Nutritional News: Zinc, Seeds and the Phytate Question

October 10, 2026

Series 15: Zinc

Zinc is one of the minerals where the amount in a food can say very little about what the body absorbs. The most zinc-containing plant foods, seeds, nuts and wholegrains, also contain phytate, a compound that binds the mineral in the gut. This article looks at zinc through the seeds and nuts we work with.

What zinc does

According to the NIH Office of Dietary Supplements, zinc is required for the catalytic activity of hundreds of enzymes. It supports immune function, protein and DNA synthesis, wound healing, and cell signalling and division, and it is involved in taste. The NHS describes it as supporting the creation of new cells and enzymes, helping the body process carbohydrate, fat and protein, and aiding wound healing.

How much do we need?

The NHS gives UK reference amounts of about 9.5 mg a day for men aged 19 to 64 and about 7 mg for women, and says most people can get this from their diet. US recommended allowances are 11 mg for men and 8 mg for women, rising to 11 mg in pregnancy and 12 mg during lactation.

The absorption question

The NIH reports that zinc absorption from food ranges from 5% to more than 50%, depending largely on the phytate content of the diet. Phytates bind zinc in the intestine into an insoluble complex that cannot be absorbed. Absorption is lower from mixed or plant-based diets than from animal-based diets, and vegetarians often have lower zinc intakes and serum levels.

The NIH notes that soaking beans, grains and seeds before cooking, and the organic acids in fermented foods, may increase absorption. It does not give a figure for how much. Iron supplements of 25 mg or more taken together with zinc can reduce zinc absorption, although iron in fortified foods does not significantly interfere.

Our ingredients and zinc

Pumpkin seeds. They are the best-documented plant source in the NIH table, at 2.2 mg of zinc per 28 g of roasted seeds. Pumpkin seeds are the main ingredient of our raw pumpkin seed butter and pumpkin seed protein powder.

Sesame and tahini. Sesame seeds and the tahini made from them (white and black) are seeds, so the phytate point above applies. The NIH food table does not list sesame, so no figure is quoted here.

Hemp. Hulled hemp seeds, hemp seed butter and hemp seed protein powder are not in the NIH table either, so the article doesn't give a number.

Cashews. Cashew butter is made from a nut that the NIH does not list in its zinc table, so again no figure is quoted.

Sunflower seeds and oats. Sprouted sunflower seeds and sprouted rolled naked oats are seeds and grains that have been soaked and germinated. The NIH says soaking may increase zinc absorption, but it does not comment on sprouting or give a figure. Our earlier articles on sprouted seeds and activated nuts look at the evidence on soaking and germination in more detail.

None of this is a claim about the zinc content of our products. For the amount in any food, check the pack.

Who may fall short?

The NIH lists these groups as at risk of inadequate zinc:

People with inflammatory bowel disease, or who have had gastrointestinal or bariatric surgery. Deficiency is reported in about 15 to 40% of people with IBD.
People with newly diagnosed coeliac disease, about half of whom are at high risk of inadequacy.
People following vegetarian or vegan diets.
Pregnant or breastfeeding women, and exclusively breastfed infants after six months.
People with alcohol use disorder.

In US survey data, about 15% of adults and 20.9% of adolescent girls had intakes below the estimated average requirement.

What the research says

The common cold. A 2024 Cochrane review (34 trials, 8,526 participants) found that zinc may shorten colds by about two days, with little to no effect on preventing them. The certainty of evidence was low to very low. Individual trials disagree: one found gluconate lozenges shortened colds by a day while acetate lozenges at 5 to 11.5 mg had no effect, and another found 13.3 mg acetate lozenges shortened colds by three days. These are lozenge studies, at doses and in forms that foods don't provide.

Eye health. The AREDS trial (4,757 participants at high risk of advanced age-related macular degeneration) found a 25% lower risk of progression with 80 mg of zinc plus antioxidants and copper over five years. AREDS2 reported a similar effect with 25 mg, but the researchers called this preliminary. In an Australian cohort of 2,464 adults, those in the top tenth of zinc intake (15.8 mg a day or more) had 44% lower risk of any AMD. These findings come from supplement trials in a specific high-risk group.

Childhood diarrhoea. A 2016 Cochrane review (33 trials, 10,841 children) found zinc shortened diarrhoea by about half a day in children over six months. The benefit may be marginal in well-nourished children, and WHO and UNICEF recommend zinc in this setting as a clinical treatment, not as dietary advice.

Wound healing and immunity. Zinc deficiency in older adults can delay wound healing, but the NIH cites no trial data supporting supplements for people who are not deficient. Doses of 50 mg or more taken for weeks can reduce immune function.

Too much zinc

The NIH sets an upper limit of 40 mg a day for adults. The NHS advice is not to take more than 25 mg a day from supplements unless a doctor advises it. Excess causes nausea, dizziness, headaches, stomach upset and loss of appetite. Doses of 50 mg or more for weeks can impair copper absorption, which can lead to anaemia and weakened bones, and can lower HDL cholesterol.

Authorised health claims

Under GB nutrition and health claims rules, zinc has authorised claims. Zinc contributes to normal cognitive function, to normal DNA synthesis and cell division, to normal protein synthesis, to normal carbohydrate and macronutrient metabolism, to normal fatty acid metabolism, to normal fertility and reproduction, to the maintenance of normal testosterone levels, to the maintenance of normal bones, hair, nails, skin and vision, to the normal function of the immune system and to the protection of cells from oxidative stress. A food can only carry these claims if it meets the conditions of use set out in the rules.

Editorial note

This article summarises published research and reference data for general information. It is not medical advice. Anyone considering zinc supplements should speak to a GP or pharmacist, particularly if they take other supplements or have a gastrointestinal condition.