In the news: People with MetS Need More Vitamin C; Probiotics May Benefit Brain Health

Metabolic Syndrome May Raise Vitamin C Needs

Regular readers of Staying Healthy newsletters are probably familiar with Metabolic Syndrome (MetS) – a condition often caused by insulin resistance, overweight and inactivity. MetS is thought to affect over 35% of adults and raises the risk for heart disease and type 2 diabetes.

The condition is associated with a constellation of symptoms such as high blood pressure, high blood sugar, abdominal obesity (large waistline), elevated triglycerides and low HDL (‘good’ cholesterol) levels. It is also characterized by low grade chronic inflammation and oxidative stress.

Vitamin C, ascorbic acid, is one of the most potent water-soluble antioxidants in blood and tissues. Previous studies have observed that both intake and blood levels of this vitamin are lower in people with MetS than in healthy people.

These findings led university researchers in New Zealand to explore the relationship between MetS and vitamin C to determine requirements of the vitamin in people who ranged in MetS severity, based on the number and severity of MetS symptoms. To do this they looked at participants in the US National Health and Nutrition Examination Survey.

They found an inverse association between MetS severity and blood vitamin C values: lower vitamin C levels were linked to higher severity scores.

When the participants were divided into three groups by their severity scores, those in the group with the highest scores required a 2.7-fold higher intake to meet an adequate blood concentration of circulating vitamin C.

In short, the study (1)shows that people with worse MetS symptoms have lower levels of vitamin C than those with less severe MetS, and that they need to consume higher amounts of vitamin C due to increased oxidative stress and inflammation.

MetS individuals may have lower circulating vitamin C levels even with adequate intake, suggesting higher consumption is needed to reach healthy levels.

Do Probiotics Help with Cognitive Impairment?

Much research is exploring whether probiotics can help the brains of older, cognitively impaired people.

It’s known, for example, that the GI tract and the brain communicate in maintaining physical and mental health (the gut-brain axis as it’s called), and that bacteria in the gut influence that communication. In addition, older adults often have less diverse gut bacteria than younger people.

A recent review(2) analyzed 10 placebo-controlled trials that tested probiotics in 778 total participants with cognitive impairment, including Alzheimer’s.

Probiotic supplementation lasted for 4–52 weeks in the trials, and the probiotics often included lactobacilli and bifidobacteria strains.

The main finding was that probiotics moderately improved cognitive function compared to placebo.

Probing further, they found that probiotics improved cognitive function in studies that used both single strains and multiple strains, though the effect was larger with single strains, smaller with multiple strains.

Some theorize that multiple strains of probiotics may reduce their effectiveness because the strains compete for resources or inhibit one another. More research is needed to understand these interactions, as well as to learn how probiotics exert their benefit.

Another finding was that the beneficial probiotic effect was not apparent in trials lasting longer than 12 weeks. Not all previous investigations have reported this so, again, more research is needed.

The review did not offer information on the daily dose of the probiotics studied. However, at least one international health organization suggests a daily minimum count of at least 1 billion CFU.

References

1. Carr AC, et al. Metabolic syndrome is associated with increased vitamin C requirements in the US National Health and Nutrition Examination Survey. Nutr Res. 141:1-9, 2025.
2. Ma M, et al. Efficacy of probiotics in patients with cognitive impairment: A systematic review and meta-analysis. PLoS One. 20(5):e03221567, 2025.