Vitamin K (Phylloquinone and Menaquinones): ICMR-NIN Value, Indian Greens, the Birth Dose and Warfarin

Vitamin K is a family of fat-soluble compounds that the liver uses to switch on the proteins that make blood clot. Plants supply it as phylloquinone, or K1, and bacteria make the menaquinones, or K2. ICMR-NIN's Nutrient Requirements for Indians 2020 recommends 55 mcg a day for adults, a figure one helping of green leafy vegetables passes several times over. This entry in the vitamins section of the handbook sets out the requirement, the Indian foods, the injection every newborn is meant to receive, and what steady intake means for someone on warfarin.

What does vitamin K do in the body?

It completes the clotting proteins. The FAO/WHO expert consultation on vitamin and mineral requirements describes vitamin K as the cofactor for one reaction that alters particular building blocks of certain proteins so that they can bind calcium. Four clotting factors made in the liver depend on it: factor II, also called prothrombin, and factors VII, IX and X. Without that step they circulate in a form that cannot do its work, and bleeding follows.

The same reaction acts on proteins outside the liver. Two are well described: osteocalcin in bone, and matrix Gla protein in cartilage and the walls of blood vessels, which appears to hold back mineral deposits. The consultation noted that no clear biological role for osteocalcin had been established, and that a link between low vitamin K status and fracture risk remained to be confirmed. That caution still shapes how the bone evidence should be read.

K1 and K2: phylloquinone and the menaquinones

Phylloquinone, K1, is the form in plants and by far the main one in the diet and in the blood. It is concentrated in photosynthetic tissue, which is why dark leaves hold the most. The menaquinones, K2, are made by bacteria and are numbered by the length of their side chain, from MK-4 upwards. In food they turn up in animal livers and in products with a bacterial fermentation stage, such as cheeses and natto, the Japanese fermented soyabean.

Bacteria in the human gut also make menaquinones, and about 90 per cent of the vitamin K stored in the liver is in that form. How much of it the body can use is not settled, and the consultation listed it among the questions for research. The body's reserve of phylloquinone is small and turns over fast: on a severely depleted diet, liver levels fell to about 25 per cent of the starting value in three days.

How much vitamin K do you need in India?

An adult needs 55 mcg a day on ICMR-NIN's 2020 report, which states the figure for adults and says it is in tune with the FAO/WHO recommendation. The report prints no table by age, and its table of upper limits has no column for vitamin K. For other ages the FAO/WHO values are given below, labelled as such. They rest on an intake of about 1 mcg for each kilogram of body weight, the amount that keeps clotting normal.

Two notes go with the table. The consultation saw no basis for a different figure in pregnancy or lactation. And it considered whether the recommendation should be raised for the sake of bone, since intakes between 100 and 420 mcg a day improve one marker of osteocalcin, but judged that step unwise without proof that the marker matters for bone health.

Which Indian foods are richest in vitamin K?

Green leafy vegetables are, by a wide margin, and the herbs in a chutney count too. The Indian Food Composition Tables 2017 measured phylloquinone in plant foods and menaquinones in animal foods. The table converts those values per 100 g into household portions. Every leaf listed gives more than the 55 mcg adult figure in a single helping, and the full range is in the food tables' section on green leafy vegetables.

Absorption is the catch. The FAO/WHO consultation estimated that no more than 10 per cent of the phylloquinone in boiled spinach eaten with butter is absorbed, against about 80 per cent for the free form, because in a leaf the vitamin is bound tightly inside the chloroplast. Fat still helps, as ICMR-NIN's 2024 Dietary Guidelines note for all four fat-soluble vitamins, so cook greens with a little oil. The pages on methi leaves and on spinach compared with methi show what else each leaf carries.

Why is every newborn in India meant to get a vitamin K injection?

Because babies are born with very little vitamin K and a few of them bleed. The Ministry of Health and Family Welfare's operational guidelines give three reasons for the low level: vitamin K crosses the placenta poorly, breast milk contains little, and the gut bacteria that make it take a few days to settle in. The result is vitamin K deficiency bleeding, once called haemorrhagic disease of the newborn, which takes three forms.

The guidelines recommend that every baby born in a health facility, down to the sub-centre, receives a single injection of vitamin K1 into the thigh muscle soon after birth: 1 mg for a birth weight of 1,000 g or more and 0.5 mg below that. This is the programme's dose, given by trained staff and reported here as such. A Cochrane review found that one 1 mg intramuscular dose is effective against the classical form, while noting that randomised trials have not tested any regimen against the late form.

