Some foods contribute to a higher dietary acid load while others decrease it. Study author Hana Kahleova, MD, PhD explained the following to Medical News Today:

“Animal products including meat, fish, eggs, and cheese cause the body to produce more acid, increasing dietary acid load, which is linked to chronic inflammation that disrupts metabolism and can lead to increased body weight. Plant-based diets, on the other hand, which are more alkaline, are associated with weight loss, improved insulin sensitivity, and lower blood pressure.”

This research was a secondary analysis of a previous study involving overweight adult participants who followed the Mediterranean diet and a low-fat vegan diet. In the current analysis, researchers sought to look at dietary acid load in these diets and how it related to weight.

The original study was of a group of 62 overweight adults. The participants were divided into two groups. One group was on a Mediterranean diet, and the other was on a low-fat vegan diet for 16 weeks. After a 4-week break, the groups switched to the other diet.

Participants kept track of what they ate via food diaries at certain weeks, and researchers also had data on physical activity and body composition.

Researchers used two scoring systems to calculate participant dietary acid load. The authors explain that one estimation looks at five nutrients, and the other does as well but also takes into account weight and height.

Overall, both dietary acid load scores decreased on the low-fat vegan diet but stayed the same on the Mediterranean diet.

Researchers also found that participants lost weight, likely primarily from decreased body fat, while on the low-fat vegan diet but did not lose weight while on the Mediterranean diet.

Researchers also found that changes in dietary acid load were positively associated with weight changes. So, a decrease in dietary acid load was associated with a decrease in body weight.

The associations did decrease when researchers adjusted “for changes in energy intake” in the first 16 weeks of the study. However, in the second 16 weeks of the study, the associations were still significant after the adjustment.

This research does have certain limitations. Firstly, the original study had limitations such as a small number of participants, a short intervention time, and data from only one center. However, researchers note that the time on each diet was long enough for adaptation to occur.

Since the participants were volunteers, the authors acknowledge that the study sample “may not represent the general population.”

The other major limitation was that the analysis relied on dietary reports from participants. Data on physical activity was also participant-reported. Researchers also acknowledge the risk of attrition in studies about diet and that 16% of participants did not finish the study.

However, they also note that there was high dietary adherence throughout the study.

Kahleova explained that “future studies can focus on the most effective strategies to alkalize the diet and look at possible links with diabetes, cardiovascular disease, and other chronic diseases.”

The authors of the study also note that there is a need for randomized trials that examine how the Mediterranean diet impacts dietary acid load.

Mir Ali, MD, a board-certified general surgeon, bariatric surgeon and medical director of MemorialCare Surgical Weight Loss Center at Orange Coast Medical Center in Fountain Valley, CA, who was not involved in the study, also noted that it “shows that a low-fat vegan diet may be superior to a diet containing animal products; again, further research is required to further elucidate the benefits and mechanism.”

This research suggests that diets that contribute to a lower dietary acid load offer certain benefits and that the alkalizing effect of a low-fat vegan diet might help with weight loss. It highlights another potential benefit of following a low-fat vegan diet, which people can do with guidance from dietary experts.

Alexander S. Ford, DO, a board-certified osteopathic family physician and registered dietitian, not involved in the current research, noted the following about the study to MNT:

“While a low-fat vegan diet may not be appropriate for every individual, the results of this study showed lower dietary acid loads in low-fat vegan diets versus the Mediterranean diet, a benefit linked to weight loss, independent of caloric intake, while promoting an alkalizing effect on the body that could benefit individuals with chronic diseases like morbid obesity and other conditions such as gout, arterial diseases, and rheumatoid arthritis, that have pro-inflammatory linkages.”

Ford also noted that the study also supports the importance of following a well-balanced diet: “This study also reemphasizes the importance of consuming a balanced diet, adequate in fruits, vegetables, and other plant-based foods. This emphasis should reassure you that regardless of your diet preference, a balanced diet is good for maintaining great health.”