Research review
Does alfalfa cause weight gain? What the research shows
No human trial has tested alfalfa supplements for weight gain or weight loss. The entire human research record for alfalfa is two small studies — one on cholesterol, one on fertility — and neither measured body weight as an outcome.
The evidence doesn't support alfalfa supplements causing weight gain, weight loss, or a change in appetite in people. No controlled human trial has tested alfalfa for any of those outcomes — the entire human research record for this ingredient is two small studies, on cholesterol and on fertility, and neither one measured body weight.
What the evidence doesn't support
It doesn't support alfalfa, in any form, as something that makes a person gain weight, lose weight, or eat more or less. It doesn't support "alfalfa tea" or "alfalfa tonic" products marketed for either purpose. That's not a finding that alfalfa has no effect on weight — it's that the question hasn't been tested in a controlled human study at all, which is a different thing from a trial that looked and found nothing.
What the trials found
A 1980 study gave three human volunteers a diet containing whole alfalfa seeds for three weeks and tracked their cholesterol levels; the published report doesn't mention body weight as something the researchers measured. A 2024 randomized trial gave 60 men with a fertility diagnosis 6 grams a day of alfalfa seed powder alongside vitamin E for 12 weeks and tracked sperm count, motility and shape; it recorded two withdrawals (one for bloating, one for a respiratory allergic reaction) but, again, no body-weight measurement. Between them, these two trials are the entire controlled human record for alfalfa, and neither one answers a question about weight one way or the other.
Outside humans, a 2014 study fed a concentrated alfalfa saponin extract to 40 hyperlipidemic rats and recorded body weight gain among the measurements taken, alongside cholesterol and liver markers. The published results report what happened to the rats' cholesterol and liver enzyme activity in detail, but don't state a body-weight result — so even the one study that measured weight in an animal doesn't give a usable answer to point to here.
Questions people ask
Does alfalfa make you gain weight?
No trial has tested this in people. The two small human studies that exist looked at cholesterol and sperm quality, not weight, so there's no trial data supporting the idea that alfalfa causes weight gain — or weight loss, for that matter.
What is alfalfa tea good for?
No trial has tested alfalfa tea specifically, for weight or anything else. The closest human research used whole seeds and seed powder, not brewed leaf — see alfalfa tea for what those studies actually used, and alfalfa benefits: what the research does and doesn't show for the fuller research picture.
Can alfalfa supplements help you gain weight if you're underweight?
There's no trial evidence either way. Being significantly underweight is a reason to see a doctor and get an evaluation, not a reason to self-treat with a supplement that hasn't been tested for that purpose.
When to talk to a doctor
Alfalfa is not a treatment for being underweight, overweight, or for obesity, and nothing above should stand in for a doctor's evaluation of an unexplained weight change. If you're managing your weight for a diagnosed reason, that's a conversation for your doctor, not a decision to make from a supplement label. See alfalfa side effects and who should not take alfalfa for the documented safety picture.
Sources
- Alfalfa seeds: effects on cholesterol metabolism In 1980, three people who ate alfalfa seeds for three weeks had lower plasma cholesterol afterward, with no toxicity detected on blood tests during that short period — the entire human record on alfalfa and cholesterol.
- Effect of Medicago sativa seed powder (Plus vitamin E vs. vitamin E alone) on semen analysis in men with idiopathic infertility: A double blind randomized clinical trial In a 2024 trial, 60 men with a fertility diagnosis who took 6 g/day of alfalfa seed powder alongside vitamin E for 12 weeks had bigger improvements in sperm count, motility and shape than men taking vitamin E alone; one person dropped out with bloating and one with an allergic reaction.
- The regulation of alfalfa saponin extract on key genes involved in hepatic cholesterol metabolism in hyperlipidemic rats In rats fed a high-fat diet, a concentrated alfalfa saponin extract changed liver gene activity in a pattern consistent with the liver clearing more cholesterol — a plausible mechanism, but from an animal study using an extract, not a human trial.
*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.