Probiotic drinks have exploded in popularity in the UK — but when you're standing in the supermarket chiller aisle, should you reach for Actimel, Yakult, or kefir? They all claim gut health benefits, but they're very different products with different calorie counts, bacterial strains, and price points.
This guide breaks down Actimel vs Yakult vs kefir across every metric that matters — calories, bacterial content, taste, price, and evidence — so you can choose the best probiotic drink for your needs.
| Drink | Serving Size | Calories | Bacteria Strains | Bacteria Count | Price (approx) | SW Syns | WW Points |
|---|---|---|---|---|---|---|---|
| Actimel Original | 100ml | 68 kcal | 1 (L. Casei) | ~10 billion | ~£0.45/bottle | 3.5 | 2 |
| Actimel 0% Fat | 100ml | 35 kcal | 1 (L. Casei) | ~10 billion | ~£0.45/bottle | 1.5 | 1 |
| Yakult Original | 65ml | 46 kcal | 1 (L. Casei Shirota) | 6.5 billion | ~£0.35/bottle | 2 | 1 |
| Yakult Light | 65ml | 25 kcal | 1 (L. Casei Shirota) | 6.5 billion | ~£0.35/bottle | 1 | 1 |
| Biotiful Kefir (plain) | 250ml | ~130 kcal | 30+ strains | Billions+ | ~£1.30/serving | 6.5 | 4 |
Prices are approximate and vary by retailer. Calorie figures per stated serving. SW syn values based on calorie content; verify in official app. WW SmartPoints are approximate.
Actimel (by Danone) is the best-selling probiotic drink in the UK. Each 100ml bottle contains the L. Casei Danone bacterial strain plus vitamins B6 and D. The original variety is 68 calories — around 3.5 syns on Slimming World — while the 0% fat version is 35 calories (1.5 syns), making it the better choice for calorie-counters.
Who it's best for: People who want a convenient, well-researched probiotic drink they can grab at any supermarket. Actimel has decades of research behind the L. Casei strain for immune and gut health support.
Flavours available: Original (plain), strawberry, mango, raspberry, pomegranate, and more. The 0% fat range mirrors most flavours.
Yakult was the world's first commercially produced probiotic drink, invented in Japan in 1935. Each tiny 65ml bottle contains 6.5 billion L. Casei Shirota bacteria — a strain that has been researched for over 80 years. The original Yakult is 46 calories, while Yakult Light is just 25 calories (approximately 1 syn) — making it the lowest-calorie probiotic shot on the market.
Yakult doesn't contain added vitamins like Actimel does, but the L. Casei Shirota strain has more peer-reviewed research behind it than virtually any other single probiotic strain.
Who it's best for: Calorie-counters who want the most researched probiotic strain in the smallest, lowest-calorie format. Yakult Light at 25 calories is the best option for Slimming World and Weight Watchers members.
Kefir is a fermented milk drink that originated in the Caucasus region. Unlike Actimel and Yakult, which each contain a single bacterial strain, kefir contains 30+ different bacterial and yeast strains. This diversity is thought to be more beneficial for gut microbiome health, although the science on optimal strain diversity is still developing.
The most widely available kefir brand in UK supermarkets is Biotiful, found at Tesco, Sainsbury's, Asda, and Waitrose. A 250ml serving of Biotiful plain kefir is approximately 130 calories — significantly more than Actimel or Yakult — but it's also a much larger, more filling serving that can replace a yogurt or snack.
Who it's best for: People who prioritise gut microbiome diversity over convenience. Kefir is higher in calories but also higher in protein and calcium per serving. It works well as a yogurt replacement in smoothies, dressings, and as a standalone snack.
At just 25 calories and approximately 1 syn, Yakult Light is the clear winner for anyone counting calories or following Slimming World. The 6.5 billion bacteria per bottle is a solid dose from a well-researched strain.
If your goal is broad gut microbiome support, kefir's 30+ bacterial and yeast strains offer significantly more diversity than the single-strain drinks. The science increasingly suggests diversity matters — but this is an evolving area of research.
Actimel 0% fat (35 cal) is available in multipacks at all major UK supermarkets at competitive prices, comes in multiple flavours, and provides vitamins B6 and D alongside the probiotic bacteria. It's the most convenient everyday option.
The L. Casei Shirota strain in Yakult has over 80 years of research behind it — more than any competing strain. If you want the probiotic drink most backed by clinical evidence, Yakult is the answer.
The evidence for probiotic drinks is generally positive but nuanced. Studies support benefits for:
The key is consistency — occasional use shows limited benefit, while daily consumption over several weeks is where the evidence is strongest.
Actimel contains approximately 10 billion bacteria per bottle vs Yakult's 6.5 billion. However, bacteria count isn't the only measure of effectiveness — strain quality and research backing matter more than raw numbers. Both are in the range considered effective for gut health support.
For a related breakdown of probiotic drink syn values, see our Actimel syns guide for the full Actimel range breakdown.
Both are effective probiotic drinks with good research behind them. Yakult's L. Casei Shirota strain has over 80 years of research, making it possibly the most evidence-backed single probiotic strain available. Actimel offers more bacteria per bottle (10 billion vs 6.5 billion) and added vitamins. For calorie efficiency, Yakult Light (25 cal) is significantly better than Actimel Original (68 cal).
Yakult Original is 46 calories per 65ml bottle; Yakult Light is 25 calories. Actimel Original is 68 calories per 100ml bottle; Actimel 0% Fat is 35 calories. Yakult Light is the lowest calorie probiotic drink of the main UK brands.
Kefir offers significantly more bacterial diversity (30+ strains vs 1) and is more filling per serving. However, it's higher in calories (130 cal per 250ml serving) and more expensive. If gut microbiome diversity is your priority, kefir is the better choice. If convenience and low calories matter more, Yakult Light wins.
Actimel Original is approximately 3.5 syns per 100ml bottle. Actimel 0% Fat is approximately 1.5 syns. Yakult Light is approximately 1 syn. Always verify current values in the official Slimming World app as products can change.
Daily consumption is where both products show the most benefit in research. One bottle per day consistently over 4+ weeks is the typical protocol used in studies. Both are safe for daily use for most people.
There is some evidence that kefir supports a healthy gut microbiome, which is linked to weight management. However, kefir at 130 calories per serving is higher in calories than Actimel or Yakult. As part of a calorie-controlled diet, kefir can be a healthy addition — but it's not a weight loss product in itself.
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