/or yeast) ferment (or digest) food components to form new foods. Examples include yoghurt, cheese, kefir, kombucha, wine, beer, sauerkraut and kimchi.

As a result of fermentation, the food becomes acidic, extending its shelf life (food-spoilage microbes are less likely to grow under these conditions). This makes fermentation one of the earliest forms of food processing.

Fermentation also leads to new nutrients being made. Beneficial microbes (probiotics) digest nutrients and components in the food to produce new bioactive components (postbiotics). These postbiotics are thought to contribute to the health benefits of the fermented foods, alongside the health benefits of the bacteria themselves.

What does the evidence say?

A study published last week has provided some preliminary evidence eating kimchi – the popular Korean fermented food – is associated with a lower risk of obesity in some instances. But there were mixed results.

The South Korean study involved 115,726 men and women aged 40-69 who reported how much kimchi they’d eaten over the previous year. The study was funded by the World Institute of Kimchi, which specialises in researching the country’s national dish.

Eating one to three servings of any type of kimchi a day was associated with a lower risk of obesity in men.

Men who ate more than three serves a day of cabbage kimchi (baechu) were less likely to have obesity and abdominal obesity (excess fat deposits around their middle). And women who ate two to three serves a day of baechu were less likely to have obesity and abdominal obesity.

Eating more radish kimchi (kkakdugi) was associated with less abdominal obesity in both men and women.

However, people who ate five or more serves of any type of kimchi weighed more, had a larger waist sizes and were more likely to be obese.

The study had limitations. The authors acknowledged the questionnaire they used may make it difficult to say exactly how much kimchi people actually ate.

The study also relied on people to report past eating habits. This may make it hard for them to accurately recall what they ate.

This study design can also only tell us if something is linked (kimchi and obesity), not if one thing causes another (if kimchi causes weight loss). So it is important to look at experimental studies where researchers make changes to people’s diets then look at the results.

How about evidence from experimental trials?

There have been several experimental studies looking at how much weight people lose after eating various types of fermented foods. Other studies looked at markers or measures of appetite, but not weight loss.

One study showed the stomach of men who drank 1.4 litres of fermented milk during a meal took longer to empty (compared to those who drank the same quantity of whole milk). This is related to feeling fuller for longer, potentially having less appetite for more food.

Another study showed drinking 200 millilitres of kefir (a small glass) reduced participants’ appetite after the meal, but only when the meal contained quickly-digested foods likely to make blood glucose levels rise rapidly. This study did not measure changes in weight.

Another study looked at Indonesian young women with obesity. Eating tempeh (a fermented soybean product) led to changes in an appetite hormone. But this did not impact their appetite or whether they felt full. Weight was not measured in this study.

A study in South Korea asked people to eat about 70g a day of chungkookjang (fermented soybean). There were improvements in some measures of obesity, including percentage body fat, lean body mass, waist-to-hip ratio and waist circumference in women. However there were no changes in weight for men or women.

A systematic review of all studies that looked at the impact of fermented foods on satiety (feeling full) showed no effect.

What should I do?

The evidence so far is very weak to support or recommend fermented foods for weight loss. These experimental studies have been short in length, and many did not report weight changes.

To date, most of the studies have used different fermented foods, so it is difficult to generalise across them all.

Nevertheless, fermented foods are still useful as part of a healthy, varied and balanced diet, particularly if you enjoy them. They are rich in healthy bacteria, and nutrients.

Are there downsides?

Some fermented foods, such as kimchi and sauerkraut, have added salt. The latest kimchi study said the average amount of kimchi South Koreans eat provides about 490mg of salt a day. For an Australian, this would represent about 50% of the suggested dietary target for optimal health.

Eating too much salt increases your risk of high blood pressure, heart disease and stroke.

Evangeline Mantzioris, Program Director of Nutrition and Food Sciences, Accredited Practising Dietitian, University of South Australia

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Catherine, Princess of Wales, is undergoing treatment for cancer. In a video thanking followers for their messages of support after her major abdominal surgery, the Princess of Wales explained, “tests after the operation found cancer had been present.”

“My medical team therefore advised that I should undergo a course of preventative chemotherapy and I am now in the early stages of that treatment,” she said in the two-minute video.

No further details have been released about the Princess of Wales’ treatment.

But many have been asking what preventive chemotherapy is and how effective it can be. Here’s what we know about this type of treatment.

It’s not the same as preventing cancer

To prevent cancer developing, lifestyle changes such as diet, exercise and sun protection are recommended.

Tamoxifen, a hormone therapy drug can be used to reduce the risk of cancer for some patients at high risk of breast cancer.

Aspirin can also be used for those at high risk of bowel and other cancers.

How can chemotherapy be used as preventive therapy?

In terms of treating cancer, prevention refers to giving chemotherapy after the cancer has been removed, to prevent the cancer from returning.

If a cancer is localised (limited to a certain part of the body) with no evidence on scans of it spreading to distant sites, local treatments such as surgery or radiotherapy can remove all of the cancer.

If, however, cancer is first detected after it has spread to distant parts of the body at diagnosis, clinicians use treatments such as chemotherapy (anti-cancer drugs), hormones or immunotherapy, which circulate around the body .

The other use for chemotherapy is to add it before or after surgery or radiotherapy, to prevent the primary cancer coming back. The surgery may have cured the cancer. However, in some cases, undetectable microscopic cells may have spread into the bloodstream to distant sites. This will result in the cancer returning, months or years later.

With some cancers, treatment with chemotherapy, given before or after the local surgery or radiotherapy, can kill those cells and prevent the cancer coming back.

If we can’t see these cells, how do we know that giving additional chemotherapy to prevent recurrence is effective? We’ve learnt this from clinical trials. Researchers have compared patients who had surgery only with those whose surgery was followed by additional (or often called adjuvant) chemotherapy. The additional therapy resulted in patients not relapsing and surviving longer.

How effective is preventive therapy?

The effectiveness of preventive therapy depends on the type of cancer and the type of chemotherapy.

Let’s consider the common example of bowel cancer, which is at high risk of returning after surgery because of its size or spread to local lymph glands. The first chemotherapy tested improved survival by 15%. With more intense chemotherapy, the chance of surviving six years is approaching 80%.

Preventive chemotherapy is usually given for three to six months.

How does chemotherapy work?

Many of the chemotherapy drugs stop cancer cells dividing by disrupting the DNA (genetic material) in the centre of the cells. To improve efficacy, drugs which work at different sites in the cell are given in combinations.

Chemotherapy is not selective for cancer cells. It kills any dividing cells.

But cancers consist of a higher proportion of dividing cells than the normal body cells. A greater proportion of the cancer is killed with each course of chemotherapy.

Normal cells can recover between courses, which are usually given three to four weeks apart.

What are the side effects?

The side effects of chemotherapy are usually reversible and are seen in parts of the body where there is normally a high turnover of cells.

The production of blood cells, for example, is temporarily disrupted. When your white blood cell count is low, there is an increased risk of infection.

Cell death in the lining of the gut leads to mouth ulcers, nausea and vomiting and bowel disturbance.

Certain drugs sometimes given during chemotherapy can attack other organs, such as causing numbness in the hands and feet.

There are also generalised symptoms such as fatigue.

Given that preventive chemotherapy given after surgery starts when there is no evidence of any cancer remaining after local surgery, patients can usually resume normal activities within weeks of completing the courses of chemotherapy.

Ian Olver, Adjunct Professsor, School of Psychology, Faculty of Health and Medical Sciences, University of Adelaide

This article is republished from The Conversation under a Creative Commons license. Read the original article.