October 13, 2025, 9:03 am | Read time: 5 minutes
In “Highway to Health – Studies in Brief,” this time it’s about the impact of targeted nutrient strategies on body and mind. A review shows how vitamin D supplementation can affect mood and memory. A long-term study from Japan examines whether increased intake of certain B vitamins is associated with a lower risk of dementia. And an international meta-analysis explores how low-carbohydrate diets change heart health and body composition.
Vitamin D Supplementation Can Boost Mood and Memory–Especially in Cases of Deficiency
What was studied? A review published in “Nutrients” analyzed 13 studies, including several controlled clinical trials and animal experiments, focusing on the influence of vitamin D on mood, cognitive performance, and a specific brain protein called BDNF.1
BDNF (Brain-Derived Neurotrophic Factor) is a growth-promoting protein that protects nerve cells and plays a central role in learning, memory, and mental well-being.
Results: A daily intake of at least 2,000 international units (IU) of vitamin D over 8 to 12 weeks increased BDNF levels in the blood by about 7 percent and reduced depressive symptoms–depending on the study, by up to 7.6 points on a 63-point scale, which corresponds to a noticeable improvement. In observational studies, higher vitamin D levels were also associated with better cognitive performance: In older adults, the score on the so-called Mini-Mental Test increased by 0.6 points (about 2 to 3 percent) on a scale of 0 to 30 points when the vitamin D level was 10 ng/ml higher. Vitamin D was particularly helpful at baseline levels below 30 ng/ml.
Significance: Vitamin D could help with depressive symptoms and declining cognitive performance–especially when there is a deficiency. The beneficial effect seems to be enhanced by additional intake of magnesium, zinc, omega-3 fatty acids, or exercise. Long-term studies are needed to better understand the exact biological connections. Incidentally, a study from 2022 had already suggested how positively vitamin D can affect the brain (FITBOOK reported).
Also interesting: Recommended Vitamin D Supplements Reviewed
When Cholesterol Levels Become Critical — and How to Lower Them
Mediterranean and Keto Diets Compared: Effects on Weight and Blood Pressure
Higher Intake of Vitamin B2, B6, and Folic Acid Linked to Lower Dementia Risk
What was studied? A Japanese long-term study, published in the “European Journal of Clinical Nutrition,” examined whether higher intake of certain B vitamins–specifically riboflavin (vitamin B₂), vitamin B6, vitamin B12, and folic acid–influences the development of dementia requiring care.2 The study was part of the large-scale “Circulatory Risk in Communities Study” and followed 4,171 people aged 40 to 69 over an average period of 15.4 years. Nutrient intake was recorded using a 24-hour dietary questionnaire.
Results: During the observation period, 887 participants developed dementia requiring care. Those with the highest riboflavin intake had a 49 percent lower incidence rate compared to the group with the lowest intake. The incidence was also significantly lower for vitamin B6 (−20 percent) and folic acid (−21 percent). No statistically significant association was found for vitamin B12.
Significance: The results suggest that higher intake of riboflavin, vitamin B6, and folic acid through diet can help slow the development of dementia requiring care in old age. Targeted intake of these vitamins could be a simple preventive approach in aging societies.
Low-Carbohydrate Diets Promote Heart Health and Body Composition
What was studied? A meta-analysis published in “The American Journal of Clinical Nutrition” of 174 clinical studies with a total of 11,481 adults from 27 countries examined how a diet with reduced carbohydrate content (maximum 45 percent of calories) affects heart health and body composition.3 Different diet types (such as ketogenic, low carb, moderately low carb), various substitutes (fat, protein), and factors like gender, overweight, and diabetes were considered. All studies were randomized–participants were randomly assigned to different groups to avoid bias.
Results: The low-carbohydrate diets led to partly contradictory but overall favorable effects on cardiovascular and metabolic parameters. The overall risk of cardiovascular diseases decreased significantly by 1.05 percent.
Blood lipids:
- Triglycerides (TG) decreased significantly–on average by 15.11 mg/dL, a clearly positive effect for heart health.
- The unfavorable LDL cholesterol and total cholesterol increased slightly, but so did the favorable HDL cholesterol.
Important: The ratios of blood lipid levels (LDL/HDL, TG/HDL) improved significantly–an indication of an overall favorable lipid profile, despite a slight increase in LDL.
Inflammation markers:
- C-reactive protein (CRP), a marker for inflammation, decreased significantly.
Body composition:
All measured markers improved significantly:
- Body weight: –1.75 kg on average
- Fat mass: significant decrease
- Body fat percentage: significant decrease
- Visceral fat (abdominal fat): significant decrease
- Waist and hip circumference: significant reduction
Diet types compared:
- Ketogenic diets: greater weight loss, but also higher LDL increases, which may be undesirable.
- Moderate low-carb diets (26 to 45 percent carbohydrates): best benefit-risk profile.
- Substitution with fat and protein led to the most favorable overall effects.
Significance: Low-carbohydrate diets can effectively improve blood lipid levels, inflammation markers, and body composition–especially in cases of overweight. Moderate forms are considered the most tolerable, as they harness positive effects without risking the unwanted side effects of strict ketogenic variants. Medical supervision is advisable, especially for long-term or significantly low-carbohydrate diets.
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