Dietitian tests snack bars that promise anti‑inflammatory, brain‑boosting and anti‑ageing benefits

A dietitian who assessed a range of commercially marketed snack bars found that some products provide useful fibre or a caffeine lift, but many of the more ambitious claims — including those about "vegan collagen" and anti‑ageing — lack robust evidence and several bars are highly processed.

Rosie Carr, a registered dietitian working with the weight‑loss service Second Nature, rated and tasted a selection of bars sold in UK retailers. Her review examined nutrition panels and ingredient lists, weighed advertised health claims, and assigned scores based on nutritional profile and likely consumer benefit.

One product marketed as "anti‑ageing" — the Jade & Joy Marshmallow Biscuit Vegan Collagen bar (50 g, £1.66) — contains pea and soya protein and lists a 15 g protein content, but Carr concluded that consuming amino acids in a bar does not equate to the targeted stimulation of collagen synthesis in skin, hair or nails. The bar was rated 2 out of 10; it was described as ultra‑processed because of additives such as maltitol and polydextrose, and contained less fibre than most competitors despite a relatively high protein content.

A caffeinated option, the Rheal Energy Caffeinated Superfood Bar in Blueberry Muffin flavour (40 g, £1.33), provides about 68 mg of caffeine per bar — roughly equivalent to a single espresso — courtesy of guarana. Carr gave it a score of 5 out of 10, noting the bar also supplies about 5.7 g of fibre but contains added sugars from date syrup, brown rice syrup and coconut sugar. She said the combination of caffeine and added sugars may cause a short‑lived boost followed by a drop in energy.

The Butter High Fibre Bar (35 g, £1.30) earned a comparatively higher score of 6 out of 10. With 10.4 g of fibre per bar — roughly a third of an adult's recommended daily intake — and a short ingredient list that includes date paste, chicory fibre, peanuts and sunflower seeds, Carr highlighted that it can aid bowel function and be filling. She noted, however, that a handful of mixed nuts could provide similar nutrition without the sugar content found in the bar.

An M&S product billed as "Brain Food" — the Mixed Berry Bar (35 g, £1) — combines date paste, almonds, chicory fibre and freeze‑dried berries with added vitamins, iron and zinc. Carr scored it 4 out of 10, saying iron and zinc do contribute to normal cognitive function but are better supplied through a balanced diet; she also flagged that the bar's sugar content is high (about 40 percent of the bar by weight), coming primarily from dates and dried fruit, which can produce blood sugar spikes that may impair concentration.

Carr's assessments emphasised a distinction between isolated nutrient claims on packaging and how nutrients act in the body. In the case of so‑called vegan collagen, proteins and amino acids consumed in a mixed meal are broken down and redistributed by the body; a single food item with protein does not guarantee targeted effects on skin collagen. Fortified vitamins and minerals can help address deficiencies but do not replace a balanced diet as the primary source of nutrients.

The review also highlighted the role of added sugars, sugar alcohols and other sweeteners. Bars that rely on syrups and concentrated fruit for sweetness deliver rapidly absorbable carbohydrates that can raise blood glucose and prompt an insulin response. Some sugar substitutes, such as maltitol, and bulking agents like polydextrose, can reduce calorie density but also qualify a product as processed.

Fibre content varied significantly across the sampled bars. Insoluble fibres from ingredients such as dates, nuts and chicory root were noted for promoting bowel regularity, while soluble fibres can support gut bacteria. Carr pointed out that a bar supplying multiple grams of fibre may offer a useful on‑the‑go source of the nutrient, but whole foods such as pulses, whole grains, vegetables and nuts remain primary recommendations for sustained fibre intake.

Caffeine sources such as guarana were assessed for their likely physiological effect. The reviewer observed that naturally caffeinated ingredients can raise alertness but that accompanying sugars and the speed of carbohydrate absorption influence the pattern of energy and concentration over time.

Overall, Carr’s testing found that a small number of bars can contribute positively to fibre or provide a short caffeine boost, but many health claims printed on packaging — including bold statements about halting ageing or directly improving cognition — are not supported by high‑quality evidence when attached to a single snack. She recommended that consumers view fortified or marketed snack bars as occasional conveniences rather than substitutes for balanced meals based on whole foods.

The tested products were purchased from UK retailers including Holland & Barrett, Sainsbury's and M&S, and prices and nutrition information were noted on product packaging. The review and ratings were summarised in a Daily Mail feature that detailed calorie counts, macronutrient breakdowns and taste impressions for each bar.