Responsiveness of one-carbon metabolites to a high-protein diet in older men: Results from a 10-wk randomized controlled trial.
Study Goal
The researchers aimed to determine whether a higher-protein diet (double the RDA) compared to standard protein intake affects one-carbon (1C) metabolite status in older men, particularly focusing on homocysteine levels and related metabolites.
Results Summary
Both diets reduced plasma homocysteine concentrations. The standard protein diet (RDA) showed specific changes in betaine-dependent remethylation ratios, while the higher-protein diet (2RDA) was associated with altered folate and choline metabolite responses. The health implications of these differential responses remain uncertain.
Population
Older men (age 74 ± 3 years).
Effective Dosage
0.8 g/kg body weight/day (RDA) vs. 1.6 g/kg body weight/day (2RDA).
Duration
10 weeks.
Interactions
None mentioned.
| Intervention | Direction | Endpoint | Population | Dosage | Impact | Claim # |
|---|---|---|---|---|---|---|
higher-protein diet | decrease | homocysteine | older men | - | supports a reduction of | #1 |
higher-protein diet | increase | B vitamins (folate, riboflavin, and vitamins B6 and B12) and methyl donors (choline) | older men | - | benefit 1C regulation by the supply of | #2 |
RDA diet (0.8 g/kg body weight/d) | decrease | plasma homocysteine concentrations | older men | - | reduced | #3 |
2RDA diet (double RDA protein) | decrease | plasma homocysteine concentrations | older men | - | reduced | #4 |
RDA diet | increase | betaine-to-choline ratio | older men | - | increase in | #5 |
RDA diet | decrease | dimethylglycine-to-betaine ratio | older men | - | decrease in | #6 |
increasing folate intake | increase | choline concentration | 2RDA group | - | positively associated with a change in | #7 |
increasing folate intake | decrease | betaine-to-choline ratio | 2RDA group | - | inversely associated with | #8 |
higher-protein diet | no change | skeletal muscle mass and physical function | older people | - | preserve | #9 |
increased B-vitamin intake | decrease | cognitive decline and cardiovascular disease | - | - | reduces the risk of | #10 |
OBJECTIVES: Dietary strategies to promote successful aging are divergent. Higher-protein diets are recommended to preserve skeletal muscle mass and physical function. Conversely, increased B-vitamin intake, supporting one-carbon (1C) metabolism, reduces the risk of cognitive decline and cardiovascular disease. On the hypothesis that higher protein intake through animal-based sources will benefit 1C regulation by the supply of B vitamins (folate, riboflavin, and vitamins B6 and B12) and methyl donors (choline) despite higher methionine intake, this study explored the effect of a higher-protein diet on 1C metabolite status in older men compared to current protein recommendations. METHODS: Older men (age, 74 ± 3 y) were randomized to receive a diet for 10 wk containing either the recommended dietary allowance (RDA) of protein (0.8 g/kg body weight/d, n = 14), or double that amount (2RDA, n = 15), with differences in protein accounted for by modifying carbohydrate intake. Intervention diets were matched to each individual's energy requirements based on the Harris-Benedict equation and adjusted fortnightly as required depending on physical activity and satiety. Fasting plasma 1C metabolite concentrations were quantified by liquid chromatography coupled with mass spectrometry at baseline and after 10 wk of intervention. RESULTS: Plasma homocysteine concentrations were reduced from baseline to follow-up with both diets. Changes in metabolite ratios reflective of betaine-dependent homocysteine remethylation were specific to the RDA diet, with an increase in the betaine-to-choline ratio and a decrease in the dimethylglycine-to-betaine ratio. Comparatively, increasing folate intake was positively associated with a change in choline concentration and inversely with the betaine-to-choline ratio for the 2RDA group. CONCLUSIONS: Adding to the known benefits of higher protein intake in older people, this study supports a reduction of homocysteine with increased consumption of animal-based protein, although the health effects of differential response of choline metabolites to a higher-protein diet remain uncertain.