THE ARISING · Longevity & Healthspan · Long reads
Could Methionine Restriction Backfire on the Liver After Menopause? A Testable Idea About Choline, Rated 60 Percent
Our research desk proposes that after estrogen falls, low choline intake could turn a celebrated longevity diet into a fatty-liver risk, even while a favorable hormone signal rises. The chemistry is credible; the effect size is unknown.
Methionine restriction is one of the most reproducible ways to extend life in rodents without making them eat less. It is also drawing interest from people who want the benefits of fasting without the hunger. Our research desk asks whether it could quietly work against the liver in one large group: women after menopause.
Methionine is an essential amino acid. It also supplies methyl groups, which the liver uses to make phosphatidylcholine, a molecule needed to package fat for export. The liver can make phosphatidylcholine through an enzyme called PEMT, or build it from dietary choline.
Estrogen boosts PEMT. The desk's proposal is an interaction: after menopause, with PEMT support reduced, moderate methionine restriction plus marginal choline intake could lower phosphatidylcholine enough to impair fat export. Liver fat would rise, even as the liver hormone FGF21 climbs and looks like a sign the diet is working. Adequate choline should prevent that reversal.
The test is a twelve-week mouse experiment with three factors: ovary removal or sham surgery, normal or restricted methionine, and marginal or adequate choline, with calories matched. The scored prediction: in hormone-depleted, methioninerestricted mice, adequate choline lowers liver triglycerides by at least 20 percent versus marginal choline. The desk gives this 60 percent.
The headline animal result checks out. Orentreich and colleagues reported in 1993 that lowering dietary methionine from 0.86 to 0.17 percent produced about a 30 percent longer life span. One detail matters here: those were male Fischer 344 rats, so the founding result says nothing about females or menopause.
FGF21 is central to the diet's effects. A 2021 review from the Pennington group reports that methionine restriction produces a persistent 5to 10-fold rise in serum FGF21 in rodents, and that FGF21 is required for the diet's effects on energy balance and insulin sensitivity. Earlier work showed an 80 percent restriction raised energy expenditure by 31 percent in mice.
The human choline evidence is strong and directly relevant. In a controlled feeding study of 57 adults, Fischer and colleagues found that on a low-choline diet, 77 percent of men and 80 percent of postmenopausal women developed fatty liver or muscle damage, versus 44 percent of premenopausal women. Steven Zeisel's review attributes that difference to estrogen inducing the PEMT gene.
This is a useful warning about biomarkers. A rising FGF21 level could reassure someone that a restriction diet is working while their liver fat moves the wrong way. More broadly, a longevity diet tested mainly in young male animals may behave differently in older women. Interventions need to be checked in the people who will use them.
The weakest link is whether moderate restriction actually crosses the threshold. The liver can conserve methyl groups, make less fat to begin with, or use other pathways. Severe methionine-and-choline-deficient diets do cause fatty liver, but those are deliberately damaging models, not longevity diets.
Surgical ovary removal is also an abrupt stand-in for gradual human menopause. And a liver-fat result, either way, would not show anything about lifespan.
• If you are postmenopausal and considering a low-methionine or very low-protein eating pattern, discuss it with your doctor first, especially if you have fatty liver or elevated liver enzymes. • Make sure your diet includes choline-rich foods such as eggs, fish, poultry, legumes and cruciferous vegetables, unless your doctor advises otherwise. • Ask about a liver check (enzymes, and imaging if indicated) before and after any major dietary change.
• A factorial mouse study crossing hormone status, methionine level and choline intake. • Human methionine-restriction trials that report results separately for postmenopausal women and track liver fat. • Whether FGF21 continues to rise even in groups where liver fat worsens.
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