Diet plays an important role in shaping our gut bacteria composition and function which in turn affects our general health. Mediterranean diet, rich in fruit, vegetables, pulses, nuts and fish with moderate or low intake of dairy, meats, and wine, has been recommended as a way to reduce the risks of non-communicable diseases such as obesity, type 2 diabetes, heart disease or cancer. There is little information in humans on the impact of Mediterranean diet intervention on gut bacteria composition and function and metabolism.
This study was published in the Gut Journal. It looked at the impact of Mediterranean diet intervention on gut bacteria. As well as general markers of health among overweight and obese people at risk of heart disease.
Types of Study
This was a parallel randomised controlled study where overweight and obese people (men and women) were randomised into 2 groups: 43 participants consumed a Mediterranean Diet adapted to their energy intake and 39 participants maintained their usual diets (control group). This intervention lasted 8 weeks. Participants were asked not to change their physical activity habits throughout the study and they provided urine, blood and faeces at baseline (beginning of the study), 4 weeks and 8 weeks. They kept dietary records that assessed their compliance with the dietary intervention (Mediterranean or control diet).
People on the Mediterranean diet showed a decrease in blood cholesterol levels as a result of their diet. This is when compared to people who were on their usual diets (control group). These benefits were even more obvious among people with higher Mediterranean diet adherence. As a result of consuming more plant-based foods, the number of gut bacteria associated with fibre intake increased. Whereas gut bacteria associated with inflammation were in lower amounts. Analysis of blood and urine chemicals showed lower levels of bile acids (chemicals associated with intake of meat and fatty foods) and higher insulin sensitivity (lower risk of type 2 diabetes).
The intervention lasted 8 weeks and didn’t have a follow-up. Therefore the long-term consequences of the Mediterranean diet on lipid levels, metabolism and gut bacteria composition are unknown. In addition, body weight and composition (fat and muscle masses) were not assessed throughout the study. As a result, we don’t know whether the Mediterranean diet intervention affected these characteristics.
I’m a big believer in aiming to get the nutrients we need from food, but this isn’t always possible. Since vitamin D is only found in a small number of foods, it can be difficult to get enough from our diets. A survey found that the average person only gets 3 micrograms per day of vitamin D from their diet (8). Therefore Public Health England suggests that you should consider taking a daily Vitamin D supplement containing 10 micrograms during the winter months. And all year round if you are in the ‘as risk’ group (9).
When it comes to supplements, cheaper does not always mean inferior! Do not be fooled by the packaging and advertising of some. Just because a supplement is more expensive does not necessarily mean it is better. As long as you are choosing a supplement that contains the recommended amount of vitamin D, and it is brought from a reputable source, then feel free to choose the cheaper one! Just remember that too much of anything can be bad for us, supplements are no different. Vitamin D can be harmful in large doses (10). So if you choose to take a supplement make sure you only take 1. And do not exceed the recommended daily dose of 10 micrograms (unless advised by your doctor!).