The injection is not a comment on breastfeeding, which the guidelines ask to be started before the dose is given. The 2019-21 National Family Health Survey (NFHS-5) found that 89 per cent of live births took place in a health facility, so most babies are within reach of the dose and about one in nine is born outside the setting the guideline covers. If your baby was born at home, ask a doctor or health worker about it promptly. The pregnancy diet guide covers the months before.

Too little: bleeding, and who is at risk

In adults, deficiency that shows as bleeding is almost unknown unless an illness impairs absorption, according to the FAO/WHO consultation. Volunteers fed under 10 mcg a day for several weeks showed no change in ordinary clotting tests, though a more sensitive marker rose. Since vitamin K is absorbed with fat and needs bile, long-standing fat malabsorption and bile duct disease are the usual medical causes. No Indian survey read for this entry reports vitamin K status in the population.

What does the evidence say about vitamin K, bones and the heart?

For bone, the evidence is suggestive and no more. A 2019 systematic review of 36 randomised trials found that in post-menopausal or osteoporotic patients the odds of any clinical fracture were lower with vitamin K supplements, at 0.72, but the result weakened to 0.76 and lost statistical significance when only trials at low risk of bias were counted. There was no difference in vertebral fractures. The authors concluded that the evidence is insufficient to confirm a benefit.

For the heart, there is almost nothing to weigh. A Cochrane review of vitamin K supplements for preventing cardiovascular disease found a single small trial of 60 healthy adults given menaquinone for three months. It reported no clinical events and showed no effect on blood pressure or lipids. Claims that K2 capsules protect the arteries therefore rest on mechanism, not on trials. The handbook's entry on calcium and its entry on vitamin D cover the nutrients with firmer bone evidence.

A worked example: a day of greens in Coimbatore

This is an illustration, not a real person. Take a 34-year-old vegetarian accountant in Coimbatore who takes no medicines. Her day includes 75 g of palak cooked into dal (244 mcg), a cabbage poriyal made from 100 g of cabbage (113 mcg) and a chutney with 10 g of coriander leaves (27 mcg). That is 384 mcg of vitamin K1, about seven times the 55 mcg recommended for an adult. Even a day with only the chutney and the cabbage would reach 140 mcg.

A bowl of dal palak or a winter plate of sarson ka saag with makki di roti does the job without any counting. The older site article on vitamin K and its deficiency gives a shorter account of the same ground.

Warfarin and vitamin K: steady intake, as your doctor advises

Warfarin and the related coumarin medicines work by blocking the enzyme that recycles vitamin K, which is how they slow clotting. For years patients were told to avoid leafy vegetables. A 2016 systematic review of two diet trials and nine observational studies found the evidence conflicting, with an effect on clotting tests detectable only at high intakes, above 150 mcg a day. It concluded that restricting vitamin K is not a valid way to improve anticoagulation and that keeping dietary habits stable matters more.

The numbers explain the caution. A single 100 g helping of methi holds 428 mcg, nearly three times the level at which the review saw an effect, so a week of daily saag after months without it is a real change in intake. Never stop or adjust warfarin yourself in response to a meal. If you take a different blood thinner, whether diet matters for it is a question for your doctor.

Common mistakes and myths about vitamin K

Other mistakes are common. One is to refuse the injection for a newborn in the belief that breast milk supplies enough, when the FAO/WHO table says plainly that the infant figure cannot be met on breast milk alone. Another is to confuse vitamin K with potassium, whose chemical symbol is K. A third is to take a K2 capsule for the bones or arteries on the strength of advertising, when the trials do not confirm a benefit.

Safety, supplements and when to see a doctor

Neither ICMR-NIN nor FAO/WHO sets an upper limit. The consultation records that natural K vitamins taken by mouth seem free of toxic side effects, while advising against synthetic menadione, which has been linked to damage to red blood cells and the liver in newborns. In India, FSSAI's health supplement regulations permit vitamin K1 as phylloquinone and K2 as MK-7 and MK-4, cap nutrients in tablets and capsules at one recommended dietary allowance, and require the label to carry the words NOT FOR MEDICINAL USE.

Studying this with NNWA

Vitamin K comes up at NNWA in the teaching on fat-soluble vitamins, infant nutrition and food and medicine interactions. NNWA is a private skill academy in Kolkata whose classes run online, in Hindi and in English. Its courses train people to coach healthy clients and to pass medical cases to a doctor; not one of them is a degree or a dietitian qualification. The Clinical Nutrition course deals with nutrition beside medical treatment, and the Diploma in Nutrition, Dietetics and Public Health covers requirements across the life cycle.