Vitamin B2 R5P Liquid

A serving of these riboflavin drops is 10 drops, providing 1.6 mg of riboflavin as riboflavin 5-phosphate, which is 114% of the nutrient reference value. Take 10 drops per day in water with food, as the label directs. A 100ml bottle holds 138 servings, and the liquid also comes in 250ml and 500ml. The ingredients are purified water, riboflavin 5-phosphate and citric acid. Keep the bottle out of direct light, because daylight destroys the vitamin.

Sources: NIH Office of Dietary Supplements; product label.

R5P is the short name for riboflavin 5-phosphate: vitamin B2 with a phosphate group attached. It is one of the two coenzyme forms the body builds from the vitamin. Chemists know it as flavin mononucleotide, or FMN; the other coenzyme is flavin adenine dinucleotide, FAD, which the body makes from FMN. Riboflavin itself is the plain form of the vitamin, a yellow compound that is destroyed by light. Vitamin B2 dissolves in water, so the body stores very little and needs a supply every day. This liquid contains R5P only, not plain riboflavin.

Sources: NIH Office of Dietary Supplements; Food Standards Scotland.

R5P drops and plain riboflavin end up in the same place. The body absorbs the vitamin as free riboflavin and then attaches the phosphate itself, and NIH reports that the bioavailability of free riboflavin is similar to that of the FMN and FAD forms. Taking the phosphate form therefore does not skip a step, and the choice between them is about form rather than absorption. What limits how much of any form is kept is the amount: about 95% of vitamin B2 is absorbed up to a ceiling of roughly 27 mg in one dose, and little is absorbed above that.

Sources: NIH Office of Dietary Supplements.

R5P supplies vitamin B2, whose two coenzymes sit at the centre of energy production: they let cells release energy from carbohydrate, fat and protein. The vitamin also activates two other vitamins, since converting vitamin B6 to its active form needs FMN and making niacin from tryptophan needs FAD, and it helps the body absorb iron from food. It helps keep homocysteine in the normal range and keeps skin, eyes, the nervous system and the lining of the mouth healthy. Research on doses far above the daily need centres on migraine: in one trial of 55 adults, 400 mg a day reduced attacks by two a month against placebo, while two small trials in children found no effect.

Sources: NIH Office of Dietary Supplements; Food Standards Scotland.

R5P drops are for people who want an active B2 supplement, the coenzyme form of vitamin B2, at a daily maintenance level. That includes people taking methylfolate and B12 who want the third cofactor in the same routine, vegans, who get less B2 without dairy, and anyone who finds capsules hard to swallow or prefers to adjust an amount drop by drop. UK adults need about 1.3 mg a day for men and 1.1 mg for women, so one serving covers maintenance. Anyone wanting more than the liquid gives, for instance on a practitioner's advice, can use the R5P capsules at 47.5 mg a capsule.

Sources: Food Standards Scotland; NIH Office of Dietary Supplements; product label.

Yes: riboflavin turns urine bright yellow within hours of taking it. That is harmless and is simply the vitamin the body did not need leaving. It is the one effect almost everyone taking more than a few milligrams notices.

Sources: NIH Office of Dietary Supplements.

R5P is most often taken with the other B vitamins, and it works closely with them. It is needed to activate vitamin B6 and to make niacin. NIH lists no known interactions between vitamin B2 and prescription drugs. Some drugs and long courses of light treatment can lower the body's vitamin B2, but that is a reason to check status, not to avoid the supplement. Anyone on regular prescriptions should ask a pharmacist first.

Sources: NIH Office of Dietary Supplements; Food Standards Scotland.

R5P has no reported adverse effects from food or supplements beyond yellow urine. That holds at amounts up to 400 mg a day for three months or more, which is why the United States set no upper limit. NIH adds that the absence of reports does not prove that very high intakes are harmless, and Food Standards Scotland advises staying at 40 mg or less a day from supplements. One serving of these drops is 1.6 mg. Anyone pregnant or breastfeeding, or taking prescribed tablets, should speak to a GP or pharmacist first.

Sources: NIH Office of Dietary Supplements; Food Standards Scotland.