The Make America Healthy Again (MAHA) initiative, led by US Secretary of Health Robert F. Kennedy Jr, aims to “tackle chronic diseases, improve nutrition and reduce healthcare costs.” To achieve these laudable goals, members of the MAHA movement have set out to reform American health policies on issues such as nutrition and vaccines and what they see as over-reliance on medications. Such enormous changes in the United States are likely to have ripple effects around the world.

Kennedy says MAHA’s policies are based on “gold standard” science. Some aspects have obtained support from the research community. But in other areas, critics say, the MAHA platform includes claims that are misleading or hyperbolic, for example those related to vaccine effectiveness and risk factors for autism spectrum disorder.

What does science say? Nature He spoke with researchers about some of the notable talking points from the MAHA initiative.

‘Eat more meat and dairy to stay healthy’

On January 7, the US departments of health and agriculture released their Dietary Guidelines for Americans for 2025 to 2030, a set of recommendations that will shape the country’s nutrition and health policies, such as establishing food options in schools. The guidelines call for U.S. citizens to “eat more real foods,” particularly diets rich in red meat, full-fat dairy products, and fresh fruits and vegetables, with strict limits on added sugars and ultra-processed foods. “Most of their claims are consistent with older claims of focusing on real foods,” says Christopher Gardner, director of nutrition studies at the Stanford Prevention Research Center in Palo Alto, California.

But, Gardner says, the guidelines’ emphasis on red meat and dairy results in an increase in the recommended protein intake: from 0.8 grams per kilogram of body weight per day to between 1.2 and 1.6 grams. The recommendation therefore circumvents a 2025 systematic review on protein requirements, which concluded there was insufficient evidence to change the 0.8 gram suggestion.¹. Previously, dietary guidelines made recommendations in terms of servings of food rather than grams of nutrients. As a result, Gardner says, “the new number was off.”

Gardner was one of 20 people appointed to the 2025 Dietary Guidelines Advisory Committee (DGAC), an independent group that advises the U.S. Department of Health and Human Services (HHS) and the Department of Agriculture on the development of dietary guidelines. In December 2024, the committee prepared a 421-page report that compiles the latest scientific data supporting the guidance.

A separate supplemental review was subsequently conducted by a nine-person committee appointed by US President Donald Trump’s administration. This was used in the creation of the 2025-2030 guidelines, along with some recommendations from the DGAC.

Walter Willett, a physician and nutrition researcher at the Harvard TH Chan School of Public Health in Boston, Massachusetts, says some of the research behind the latest guidelines did not undergo a substantive review process that was open to public comment. “The documents attached to the guidelines do not have anywhere near the rigor of the published report by the original expert committee,” he says.

Despite those concerns, some groups of people could benefit from higher protein intake, particularly older adults and athletes who want to gain muscle. Stuart Phillips, a health researcher at McMaster University in Hamilton, Canada, and his colleagues argued in a 2018 study that older adults should eat at least 1.2 grams of protein per kilogram of body weight to combat muscle loss.². However, too much animal protein may increase the risk of developing kidney stones, according to a 2023 study.³. A systematic review and meta-analysis of the evidence in 2010 found that diets high in processed meats are associated with increased risks of coronary heart disease and diabetes.⁴.

“Ultra-processed foods cause chronic diseases”

The 2025-2030 guidelines recommend avoiding highly processed, prepared and ready-to-eat foods, as well as sugary drinks and products containing added sugar or non-nutritive sweeteners. This eliminates most carbonated soft drinks, fruit and energy drinks.

A 2024 review of 45 meta-analyses, published in He B.M.J.found that greater exposure to ultra-processed foods was associated with a higher risk of death and cardiometabolic and mental health disorders.⁵. Additionally, a 2024 prospective study in The BMJ involving more than 100,000 participants found slightly higher mortality rates in those with high consumption of ultra-processed foods⁶.

In response to the guidelines, the American Medical Association issued a statement on Jan. 7 saying it “applauds the Administration’s new Dietary Guidelines for shining a spotlight on highly processed foods, sugary drinks, and excess sodium that fuel heart disease, diabetes, obesity, and other chronic illnesses.”

But Josiemer Mattei, a nutrition researcher at the Harvard TH Chan School of Public Health, points out that not all ultra-processed foods are created equal. So far, scientists have isolated the negative health impacts of only two types of ultra-processed foods: sugary drinks, particularly carbonated soft drinks, and cured or processed meats such as sausages, hot dogs and bacon. Beyond those groups, it’s really difficult to separate the health effects, Mattei says.

All foods that contain additives, colorings, added sugars, colorings or stabilizers, or that are subject to certain industrialized processes, are considered ultra-processed, explains Mattei. By that definition, sweetened yogurt and bread that contains preservatives are in this category. “It gets murky, because some ultra-processed foods have very valuable nutrients; for example, bread that has a stabilizer can also be high in fiber and B vitamins,” he says.

“Additives in general are not necessarily bad,” Willett says. “Many additives are harmless; in fact, many are good.”

‘Seed oils have a role in inflammation’

Seed oils (the fats extracted from the seeds of soybeans and canola, sunflower, and other plants) are commonly called vegetable oils. They are typically high in unsaturated fats, but also contain high levels of omega-6 fatty acids, which, when considered in dietary proportion with related omega-3 fatty acids, have a complicated effect on inflammation that researchers have not yet fully analyzed. A May 2025 White House MAHA report highlighted the shift of American dietary fats toward seed oils and noted their potential role in inflammation. Kennedy has also said that seed oils can poison people, a claim that is “not supported by scientific research,” Mattei says.

Scientific literature generally agrees that consuming plant-based oils is healthier than swapping them for saturated fats.⁷ as dietary guidelines suggest, says Mattei. Seed oils are rich in omega-6 fatty acids, such as linoleic acid, which the body cannot produce itself, and salmon and other fatty fish contain omega-3 fatty acids, although fish consumption in the United States is low compared to other high-income countries.

The idea that seed oils are unhealthy, Willett says, goes back to changes in fatty acid consumption. A 2016 review noted that modern Western diets now have a much higher ratio of omega-6 to omega-3 fatty acids consumed: from 1:1 in the prehistoric diet to 20:1 today.⁸. However, there was no evidence of an increase in cardiovascular disease or cancer, Willett adds. In the last decade, other researchers and health influencers have focused on seed oils, identifying corn, canola, soybean, and sunflower oils among the “hateful eight.”

What is the science behind “science-backed” supplements?

Willett says there have been dozens of studies and reviews to determine whether these fatty acids cause inflammation or have other effects.⁹. “None of these studies showed an increase in inflammatory factors and some showed a decrease in inflammatory factors,” he says.

Research consistently reports that omega-6 fatty acids reduce blood cholesterol levels and that higher dietary intake and blood levels of both omega acids are associated with a lower risk of cardiovascular disease.¹⁰. A 2024 study concluded that evidence on the omega-6 to omega-3 ratio is not informative¹¹. Concerns about seed oils “have been refuted in dozens of randomized trials and long-term epidemiological studies over decades,” Willett says.

‘Artificial food dyes are linked to ADHD and cancer’

At an April 2025 press conference, Kennedy announced that the Trump administration would phase out petroleum-based synthetic dyes, starting with FD&C Red No. 3, also known as erythrosine. The 2025 MAHA report states that some food additives have been linked to increased risks of attention deficit hyperactivity disorder (ADHD) and cancer.

According to Mattei, “the causes of ADHD are not nutritional. They are more genetic and developmental.”